Posts Tagged ‘servers’

How to monitor Haproxy Application server backends with Zabbix userparameter autodiscovery scripts

Friday, May 13th, 2022

zabbix-backend-monitoring-logo

Haproxy is doing quite a good job in High Availability tasks where traffic towards multiple backend servers has to be redirected based on the available one to sent data from the proxy to. 

Lets say haproxy is configured to proxy traffic for App backend machine1 and App backend machine2.

Usually in companies people configure a monitoring like with Icinga or Zabbix / Grafana to keep track on the Application server is always up and running. Sometimes however due to network problems (like burned Network Switch / router or firewall misconfiguration) or even an IP duplicate it might happen that Application server seems to be reporting reachable from some monotoring tool on it but unreachable from  Haproxy server -> App backend machine2 but reachable from App backend machine1. And even though haproxy will automatically switch on the traffic from backend machine2 to App machine1. It is a good idea to monitor and be aware that one of the backends is offline from the Haproxy host.
In this article I'll show you how this is possible by using 2 shell scripts and userparameter keys config through the autodiscovery zabbix legacy feature.
Assumably for the setup to work you will need to have as a minimum a Zabbix server installation of version 5.0 or higher.

1. Create the required  haproxy_discovery.sh  and haproxy_stats.sh scripts 

You will have to install the two scripts under some location for example we can put it for more clearness under /etc/zabbix/scripts

[root@haproxy-server1 ]# mkdir /etc/zabbix/scripts

[root@haproxy-server1 scripts]# vim haproxy_discovery.sh 
#!/bin/bash
#
# Get list of Frontends and Backends from HAPROXY
# Example: ./haproxy_discovery.sh [/var/lib/haproxy/stats] FRONTEND|BACKEND|SERVERS
# First argument is optional and should be used to set location of your HAPROXY socket
# Second argument is should be either FRONTEND, BACKEND or SERVERS, will default to FRONTEND if not set
#
# !! Make sure the user running this script has Read/Write permissions to that socket !!
#
## haproxy.cfg snippet
#  global
#  stats socket /var/lib/haproxy/stats  mode 666 level admin

HAPROXY_SOCK=""/var/run/haproxy/haproxy.sock
[ -n “$1” ] && echo $1 | grep -q ^/ && HAPROXY_SOCK="$(echo $1 | tr -d '\040\011\012\015')"

if [[ “$1” =~ (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?):[0-9]{1,5} ]];
then
    HAPROXY_STATS_IP="$1"
    QUERYING_METHOD="TCP"
fi

QUERYING_METHOD="${QUERYING_METHOD:-SOCKET}"

query_stats() {
    if [[ ${QUERYING_METHOD} == “SOCKET” ]]; then
        echo "show stat" | socat ${HAPROXY_SOCK} stdio 2>/dev/null
    elif [[ ${QUERYING_METHOD} == “TCP” ]]; then
        echo "show stat" | nc ${HAPROXY_STATS_IP//:/ } 2>/dev/null
    fi
}

get_stats() {
        echo "$(query_stats)" | grep -v "^#"
}

[ -n “$2” ] && shift 1
case $1 in
        B*) END="BACKEND" ;;
        F*) END="FRONTEND" ;;
        S*)
                for backend in $(get_stats | grep BACKEND | cut -d, -f1 | uniq); do
                        for server in $(get_stats | grep "^${backend}," | grep -v BACKEND | grep -v FRONTEND | cut -d, -f2); do
                                serverlist="$serverlist,\n"'\t\t{\n\t\t\t"{#BACKEND_NAME}":"'$backend'",\n\t\t\t"{#SERVER_NAME}":"'$server'"}'
                        done
                done
                echo -e '{\n\t"data":[\n’${serverlist#,}’]}'
                exit 0
        ;;
        *) END="FRONTEND" ;;
esac

for frontend in $(get_stats | grep "$END" | cut -d, -f1 | uniq); do
    felist="$felist,\n"'\t\t{\n\t\t\t"{#'${END}'_NAME}":"'$frontend'"}'
done
echo -e '{\n\t"data":[\n’${felist#,}’]}'

 

[root@haproxy-server1 scripts]# vim haproxy_stats.sh 
#!/bin/bash
set -o pipefail

if [[ “$1” = /* ]]
then
  HAPROXY_SOCKET="$1"
  shift 0
else
  if [[ “$1” =~ (25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?):[0-9]{1,5} ]];
  then
    HAPROXY_STATS_IP="$1"
    QUERYING_METHOD="TCP"
    shift 1
  fi
fi

pxname="$1"
svname="$2"
stat="$3"

DEBUG=${DEBUG:-0}
HAPROXY_SOCKET="${HAPROXY_SOCKET:-/var/run/haproxy/haproxy.sock}"
QUERYING_METHOD="${QUERYING_METHOD:-SOCKET}"
CACHE_STATS_FILEPATH="${CACHE_STATS_FILEPATH:-/var/tmp/haproxy_stats.cache}"
CACHE_STATS_EXPIRATION="${CACHE_STATS_EXPIRATION:-1}" # in minutes
CACHE_INFO_FILEPATH="${CACHE_INFO_FILEPATH:-/var/tmp/haproxy_info.cache}" ## unused
CACHE_INFO_EXPIRATION="${CACHE_INFO_EXPIRATION:-1}" # in minutes ## unused
GET_STATS=${GET_STATS:-1} # when you update stats cache outsise of the script
SOCAT_BIN="$(which socat)"
NC_BIN="$(which nc)"
FLOCK_BIN="$(which flock)"
FLOCK_WAIT=15 # maximum number of seconds that "flock" waits for acquiring a lock
FLOCK_SUFFIX='.lock'
CUR_TIMESTAMP="$(date '+%s')"

debug() {
  [ “${DEBUG}” -eq 1 ] && echo "DEBUG: $@" >&2 || true
}

debug "SOCAT_BIN        => $SOCAT_BIN"
debug "NC_BIN           => $NC_BIN"
debug "FLOCK_BIN        => $FLOCK_BIN"
debug "FLOCK_WAIT       => $FLOCK_WAIT seconds"
debug "CACHE_FILEPATH   => $CACHE_FILEPATH"
debug "CACHE_EXPIRATION => $CACHE_EXPIRATION minutes"
debug "HAPROXY_SOCKET   => $HAPROXY_SOCKET"
debug "pxname   => $pxname"
debug "svname   => $svname"
debug "stat     => $stat"

# check if socat is available in path
if [ “$GET_STATS” -eq 1 ] && [[ $QUERYING_METHOD == “SOCKET” && -z “$SOCAT_BIN” ]] || [[ $QUERYING_METHOD == “TCP” &&  -z “$NC_BIN” ]]
then
  echo 'ERROR: cannot find socat binary'
  exit 126
fi

# if we are getting stats:
#   check if we can write to stats cache file, if it exists
#     or cache file path, if it does not exist
#   check if HAPROXY socket is writable
# if we are NOT getting stats:
#   check if we can read the stats cache file
if [ “$GET_STATS” -eq 1 ]
then
  if [ -e “$CACHE_FILEPATH” ] && [ ! -w “$CACHE_FILEPATH” ]
  then
    echo 'ERROR: stats cache file exists, but is not writable'
    exit 126
  elif [ ! -w ${CACHE_FILEPATH%/*} ]
  then
    echo 'ERROR: stats cache file path is not writable'
    exit 126
  fi
  if [[ $QUERYING_METHOD == “SOCKET” && ! -w $HAPROXY_SOCKET ]]
  then
    echo "ERROR: haproxy socket is not writable"
    exit 126
  fi
elif [ ! -r “$CACHE_FILEPATH” ]
then
  echo 'ERROR: cannot read stats cache file'
  exit 126
fi

# index:name:default
MAP="
1:pxname:@
2:svname:@
3:qcur:9999999999
4:qmax:0
5:scur:9999999999
6:smax:0
7:slim:0
8:stot:@
9:bin:9999999999
10:bout:9999999999
11:dreq:9999999999
12:dresp:9999999999
13:ereq:9999999999
14:econ:9999999999
15:eresp:9999999999
16:wretr:9999999999
17:wredis:9999999999
18:status:UNK
19:weight:9999999999
20:act:9999999999
21:bck:9999999999
22:chkfail:9999999999
23:chkdown:9999999999
24:lastchg:9999999999
25:downtime:0
26:qlimit:0
27:pid:@
28:iid:@
29:sid:@
30:throttle:9999999999
31:lbtot:9999999999
32:tracked:9999999999
33:type:9999999999
34:rate:9999999999
35:rate_lim:@
36:rate_max:@
37:check_status:@
38:check_code:@
39:check_duration:9999999999
40:hrsp_1xx:@
41:hrsp_2xx:@
42:hrsp_3xx:@
43:hrsp_4xx:@
44:hrsp_5xx:@
45:hrsp_other:@
46:hanafail:@
47:req_rate:9999999999
48:req_rate_max:@
49:req_tot:9999999999
50:cli_abrt:9999999999
51:srv_abrt:9999999999
52:comp_in:0
53:comp_out:0
54:comp_byp:0
55:comp_rsp:0
56:lastsess:9999999999
57:last_chk:@
58:last_agt:@
59:qtime:0
60:ctime:0
61:rtime:0
62:ttime:0
"

_STAT=$(echo -e "$MAP" | grep :${stat}:)
_INDEX=${_STAT%%:*}
_DEFAULT=${_STAT##*:}

debug "_STAT    => $_STAT"
debug "_INDEX   => $_INDEX"
debug "_DEFAULT => $_DEFAULT"

# check if requested stat is supported
if [ -z “${_STAT}” ]
then
  echo "ERROR: $stat is unsupported"
  exit 127
fi

# method to retrieve data from haproxy stats
# usage:
# query_stats "show stat"
query_stats() {
    if [[ ${QUERYING_METHOD} == “SOCKET” ]]; then
        echo $1 | socat ${HAPROXY_SOCKET} stdio 2>/dev/null
    elif [[ ${QUERYING_METHOD} == “TCP” ]]; then
        echo $1 | nc ${HAPROXY_STATS_IP//:/ } 2>/dev/null
    fi
}

# a generic cache management function, that relies on 'flock'
check_cache() {
  local cache_type="${1}"
  local cache_filepath="${2}"
  local cache_expiration="${3}"  
  local cache_filemtime
  cache_filemtime=$(stat -c '%Y' "${cache_filepath}" 2> /dev/null)
  if [ $((cache_filemtime+60*cache_expiration)) -ge ${CUR_TIMESTAMP} ]
  then
    debug "${cache_type} file found, results are at most ${cache_expiration} minutes stale.."
  elif "${FLOCK_BIN}" –exclusive –wait "${FLOCK_WAIT}" 200
  then
    cache_filemtime=$(stat -c '%Y' "${cache_filepath}" 2> /dev/null)
    if [ $((cache_filemtime+60*cache_expiration)) -ge ${CUR_TIMESTAMP} ]
    then
      debug "${cache_type} file found, results have just been updated by another process.."
    else
      debug "no ${cache_type} file found, querying haproxy"
      query_stats "show ${cache_type}" > "${cache_filepath}"
    fi
  fi 200> "${cache_filepath}${FLOCK_SUFFIX}"
}

# generate stats cache file if needed
get_stats() {
  check_cache 'stat' "${CACHE_STATS_FILEPATH}" ${CACHE_STATS_EXPIRATION}
}

# generate info cache file
## unused at the moment
get_info() {
  check_cache 'info' "${CACHE_INFO_FILEPATH}" ${CACHE_INFO_EXPIRATION}
}

# get requested stat from cache file using INDEX offset defined in MAP
# return default value if stat is ""
get() {
  # $1: pxname/svname
  local _res="$("${FLOCK_BIN}" –shared –wait "${FLOCK_WAIT}" "${CACHE_STATS_FILEPATH}${FLOCK_SUFFIX}" grep $1 "${CACHE_STATS_FILEPATH}")"
  if [ -z “${_res}” ]
  then
    echo "ERROR: bad $pxname/$svname"
    exit 127
  fi
  _res="$(echo $_res | cut -d, -f ${_INDEX})"
  if [ -z “${_res}” ] && [[ “${_DEFAULT}” != “@” ]]
  then
    echo "${_DEFAULT}"  
  else
    echo "${_res}"
  fi
}

# not sure why we'd need to split on backslash
# left commented out as an example to override default get() method
# status() {
#   get "^${pxname},${svnamem}," $stat | cut -d\  -f1
# }

# this allows for overriding default method of getting stats
# name a function by stat name for additional processing, custom returns, etc.
if type get_${stat} >/dev/null 2>&1
then
  debug "found custom query function"
  get_stats && get_${stat}
else
  debug "using default get() method"
  get_stats && get "^${pxname},${svname}," ${stat}
fi


! NB ! Substitute in the script /var/run/haproxy/haproxy.sock with your haproxy socket location

You can download the haproxy_stats.sh here and haproxy_discovery.sh here

2. Create the userparameter_haproxy_backend.conf

[root@haproxy-server1 zabbix_agentd.d]# cat userparameter_haproxy_backend.conf 
#
# Discovery Rule
#

# HAProxy Frontend, Backend and Server Discovery rules
UserParameter=haproxy.list.discovery[*],sudo /etc/zabbix/scripts/haproxy_discovery.sh SERVER
UserParameter=haproxy.stats[*],sudo /etc/zabbix/scripts/haproxy_stats.sh  $2 $3 $4

# support legacy way

UserParameter=haproxy.stat.downtime[*],sudo /etc/zabbix/scripts/haproxy_stats.sh  $2 $3 downtime

UserParameter=haproxy.stat.status[*],sudo /etc/zabbix/scripts/haproxy_stats.sh  $2 $3 status

UserParameter=haproxy.stat.last_chk[*],sudo /etc/zabbix/scripts/haproxy_stats.sh  $2 $3 last_chk

 

3. Create new simple template for the Application backend Monitoring and link it to monitored host

create-configuration-template-backend-monitoring

create-template-backend-monitoring-macros

 

Go to Configuration -> Hosts (find the host) and Link the template to it


4. Restart Zabbix-agent, in while check autodiscovery data is in Zabbix Server

[root@haproxy-server1 ]# systemctl restart zabbix-agent


Check in zabbix the userparameter data arrives, it should not be required to add any Items or Triggers as autodiscovery zabbix feature should automatically create in the server what is required for the data regarding backends to be in.

To view data arrives go to Zabbix config menus:

Configuration -> Hosts -> Hosts: (lookup for the haproxy-server1 hostname)

zabbix-discovery_rules-screenshot

The autodiscovery should have automatically created the following prototypes

zabbix-items-monitoring-prototypes
Now if you look inside Latest Data for the Host you should find some information like:

HAProxy Backend [backend1] (3 Items)
        
HAProxy Server [backend-name_APP/server1]: Connection Response
2022-05-13 14:15:04            History
        
HAProxy Server [backend-name/server2]: Downtime (hh:mm:ss)
2022-05-13 14:13:57    20:30:42        History
        
HAProxy Server [bk_name-APP/server1]: Status
2022-05-13 14:14:25    Up (1)        Graph
        ccnrlb01    HAProxy Backend [bk_CCNR_QA_ZVT] (3 Items)
        
HAProxy Server [bk_name-APP3/server1]: Connection Response
2022-05-13 14:15:05            History
        
HAProxy Server [bk_name-APP3/server1]: Downtime (hh:mm:ss)
2022-05-13 14:14:00    20:55:20        History
        
HAProxy Server [bk_name-APP3/server2]: Status
2022-05-13 14:15:08    Up (1)

To make alerting in case if a backend is down which usually you would like only left thing is to configure an Action to deliver alerts to some email address.

Create Linux High Availability Load Balancer Cluster with Keepalived and Haproxy on Linux

Tuesday, March 15th, 2022

keepalived-logo-linux

Configuring a Linux HA (High Availibiltiy) for an Application with Haproxy is already used across many Websites on the Internet and serious corporations that has a crucial infrastructure has long time
adopted and used keepalived to provide High Availability Application level Clustering.
Usually companies choose to use HA Clusters with Haproxy with Pacemaker and Corosync cluster tools.
However one common used alternative solution if you don't have the oportunity to bring up a High availability cluster with Pacemaker / Corosync / pcs (Pacemaker Configuration System) due to fact machines you need to configure the cluster on are not Physical but VMWare Virtual Machines which couldn't not have configured a separate Admin Lans and Heartbeat Lan as we usually do on a Pacemaker Cluster due to the fact the 5 Ethernet LAN Card Interfaces of the VMWare Hypervisor hosts are configured as a BOND (e.g. all the incoming traffic to the VMWare vSphere  HV is received on one Virtual Bond interface).

I assume you have 2 separate vSphere Hypervisor Physical Machines in separate Racks and separate switches hosting the two VMs.
For the article, I'll call the two brand new brought Virtual Machines with some installation automation software such as Terraform or Ansible – vm-server1 and vm-server2 which would have configured some recent version of Linux.

In that scenario to have a High Avaiability for the VMs on Application level and assure at least one of the two is available at a time if one gets broken due toe malfunction of the HV, a Network connectivity issue, or because the VM OS has crashed.
Then one relatively easily solution is to use keepalived and configurea single High Availability Virtual IP (VIP) Address, i.e. 10.10.10.1, which would float among two VMs using keepalived so at a time at least one of the two VMs would be reachable on the Network.

haproxy_keepalived-vip-ip-diagram-linux

Having a VIP IP is quite a common solution in corporate world, as it makes it pretty easy to add F5 Load Balancer in front of the keepalived cluster setup to have a 3 Level of security isolation, which usually consists of:

1. Physical (access to the hardware or Virtualization hosts)
2. System Access (The mechanism to access the system login credetials users / passes, proxies, entry servers leading to DMZ-ed network)
3. Application Level (access to different programs behind L2 and data based on the specific identity of the individual user,
special Secondary UserID,  Factor authentication, biometrics etc.)

 

1. Install keepalived and haproxy on machines

Depending on the type of Linux OS:

On both machines
 

[root@server1:~]# yum install -y keepalived haproxy

If you have to install keepalived / haproxy on Debian / Ubuntu and other Deb based Linux distros

[root@server1:~]# apt install keepalived haproxy –yes

2. Configure haproxy (haproxy.cfg) on both server1 and server2

 

Create some /etc/haproxy/haproxy.cfg configuration

 

[root@server1:~]vim /etc/haproxy/haproxy.cfg

#———————————————————————
# Global settings
#———————————————————————
global
    log          127.0.0.1 local6 debug
    chroot       /var/lib/haproxy
    pidfile      /run/haproxy.pid
    stats socket /var/lib/haproxy/haproxy.sock mode 0600 level admin 
    maxconn      4000
    user         haproxy
    group        haproxy
    daemon
    #debug
    #quiet

#———————————————————————
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#———————————————————————
defaults
    mode        tcp
    log         global
#    option      dontlognull
#    option      httpclose
#    option      httplog
#    option      forwardfor
    option      redispatch
    option      log-health-checks
    timeout connect 10000 # default 10 second time out if a backend is not found
    timeout client 300000
    timeout server 300000
    maxconn     60000
    retries     3

#———————————————————————
# round robin balancing between the various backends
#———————————————————————

listen FRONTEND_APPNAME1
        bind 10.10.10.1:15000
        mode tcp
        option tcplog
#        #log global
        log-format [%t]\ %ci:%cp\ %bi:%bp\ %b/%s:%sp\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
        balance roundrobin
        timeout client 350000
        timeout server 350000
        timeout connect 35000
        server app-server1 10.10.10.55:30000 weight 1 check port 68888
        server app-server2 10.10.10.55:30000 weight 2 check port 68888

listen FRONTEND_APPNAME2
        bind 10.10.10.1:15000
        mode tcp
        option tcplog
        #log global
        log-format [%t]\ %ci:%cp\ %bi:%bp\ %b/%s:%sp\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
        balance roundrobin
        timeout client 350000
        timeout server 350000
        timeout connect 35000
        server app-server1 10.10.10.55:30000 weight 5
        server app-server2 10.10.10.55:30000 weight 5 

 

You can get a copy of above haproxy.cfg configuration here.
Once configured roll it on.

[root@server1:~]#  systemctl start haproxy
 
[root@server1:~]# ps -ef|grep -i hapro
root      285047       1  0 Mar07 ?        00:00:00 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid
haproxy   285050  285047  0 Mar07 ?        00:00:26 /usr/sbin/haproxy -Ws -f /etc/haproxy/haproxy.cfg -p /run/haproxy.pid

Bring up the haproxy also on server2 machine, by placing same configuration and starting up the proxy.
 

[root@server1:~]vim /etc/haproxy/haproxy.cfg


 

3. Configure keepalived on both servers

We'll be configuring 2 nodes with keepalived even though if necessery this can be easily extended and you can add more nodes.
First we make a copy of the original or existing server configuration keepalived.conf (just in case we need it later on or if you already had something other configured manually by someone – that could be so on inherited servers by other sysadmin)
 

[root@server1:~]# mv /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.orig
[root@server2:~]# mv /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.orig

a. Configure keepalived to serve as a MASTER Node

 

[root@server1:~]# vim /etc/keepalived/keepalived.conf

Master Node
global_defs {
  router_id server1-fqdn # The hostname of this host.
  
  enable_script_security
  # Synchro of the state of the connections between the LBs on the eth0 interface
   lvs_sync_daemon eth0
 
notification_email {
        linuxadmin@notify-domain.com     # Email address for notifications 
    }
 notification_email_from keepalived@server1-fqdn        # The from address for the notifications
    smtp_server 127.0.0.1                       # SMTP server address
    smtp_connect_timeout 15
}

vrrp_script haproxy {
  script "killall -0 haproxy"
  interval 2
  weight 2
  user root
}

vrrp_instance LB_VIP_QA {
  virtual_router_id 50
  advert_int 1
  priority 51

  state MASTER
  interface eth0
  smtp_alert          # Enable Notifications Via Email
  
  authentication {
              auth_type PASS
              auth_pass testp141

    }
### Commented because running on VM on VMWare
##    unicast_src_ip 10.44.192.134 # Private IP address of master
##    unicast_peer {
##        10.44.192.135           # Private IP address of the backup haproxy
##   }

#        }
# master node with higher priority preferred node for Virtual IP if both keepalived up
###  priority 51
###  state MASTER
###  interface eth0
  virtual_ipaddress {
     10.10.10.1 dev eth0 # The virtual IP address that will be shared between MASTER and BACKUP
  }
  track_script {
      haproxy
  }
}

 

 To dowload a copy of the Master keepalived.conf configuration click here

Below are few interesting configuration variables, worthy to mention few words on, most of them are obvious by their names but for more clarity I'll also give a list here with short description of each:

 

  • vrrp_instance – defines an individual instance of the VRRP protocol running on an interface.
  • state – defines the initial state that the instance should start in (i.e. MASTER / SLAVE )state –
  • interface – defines the interface that VRRP runs on.
  • virtual_router_id – should be unique value per Keepalived Node (otherwise slave master won't function properly)
  • priority – the advertised priority, the higher the priority the more important the respective configured keepalived node is.
  • advert_int – specifies the frequency that advertisements are sent at (1 second, in this case).
  • authentication – specifies the information necessary for servers participating in VRRP to authenticate with each other. In this case, a simple password is defined.
    only the first eight (8) characters will be used as described in  to note is Important thing
    man keepalived.conf – keepalived.conf variables documentation !!! Nota Bene !!! – Password set on each node should match for nodes to be able to authenticate !
  • virtual_ipaddress – defines the IP addresses (there can be multiple) that VRRP is responsible for.
  • notification_email – the notification email to which Alerts will be send in case if keepalived on 1 node is stopped (e.g. the MASTER node switches from host 1 to 2)
  • notification_email_from – email address sender from where email will originte
    ! NB ! In order for notification_email to be working you need to have configured MTA or Mail Relay (set to local MTA) to another SMTP – e.g. have configured something like Postfix, Qmail or Postfix

b. Configure keepalived to serve as a SLAVE Node

[root@server1:~]vim /etc/keepalived/keepalived.conf
 

#Slave keepalived
global_defs {
  router_id server2-fqdn # The hostname of this host!

  enable_script_security
  # Synchro of the state of the connections between the LBs on the eth0 interface
  lvs_sync_daemon eth0
 
notification_email {
        linuxadmin@notify-host.com     # Email address for notifications
    }
 notification_email_from keepalived@server2-fqdn        # The from address for the notifications
    smtp_server 127.0.0.1                       # SMTP server address
    smtp_connect_timeout 15
}

vrrp_script haproxy {
  script "killall -0 haproxy"
  interval 2
  weight 2
  user root
}

vrrp_instance LB_VIP_QA {
  virtual_router_id 50
  advert_int 1
  priority 50

  state BACKUP
  interface eth0
  smtp_alert          # Enable Notifications Via Email

authentication {
              auth_type PASS
              auth_pass testp141
}
### Commented because running on VM on VMWare    
##    unicast_src_ip 10.10.192.135 # Private IP address of master
##    unicast_peer {
##        10.10.192.134         # Private IP address of the backup haproxy
##   }

###  priority 50
###  state BACKUP
###  interface eth0
  virtual_ipaddress {
     10.10.10.1 dev eth0 # The virtual IP address that will be shared betwee MASTER and BACKUP.
  }
  track_script {
    haproxy
  }
}

 

Download the keepalived.conf slave config here

 

c. Set required sysctl parameters for haproxy to work as expected
 

[root@server1:~]vim /etc/sysctl.conf
#Haproxy config
# haproxy
net.core.somaxconn=65535
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.ip_nonlocal_bind = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_max_syn_backlog = 10240
net.ipv4.tcp_max_tw_buckets = 400000
net.ipv4.tcp_max_orphans = 60000
net.ipv4.tcp_synack_retries = 3

4. Test Keepalived keepalived.conf configuration syntax is OK

 

[root@server1:~]keepalived –config-test
(/etc/keepalived/keepalived.conf: Line 7) Unknown keyword 'lvs_sync_daemon_interface'
(/etc/keepalived/keepalived.conf: Line 21) Unable to set default user for vrrp script haproxy – removing
(/etc/keepalived/keepalived.conf: Line 31) (LB_VIP_QA) Specifying lvs_sync_daemon_interface against a vrrp is deprecated.
(/etc/keepalived/keepalived.conf: Line 31)              Please use global lvs_sync_daemon
(/etc/keepalived/keepalived.conf: Line 35) Truncating auth_pass to 8 characters
(/etc/keepalived/keepalived.conf: Line 50) (LB_VIP_QA) track script haproxy not found, ignoring…

I've experienced this error because first time I've configured keepalived, I did not mention the user with which the vrrp script haproxy should run,
in prior versions of keepalived, leaving the field empty did automatically assumed you have the user with which the vrrp script runs to be set to root
as of RHELs keepalived-2.1.5-6.el8.x86_64, i've been using however this is no longer so and thus in prior configuration as you can see I've
set the user in respective section to root.
The error Unknown keyword 'lvs_sync_daemon_interface'
is also easily fixable by just substituting the lvs_sync_daemon_interface and lvs_sync_daemon and reloading
keepalived etc.

Once keepalived is started and you can see the process on both machines running in process list.

[root@server1:~]ps -ef |grep -i keepalived
root     1190884       1  0 18:50 ?        00:00:00 /usr/sbin/keepalived -D
root     1190885 1190884  0 18:50 ?        00:00:00 /usr/sbin/keepalived -D

Next step is to check the keepalived statuses as well as /var/log/keepalived.log

If everything is configured as expected on both keepalived on first node you should see one is master and one is slave either in the status or the log

[root@server1:~]#systemctl restart keepalived

 

[root@server1:~]systemctl status keepalived|grep -i state
Mar 14 18:59:02 server1-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) Entering MASTER STATE

[root@server1:~]systemctl status keepalived

● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Mon 2022-03-14 18:15:51 CET; 32min ago
  Process: 1187587 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 1187589 (code=exited, status=0/SUCCESS)

Mar 14 18:15:04 server1lb-fqdn Keepalived_vrrp[1187590]: Sending gratuitous ARP on eth0 for 10.44.192.142
Mar 14 18:15:50 server1lb-fqdn systemd[1]: Stopping LVS and VRRP High Availability Monitor…
Mar 14 18:15:50 server1lb-fqdn Keepalived[1187589]: Stopping
Mar 14 18:15:50 server1lb-fqdn Keepalived_vrrp[1187590]: (LB_VIP_QA) sent 0 priority
Mar 14 18:15:50 server1lb-fqdn Keepalived_vrrp[1187590]: (LB_VIP_QA) removing VIPs.
Mar 14 18:15:51 server1lb-fqdn Keepalived_vrrp[1187590]: Stopped – used 0.002007 user time, 0.016303 system time
Mar 14 18:15:51 server1lb-fqdn Keepalived[1187589]: CPU usage (self/children) user: 0.000000/0.038715 system: 0.001061/0.166434
Mar 14 18:15:51 server1lb-fqdn Keepalived[1187589]: Stopped Keepalived v2.1.5 (07/13,2020)
Mar 14 18:15:51 server1lb-fqdn systemd[1]: keepalived.service: Succeeded.
Mar 14 18:15:51 server1lb-fqdn systemd[1]: Stopped LVS and VRRP High Availability Monitor

[root@server2:~]systemctl status keepalived|grep -i state
Mar 14 18:59:02 server2-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Entering BACKUP STATE

[root@server1:~]# grep -i state /var/log/keepalived.log
Mar 14 18:59:02 server1lb-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Entering MASTER STATE
 

a. Fix Keepalived SECURITY VIOLATION – scripts are being executed but script_security not enabled.
 

When configurating keepalived for a first time we have faced the following strange error inside keepalived status inside keepalived.log 
 

Feb 23 14:28:41 server1 Keepalived_vrrp[945478]: SECURITY VIOLATION – scripts are being executed but script_security not enabled.

 

To fix keepalived SECURITY VIOLATION error:

Add to /etc/keepalived/keepalived.conf on the keepalived node hosts
inside 

global_defs {}

After chunk
 

enable_script_security

include

# Synchro of the state of the connections between the LBs on the eth0 interface
  lvs_sync_daemon_interface eth0

 

5. Prepare rsyslog configuration and Inlcude additional keepalived options
to force keepalived log into /var/log/keepalived.log

To force keepalived log into /var/log/keepalived.log on RHEL 8 / CentOS and other Redhat Package Manager (RPM) Linux distributions

[root@server1:~]# vim /etc/rsyslog.d/48_keepalived.conf

#2022/02/02: HAProxy logs to local6, save the messages
local7.*                                                /var/log/keepalived.log
if ($programname == 'Keepalived') then -/var/log/keepalived.log
if ($programname == 'Keepalived_vrrp') then -/var/log/keepalived.log
& stop

[root@server:~]# touch /var/log/keepalived.log

Reload rsyslog to load new config
 

[root@server:~]# systemctl restart rsyslog
[root@server:~]# systemctl status rsyslog

 

rsyslog.service – System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
  Drop-In: /etc/systemd/system/rsyslog.service.d
           └─rsyslog-service.conf
   Active: active (running) since Mon 2022-03-07 13:34:38 CET; 1 weeks 0 days ago
     Docs: man:rsyslogd(8)

           https://www.rsyslog.com/doc/
 Main PID: 269574 (rsyslogd)
    Tasks: 6 (limit: 100914)
   Memory: 5.1M
   CGroup: /system.slice/rsyslog.service
           └─269574 /usr/sbin/rsyslogd -n

Mar 15 08:15:16 server1lb-fqdn rsyslogd[269574]: — MARK —
Mar 15 08:35:16 server1lb-fqdn rsyslogd[269574]: — MARK —
Mar 15 08:55:16 server1lb-fqdn rsyslogd[269574]: — MARK —

 

If once keepalived is loaded but you still have no log written inside /var/log/keepalived.log

[root@server1:~]# vim /etc/sysconfig/keepalived
 KEEPALIVED_OPTIONS="-D -S 7"

[root@server2:~]# vim /etc/sysconfig/keepalived
 KEEPALIVED_OPTIONS="-D -S 7"

[root@server1:~]# systemctl restart keepalived.service
[root@server1:~]#  systemctl status keepalived

● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: active (running) since Thu 2022-02-24 12:12:20 CET; 2 weeks 4 days ago
 Main PID: 1030501 (keepalived)
    Tasks: 2 (limit: 100914)
   Memory: 1.8M
   CGroup: /system.slice/keepalived.service
           ├─1030501 /usr/sbin/keepalived -D
           └─1030502 /usr/sbin/keepalived -D

Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

[root@server2:~]# systemctl restart keepalived.service
[root@server2:~]# systemctl status keepalived

6. Monitoring VRRP traffic of the two keepaliveds with tcpdump
 

Once both keepalived are up and running a good thing is to check the VRRP protocol traffic keeps fluently on both machines.
Keepalived VRRP keeps communicating over the TCP / IP Port 112 thus you can simply snoop TCP tracffic on its protocol.
 

[root@server1:~]# tcpdump proto 112

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:08:07.356187 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:08.356297 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:09.356408 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:10.356511 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:11.356655 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20

[root@server2:~]# tcpdump proto 112

tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
​listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:08:07.356187 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:08.356297 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:09.356408 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:10.356511 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20
11:08:11.356655 IP server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20

As you can see the VRRP traffic on the network is originating only from server1lb-fqdn, this is so because host server1lb-fqdn is the keepalived configured master node.

It is possible to spoof the password configured to authenticate between two nodes, thus if you're bringing up keepalived service cluster make sure your security is tight at best the machines should be in a special local LAN DMZ, do not configure DMZ on the internet !!! 🙂 Or if you eventually decide to configure keepalived in between remote hosts, make sure you somehow use encrypted VPN or SSH tunnels to tunnel the VRRP traffic.

[root@server1:~]tcpdump proto 112 -vv
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
11:36:25.530772 IP (tos 0xc0, ttl 255, id 59838, offset 0, flags [none], proto VRRP (112), length 40)
    server1lb-fqdn > vrrp.mcast.net: vrrp server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20, addrs: VIPIP_QA auth "testp431"
11:36:26.530874 IP (tos 0xc0, ttl 255, id 59839, offset 0, flags [none], proto VRRP (112), length 40)
    server1lb-fqdn > vrrp.mcast.net: vrrp server1lb-fqdn > vrrp.mcast.net: VRRPv2, Advertisement, vrid 50, prio 53, authtype simple, intvl 1s, length 20, addrs: VIPIP_QA auth "testp431"

Lets also check what floating IP is configured on the machines:

[root@server1:~]# ip -brief address show
lo               UNKNOWN        127.0.0.1/8 
eth0             UP             10.10.10.5/26 10.10.10.1/32 

The 10.10.10.5 IP is the main IP set on LAN interface eth0, 10.10.10.1 is the floating IP which as you can see is currently set by keepalived to listen on first node.

[root@server2:~]# ip -brief address show |grep -i 10.10.10.1

An empty output is returned as floating IP is currently configured on server1

To double assure ourselves the IP is assigned on correct machine, lets ping it and check the IP assigned MAC  currently belongs to which machine.
 

[root@server2:~]# ping 10.10.10.1
PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
64 bytes from 10.10.10.1: icmp_seq=1 ttl=64 time=0.526 ms
^C
— 10.10.10.1 ping statistics —
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.526/0.526/0.526/0.000 ms

[root@server2:~]# arp -an |grep -i 10.44.192.142
? (10.10.10.1) at 00:48:54:91:83:7d [ether] on eth0
[root@server2:~]# ip a s|grep -i 00:48:54:91:83:7d
[root@server2:~]# 

As you can see from below output MAC is not found in configured IPs on server2.
 

[root@server1-fqdn:~]# /sbin/ip a s|grep -i 00:48:54:91:83:7d -B1 -A1
 eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:48:54:91:83:7d brd ff:ff:ff:ff:ff:ff
inet 10.10.10.1/26 brd 10.10.1.191 scope global noprefixroute eth0

Pretty much expected MAC is on keepalived node server1.

 

7. Testing keepalived on server1 and server2 maachines VIP floating IP really works
 

To test the overall configuration just created, you should stop keeaplived on the Master node and in meantime keep an eye on Slave node (server2), whether it can figure out the Master node is gone and switch its
state BACKUP to save MASTER. By changing the secondary (Slave) keepalived to master the floating IP: 10.10.10.1 will be brought up by the scripts on server2.

Lets assume that something went wrong with server1 VM host, for example the machine crashed due to service overload, DDoS or simply a kernel bug or whatever reason.
To simulate that we simply have to stop keepalived, then the broadcasted information on VRRP TCP/IP proto port 112 will be no longer available and keepalived on node server2, once
unable to communicate to server1 should chnage itself to state MASTER.

[root@server1:~]# systemctl stop keepalived
[root@server1:~]# systemctl status keepalived

● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: inactive (dead) since Tue 2022-03-15 12:11:33 CET; 3s ago
  Process: 1192001 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 1192002 (code=exited, status=0/SUCCESS)

Mar 14 18:59:07 server1lb-fqdn Keepalived_vrrp[1192003]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:32 server1lb-fqdn systemd[1]: Stopping LVS and VRRP High Availability Monitor…
Mar 15 12:11:32 server1lb-fqdn Keepalived[1192002]: Stopping
Mar 15 12:11:32 server1lb-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) sent 0 priority
Mar 15 12:11:32 server1lb-fqdn Keepalived_vrrp[1192003]: (LB_VIP_QA) removing VIPs.
Mar 15 12:11:33 server1lb-fqdn Keepalived_vrrp[1192003]: Stopped – used 2.145252 user time, 15.513454 system time
Mar 15 12:11:33 server1lb-fqdn Keepalived[1192002]: CPU usage (self/children) user: 0.000000/44.555362 system: 0.001151/170.118126
Mar 15 12:11:33 server1lb-fqdn Keepalived[1192002]: Stopped Keepalived v2.1.5 (07/13,2020)
Mar 15 12:11:33 server1lb-fqdn systemd[1]: keepalived.service: Succeeded.
Mar 15 12:11:33 server1lb-fqdn systemd[1]: Stopped LVS and VRRP High Availability Monitor.

 

On keepalived off, you will get also a notification Email on the Receipt Email configured from keepalived.conf from the working keepalived node with a simple message like:

=> VRRP Instance is no longer owning VRRP VIPs <=

Once keepalived is back up you will get another notification like:

=> VRRP Instance is now owning VRRP VIPs <=

[root@server2:~]# systemctl status keepalived
● keepalived.service – LVS and VRRP High Availability Monitor
   Loaded: loaded (/usr/lib/systemd/system/keepalived.service; enabled; vendor preset: disabled)
   Active: active (running) since Mon 2022-03-14 18:13:52 CET; 17h ago
  Process: 297366 ExecStart=/usr/sbin/keepalived $KEEPALIVED_OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 297367 (keepalived)
    Tasks: 2 (limit: 100914)
   Memory: 2.1M
   CGroup: /system.slice/keepalived.service
           ├─297367 /usr/sbin/keepalived -D -S 7
           └─297368 /usr/sbin/keepalived -D -S 7

Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: Remote SMTP server [127.0.0.1]:25 connected.
Mar 15 12:11:33 server2lb-fqdn Keepalived_vrrp[297368]: SMTP alert successfully sent.
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: (LB_VIP_QA) Sending/queueing gratuitous ARPs on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1
Mar 15 12:11:38 server2lb-fqdn Keepalived_vrrp[297368]: Sending gratuitous ARP on eth0 for 10.10.10.1

[root@server2:~]#  ip addr show|grep -i 10.10.10.1
    inet 10.10.10.1/32 scope global eth0
    

As you see the VIP is now set on server2, just like expected – that's OK, everything works as expected. If the IP did not move double check the keepalived.conf on both nodes for errors or misconfigurations.

To recover the initial order of things so server1 is MASTER and server2 SLAVE host, we just have to switch on the keepalived on server1 machine.

[root@server1:~]# systemctl start keepalived

The automatic change of server1 to MASTER node and respective move of the VIP IP is done because of the higher priority (of importance we previously configured on server1 in keepalived.conf).
 

What we learned?
 

So what we learned in  this article?
We have seen how to easily install and configure a High Availability Load balancer with Keepalived with single floating VIP IP address with 1 MASTER and 1 SLAVE host and a Haproxy example config with few frontends / App backends. We have seen how the config can be tested for potential errors and how we can monitor whether the VRRP2 network traffic flows between nodes and how to potentially debug it further if necessery.
Further on rawly explained some of the keepalived configurations but as keepalived can do pretty much more,for anyone seriously willing to deal with keepalived on a daily basis or just fine tune some already existing ones, you better read closely its manual page "man keepalived.conf" as well as the official Redhat Linux documentation page on setting up a Linux cluster with Keepalived (Be prepare for a small nightmare as the documentation of it seems to be a bit chaotic, and even I would say partly missing or opening questions on what does the developers did meant – not strange considering the havoc that is pretty much as everywhere these days.)

Finally once keepalived hosts are prepared, it was shown how to test the keepalived application cluster and Floating IP does move between nodes in case if one of the 2 keepalived nodes is inaccessible.

The same logic can be repeated multiple times and if necessery you can set multiple VIPs to expand the HA reachable IPs solution.

high-availability-with-two-vips-example-diagram

The presented idea is with haproxy forward Proxy server to proxy requests towards Application backend (servince machines), however if you need to set another set of server on the flow to  process HTML / XHTML / PHP / Perl / Python  programming code, with some common Webserver setup ( Nginx / Apache / Tomcat / JBOSS) and enable SSL Secure certificate with lets say Letsencrypt, this can be relatively easily done. If you want to implement letsencrypt and a webserver check this redundant SSL Load Balancing with haproxy & keepalived article.

That's all folks, hope you enjoyed.
If you need to configure keepalived Cluster or a consultancy write your query here 🙂

How to move transfer binary files encoded with base64 on Linux with Copy Paste of text ASCII encoded string

Monday, October 25th, 2021

base64-encode-decode-binary-files-to-transfer-between-servers-base64-artistic-logo

If you have to work on servers in a protected environments that are accessed via multiple VPNs, Jump hosts or Web Citrix and you have no mean to copy binary files to your computer or from your computer because you have all kind of FTP / SFTP or whatever Data Copy clients disabled on remote jump host side or CITRIX server and you still are looking for a way to copy files between your PC and the Remote server Side.
Or for example if you have 2 or more servers that are in a special Demilitarized Network Zones ( DMZ ) and the machines does not have SFTP / FTP / WebServer or other kind of copy protocol service that can be used to copy files between the hosts and you still need to copy some files between the 2 or more machines in a slow but still functional way, then you might not know of one old school hackers trick you can employee to complete the copy of files between DMZ-ed Server Host A lets say with IP address (192.168.50.5) -> Server Host B (192.168.30.7). The way to complete the binary file copy is to Encode the binary on Server Host A and then, use cat  command to display the encoded string and copy whole encoded cat command output  to your (local PC buffer from where you access the remote side via SSH via the CITRIX or Jump host.). Then decode the encoded file with an encoding tool such as base64 or uuencode. In this article, I'll show how this is done with base64 and uuencode. Base64 binary is pretty standard in most Linux / Unix OS-es today on most Linux distributions it is part of the coreutils package.
The main use of base64 encoding to encode non-text Attachment files to Electronic Mail, but for our case it fits perfectly.
Keep in mind, that this hack to copy the binary from Machine A to Machine B of course depends on the Copy / Paste buffer being enabled both on remote Jump host or Citrix from where you reach the servers as well as your own PC laptop from where you access the remote side.

base64-character-encoding-string-table

Base64 Encoding and Decoding text strings legend

The file copy process to the highly secured PCI host goes like this:
 

1. On Server Host A encode with md5sum command

[root@serverA ~]:# md5sum -b /tmp/inputbinfile-to-encode
66c4d7b03ed6df9df5305ae535e40b7d *inputbinfile-to-encode

 

As you see one good location to encode the file would be /tmp as this is a temporary home or you can use alternatively your HOME dir

but you have to be quite careful to not run out of space if you produce it anywhere 🙂

 

2. Encode the binary file with base64 encoding

 [root@serverB ~]:# base64 -w0 inputbinfile-to-encode > outputbin-file.base64

The -w0 option is given to disable line wrapping. Line wrapping is perhaps not needed if you will copy paste the data.

base64-encoded-binary-file-text-string-linux-screenshot

Base64 Encoded string chunk with line wrapping

For a complete list of possible accepted arguments check here.

3. Cat the inputbinfile-to-encode just generated to display the text encoded file in your SecureCRT / Putty / SuperPutty etc. remote ssh access client

[root@serverA ~]:# cat /tmp/inputbinfile-to-encode
f0VMRgIBAQAAAAAAAAAAAAMAPgABAAAAMGEAAAAAAABAAAAAAAAAACgXAgAAAAAAAAAAA
EAAOAALAEAAHQAcAAYAAAAEAAA ……………………………………………………………… cTD6lC+ViQfUCPn9bs

 

4. Select the cat-ted string and copy it to your PC Copy / Paste buffer


If the bin file is not few kilobytes, but few megabytes copying the file might be tricky as the string produced from cat command would be really long, so make sure the SSH client you're using is configured to have a large buffer to scroll up enough and be able to select the whole encoded string until the end of the cat command and copy it to Copy / Paste buffer.

 

5. On Server Host B paste the bas64 encoded binary inside a newly created file

Open with a text editor vim / mc or whatever is available

[root@serverB ~]:# vi inputbinfile-to-encode

Some very paranoid Linux / UNIX systems might not have even a normal text editor like 'vi' if you happen to need to copy files on such one a useful thing is to use a simple cat on the remote side to open a new File Descriptor buffer, like this:

[root@server2 ~]:# cat >> inputbinfile-to-encode <<'EOF'
Paste the string here

 

6. Decode the encoded binary with base64 cmd again

[root@serverB ~]:# base64 –decode outputbin-file.base64 > inputbinfile-to-encode

 

7. Set proper file permissions (the same as on Host A)

[root@serverB ~]:#  chmod +x inputbinfile-to-encode

 

8. Check again the binary file checksum on Host B is identical as on Host A

[root@serverB ~]:# md5sum -b inputbinfile-to-encode
66c4d7b03ed6df9df5305ae535e40b7d *inputbinfile-to-encode

As you can md5sum match on both sides so file should be OK.

 

9. Encoding and decoding files with uuencode


If you are lucky and you have uuencode installed (sharutils) package is present on remote machine to encode lets say an archived set of binary files in .tar.gz format do:

Prepare the archive of all the files you want to copy with tar on Host A:

[root@Machine1 ~]:#  tar -czvf /bin/whatever /usr/local/bin/htop /usr/local/bin/samhain /etc/hosts archived-binaries-and-configs.tar.gz

[root@Machine1 ~]:# uuencode archived-binaries-and-configs.tar.gz archived-binaries-and-configs.uu

Cat / Copy / paste the encoded content as usual to a file on Host B:

Then on Machine 2 decode:

[root@Machine2 ~]:# uuencode -c < archived-binaries-and-configs.tar.gz.uu

 

Conclusion


In this short method I've shown you a hack that is used often by script kiddies to copy over files between pwn3d machines, a method which however is very precious and useful for sysadmins like me who has to admin a paranoid secured servers that are placed in a very hard to access environments.

With the same method you can encode or decode not only binary file but also any standard input/output file content. base64 encoding is quite useful stuff to use also in bash scripts or perl where you want to have the script copy file in a plain text format . Datas are encoded and decoded to make the data transmission and storing process easier. You have to keep in mind always that Encoding and Decoding are not similar to encryption and decryption as encr. deprytion gives a special security layers to the encoded that. Encoded data can be easily revealed by decoding, so if you need to copy between the servers very sensitive data like SSL certificates Private RSA / DSA key, this command line utility tool better to be not used for sesitive data copying.

 

 

Install and enable Sysstats IO / DIsk / CPU / Network monitoring console suite on Redhat 8.3, Few sar useful command examples

Tuesday, September 28th, 2021

linux-sysstat-monitoring-logo

 

Why to monitoring CPU, Memory, Hard Disk, Network usage etc. with sysstats tools?
 

Using system monitoring tools such as Zabbix, Nagios Monit is a good approach, however sometimes due to zabbix server interruptions you might not be able to track certain aspects of system performance on time. Thus it is always a good idea to 
Gain more insights on system peroformance from command line. Of course there is cmd tools such as iostat and top, free, vnstat that provides plenty of useful info on system performance issues or bottlenecks. However from my experience to have a better historical data that is systimized and all the time accessible from console it is a great thing to have sysstat package at place. Since many years mostly on every server I administer, I've been using sysstats to monitor what is going on servers over a short time frames and I'm quite happy with it. In current company we're using Redhats and CentOS-es and I had to install sysstats on Redhat 8.3. I've earlier done it multiple times on Debian / Ubuntu Linux and while I've faced on some .deb distributions complications of making sysstat collect statistics I've come with an article on Howto fix sysstat Cannot open /var/log/sysstat/sa no such file or directory” on Debian / Ubuntu Linux
 

Sysstat contains the following tools related to collecting I/O and CPU statistics:
iostat
Displays an overview of CPU utilization, along with I/O statistics for one or more disk drives.
mpstat
Displays more in-depth CPU statistics.
Sysstat also contains tools that collect system resource utilization data and create daily reports based on that data. These tools are:
sadc
Known as the system activity data collector, sadc collects system resource utilization information and writes it to a file.
sar
Producing reports from the files created by sadc, sar reports can be generated interactively or written to a file for more intensive analysis.

My experience with CentOS 7 and Fedora to install sysstat it was pretty straight forward, I just had to install it via yum install sysstat wait for some time and use sar (System Activity Reporter) tool to report collected system activity info stats over time.
Unfortunately it seems on RedHat 8.3 as well as on CentOS 8.XX instaling sysstats does not work out of the box.

To complete a successful installation of it on RHEL 8.3, I had to:

[root@server ~]# yum install -y sysstat


To make sysstat enabled on the system and make it run, I've enabled it in sysstat

[root@server ~]# systemctl enable sysstat


Running immediately sar command, I've faced the shitty error:


Cannot open /var/log/sysstat/sa18:
No such file or directory. Please check if data collecting is enabled”

 

Once installed I've waited for about 5 minutes hoping, that somehow automatically sysstat would manage it but it didn't.

To solve it, I've had to create additionally file /etc/cron.d/sysstat (weirdly RPM's post install instructions does not tell it to automatically create it)

[root@server ~]# vim /etc/cron.d/sysstat

# run system activity accounting tool every 10 minutes
0 * * * * root /usr/lib64/sa/sa1 60 59 &
# generate a daily summary of process accounting at 23:53
53 23 * * * root /usr/lib64/sa/sa2 -A &

 

  • /usr/local/lib/sa1 is a shell script that we can use for scheduling cron which will create daily binary log file.
  • /usr/local/lib/sa2 is a shell script will change binary log file to human-readable form.

 

[root@server ~]# chmod 600 /etc/cron.d/sysstat

[root@server ~]# systemctl restart sysstat


In a while if sysstat is working correctly you should get produced its data history logs inside /var/log/sa

[root@server ~]# ls -al /var/log/sa 


Note that the standard sysstat history files on Debian and other modern .deb based distros such as Debian 10 (in  y.2021) is stored under /var/log/sysstat

Here is few useful uses of sysstat cmds


1. Check with sysstat machine history SWAP and RAM Memory use


To lets say check last 10 minutes SWAP memory use:

[hipo@server yum.repos.d] $ sar -W  |last -n 10
 

Linux 4.18.0-240.el8.x86_64 (server)       09/28/2021      _x86_64_        (8 CPU)

12:00:00 AM  pswpin/s pswpout/s
12:00:01 AM      0.00      0.00
12:01:01 AM      0.00      0.00
12:02:01 AM      0.00      0.00
12:03:01 AM      0.00      0.00
12:04:01 AM      0.00      0.00
12:05:01 AM      0.00      0.00
12:06:01 AM      0.00      0.00

[root@ccnrlb01 ~]# sar -r | tail -n 10
14:00:01        93008   1788832     95.06         0   1357700    725740      9.02    795168    683484        32
14:10:01        78756   1803084     95.81         0   1358780    725740      9.02    827660    652248        16
14:20:01        92844   1788996     95.07         0   1344332    725740      9.02    813912    651620        28
14:30:01        92408   1789432     95.09         0   1344612    725740      9.02    816392    649544        24
14:40:01        91740   1790100     95.12         0   1344876    725740      9.02    816948    649436        36
14:50:01        91688   1790152     95.13         0   1345144    725740      9.02    817136    649448        36
15:00:02        91544   1790296     95.14         0   1345448    725740      9.02    817472    649448        36
15:10:01        91108   1790732     95.16         0   1345724    725740      9.02    817732    649340        36
15:20:01        90844   1790996     95.17         0   1346000    725740      9.02    818016    649332        28
Average:        93473   1788367     95.03         0   1369583    725074      9.02    800965    671266        29

 

2. Check system load? Are my processes waiting too long to run on the CPU?

[root@server ~ ]# sar -q |head -n 10
Linux 4.18.0-240.el8.x86_64 (server)       09/28/2021      _x86_64_        (8 CPU)

12:00:00 AM   runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
12:00:01 AM         0       272      0.00      0.02      0.00         0
12:01:01 AM         1       271      0.00      0.02      0.00         0
12:02:01 AM         0       268      0.00      0.01      0.00         0
12:03:01 AM         0       268      0.00      0.00      0.00         0
12:04:01 AM         1       271      0.00      0.00      0.00         0
12:05:01 AM         1       271      0.00      0.00      0.00         0
12:06:01 AM         1       265      0.00      0.00      0.00         0


3. Show various CPU statistics per CPU use
 

On a multiprocessor, multi core server sometimes for scripting it is useful to fetch processor per use historic data, 
this can be attained with:

 

[hipo@server ~ ] $ mpstat -P ALL
Linux 4.18.0-240.el8.x86_64 (server)       09/28/2021      _x86_64_        (8 CPU)

06:08:38 PM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest  %gnice   %idle
06:08:38 PM  all    0.17    0.02    0.25    0.00    0.05    0.02    0.00    0.00    0.00   99.49
06:08:38 PM    0    0.22    0.02    0.28    0.00    0.06    0.03    0.00    0.00    0.00   99.39
06:08:38 PM    1    0.28    0.02    0.36    0.00    0.08    0.02    0.00    0.00    0.00   99.23
06:08:38 PM    2    0.27    0.02    0.31    0.00    0.06    0.01    0.00    0.00    0.00   99.33
06:08:38 PM    3    0.15    0.02    0.22    0.00    0.03    0.01    0.00    0.00    0.00   99.57
06:08:38 PM    4    0.13    0.02    0.20    0.01    0.03    0.01    0.00    0.00    0.00   99.60
06:08:38 PM    5    0.14    0.02    0.27    0.00    0.04    0.06    0.01    0.00    0.00   99.47
06:08:38 PM    6    0.10    0.02    0.17    0.00    0.04    0.02    0.00    0.00    0.00   99.65
06:08:38 PM    7    0.09    0.02    0.15    0.00    0.02    0.01    0.00    0.00    0.00   99.70


 

sar-sysstat-cpu-statistics-screenshot

Monitor processes and threads currently being managed by the Linux kernel.

[hipo@server ~ ] $ pidstat

pidstat-various-random-process-statistics

[hipo@server ~ ] $ pidstat -d 2


pidstat-show-processes-with-most-io-activities-linux-screenshot

This report tells us that there is few processes with heave I/O use Filesystem system journalling daemon jbd2, apache, mysqld and supervise, in 3rd column you see their respective PID IDs.

To show threads used inside a process (like if you press SHIFT + H) inside Linux top command:

[hipo@server ~ ] $ pidstat -t -p 10765 1 3

Linux 4.19.0-14-amd64 (server)     28.09.2021     _x86_64_    (10 CPU)

21:41:22      UID      TGID       TID    %usr %system  %guest   %wait    %CPU   CPU  Command
21:41:23      108     10765         –    1,98    0,99    0,00    0,00    2,97     1  mysqld
21:41:23      108         –     10765    0,00    0,00    0,00    0,00    0,00     1  |__mysqld
21:41:23      108         –     10768    0,00    0,00    0,00    0,00    0,00     0  |__mysqld
21:41:23      108         –     10771    0,00    0,00    0,00    0,00    0,00     5  |__mysqld
21:41:23      108         –     10784    0,00    0,00    0,00    0,00    0,00     7  |__mysqld
21:41:23      108         –     10785    0,00    0,00    0,00    0,00    0,00     6  |__mysqld
21:41:23      108         –     10786    0,00    0,00    0,00    0,00    0,00     2  |__mysqld

10765 – is the Process ID whose threads you would like to list

With pidstat, you can further monitor processes for memory leaks with:

[hipo@server ~ ] $ pidstat -r 2

 

4. Report paging statistics for some old period

 

[root@server ~ ]# sar -B -f /var/log/sa/sa27 |head -n 10
Linux 4.18.0-240.el8.x86_64 (server)       09/27/2021      _x86_64_        (8 CPU)

15:42:26     LINUX RESTART      (8 CPU)

15:55:30     LINUX RESTART      (8 CPU)

04:00:01 PM  pgpgin/s pgpgout/s   fault/s  majflt/s  pgfree/s pgscank/s pgscand/s pgsteal/s    %vmeff
04:01:01 PM      0.00     14.47    629.17      0.00    502.53      0.00      0.00      0.00      0.00
04:02:01 PM      0.00     13.07    553.75      0.00    419.98      0.00      0.00      0.00      0.00
04:03:01 PM      0.00     11.67    548.13      0.00    411.80      0.00      0.00      0.00      0.00

 

5.  Monitor Received RX and Transmitted TX network traffic perl Network interface real time
 

To print out Received and Send traffic per network interface 4 times in a raw

sar-sysstats-network-traffic-statistics-screenshot
 

[hipo@server ~ ] $ sar -n DEV 1 4


To continusly monitor all network interfaces I/O traffic

[hipo@server ~ ] $ sar -n DEV 1


To only monitor a certain network interface lets say loopback interface (127.0.0.1) received / transmitted bytes

[hipo@server yum.repos.d] $  sar -n DEV 1 2|grep -i lo
06:29:53 PM        lo      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
06:29:54 PM        lo      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00
Average:           lo      0.00      0.00      0.00      0.00      0.00      0.00      0.00      0.00


6. Monitor block devices use
 

To check block devices use 3 times in a raw
 

[hipo@server yum.repos.d] $ sar -d 1 3


sar-sysstats-blockdevice-statistics-screenshot
 

7. Output server monitoring data in CSV database structured format


For preparing a nice graphs with Excel from CSV strucuted file format, you can dump the collected data as so:

 [root@server yum.repos.d]# sadf -d /var/log/sa/sa27 — -n DEV | grep -v lo|head -n 10
server-name-fqdn;-1;2021-09-27 13:42:26 UTC;LINUX-RESTART    (8 CPU)
# hostname;interval;timestamp;IFACE;rxpck/s;txpck/s;rxkB/s;txkB/s;rxcmp/s;txcmp/s;rxmcst/s;%ifutil
server-name-fqdn;-1;2021-09-27 13:55:30 UTC;LINUX-RESTART    (8 CPU)
# hostname;interval;timestamp;IFACE;rxpck/s;txpck/s;rxkB/s;txkB/s;rxcmp/s;txcmp/s;rxmcst/s;%ifutil
server-name-fqdn;60;2021-09-27 14:01:01 UTC;eth1;19.42;16.12;1.94;1.68;0.00;0.00;0.00;0.00
server-name-fqdn;60;2021-09-27 14:01:01 UTC;eth0;7.18;9.65;0.55;0.78;0.00;0.00;0.00;0.00
server-name-fqdn;60;2021-09-27 14:01:01 UTC;eth2;5.65;5.13;0.42;0.39;0.00;0.00;0.00;0.00
server-name-fqdn;60;2021-09-27 14:02:01 UTC;eth1;18.90;15.55;1.89;1.60;0.00;0.00;0.00;0.00
server-name-fqdn;60;2021-09-27 14:02:01 UTC;eth0;7.15;9.63;0.55;0.74;0.00;0.00;0.00;0.00
server-name-fqdn;60;2021-09-27 14:02:01 UTC;eth2;5.67;5.15;0.42;0.39;0.00;0.00;0.00;0.00

To graph the output data you can use Excel / LibreOffice's Excel equivalent Calc or if you need to dump a CSV sar output and generate it on the fly from a script  use gnuplot 


What we've learned?


How to install and enable on cron sysstats on Redhat and CentOS 8 Linux ? 
How to continuously monitor CPU / Disk and Network, block devices, paging use and processes and threads used by the kernel per process ?  
As well as how to export previously collected data to CSV to import to database or for later use inrder to generate graphic presentation of data.
Cheers ! 🙂

 

Adding proxy to yum repository on Redhat / Fedora / CentOS and other RPM based Linux distributions, Listing and enabling new RPM repositories

Tuesday, September 7th, 2021

yum-add-proxy-host-for-redhat-linux-centos-list-rpm-repositories-enable-disable-repositories

Sometimes if you work in a company that is following PCI standards with very tight security you might need to use a custom company prepared RPM repositories that are accessible only via a specific custom maintained repositories or alternatively you might need the proxy node  to access an external internet repository from the DMZ-ed firewalled zone where the servers lays .
Hence to still be able to maintain the RPM based servers up2date to the latest security patches and install software with yumone very useful feature of yum package manager is to use a proxy host through which you will reach your Redhat Package Manager files  files.

1. The http_proxy and https_proxy shell variables 

To set  a proxy host you need to define there the IP / Hostname or the Fully Qualified Domain Name (FQDN).

By default "http_proxy and https_proxy are empty. As you can guess https_proxy is used if you have a Secure Socket Layer (SSL) certificate for encrypting the communication channel (e.g. you have https:// URL).

[root@rhel: ~]# echo $http_proxy
[root@rhel: ~]#

2. Setting passwordless or password protected proxy host via http_proxy, https_proxy variables

There is a one time very straight forward to configure proxying of traffic via a specific remote configured server with server bourne again  shell (BASH)'s understood variables:
 

a.) Set password free open proxy to shell environment.

[root@centos: ~]# export https_proxy="https://remote-proxy-server:8080"


Now use yum as usual to update the available installabe package list or simply upgrade to the latest packages with lets say:

[root@rhel: ~]# yum check-update && yum update

b.) Configuring password protected proxy for yum

If your proxy is password protected for even tigher security you can provide the password on the command line as well.

[root@centos: ~]# export http_proxy="http://username:pAssW0rd@server:port/"

Note that if you have some special characters you will have to pass the string inside single quotes or escape them to make sure the password will properly handled to server, before trying out the proxy with yum, echo the variable.

[root@centos: ~]# export http_proxy='http://username:p@s#w:E@192.168.0.1:3128/'
  [root@centos: ~]# echo $http_proxy
http://username:p@s#w:E@server:port/

Then do whatever with yum:

[root@centos: ~]# yum check-update && yum search sharutils


If something is wrong and proxy is not properly connected try to reach for the repository manually with curl or wget

[root@centos: ~]# curl -ilk http://download.fedoraproject.org/pub/epel/7/SRPMS/ /epel/7/SRPMS/
HTTP/1.1 302 Found
Date: Tue, 07 Sep 2021 16:49:59 GMT
Server: Apache
X-Frame-Options: SAMEORIGIN
X-Xss-Protection: 1; mode=block
X-Content-Type-Options: nosniff
Referrer-Policy: same-origin
Location: http://mirror.telepoint.bg/epel/7/SRPMS/
Content-Type: text/plain
Content-Length: 0
AppTime: D=2264
X-Fedora-ProxyServer: proxy01.iad2.fedoraproject.org
X-Fedora-RequestID: YTeYOE3mQPHH_rxD0sdlGAAAA80
X-Cache: MISS from pcfreak
X-Cache-Lookup: MISS from pcfreak:3128
Via: 1.1 pcfreak (squid/4.6)
Connection: keep-alive


Or if you need, you can test the user, password protected proxy with wget as so:

[root@centos: ~]# wget –proxy-user=USERNAME –proxy-password=PASSWORD http://your-proxy-domain.com/optional-rpms/


If you have lynx installed on the machine you can do the remote proxy successful authentication check with it with less typing:

[root@centos: ~]# lynx -pauth=USER:PASSWORD http://proxy-domain.com/optional-rpm/

 

3. Making yum proxy connection permanent via /etc/yum.conf

 

Perhaps the easiest and quickest way to add the http_proxy / https_proxy configured is to store it to automatically load on each server ssh login in your admin user (root) in /root/.bashrc or /root/.bash_profile or in the global /etc/profile or /etc/profile.d/custom.sh etc.

However if you don't want to have hacks and have more cleanness on the systems, the recommended "Redhat way" so to say is to store the configuration inside /etc/yum.conf

To do it via /etc/yum.conf you have to have some records there like:

# The proxy server – proxy server:port number 
proxy=http://mycache.mydomain.com:3128 
# The account details for yum connections 
proxy_username=yum-user 
proxy_password=qwerty-secret-pass

4. Listing RPM repositories and their state

As I had to install sharutils RPM package to the server which contains the file /bin/uuencode (that is provided on CentOS 7.9 Linux from Repo: base/7/x86_64 I had to check whether the repository was installed on the server.

To get a list of all yum repositories avaiable 

[root@centos:/etc/yum.repos.d]# yum repolist all
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: centos.telecoms.bg
 * epel: mirrors.netix.net
 * extras: centos.telecoms.bg
 * remi: mirrors.netix.net
 * remi-php74: mirrors.netix.net
 * remi-safe: mirrors.netix.net
 * updates: centos.telecoms.bg
repo id                                repo name                                                                         status
base/7/x86_64                          CentOS-7 – Base                                                                   enabled: 10,072
base-debuginfo/x86_64                  CentOS-7 – Debuginfo                                                              disabled
base-source/7                          CentOS-7 – Base Sources                                                           disabled
c7-media                               CentOS-7 – Media                                                                  disabled
centos-kernel/7/x86_64                 CentOS LTS Kernels for x86_64                                                     disabled
centos-kernel-experimental/7/x86_64    CentOS Experimental Kernels for x86_64                                            disabled
centosplus/7/x86_64                    CentOS-7 – Plus                                                                   disabled
centosplus-source/7                    CentOS-7 – Plus Sources                                                           disabled
cr/7/x86_64                            CentOS-7 – cr                                                                     disabled
epel/x86_64                            Extra Packages for Enterprise Linux 7 – x86_64                                    enabled: 13,667
epel-debuginfo/x86_64                  Extra Packages for Enterprise Linux 7 – x86_64 – Debug                            disabled
epel-source/x86_64                     Extra Packages for Enterprise Linux 7 – x86_64 – Source                           disabled
epel-testing/x86_64                    Extra Packages for Enterprise Linux 7 – Testing – x86_64                          disabled
epel-testing-debuginfo/x86_64          Extra Packages for Enterprise Linux 7 – Testing – x86_64 – Debug                  disabled
epel-testing-source/x86_64             Extra Packages for Enterprise Linux 7 – Testing – x86_64 – Source                 disabled
extras/7/x86_64                        CentOS-7 – Extras                                                                 enabled:    500
extras-source/7                        CentOS-7 – Extras Sources                                                         disabled
fasttrack/7/x86_64                     CentOS-7 – fasttrack                                                              disabled
remi                                   Remi's RPM repository for Enterprise Linux 7 – x86_64                             enabled:  7,229
remi-debuginfo/x86_64                  Remi's RPM repository for Enterprise Linux 7 – x86_64 – debuginfo                 disabled
remi-glpi91                            Remi's GLPI 9.1 RPM repository for Enterprise Linux 7 – x86_64                    disabled
remi-glpi92                            Remi's GLPI 9.2 RPM repository for Enterprise Linux 7 – x86_64                    disabled
remi-glpi93                            Remi's GLPI 9.3 RPM repository for Enterprise Linux 7 – x86_64                    disabled
remi-glpi94                            Remi's GLPI 9.4 RPM repository for Enterprise Linux 7 – x86_64                    disabled
remi-modular                           Remi's Modular repository for Enterprise Linux 7 – x86_64                         disabled
remi-modular-test                      Remi's Modular testing repository for Enterprise Linux 7 – x86_64                 disabled
remi-php54                             Remi's PHP 5.4 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php55                             Remi's PHP 5.5 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php55-debuginfo/x86_64            Remi's PHP 5.5 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
!remi-php56                            Remi's PHP 5.6 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php56-debuginfo/x86_64            Remi's PHP 5.6 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php70                             Remi's PHP 7.0 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php70-debuginfo/x86_64            Remi's PHP 7.0 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php70-test                        Remi's PHP 7.0 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php70-test-debuginfo/x86_64       Remi's PHP 7.0 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
remi-php71                             Remi's PHP 7.1 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php71-debuginfo/x86_64            Remi's PHP 7.1 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php71-test                        Remi's PHP 7.1 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php71-test-debuginfo/x86_64       Remi's PHP 7.1 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
!remi-php72                            Remi's PHP 7.2 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php72-debuginfo/x86_64            Remi's PHP 7.2 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php72-test                        Remi's PHP 7.2 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php72-test-debuginfo/x86_64       Remi's PHP 7.2 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
remi-php73                             Remi's PHP 7.3 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php73-debuginfo/x86_64            Remi's PHP 7.3 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php73-test                        Remi's PHP 7.3 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php73-test-debuginfo/x86_64       Remi's PHP 7.3 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
remi-php74                             Remi's PHP 7.4 RPM repository for Enterprise Linux 7 – x86_64                     enabled:    423
remi-php74-debuginfo/x86_64            Remi's PHP 7.4 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php74-test                        Remi's PHP 7.4 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php74-test-debuginfo/x86_64       Remi's PHP 7.4 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
remi-php80                             Remi's PHP 8.0 RPM repository for Enterprise Linux 7 – x86_64                     disabled
remi-php80-debuginfo/x86_64            Remi's PHP 8.0 RPM repository for Enterprise Linux 7 – x86_64 – debuginfo         disabled
remi-php80-test                        Remi's PHP 8.0 test RPM repository for Enterprise Linux 7 – x86_64                disabled
remi-php80-test-debuginfo/x86_64       Remi's PHP 8.0 test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo    disabled
remi-safe                              Safe Remi's RPM repository for Enterprise Linux 7 – x86_64                        enabled:  4,549
remi-safe-debuginfo/x86_64             Remi's RPM repository for Enterprise Linux 7 – x86_64 – debuginfo                 disabled
remi-test                              Remi's test RPM repository for Enterprise Linux 7 – x86_64                        disabled
remi-test-debuginfo/x86_64             Remi's test RPM repository for Enterprise Linux 7 – x86_64 – debuginfo            disabled
updates/7/x86_64                       CentOS-7 – Updates                                                                enabled:  2,741
updates-source/7                       CentOS-7 – Updates Sources                                                        disabled
zabbix/x86_64                          Zabbix Official Repository – x86_64                                               enabled:    178
zabbix-debuginfo/x86_64                Zabbix Official Repository debuginfo – x86_64                                     disabled
zabbix-frontend/x86_64                 Zabbix Official Repository frontend – x86_64                                      disabled
zabbix-non-supported/x86_64            Zabbix Official Repository non-supported – x86_64                                 enabled:      5
repolist: 39,364

[root@centos:/etc/yum.repos.d]# yum repolist all|grep -i 'base/7/x86_64'
base/7/x86_64                       CentOS-7 – Base              enabled: 10,072

 

As you can see in CentOS 7 sharutils is enabled from default repositories, however this is not the case on Redhat 7.9, hence to install sharutils there you can one time enable RPM repository to install sharutils 

[root@centos:/etc/yum.repos.d]# yum –enablerepo=rhel-7-server-optional-rpms install sharutils

To install zabbix-agent on the same Redhat server, without caring that I need precisely  know the RPM repository that is providing zabbix agent that in that was (Repo: 3party/7Server/x86_64)  I had to:

[root@centos:/etc/yum.repos.d]# yum –enablerepo \* install zabbix-agent zabbix-sender


Permanently enabling repositories of course is possible via editting or creating fresh new file configuration manually on CentOS / Fedora under directory /etc/yum.repos.d/
On Redhat Enterprise Linux  servers it is easier to use the subscription-manager command instead, like this:
 

[root@rhel:/root]# subscription-manager repos –disable=epel/7Server/x86_64

[root@rhel:/root]# subscription-manager repos –enable=rhel-6-server-optional-rpms

Disable NetworkManager automatic Ethernet Interface Management on Redhat Linux , CentOS 6 / 7 / 8

Friday, February 5th, 2021

rhel-centos-fedora-network-manager-disable-automatic-lan-interface-management

Most of Linux distributions had introduced the NetworkManager service and are slowly trying to push out the old ways and use entirely it to manage network configs. Though at times this is very helpful stuff especially if you have Linux running on Laptop on servers is a guarantee for troubles.

If you are a system administrator like me and you need that needs to configure a New server with lets say 8 (Ethernet interface) LAN cards each to be configured with different IPs and you have a mixture of configuration where some eth1,eth2 etc. (4 of the interface IPs has to be static IPs and others has to be taken from a DHCP lease. NetworkManager is not something that you will want as usually you don't expect soon a network IP topology change. Below is example from a Living Hypervisor server machine that has 8 Network Interfaces configured together with few Virtual Interfaces used by the running KVM Virtual Machines.
 

[root@redhat :~ ]# ip address show |grep ": <"
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
2: ens1f0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master team0 state UP group default qlen 1000
3: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master team0 state UP group default qlen 1000
4: ens1f1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br2 state UP group default qlen 1000
5: ens1f2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
6: eno2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq master br1 state UP group default qlen 1000
7: ens1f3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
8: eno3: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
9: eno4: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
10: venet0: <BROADCAST,POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default
11: br1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
12: br2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
13: team0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master br0 state UP group default qlen 1000
14: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
15: host-routed: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
16: virbr0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
17: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr0 state DOWN group default qlen 1000
18: virbr1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
19: virbr1-nic: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master virbr1 state DOWN group default qlen 1000
26: vme52540019e701: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UNKNOWN group default qlen 1000
27: vme52540081868b: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br1 state UNKNOWN group default qlen 1000
28: vme525400a13f03: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br2 state UNKNOWN group default qlen 1000


Having a NM managing so many LAN connected Ethernets can create you A LOT of surprises even if your servers are in a Highly Secured data center where chance of sudden IP change or network misbehaves are minimal. Even minimal some in Housing might do something wrong on the Rack mixing up with another server or switch andyour server might end up easily with unexplainable Network problems because of this NM service which is trying 'to balance' any network issues according to some algorithms …

Thus to save yourlself the troubles and completely disable NetworkManager (NM) Ethernets handling.

As a hint some of the troubles you might get especially if the System Hardware has issues with the Integrated Motherboard LAN Controllers such as of Dell PowerEdge R640 Rack Server.
I've recently observed one such Dell Rack mounted machine I had to configure from scratch which has out of the box 
NM preinstalled by a colleague and was doing strange stuff with the routings causing it to become remotely inacessible after reboot.
Even though I have started configuring the IPs and have double and triple check the configuration and machine had proper set of /etc/sysconfig/network-scripts/ifcfg-* configuration it still failed to boot with a network properly brought up and become unreachable via remote SSH connection immediately after sending machine to init 6 with /usr/sbin/init 6 (alias for shutdown -r now or reboot -f now :)

On Redhat 8 / CentOS 8 to Disabling permanently NM you have to disable NM systemd services permanently and add NM_CONTROLLED=no to each of the Ethernet configurations listed in network-scripts/ifcfg-eno3 eno4 eno1np0 etc. ifaces.

1. Disable completely Network Manager service and mask it

[root@redhat :~ ]# systemctl mask NetworkManager.service
[root@redhat :~ ]# systemctl stop NetworkManager.service
[root@redhat :~ ]# systemctl disable NetworkManager.service

2. Check if all systemd networkmanager components scripts are really disabled

# systemctl list-unit-files | grep NetworkManager

NetworkManager-dispatcher.service disabled
NetworkManager-wait-online.service enabled
NetworkManager.service disabled


NetworkManager-wait-online.service seems to be also enabled so we have to disable it.

[root@redhat :~ ]#  systemctl mask NetworkManager-wait-online.service
[root@redhat :~ ]#  systemctl disable NetworkManager-wait-online.service

Double check NM services

[root@redhat :~ ]#  systemctl list-unit-files | grep NetworkManager
  …

3. Install / Enable old (legacy) network-scripts 


network-scripts is disabled by default due to it doesn't play well with NM.
Install the rpm package to enable it back
 

[root@redhat :~ ]#  yum install -y network-scripts 

4. Test if network-scripts is really enabled


Use Redhat's nmcli command for controlling network manager if it reports NM not running then you're fine

[root@redhat :~ ]#  nmcli device
Error: NetworkManager is not running.

5. Disable legacy use network-scripts print outs


Bring down some interface with ifdown Redhat script frontend to ifconfig and bring it up with ifup iface-name
 

# ifup eno4
WARN      : [ifup] You are using 'ifup' script provided by 'network-scripts', which are now deprecated.
WARN      : [ifup] 'network-scripts' will be removed in one of the next major releases of RHEL.
WARN      : [ifup] It is advised to switch to 'NetworkManager' instead – it provides 'ifup/ifdown' scripts as well.


Notice the warnings they're harmless and safe to ignore however it is pretty annoying to see them, to disable them:

[root@redhat :~ ]#  touch /etc/sysconfig/disable-deprecation-warnings

6. Use network.service old-fashioned systemd service


From now on you can start using the good old well known and properly working network.service

[root@redhat :~ ]#  systemctl status network


To enable the network service to start after boot:

[root@redhat :~ ]#  systemctl enable network

7. Disable NetworkManager use from Network configuration scripts ifcfg-* for all server available configured ethernet cards


Open with text editor every network script and append NM_CONTROLLED="no" to the end of the file.
 

[root@redhat :~ ]#  vi /etc/sysconfig/network-scripts/ifcfg-ethernetX
NM_CONTROLLED="no"

To save yourself the time if you want to disable NetworkManager use for all /etc/sysconfig/network-scripts/ifcfg-* use a simple shell loop:
 

[root@redhat :~ ]# cd /etc/sysconfig/network-scripts/
[root@redhat :/etc/sysconfig/network-scripts ]# for i in *ifcfg*; do echo NM_CONTROLLED="no" >> $i; done


To load the new network settings do another network reload / restart
 

[root@redhat :~ ]# systemctl restart network


To disable NetworkManager on older CentOS 6 / Redhat 6 / SuSE / Fedora Linux where the OS still not systemd enabled instead of using systemctl you can straight do it with old and well known chkconfig redhat script.
 

[root@centos6 :~ ]# service NetworkManager stop
[root@centos6 :~ ]# chkconfig NetworkManager off

Hack: Using ssh / curl or wget to test TCP port connection state to remote SSH, DNS, SMTP, MySQL or any other listening service in PCI environment servers

Wednesday, December 30th, 2020

using-curl-ssh-wget-to-test-tcp-port-opened-or-closed-for-web-mysql-smtp-or-any-other-linstener-in-pci-linux-logo

If you work on PCI high security environment servers in isolated local networks where each package installed on the Linux / Unix system is of importance it is pretty common that some basic stuff are not there in most cases it is considered a security hole to even have a simple telnet installed on the system. I do have experience with such environments myself and thus it is pretty daunting stuff so in best case you can use something like a simple ssh client if you're lucky and the CentOS / Redhat / Suse Linux whatever distro has openssh-client package installed.
If you're lucky to have the ssh onboard you can use telnet in same manner as netcat or the swiss army knife (nmap) network mapper tool to test whether remote service TCP / port is opened or not. As often this is useful, if you don't have access to the CISCO / Juniper or other (networ) / firewall equipment which is setting the boundaries and security port restrictions between networks and servers.

Below is example on how to use ssh client to test port connectivity to lets say the Internet, i.e.  Google / Yahoo search engines.
 

[root@pciserver: /home ]# ssh -oConnectTimeout=3 -v google.com -p 23
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to google.com [172.217.169.206] port 23.
debug1: connect to address 172.217.169.206 port 23: Connection timed out
debug1: Connecting to google.com [2a00:1450:4017:80b::200e] port 23.
debug1: connect to address 2a00:1450:4017:80b::200e port 23: Cannot assign requested address
ssh: connect to host google.com port 23: Cannot assign requested address
root@pcfreak:/var/www/images# ssh -oConnectTimeout=3 -v google.com -p 80
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to google.com [172.217.169.206] port 80.
debug1: connect to address 172.217.169.206 port 80: Connection timed out
debug1: Connecting to google.com [2a00:1450:4017:807::200e] port 80.
debug1: connect to address 2a00:1450:4017:807::200e port 80: Cannot assign requested address
ssh: connect to host google.com port 80: Cannot assign requested address
root@pcfreak:/var/www/images# ssh google.com -p 80
ssh_exchange_identification: Connection closed by remote host
root@pcfreak:/var/www/images# ssh google.com -p 80 -v -oConnectTimeout=3
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to google.com [172.217.169.206] port 80.
debug1: connect to address 172.217.169.206 port 80: Connection timed out
debug1: Connecting to google.com [2a00:1450:4017:80b::200e] port 80.
debug1: connect to address 2a00:1450:4017:80b::200e port 80: Cannot assign requested address
ssh: connect to host google.com port 80: Cannot assign requested address
root@pcfreak:/var/www/images# ssh google.com -p 80 -v -oConnectTimeout=5
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to google.com [142.250.184.142] port 80.
debug1: connect to address 142.250.184.142 port 80: Connection timed out
debug1: Connecting to google.com [2a00:1450:4017:80c::200e] port 80.
debug1: connect to address 2a00:1450:4017:80c::200e port 80: Cannot assign requested address
ssh: connect to host google.com port 80: Cannot assign requested address
root@pcfreak:/var/www/images# ssh google.com -p 80 -v
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to google.com [172.217.169.206] port 80.
debug1: Connection established.
debug1: identity file /root/.ssh/id_rsa type 0
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: identity file /root/.ssh/id_ecdsa type -1
debug1: identity file /root/.ssh/id_ecdsa-cert type -1
debug1: identity file /root/.ssh/id_ed25519 type -1
debug1: identity file /root/.ssh/id_ed25519-cert type -1
debug1: identity file /root/.ssh/id_xmss type -1
debug1: identity file /root/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_7.9p1 Debian-10+deb10u2
debug1: ssh_exchange_identification: HTTP/1.0 400 Bad Request

 


debug1: ssh_exchange_identification: Content-Type: text/html; charset=UTF-8


debug1: ssh_exchange_identification: Referrer-Policy: no-referrer


debug1: ssh_exchange_identification: Content-Length: 1555


debug1: ssh_exchange_identification: Date: Wed, 30 Dec 2020 14:13:25 GMT


debug1: ssh_exchange_identification:


debug1: ssh_exchange_identification: <!DOCTYPE html>

debug1: ssh_exchange_identification: <html lang=en>

debug1: ssh_exchange_identification:   <meta charset=utf-8>

debug1: ssh_exchange_identification:   <meta name=viewport content="initial-scale=1, minimum-scale=1, width=device-width">

debug1: ssh_exchange_identification:   <title>Error 400 (Bad Request)!!1</title>

debug1: ssh_exchange_identification:   <style>

debug1: ssh_exchange_identification:     *{margin:0;padding:0}html,code{font:15px/22px arial,sans-serif}html{background:#fff;color:#222;padding:15px}body{margin:7% auto 0;max-width:390px;min-height:180px;padding:30px 0 15px}* > body{background:url(//www.google.com/images/errors/robot.png) 10
debug1: ssh_exchange_identification: 0% 5px no-repeat;padding-right:205px}p{margin:11px 0 22px;overflow:hidden}ins{color:#777;text-decoration:none}a img{border:0}@media screen and (max-width:772px){body{background:none;margin-top:0;max-width:none;padding-right:0}}#logo{background:url(//www.g
debug1: ssh_exchange_identification: oogle.com/images/branding/googlelogo/1x/googlelogo_color_150x54dp.png) no-repeat;margin-left:-5px}@media only screen and (min-resolution:192dpi){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat 0
debug1: ssh_exchange_identification: % 0%/100% 100%;-moz-border-image:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) 0}}@media only screen and (-webkit-min-device-pixel-ratio:2){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_
debug1: ssh_exchange_identification: color_150x54dp.png) no-repeat;-webkit-background-size:100% 100%}}#logo{display:inline-block;height:54px;width:150px}

debug1: ssh_exchange_identification:   </style>

debug1: ssh_exchange_identification:   <a href=//www.google.com/><span id=logo aria-label=Google></span></a>

debug1: ssh_exchange_identification:   <p><b>400.</b> <ins>That\342\200\231s an error.</ins>

debug1: ssh_exchange_identification:   <p>Your client has issued a malformed or illegal request.  <ins>That\342\200\231s all we know.</ins>

ssh_exchange_identification: Connection closed by remote host

 

Here is another example on how to test remote host whether a certain service such as DNS (bind) or telnetd is enabled and listening on remote local network  IP with ssh

[root@pciserver: /home ]# ssh 192.168.1.200 -p 53 -v -oConnectTimeout=5
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to 192.168.1.200 [192.168.1.200] port 53.
debug1: connect to address 192.168.1.200 port 53: Connection timed out
ssh: connect to host 192.168.1.200 port 53: Connection timed out

[root@server: /home ]# ssh 192.168.1.200 -p 23 -v -oConnectTimeout=5
OpenSSH_7.9p1 Debian-10+deb10u2, OpenSSL 1.1.1g  21 Apr 2020
debug1: Connecting to 192.168.1.200 [192.168.1.200] port 23.
debug1: connect to address 192.168.1.200 port 23: Connection timed out
ssh: connect to host 192.168.1.200 port 23: Connection timed out


But what if Linux server you have tow work on is so paranoid that you even the ssh client is absent? Well you can use anything else that is capable of doing a connectivity to remote port such as wget or curl. Some web servers or application servers usually have wget or curl as it is integral part for some local shell scripts doing various operation needed for proper services functioning or simply to test locally a local or remote listener services, if that's the case we can use curl to connect and get output of a remote service simulating a normal telnet connection like this:

host:~# curl -vv 'telnet://remote-server-host5:22'
* About to connect() to remote-server-host5 port 22 (#0)
*   Trying 10.52.67.21… connected
* Connected to aflpvz625 (10.52.67.21) port 22 (#0)
SSH-2.0-OpenSSH_5.3

Now lets test whether we can connect remotely to a local net remote IP's Qmail mail server with curls telnet simulation mode:

host:~#  curl -vv 'telnet://192.168.0.200:25'
* Expire in 0 ms for 6 (transfer 0x56066e5ab900)
*   Trying 192.168.0.200…
* TCP_NODELAY set
* Expire in 200 ms for 4 (transfer 0x56066e5ab900)
* Connected to 192.168.0.200 (192.168.0.200) port 25 (#0)
220 This is Mail Pc-Freak.NET ESMTP

Fine it works, lets now test whether a remote server who has MySQL listener service on standard MySQL port TCP 3306 is reachable with curl

host:~#  curl -vv 'telnet://192.168.0.200:3306'
* Expire in 0 ms for 6 (transfer 0x5601fafae900)
*   Trying 192.168.0.200…
* TCP_NODELAY set
* Expire in 200 ms for 4 (transfer 0x5601fafae900)
* Connected to 192.168.0.200 (192.168.0.200) port 3306 (#0)
Warning: Binary output can mess up your terminal. Use "–output -" to tell
Warning: curl to output it to your terminal anyway, or consider "–output
Warning: <FILE>" to save to a file.
* Failed writing body (0 != 107)
* Closing connection 0
root@pcfreak:/var/www/images#  curl -vv 'telnet://192.168.0.200:3306'
* Expire in 0 ms for 6 (transfer 0x5598ad008900)
*   Trying 192.168.0.200…
* TCP_NODELAY set
* Expire in 200 ms for 4 (transfer 0x5598ad008900)
* Connected to 192.168.0.200 (192.168.0.200) port 3306 (#0)
Warning: Binary output can mess up your terminal. Use "–output -" to tell
Warning: curl to output it to your terminal anyway, or consider "–output
Warning: <FILE>" to save to a file.
* Failed writing body (0 != 107)
* Closing connection 0

As you can see the remote connection is returning binary data which is unknown to a standard telnet terminal thus to get the output received we need to pass curl suggested arguments.

host:~#  curl -vv 'telnet://192.168.0.200:3306' –output –
* Expire in 0 ms for 6 (transfer 0x55b205c02900)
*   Trying 192.168.0.200…
* TCP_NODELAY set
* Expire in 200 ms for 4 (transfer 0x55b205c02900)
* Connected to 192.168.0.200 (192.168.0.200) port 3306 (#0)
g


The curl trick used to troubleshoot remote port to remote host from a Windows OS host which does not have telnet installed by default but have curl instead.

Also When troubleshooting vSphere Replication, it is often necessary to troubleshoot port connectivity as common Windows utilities are not available.
As Curl is available in the VMware vCenter Server Appliance command line interface.

On servers where curl is not there but you have wget is installed you can use it also to test a remote port

 

# wget -vv -O /dev/null http://google.com:554 –timeout=5
–2020-12-30 16:54:22–  http://google.com:554/
Resolving google.com (google.com)… 172.217.169.206, 2a00:1450:4017:80b::200e
Connecting to google.com (google.com)|172.217.169.206|:554… failed: Connection timed out.
Connecting to google.com (google.com)|2a00:1450:4017:80b::200e|:554… failed: Cannot assign requested address.
Retrying.

–2020-12-30 16:54:28–  (try: 2)  http://google.com:554/
Connecting to google.com (google.com)|172.217.169.206|:554… ^C

As evident from output the port 554 is filtered in google which is pretty normal.

If curl or wget is not there either as a final alternative you can either install some perl, ruby, python or bash script etc. that can opens a remote socket to the remote IP.

Add Zabbix time synchronization ntp userparameter check script to Monitor Linux servers

Tuesday, December 8th, 2020

Zabbix-logo-how-to-make-ntpd-time-server-monitoring-article

 

How to add Zabbix time synchronization ntp userparameter check script to Monitor Linux servers?

We needed to set on some servers at my work an elementary check with Zabbix monitoring to check whether servers time is correctly synchronized with ntpd time service as well report if the ntp daemon is correctly running on the machine. For that a userparameter script was developed called userparameter_ntp.conf the script is simplistic and few a lines of bash shell scripting 
stuff is based on gresping information required from ntpq and ntpstat common ntp client commands to get information about the status of time synchronization on the servers.
 

[root@linuxserver ]# ntpstat
synchronised to NTP server (10.80.200.30) at stratum 3
   time correct to within 47 ms
   polling server every 1024 s

 

[root@linuxserver ]# ntpq -c peers
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
+timeserver1 10.26.239.41     2 u  319 1024  377   15.864    1.270   0.262
+timeserver2 10.82.239.41     2 u  591 1024  377   16.287   -0.334   1.748
*timeserver3 10.82.239.43     2 u   47 1024  377   15.613   -0.553   0.251
 timeserver4 .INIT.          16 u    – 1024    0    0.000    0.000   0.000


Below is Zabbix UserParameter script that does report us 3 important values we monitor to make sure time server synchronization works as expected the zabbix keys we set are ntp.offset, ntp.sync, ntp.exact in attempt to describe what we're fetching from ntp client:

[root@linuxserver ]# cat /etc/zabbix/zabbix-agent.d/userparameter_ntp.conf

UserParameter=ntp.offset,(/usr/sbin/ntpq -pn | /usr/bin/awk 'BEGIN { offset=1000 } $1 ~ /\*/ { offset=$9 } END { print offset }')
#UserParameter=ntp.offset,(/usr/sbin/ntpq -pn | /usr/bin/awk 'FNR==4{print $9}')
UserParameter=ntp.sync,(/usr/bin/ntpstat | cut -f 1 -d " " | tr -d ' \t\n\r\f')
UserParameter=ntp.exact,(/usr/bin/ntpstat | /usr/bin/awk 'FNR==2{print $5,$6}')

In Zabbix the monitored ntpd parameters set-upped looks like this:

 

ntp_time_synchronization_check-zabbix-screenshot.

 

!Note that in above userparameter example, the commented userparameter script is a just another way to do an ntpd offset returned value which was developed before the more sophisticated with more regular expression checks from the /usr/sbin/ntpd via ntpq, perhaps if you want to extend it you can also use another script to report more verbose information to Zabbix if that is required like ouput from ntpq -c peers command:
 

UserParameter=ntp.verbose,(/usr/sbin/ntpq -c peers)

Of course to make the Zabbix fetch necessery data from monitored hosts, we need to set-up further new Zabbix Template with the respective Trigger and Items.

Below are few screenshots including the triggers used.

ntpd_server-time_synchronization_check-zabbix-screenshot-triggers

  • ntpd.trigger

{NTP:net.udp.service[ntp].last(0)}<1

  • NTP Synchronization trigger

{NTP:ntp.sync.iregexp(unsynchronised)}=1

 

 

As you can see from history we have setup our items to Store history of reported data to Zabbix from parameter script for 90 days and update our monitor check, every 30 seconds from the monitored hosts to which Tempate is applied.

Well that's all folks, time synchronization issues we'll be promptly triggering a new Alarm in Zabbix !

Howto Upgrade IBM Spectrum Protect Backup Client TSM 7.X to 8.1.8, Update Tivoli 8.1.8 to 8.1.11 on CentOS and Redhat Linux

Thursday, December 3rd, 2020

 

IBM-spectrum-protect-backup-logo-tivoli-tsm-logo

Having another day of a system administrator boredom, we had a task to upgrade some Tivoli TSM Backup clients running on a 20+ machines powered by CentOS and RHEL Linux to prepare the systems to be on the latest patched IBM Spectrum Backup client version available from IBM. For the task of patching I've used a central server where, I've initially downloaded the provided TSM client binaries archives. From this machine, we have copied TivSM*.tar to each and every system that needs to be patched and then patched. The task is not too complex as the running TSM in the machines are all at the same version and all running a recent patched version of Linux. Hence to make sure all works as expected we have tested TSM is upgraded from 7.X.X to 8.X.X on one machine and then test 8.1.8 to 8.1.11 upgrade on another one. Once having confirmed that Backups works as expected after upgrade. We have proceeded to do it massively on each of the rest 20+ hosts.
Below article's goal is to help some lazy sysadmin with the task to prepare an TSM Backup upgrade procedure to standartize TSM Upgrade, which as many of the IBM's softwares is very specific and its upgrade requires, a bit of manual work and extra cautious as there seems to be no easy way (or at least I don't know it), to do the upgrade by simply adding an RPM repository and doing, something like yum install tivsm*.


0. Check if there is at least 2G free of space

According to documentation the minimum space you need to a functional install without having it half installed or filling up your filesystem is 2 Gigabytes of Free Memory on a filesystem where the .tar and rpms will be living.

Thus check what is the situation with your filesystem where you wills store the .tar archice and extract .RPM files / install the RPM files.

# df -h

1. Download the correct tarball with 8.1 Client

On one central machine you would need to download the Tivoli you can do that via wget / curl / lynx whatever is at hand on the Linux server.

As of time of writting this article TSM's 8.1.11 location is at
URL:

http://public.dhe.ibm.com/storage/tivoli-storage-management/maintenance/client/v8r1/Linux/LinuxX86/BA/v8111/

I've made a local download mirror of Tivoli TSM 8.1.11 here.
In case you need to install IBM Spectrum Backup Client to a PCI secured environment to a DMZ-ed LAN network from a work PC you can Download it first from your local PC and via Citrix client upload program or WinSCP upload it to a central replication host from where you will later copy to each of the other server nodes that needs to be upgraded.

Lets Copy archive to all Server hosts where you want it later installed, using a small hack

Assuming you already have an Excel document or a Plain text document with all the IPs of the affected hosts where you will need to get TSM upgraded. Extract this data and from it create a plain text file /home/user/hosts.txt containing all the machine IPs lined up separated with carriage return separations (\n), so you can loop over each one and use scp to send the files.

– Replicate Tivoli tar to all machine hosts where you want to get IBM Spectrum installed or upgraded.
Do it with a loop like this:

# for i in $(cat hosts.txt); do scp 8.1.11.0-TIV-TSMBAC-LinuxX86.tar user@$i:/home/user/; done

 Copy to a Copy buffer temporary your server password assuming all your passwords to each machine are identical and paste your login user pass for each host to initiate transfer
 

2. SSH to each of the Machine hosts IPs

Once you login to the host you want to upgrade
Go to your user $HOME /home/user and create files where we'll temporary store Tivoli archive files and extract RPMs

[root@linux-server user]# mkdir -p ~/tsm/TSM_BCK/
[root@linux-server user]# mv 8.1.11.0-TIV-TSMBAC-LinuxX86.tar ~/tsm
[root@linux-server user]# cd tsm
[root@linux-server user]# tar -xvvf 8.1.11.0-TIV-TSMBAC-LinuxX86.tar
gskcrypt64-8.0.55.17.linux.x86_64.rpm
GSKit.pub.pgp
gskssl64-8.0.55.17.linux.x86_64.rpm
README_api.htm
README.htm
RPM-GPG-KEY-ibmpkg
TIVsm-API64.x86_64.rpm
TIVsm-APIcit.x86_64.rpm
TIVsm-BAcit.x86_64.rpm
TIVsm-BAhdw.x86_64.rpm
TIVsm-BA.x86_64.rpm
TIVsm-filepath-source.tar.gz
TIVsm-JBB.x86_64.rpm
TIVsm-WEBGUI.x86_64.rpm
update.txt

3. Create backup of old backup files

It is always a good idea to keep old backup files

[root@linux-server tsm]# cp -av /opt/tivoli/tsm/client/ba/bin/dsm.opt ~/tsm/TSM_BCK/dsm.opt_bak_$(date +'%Y_%M_%H')
[root@linux-server tsm]# cp -av /opt/tivoli/tsm/client/ba/bin/dsm.sys ~/tsm/TSM_BCK/dsm.sys_bak_$(date +'%Y_%M_%H')

[root@linux-server tsm]# [[ -f /etc/adsm/TSM.PWD ]] && cp -av /etc/adsm/TSM.PWD ~/TSM_BCK/ || echo 'file doesnt exist'

/etc/adsm/TSM.PWD this file is only there as legacy for TSM it contained encrypted passwords inver 7 for updates. In TSM v.8 encryption file is not there as new mechanism for sensitive data was introduced.
Be aware that from Tivoli 8.X it will return error
exist'

!! Note – if dsm.opt , dsm.sys files are on different locations – please use correct full path locations !!

4. Stop  dsmcad – TSM Service daemon

[root@linux-server tsm]# systemctl stop dsmcad

5. Locate and deinstall all old Clients

Depending on the version to upgrade if you're upgrading from TSM version 7 to 8, you will get output like.

[root@linux-server tsm]# rpm -qa | grep 'TIVsm-'
TIVsm-BA-7.1.6-2.x86_64
TIVsm-API64-7.1.6-2.x86_64

If you're one of this paranoid admins you can remove TIVsm packs  one by one.

[root@linux-server tsm]# rpm -e TIVsm-BA-7.1.6-2.x86_64
[root@linux-server tsm]# rpm -e TIVsm-API64-7.1.6-2.x86_64

Instead if upgrading from version 8.1.8 to 8.1.11 due to the Security CVE advisory recently published by IBM e.g. (IBM Runtime Vulnerability affects IBM Spectrum Backup archive Client) and  vulnerability in Apache Commons Log4J affecting IBM Spectrum Protect Backup Archive Client.

[root@linux-server tsm]# rpm -qa | grep 'TIVsm-'
TIVsm-API64-8.1.8-0.x86_64
TIVsm-BA-8.1.8-0.x86_64

Assuming you're not scared of a bit automation you can straight do it with below one liner too 🙂

# rpm -e $(rpm -qa | grep TIVsm)

[root@linux-server tsm]# rpm -qa | grep gsk
[root@linux-server tsm]# rpm -e gskcrypt64 gskssl64

6. Check uninstallation success:

[root@linux-server tsm]# rpm -qa | grep TIVsm
[root@linux-server tsm]# rpm -qa | grep gsk

Here you should an Empty output, if packages are not on the system, e.g. Empty output is good output ! 🙂

7. Install new client IBM Spectrum Client (Tivoli Storage Manager) and lib dependencies

[root@linux-server tsm]# rpm -ivh gskcrypt64-8.0.55.4.linux.x86_64.rpm
[root@linux-server tsm]# rpm -ivh gskssl64-8.0.55.4.linux.x86_64.rpm

 If you're lazy to type you can do as well

[root@linux-server tsm]# rpm -Uvh gsk*

Next step is to install main Tivoli SM components the the API files and BA (The Backup Archive Client)

[root@linux-server tsm]# rpm -ivh TIVsm-API64.x86_64.rpm
[root@linux-server tsm]# rpm -ivh TIVsm-BA.x86_64.rpm

If you have to do it on multiple servers and you do it manually following a guide like this, you might instead want to install them with one liner.

[root@linux-server tsm]# rpm -ivh TIVsm-API64.x86_64.rpm TIVsm-BA.x86_64.rpm

There are some Not mandatory "Common Inventory Technology" components (at some cases if you're using the API install it we did not need that), just for the sake if you need them on your servers due to backup architecture, install also below commented rpm files.

## rpm -ivh TIVsm-APIcit.x86_64.rpm

## rpm -ivh TIVsm-BAcit.x86_64.rpm

These packages not needed only for operation WebGUI TSM GUI management, (JBB) Journal Based Backup, BAhdw (the ONTAP library)


— TIVsm-WEBGUI.x86_64.rpm
— TIVsm-JBB.x86_64.rpm
— TIVsm-BAhdw.x86_64.rpm

8. Start and enable dsmcad service

[root@linux-server tsm]# systemctl stop dsmcad

You will get

##Warning: dsmcad.service changed on disk. Run 'systemctl daemon-reload' to reload units.

[root@linux-server tsm]# systemctl daemon-reload

[root@linux-server tsm]# systemctl start dsmcad


## enable dsmcad – it is disabled by default after install

[root@linux-server ~]# systemctl enable dsmcad

[root@linux-server tsm]# systemctl status dsmcad

9. Check dmscad service is really running

Once enabled IBM TSM will spawn a process in the bacground dmscad if it started properly you should have the process backgrounded.

[root@linux-server tsm]# ps -ef|grep -i dsm|grep -v grep
root      2881     1  0 18:05 ?        00:00:01 /usr/bin/dsmcad

If process is not there there might be some library or something not at place preventing the process to start …

10. Check DSMCAD /var/tsm logs for errors

After having dsmcad process enabled and running in background

[root@linux-server tsm]# grep -i Version /var/tsm/sched.log|tail -1
12/03/2020 18:06:29   Server Version 8, Release 1, Level 10.000

 

[root@linux-server tsm]# cat /var/tsm/dsmerror.log

To see the current TSM configuration files we can  grep out comments *

[root@linux-server tsm]# grep -v '*' /opt/tivoli/tsm/client/ba/bin/dsm.sys

Example Configuration of the agent:
—————————————————-
   *TSM SERVER NODE Location
   Servername           tsm_server
   COMMmethod           TCPip
   TCPPort              1400
   TCPServeraddress     tsmserver2.backuphost.com
   NodeName             NODE.SERVER-TO-BACKUP-HOSTNAME.COM
   Passwordaccess       generate
   SCHEDLOGNAME         /var/tsm/sched.log
   SCHEDLOGRETENTION    21 D
   SCHEDMODE            POLLING
   MANAGEDServices      schedule
   ERRORLOGNAME         /var/tsm/dsmerror.log
   ERRORLOGRETENTION    30 D
   INCLEXCL             /opt/tivoli/tsm/client/ba/bin/inclexcl.tsm

11. Remove tsm install directory tar ball and rpms to save space on system

The current version of Tivoli service manager is 586 Megabytes.

[root@linux-server tsm]# du -hsc 8.1.11.0-TIV-TSMBAC-LinuxX86.tar
586M    8.1.11.0-TIV-TSMBAC-LinuxX86.tar

Some systems are on purpose configured to have less space under their /home directory,
hence it is a good idea to clear up unnecessery files after completion.

Lets get rid of all the IBM Spectrum archive source files and the rest of RPMs used for installation.

[root@linux-server tsm]# rm -rf ~/tsm/{*.tar,*.rpm,*.gpg,*.htm,*.txt}

12. Check backups are really created on the configured remote Central backup server

To make sure after the upgrade the backups are continuously created and properly stored on the IBM Tivoly remote central backup server, either manually initiate a backup or wait for lets say a day and run dsmc client to show all created backups from previous day. To make sure you'll not get empty output you can on purpose modify some file by simply opening it and writting over without chaning anything e.g. modify your ~/.bashrc or ~/.bash_profile

## List all backups for '/' root directory from -fromdate='DD/MM/YY'

[root@linux-server tsm]# dsmc
Protect>
IBM Spectrum Protect
Command Line Backup-Archive Client Interface
  Client Version 8, Release 1, Level 11.0
  Client date/time: 12/03/2020 18:14:03
(c) Copyright by IBM Corporation and other(s) 1990, 2020. All Rights Reserved.

Node Name: NODE.SERVER-TO-BACKUP-HOSTNAME.COM
Session established with server TSM2_SERVER: AIX
  Server Version 8, Release 1, Level 10.000
  Server date/time: 12/03/2020 18:14:04  Last access: 12/03/2020 18:06:29
 
Protect> query backup -subdir=yes "/" -fromdate=12/3/2020
           Size        Backup Date                Mgmt Class           A/I File
           —-        ———–                ———-           — —-
         6,776  B  12/03/2020 01:26:53             DEFAULT              A  /etc/freshclam.conf
         6,685  B  12/03/2020 01:26:53             DEFAULT              A  /etc/freshclam.conf-2020-12-02
         5,602  B  12/03/2020 01:26:53             DEFAULT              A  /etc/hosts
         5,506  B  12/03/2020 01:26:53             DEFAULT              A  /etc/hosts-2020-12-02
           398  B  12/03/2020 01:26:53             DEFAULT              A  /opt/tivoli/tsm/client/ba/bin/tsmstats.ini
       114,328  B  12/03/2020 01:26:53             DEFAULT              A  /root/.bash_history
           403  B  12/03/2020 01:26:53             DEFAULT              A  /root/.lesshst

How to add colorful random ASCII art picture and a bible verse on each SSH server login, joyout sysadmins life with cowsay, fortune, caca-utils and others

Tuesday, November 24th, 2020

Jesus-Christ-loves-the-world-ascii-art

There are pleny of console ASCII stuff out there that can make your console sysadmin boring life a little bit more funny and cherish some memories from the old times of 8 bit computers :).

One of this as I blogged earlier is cowsay and cowthink to generate a ascii picture with a cow with your custom message.
I've earlier blogged about that in my previous article Create ASCII Art Text bannners in Linux console / terminal with figlet and toilet

One of this cool things I'm using daily on my servers  is a cowsay console goodie together with a bash shell script that does visualize a random ASCII picture from a preset of pictures on each and every ssh login to my server.
The script I use is cowrand below is code:

#!/bin/bash
# cowsay pix randomizer by hip0
# it shows random ascii from the cowsay prog during logging. :]
a=0
b=1
cowrand='/etc/cowrand';
dir='/usr/share/cowsay/cows';
var=`ls -1 $dir | wc -l | awk '{ print $1}'`
#RANGE=$var
number=$RANDOM
let "number %= $var"
var1=`ls -1 $dir | head -n $number | tail -n 1 | head -n 1`
if [ -z “$var1” ]; then
$cowrand;
else
/usr/bin/cowsay -f $var1 Welc0m3 t0 pC-fREAK … Enj0y.
fi

 

The script is set as executable under /etc/cowrand

hipo@pcfreak:~$ ls -al /etc/cowrand
-rwxr-xr-x 1 hipo hipo 432 Nov 24 19:21 /etc/cowrand*

I've set this script to my /etc/profile to auto start on every login on my Debian Linux systems right after the comments like so:

hipo@pcfreak:~$ grep -i cowrand -A 2 -B 3 /etc/profile
# /etc/profile: system-wide .profile file for the Bourne shell (sh(1))
# and Bourne compatible shells (bash(1), ksh(1), ash(1), …).
echo '';
/etc/cowrand | lolcat
echo '';
#/usr/bin/verse

As you can see to make my life even more funnier, I've installed another fun command lolcat

lolcat-screenshot

hipo@pcfreak:~$ apt-cache show lolcat |grep -i desc -A 3
Description-en: colorful `cat`
 lolcat concatenates files like the UNIX `cat` program, but colors it for the
 lulz in a rainbow animation. Terminals with 256 colors and animations are
 supported.

Description-md5: 86f992d66ac74197cda39e0bbfcb549d
Homepage: https://github.com/busyloop/lolcat
Ruby-Versions: all
Section: games


You can think of lolcat as a standard cat command that has been made to print in colors, this gives a funny results.

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier

To add some spice to everything nice as a recipee for thethe creation of powerpuff girls, I've come up with a way to use fortune
console tool that uses to print quotes out of a database to use as a source a big database containing the Holy Bible books of Old and New Testament Books. The fortune prints me out a quote extract from the bible on each and every remote SSH login to my machine. The content of this bible database for fortune bible_quotes_fortune.tar.gz can be downloaded and used from here.

The command used to print out a verse from the holy bible is:
 

 

hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
For if thou refuse to let them go, and wilt hold them still,
        — Exodus 9:2
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And when the queen of Sheba heard of the fame of Solomon concerning
the name of the LORD, she came to prove him with hard questions.
        — 1 Kings 10:1
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And Shelemiah, and Nathan, and Adaiah,
        — Ezra 10:39
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
For by thee I have run through a troop: by my God have I leaped
over a wall.
        — 2 Samuel 22:30
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
Unto the place of the altar, which he had make there at the first:
and there Abram called on the name of the LORD.
        — Genesis 13:4
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And there shall dwell in Judah itself, and in all the cities thereof
together, husbandmen, and they that go forth with flocks.
        — Jeremiah 31:24
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And he hath put a new song in my mouth, even praise unto our God:
many shall see it, and fear, and shall trust in the LORD.
        — Psalms 40:3
hipo@pcfreak:~$ /usr/games/fortune -s /usr/local/fortune/
And Jehoshaphat made peace with the king of Israel.
        — 1 Kings 22:44
 

 

The fortune is really awesome as it reminds me often of a verses from Holy Bible I often forget, the database is using the all famous King James Bible famous as (KJB) / (KJV) from 1611 this bible version that is like a protestant standard nowadays takes its name after James VI and I (James Charles Stuart; 19 June 1566 – 27 March 1625 – King of Scotland and Ireland) who was the sponsor of KJV collection and print.

Finally after adding the /usr/games/fortune -s /usr/local/fortune/ to the beginning of /etc/profile together with cowsay and cowrand I got this beautiful and educational result that combines fun with wisdom, below is example of what you will get after you  do a remote ssh login;

 

ssh your-machine.com

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_1

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_2

cowrand-script-lolcat-os-release-how-to-make-your-linux-login-prompt-funnier_3

Those who have a Linux Graphical Environment desktop might also enjoy xcowsay

Another must I recommend to the text geeks is the caca-utils package which contains cool things such as aafire (cacafire)

cacaview-fire-screenshot-ascii-art

Or (Image to text converter) img2txt / cacaview (a text console picture viewer) that could give you a raw idea on how a png / jpg picture looks like (or at least the picture shapes) without a need for a GUI picture viewer such as Eye of the Gnome.

bear-for-you-picture-rose

Here is a original bear

cacaview-a-bear-for-you-picture-in-plain-text-ascii

And here is the one you'll see in cacaview 🙂
To read more about cacaview I have and its uses, check my previous article Viewing JPEG,GIF and PNG in ASCII with cacaview in Linux.
If you want to show off even more as a '1337 h4x0r' you might also show your sysadm 1337 5K!11Z to colleagues by showng them how you check weather via console (i've a separate article for how to ASCII art check colorful weather forecast via console / terminal ).

If you're too bored in your daily sys admin job, you might make some fun and take some useless effort to install ASCII Art Aquarium ASCIIQUARIUM

asciiquarium1

asciiquarium2

asciiquarium3

If you're crazy enough and want to torture your other sysadmin colleagues and a get a nice prank, you might install and set asciiquarium to auto run for their specific account on each and every login to some server until they control C or if you're a bit evil you can even set a small auto load on account login via ~/.bashrc shell script to 'Disable CTRL + C' combination 🙂
 

Of course there is plenty of other cool ASCII games and stuff. I've collected some of them by launching the Play Cool Ascii games service on my machine for ASCII art geeks to test out some ASCII games here.