Posts Tagged ‘script’

Automatic network restart and reboot Linux server script if ping timeout to gateway is not responding as a way to reduce connectivity downtimes

Monday, December 10th, 2018

automatic-server-network-restart-and-reboot-script-if-connection-to-server-gateway-inavailable-tux-penguing-ascii-art-bin-bash

Inability of server to come back online server automaticallyafter electricity / network outage

These days my home server  is experiencing a lot of issues due to Electricity Power Outages, a construction dig operations to fix / change waterpipe tubes near my home are in action and perhaps the power cables got ruptered by the digger machine.
The effect of all this was that my server networking accessability was affected and as I didn't have network I couldn't access it remotely anymore at a certain point the electricity was restored (and the UPS charge could keep the server up), however the server accessibility did not due restore until I asked a relative to restart it or under a more complicated cases where Tech aquanted guy has to help – Alexander (Alex) a close friend from school years check his old site here – alex.pc-freak.net helps a lot.to restart the machine physically either run a quick restoration commands on root TTY terminal or generally do check whether default router is reachable.

This kind of Pc-Freak.net downtime issues over the last month become too frequent (the machine was down about 5 times for 2 to 5 hours and this was too much (and weirdly enough it was not accessible from the internet even after electricity network was restored and the only solution to that was a physical server restart (from the Power Button).

To decrease the number of cases in which known relatives or friends has to  physically go to the server and restart it, each time after network or electricity outage I wrote a small script to check accessibility towards Default defined Network Gateway for my server with few ICMP packages sent with good old PING command
and trigger a network restart and system reboot
(in case if the network restart does fail) in a row.

1. Create reboot-if-nwork-is-downsh script under /usr/sbin or other dir

Here is the script itself:

 

#!/bin/sh
# Script checks with ping 5 ICMP pings 10 times to DEF GW and if so
# triggers networking restart /etc/inid.d/networking restart
# Then does another 5 x 10 PINGS and if ping command returns errors,
# Reboots machine
# This script is useful if you run home router with Linux and you have
# electricity outages and machine doesn't go up if not rebooted in that case

GATEWAY_HOST='192.168.0.1';

run_ping () {
for i in $(seq 1 10); do
    ping -c 5 $GATEWAY_HOST
done

}

reboot_f () {
if [ $? -eq 0 ]; then
        echo "$(date "+%Y-%m-%d %H:%M:%S") Ping to $GATEWAY_HOST OK" >> /var/log/reboot.log
    else
    /etc/init.d/networking restart
        echo "$(date "+%Y-%m-%d %H:%M:%S") Restarted Network Interfaces:" >> /tmp/rebooted.txt
    for i in $(seq 1 10); do ping -c 5 $GATEWAY_HOST; done
    if [ $? -eq 0 ] && [ $(cat /tmp/rebooted.txt) -lt ‘5’ ]; then
         echo "$(date "+%Y-%m-%d %H:%M:%S") Ping to $GATEWAY_HOST FAILED !!! REBOOTING." >> /var/log/reboot.log
        /sbin/reboot

    # increment 5 times until stop
    [[ -f /tmp/rebooted.txt ]] || echo 0 > /tmp/rebooted.txt
    n=$(< /tmp/rebooted.txt)
        echo $(( n + 1 )) > /tmp/rebooted.txt
    fi
    # if 5 times rebooted sleep 30 mins and reset counter
    if [ $(cat /tmprebooted.txt) -eq ‘5’ ]; then
    sleep 1800
        cat /dev/null > /tmp/rebooted.txt
    fi
fi

}
run_ping;
reboot_f;

You can download a copy of reboot-if-nwork-is-down.sh script here.

As you see in script successful runs  as well as its failures are logged on server in /var/log/reboot.log with respective timestamp.
Also a counter to 5 is kept in /tmp/rebooted.txt, incremented on each and every script run (rebooting) if, the 5 times increment is matched

a sleep is executed for 30 minutes and the counter is being restarted.
The counter check to 5 guarantees the server will not get restarted if access to Gateway is not continuing for a long time to prevent the system is not being restarted like crazy all time.
 

2. Create a cron job to run reboot-if-nwork-is-down.sh every 15 minutes or so 

I've set the script to re-run in a scheduled (root user) cron job every 15 minutes with following  job:

To add the script to the existing cron rules without rewriting my old cron jobs and without tempering to use cronta -u root -e (e.g. do the cron job add in a non-interactive mode with a single bash script one liner had to run following command:

 

{ crontab -l; echo "*/15 * * * * /usr/sbin/reboot-if-nwork-is-down.sh 2>&1 >/dev/null; } | crontab –


I know restarting a server to restore accessibility is a stupid practice but for home-use or small client servers with unguaranteed networks with a cheap Uninterruptable Power Supply (UPS) devices it is useful.

Summary

Time will show how efficient such a  "self-healing script practice is.
Even though I'm pretty sure that even in a Corporate businesses and large Public / Private Hybrid Clouds where access to remote mounted NFS / XFS / ZFS filesystems are failing a modifications of the script could save you a lot of nerves and troubles and unhappy customers / managers screaming at you on the phone 🙂


I'll be interested to hear from others who have a better  ideas to restore ( resurrect ) access to inessible Linux server after an outage.?
 

Install simscan on Qmail for better Mail server performance and get around unexisting suid perl in newer Linux Debian / Ubuntu servers

Tuesday, August 18th, 2015

qmail-fixing-clamdscan-errors-and-qq-errors-qmail-binary-migration-few-things-to-check-outclamav_logo-installing-clamav-antivirus-to-scan-periodically-debian-server-websites-for-viruses

I've been stuck with qmail-scanner-queue for a while on each and every new Qmail Mail server installation, I've done, this time it was not different but as time evolves and Qmail and Qmail Scanner Wrapper are not regularly updated it is getting, harder and harder to make a fully functional Qmail on newer Linux server distribution releases.

I know many would argue QMAIL is already obsolete but still I have plenty of old servers running QMAIL whose migration might cause more troubles than just continuing to use QMAIL. Moreover QMAIL once set-upped works like a charm.

I've been recently experiencing severe issues with clamdscan errors and I tried to work around this with compiling and using a suid wrapper, however still the clamdscan errors continued and as qmail-scanner is not actively developed and it is much slower than simscan, I've finally decided to give simscan as a mean to fix the clamdscan errors and thanksfully this worked as a solution.

Here is what I did "rawly" to make simscan work on this install:
 

Make sure simscan is properly installed on Debian Linux 7 or Ubuntu servers and probably (should work) on other Deb based Linuxes by following below steps:
 

a) Configure simscan with following compile time options as root (superuser)

./configure \
–enable-user=qscand \
–enable-clamav \
–enable-clamdscan=/usr/local/bin/clamdscan \
–enable-custom-smtp-reject=y \
–enable-per-domain=y \
–enable-attach=y \
–enable-dropmsg=n \
–enable-spam=y \
–enable-spam-hits=5 \
–enable-spam-passthru=y \
–enable-qmail-queue=/var/qmail/bin/qmail-queue \
–enable-ripmime=/usr/local/bin/ripmime \
–enable-sigtool-path=/usr/local/bin/sigtool \
–enable-received=y


b) Compile it

 

 make && make install-strip

c) Fix any wrong permissions of simscan queue directory

 

chmod g+s /var/qmail/simscan/

chown -R qscand:qscand /var/qmail/simscan/
chmod -R 777 simscan/chown -R qscand:qscand simscan/
chown -R qscand:qscand simscan/

d) Add some additional simscan options (how simscan is how to perform scans)

The restart qmail to make mailserver start using simscan instead of qmail-scanner, run below command (again as root):

echo ":clam=yes,spam=yes,spam_hits=8.5,attach=.vbs:.lnk:.scr:.wsh:.hta:.pif" > /var/qmail/control/simcontrol

 

e) Run /var/qmail/bin/simscanmk in order to convert /var/qmail/control/simcontrol into the /var/qmail/control/simcontrol.cdb database

/var/qmail/bin/simscanmk
/var/qmail/bin/simscanmk -g

f) Modify /service/qmail-smtpd/run to set simscan to be default Antivirus Wrapper Scanner

vim /service/qmail-smtpd/run

I'm using thibs's run script so I've uncommented the line there:

QMAILQUEUE="$VQ/bin/simscan"

Below two lines should stay commented as qmail-scanner is no longer used:

##QMAILQUEUE="$VQ/bin/qmail-scanner-queue"
##QMAILQUEUE="$VQ/bin/qmail-scanner-queue.pl"
export QMAILQUEUE

qmailctl restart
* Stopping qmail-smtpdssl.
* Stopping qmail-smtpd.
* Sending qmail-send SIGTERM and restarting.
* Restarting qmail-smtpd.
* Restarting qmail-smtpdssl.

g) Test whether simscan is properly sending / receiving emails:

echo "Testing Email" >> /tmp/mailtest.txt
env QMAILQUEUE=/var/qmail/bin/simscan SIMSCAN_DEBUG=3 /var/qmail/bin/qmail-inject hipo@my-mailserver.com < /tmp/mailtest.txt

Besides that as I'm using qscand:qscand as a user for my overall Qmail Thibs install I had to also do:

chown -R qscand:qscand /var/qmail/simscan/
chmod -R 777 simscan/
chown -R qscand:qscand simscan/

 

It might be a good idea to also place that lines in /etc/rc.local to auto change permissions on Linux boot, just in case something wents wrong with permissions.

Yeah, I know 777 is unsecure but without this permissions, I was still getting errors, plus the server doesn't have any accounts except the administrator, so I do not worry other system users might sniff on email 🙂

h) Test whether Qmail mail server send / receives fine with simscan

After that I've used another mail server with mail command to test whether mail is received:
 

mail -s "testing email1234" hipo@new-configured-qmail-server.com
asdfadsf
.
Cc:

Then it is necessery to also install latest clamav daemon from source in my case that's on Debian GNU / Linux 7, because somehow the Debian shipped binary version of clamav 0.98.5+dfsg-0+deb7u2 does fail to scan any incoming or outgoing email with error:
 

clamdscan: corrupt or unknown clamd scanner error or memory/resource/perms problem – exit status -1/72057594037927935

So to fix it you will have to install clamav on Debian Linux from source.


Voilla, that's all finally it worked !

How to Remove / Add SuSE Linux start service command

Thursday, July 2nd, 2015

opensuse-remove-add-new-service-geeko-suse-linux-mini-logo
If you happen to administer SUSE LINUX Enterprise Server 9 (x86_64) and you need to add or remove already existing /etc/init.d script or custom created Apache / Tomcat .. etc. service and you're already familiar with Fedora's / RHEL chkconfig, then the good news chkconfig is also available on SuSE and you can use in same way chkconfig to start / stop / enable / disable boot time services.

To list all available boot time init.d services use:
 

suse-linux:/etc # chkconfig –list

 

SuSEfirewall2_final       0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_init        0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_setup       0:off  1:off  2:off  3:off  4:off  5:off  6:off
Tivoli_lcfd1.bkp          0:off  1:off  2:off  3:off  4:off  5:off  6:off
activate_web_all          0:off  1:off  2:off  3:on   4:off  5:on   6:off
alsasound                 0:off  1:off  2:on   3:on   4:off  5:on   6:off
apache2                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
apache2-eis               0:off  1:off  2:off  3:on   4:off  5:off  6:off
atd                       0:off  1:off  2:off  3:off  4:off  5:off  6:off
audit                     0:off  1:off  2:off  3:off  4:off  5:off  6:off
autofs                    0:off  1:off  2:off  3:off  4:off  5:off  6:off
autoyast                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.clock                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.crypto               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.device-mapper        0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.evms                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.idedma               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ipconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.isapnp               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.klog                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ldconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.loadmodules          0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localfs              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localnet             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.lvm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.md                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.multipath            0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.proc                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.restore_permissions  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.rootfsck             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sched                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scpm                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scsidev              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.shm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.swap                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sysctl               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.udev                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
coldplug                  0:off  1:on   2:on   3:on   4:off  5:on   6:off

 

To then stop the service:
 

suse-linux:/etc # chkconfig gtiweb off


If you prefer to do it the SuSE way and learn a bit more on SuSE boot time process check out:

 

suse-linux:/etc # man insserv


Removing already existing SuSE start-up script from init.d start up with insserv is done with:

suse-linux:/etc # cd /etc/init.d/
suse-linux:etc/init.d # insserv -r gtiweb
insserv: script ipmi.hp: service ipmidrv already provided!
insserv: script boot.multipath.2008-10-29: service boot.multipath already provided!


To install a new custom written and placed into /etc/inti.d/ on SuSE's server boot time with insserv:

 

suse-linux:/etc/init.d/ # insserv your_custom_script_name

Windows add / delete services command sc.exe create/delete – Create or Delete services

Thursday, April 9th, 2015

sc-exe-command-line-program-to-create-delete--service-start-stop-service-on-ms-windows
If you end up in situation where you need to delete or create services from current existing ones with a batch script because it is existing on multiple servers and you want to automate / deploy it via batch (.bat) script you will have to use sc.exe tool – Service Controller Command Tool

SC.EXE command  is standard windows console tool to create and delete services. If you want to create a new service, you can use the "create" parameter.

1. Deleting Service with Windows Service Controller Tool

Deleting service is very easy to do you just have to know the service you like to remove not to be listed or Automatically start

sc delete SERVICE_NAME_TO_BE_REMOVED


Below is a real time example on how to remove Apache webserver configured to auto-start

 

sc.exe delete ApacheService

[SC] DeleteService SUCCESS

2. Create / Add service to existing to auto start on Windows

Before running sc.exe create command with arguments for service you will need to know following info:

  • What will be the Service Name: A single word to name the new service.
  • Full Binary Path: The path name where the executable program for new service is currently located.
  • Dispaly Name for service: A short name for the new service.

 

C:\Windows>sc.exe create ApacheService 
   binPath= "C:\local\apache\bin\httpd.exe -k runservice" 
   DisplayName= "Apache Server"

 

[SC] CreateService SUCCESS


Once service is added to be showing in services.msc GUI  you can start the newly added Apache service with:

 

C:\Windows>sc.exe start ApacheService

 

SERVICE_NAME: ApacheService
   TYPE               : 10  WIN32_OWN_PROCESS
   STATE              : 2  START_PENDING
                      (NOT_STOPPABLE,NOT_PAUSABLE,IGNORES_SHUTDOWN)
   WIN32_EXIT_CODE    : 0  (0x0)
   SERVICE_EXIT_CODE  : 0  (0x0)
   CHECKPOINT         : 0x2
   WAIT_HINT          : 0x7530
   PID                : 2552
   FLAGS              :


To stop the ApacheService or any other service:

 

C:\Windows>sc.exe stop ApacheService

SERVICE_NAME: ApacheService
   TYPE               : 10  WIN32_OWN_PROCESS
   STATE              : 3  STOP_PENDING
                      (NOT_STOPPABLE,NOT_PAUSABLE,IGNORES_SHUTDOWN)
   WIN32_EXIT_CODE    : 0  (0x0)
   SERVICE_EXIT_CODE  : 0  (0x0)
   CHECKPOINT         : 0x4
   WAIT_HINT          : 0x7530


To get the status of a running service lets say the recently ran ApacheService:

C:\Windows>sc.exe query ApacheService

 

SERVICE_NAME: ApacheService
   TYPE               : 10  WIN32_OWN_PROCESS
   STATE              : 4  RUNNING
                      (STOPPABLE,NOT_PAUSABLE,IGNORES_SHUTDOWN)
   WIN32_EXIT_CODE    : 0  (0x0)
   SERVICE_EXIT_CODE  : 0  (0x0)
   CHECKPOINT         : 0x0
   WAIT_HINT          : 0x0


As you see from above output the STATE of service is RUNNING. If Apache Webserver was not running you will get an error like:

[SC] EnumQueryServicesStatus:OpenService FAILED 1060:
The specified service does not exist as an installed service.

 

Enjoy sc-ing 🙂

Weblogic – How to change / remove IP/hostname quick and dirty howto

Wednesday, March 11th, 2015

Oracle-Weblogic-Server-logo-how-to-change-ip-hostname-weblogic-quick-and-dirty-howto

This is just quick & dirty doc on how to change/remove IP/host on Oracle WebLogic Application server

– In logs the Error message will be message like:

 

<Oct 21, 2013 1:06:51 AM SGT> <Warning> <Security> <BEA-090504> <Certificate chain received from cluster2.yourdomain.com – 192.168.1.41 failed hostname verification check. Certificate contained cluster1.yourdomain.com but check expected cluster2.yourdomain.com>

 

 

Solution:

On web console – change/remove IP/hostname

 

As root / admin supersuser:

 

– Stop Weblogic Webserver 

As this is RHEL Linux, to stop WLS use standard init script start / stop service command

 

service wls stop

 

– As Application user create directory where new key will be created

 

mkdir /home/uwls11pp/tmp_key
cd /home/uwls11pp/tmp_key

 

– Make backup of current JKS (Keystore File)

 

cp /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks_11032015

 

– Execute set env . script

 

/WLS/app/oracle/wls1036/wlserver_10.3/server/bin/setWLSEnv.sh

 

– Copy & paste output from script above and export variables

 

export CLASSPATH;
export PATH;

 

– Check old certificate in keystore

 

/WLS/app/oracle/jdk1.7.0_25/bin/keytool -list -v -keystore /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks  -storepass DemoIdentityKeyStorePassPhrase

 

– Delete old Weblogic keystore JKS file

 

/WLS/app/oracle/jdk1.7.0_25/bin/keytool -delete -alias demoidentity -keystore /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks -storepass DemoIdentityKeyStorePassPhrase

 

– Check wether proper Java version is used

 

java -version

 

– Get hostname from hosts file

 

cat /etc/hosts

 

#Replace weblogic1 with your FQDN (Fully Qualified Domain Name) – this step will create new certificate with new hostname

 

java utils.CertGen -cn weblogic1 -keyfilepass DemoIdentityPassPhrase -certfile newcert -keyfile newkey

 

#Import certificate to “official” keystore

 

java utils.ImportPrivateKey -keystore /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks -storepass DemoIdentityKeyStorePassPhrase -keyfile newkey.pem -keyfilepass DemoIdentityPassPhrase -certfile newcert.pem -alias demoidentity

 

#Recheck once again if correct certificate is in use

 

/WLS/app/oracle/jdk1.7.0_25/bin/keytool -list -v -keystore /WLS/app/oracle/wls1036/wlserver_10.3/server/lib/DemoIdentity.jks  -storepass DemoIdentityKeyStorePassPhrase


– Finally issue as root user restart Weblogic server again

 

 

service wls start

How to SSH client Login to server with password provided from command line as a script argument – Running same commands to many Linux servers

Friday, March 6th, 2015

ssh-how-to-login-with-password-provided-from-command-line-use-sshpass-to-run-same-command-to-forest-of-linux-servers

Usually admins like me who casuanlly need to administer "forests" (thousands of identicallyconfigured services Linux servers) are generating and using RSA / DSA key authentication for passwordless login, however this is not always possible as some client environments does prohibit the use of RSA / DSA non-pass authentication, thus in such environments to make routine server basic package rpm / deb upgrades or do other maintanance patching its necessery to use normal ssh user / pass login but as ssh client doesn't allow password to be provided from prompt for security reasons and therefore using some custom bash loop to issue single command to many servers (such as explained in my previous article) requires you to copy / paste password on password prompt multiple times. This works its pretty annoying so if you want to run single command on all your 500 servers with specifying the password from password prompt use sshpass tool (for non-interactive ssh password auth).

SSHPASS official site description:
 

sshpass is a utility designed for running ssh using the mode referred to as "keyboard-interactive" password authentication, but in non-interactive mode.

 

Install sshpass on Debian / Ubuntu (deb based) Linux

sshpass is installable right out of regular repositories so to install run:
 

apt-get install —yes sshpass


Install sshpass on CentOS / Fedora (RPM based) Linux


sshpass is available also across most RPM based distros too so just use yum package manager

 

yum -y install sshpass


If its not available across standard RPM distro provided repositories, there should be RPM on the net for distro just download latest one and use wget and rpm to install:

 wget -q http://dl.fedoraproject.org/pub/epel/6/x86_64/sshpass-1.05-1.el6.x86_64.rpm

 rpm -ivh sshpass-1.05-1.el6.x86_64.rpm

 

How Does SshPass Works?

 

Normally openssh (ssh) client binary uses direct TTY (/dev/tty)= an abbreviation for PhyTeleTYpewriter or (the admin jargon call Physical Console access)  instead of standard remotely defined /dev/ptsVirtual PTY.
To get around this Sshpass runs ssh in a dedicated TTY to emulate the password is indeed issues by interactive keyboard user thus  fooling remote sshd server to thinking password
is provided by interactive user.


SSHPass use

Very basic standard use which allows you to pass the password from command line is like this:
 

sshpass -p 'Your_Password_Goes_here123' ssh username@server.your-server.com


Note that the server you're working is shared with other developers they might be able to steal your username / password by using a simple process list command such as:
 

 ps auxwwef


In my case security is not a hot issue, as I'm the only user on the server (and only concern might be if someone hacks into the server 🙂 

 

Then assuming that you have a plain text file with all your administered servers, you can easily use sshpass in a Bash Script loop in order to run, lets say a package upgrade across all identical Linux version machines:
 

while read line; do
sshpass -p 'Your_Password_Goes_here123' ssh username@$line "apt-get update && apt-get upgrade && apt-get dist-upgrade" < /dev/null;
done < all_servers_list.txt

Change the command you like to issue across all machines with the string "apt-get …"
Above command can be used to keep up2date all Debian stable server packages. What you will do on servers is up to your imaginations, very common use of above line would be if you want to see uptime /netstat command output across all your network servers.

 

while read line; do
sshpass -p 'Your_Password_Goes_here123' ssh username@$line "uptime; who; netstat -tunlp; " < /dev/null;
done < all_servers_list.txt

 


As you can guess SshPass is swiss army knife tool for admins whoneed to automate things with scripts simultaneously across number of servers.
 

Happy SSH-ing 🙂

 

 

 

How to check who is flooding your Apache, NGinx Webserver – Real time Monitor statistics about IPs doing most URL requests and Stopping DoS attacks with Fail2Ban

Wednesday, August 20th, 2014

check-who-is-flooding-your-apache-nginx-webserver-real-time-monitoring-ips-doing-most-url-requests-to-webserver-and-protecting-your-webserver-with-fail2ban

If you're Linux ystem administrator in Webhosting company providing WordPress / Joomla / Drupal web-sites hosting and your UNIX servers suffer from periodic denial of service attacks, because some of the site customers business is a target of competitor company who is trying to ruin your client business sites through DoS or DDOS attacks, then the best thing you can do is to identify who and how is the Linux server being hammered. If you find out DoS is not on a network level but Apache gets crashing because of memory leaks and connections to Apache are so much that the CPU is being stoned, the best thing to do is to check which IP addresses are causing the excessive GET / POST / HEAD requests in logged.
 

There is the Apachetop tool that can give you the most accessed webserver URLs in a refreshed screen like UNIX top command, however Apachetop does not show which IP does most URL hits on Apache / Nginx webserver. 

 

1. Get basic information on which IPs accesses Apache / Nginx the most using shell cmds


Before examining the Webserver logs it is useful to get a general picture on who is flooding you on a TCP / IP network level, with netstat like so:
 

# here is howto check clients count connected to your server
netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n


If you get an extensive number of connected various IPs / hosts (like 10000 or something huge as a number), depending on the type of hardware the server is running and the previous scaling planned for the system you can determine whether the count as huge as this can be handled normally by server, if like in most cases the server is planned to serve a couple of hundreds or thousands of clients and you get over 10000 connections hanging, then your server is under attack or if its Internet server suddenly your website become famous like someone posted an article on some major website and you suddenly received a tons of hits.


There is a way using standard shell tools, to get some basic information on which IP accesses the webserver the most with:

tail -n 500 /var/log/apache2/access.log | cut -d' ' -f1 | sort | uniq -c | sort -gr

Or if you want to keep it refreshing periodically every few seconds run it through watch command:

watch "tail -n 500 /var/log/apache2/access.log | cut -d' ' -f1 | sort | uniq -c | sort -gr"

monioring-access-hits-to-webserver-by-ip-show-most-visiting-apache-nginx-ip-with-shell-tools-tail-cut-uniq-sort-tools-refreshed-with-watch-cmd


Another useful combination of shell commands is to Monitor POST / GET / HEAD requests number in access.log :
 

 awk '{print $6}' access.log | sort | uniq -c | sort -n

     1 "alihack<%eval
      1 "CONNECT
      1 "fhxeaxb0xeex97x0fxe2-x19Fx87xd1xa0x9axf5x^xd0x125x0fx88x19"x84xc1xb3^v2xe9xpx98`X'dxcd.7ix8fx8fxd6_xcdx834x0c"
      1 "x16x03x01"
      1 "xe2
      2 "mgmanager&file=imgmanager&version=1576&cid=20
      6 "4–"
      7 "PUT
     22 "–"
     22 "OPTIONS
     38 "PROPFIND
   1476 "HEAD
   1539 "-"
  65113 "POST
 537122 "GET


However using shell commands combination is plenty of typing and hard to remember, plus above tools does not show you, approximately how frequenty IP hits the webserver

 

2. Real-time monitoring IP addresses with highest URL reqests with logtop

 


Real-time monitoring on IP addresses with highest URL requests is possible with no need of "console ninja skills"  through – logtop.

 

2.1 Install logtop on Debian / Ubuntu and deb derivatives Linux

 


a) Installing Logtop the debian way

LogTop is easily installable on Debian and Ubuntu in newer releases of Debian – Debian 7.0 and Ubuntu 13/14 Linux it is part of default package repositories and can be straightly apt-get-ed with:

apt-get install –yes logtop

b) Installing Logtop from source code (install on older deb based Linuxes)

On older Debian – Debian 6 and Ubuntu 7-12 servers to install logtop compile from source code – read the README installation instructions or if lazy copy / paste below:

cd /usr/local/src
wget https://github.com/JulienPalard/logtop/tarball/master
mv master JulienPalard-logtop.tar.gz
tar -zxf JulienPalard-logtop.tar.gz

cd JulienPalard-logtop-*/
aptitude install libncurses5-dev uthash-dev

aptitude install python-dev swig

make python-module

python setup.py install

make

make install

 

mkdir -p /usr/bin/
cp logtop /usr/bin/


2.2 Install Logtop on CentOS 6.5 / 7.0 / Fedora / RHEL and rest of RPM based Linux-es

b) Install logtop on CentOS 6.5 and CentOS 7 Linux

– For CentOS 6.5 you need to rpm install epel-release-6-8.noarch.rpm
 

wget http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
rpm -ivh epel-release-6-8.noarch.rpm
links http://dl.fedoraproject.org/pub/epel/6/SRPMS/uthash-1.9.9-6.el6.src.rpm
rpmbuild –rebuild
uthash-1.9.9-6.el6.src.rpm
cd /root/rpmbuild/RPMS/noarch
rpm -ivh uthash-devel-1.9.9-6.el6.noarch.rpm


– For CentOS 7 you need to rpm install epel-release-7-0.2.noarch.rpm

 

links http://download.fedoraproject.org/pub/epel/beta/7/x86_64/repoview/epel-release.html
 

Click on and download epel-release-7-0.2.noarch.rpm

rpm -ivh epel-release-7-0.2.noarch
rpm –import /etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7
yum -y install git ncurses-devel uthash-devel
git clone https://github.com/JulienPalard/logtop.git
cd logtop
make
make install

 

2.3 Some Logtop use examples and short explanation

 

logtop shows 4 columns as follows – Line number, Count, Frequency, and Actual line

 

The quickest way to visualize which IP is stoning your Apache / Nginx webserver on Debian?

 

tail -f access.log | awk {'print $1; fflush();'} | logtop

 

 

logtop-check-which-ip-is-making-most-requests-to-your-apache-nginx-webserver-linux-screenshot

On CentOS / RHEL

tail -f /var/log/httpd/access_log | awk {'print $1; fflush();'} | logtop

 

Using LogTop even Squid Proxy caching server access.log can be monitored.
To get squid Top users by IP listed:

 

tail -f /var/log/squid/access.log | awk {'print $1; fflush();'} | logtop


logtop-visualizing-top-users-using-squid-proxy-cache
 

Or you might visualize in real-time squid cache top requested URLs
 

tail -f /var/log/squid/access.log | awk {'print $7; fflush();'} | logtop


visualizing-top-requested-urls-in-squid-proxy-cache-howto-screenshot

 

3. Automatically Filter IP addresses causing Apache / Nginx Webservices Denial of Service with fail2ban
 

Once you identify the problem if the sites hosted on server are target of Distributed DoS, probably your best thing to do is to use fail2ban to automatically filter (ban) IP addresses doing excessive queries to system services. Assuming that you have already installed fail2ban as explained in above link (On Debian / Ubuntu Linux) with:
 

apt-get install –yes fail2ban


To make fail2ban start filtering DoS attack IP addresses, you will have to set the following configurations:
 

vim /etc/fail2ban/jail.conf


Paste in file:
 

[http-get-dos]
 
enabled = true
port = http,https
filter = http-get-dos
logpath = /var/log/apache2/WEB_SERVER-access.log
# maxretry is how many GETs we can have in the findtime period before getting narky
maxretry = 300
# findtime is the time period in seconds in which we're counting "retries" (300 seconds = 5 mins)
findtime = 300
# bantime is how long we should drop incoming GET requests for a given IP for, in this case it's 5 minutes
bantime = 300
action = iptables[name=HTTP, port=http, protocol=tcp]


Before you paste make sure you put the proper logpath = location of webserver (default one is /var/log/apache2/access.log), if you're using multiple logs for each and every of hosted websites, you will probably want to write a script to automatically loop through all logs directory get log file names and automatically add auto-modified version of above [http-get-dos] configuration. Also configure maxtretry per IP, findtime and bantime, in above example values are a bit low and for heavy loaded websites which has to serve thousands of simultaneous connections originating from office networks using Network address translation (NAT), this might be low and tuned to prevent situations, where even the customer of yours can't access there websites 🙂

To finalize fail2ban configuration, you have to create fail2ban filter file:

vim /etc/fail2ban/filters.d/http-get-dos.conf


Paste:
 

# Fail2Ban configuration file
#
# Author: http://www.go2linux.org
#
[Definition]
 
# Option: failregex
# Note: This regex will match any GET entry in your logs, so basically all valid and not valid entries are a match.
# You should set up in the jail.conf file, the maxretry and findtime carefully in order to avoid false positives.
 
failregex = ^<HOST> -.*"(GET|POST).*
 
# Option: ignoreregex
# Notes.: regex to ignore. If this regex matches, the line is ignored.
# Values: TEXT
#
ignoreregex =


To make fail2ban load new created configs restart it:
 

/etc/init.d/fail2ban restart


If you want to test whether it is working you can use Apache webserver Benchmark tools such as ab or siege.
The quickest way to test, whether excessive IP requests get filtered – and make your IP banned temporary:
 

ab -n 1000 -c 20 http://your-web-site-dot-com/

This will make 1000 page loads in 20 concurrent connections and will add your IP to temporary be banned for (300 seconds) = 5 minutes. The ban will be logged in /var/log/fail2ban.log, there you will get smth like:

2014-08-20 10:40:11,943 fail2ban.actions: WARNING [http-get-dos] Ban 192.168.100.5
2013-08-20 10:44:12,341 fail2ban.actions: WARNING [http-get-dos] Unban 192.168.100.5

Extracting pages and page ranges, protect with password and remove password from PDF on GNU / Linux with QPDF – Linux Manipulating PDF files from command line

Friday, August 8th, 2014

qpdf-logo-extract-pages-page-ranges-protect-pdf-with-password-remove-password-from-pdf-linux-qpdf-manipulating-pdf-files-on-gnu-linux-and-bsd
If're a Linux user and you need to script certain page extraction from PDF files, crypt protect with password a PDF file or decrypt (remote password protection from PDF) or do some kind of structural transformation of existing PDF file you can use a QPDF command line utility. qpdf is in active development and very convenient tool for Website developers (PHP / Perl / Python), as often on websites its necessery to write code to cut / tailer / restructure PDFs.

1. Install QPDF from deb / rpm package

qpdf is instalalble by default in deb repositories on Debian / Ubuntu GNU / (deb derivative) Linux-es to install it apt-get it

apt-get install –yes qpdf

On RPM based distribution CentOS / SuSE / RHEL / Fedora Linux to install qpdf, fetch the respective distribution binary from rpmfind.net or to install latest version of qpdf build it from source code.

2. Install QPDF from source

To build latest qpdf from source

  • on RPM based distributions install with yum fullowing packages:

yum -y install zlib-devel pcre-devel gcc gcc-c++

  • on Deb based Linuces, you will need to install

apt-get install –yes build-essential gcc dpkg-dev g++ zlib1g-dev


Then to build gather latest qpdf source from here

 

cd /usr/local/src
wget -q http://www.pc-freak.net/files/qpdf-5.1.2.tar.gz
tar -zxvf qpdf-5.1.2.tar.gz
cd qpdf-5.1.2/
./configure
make
make install


Once it is installed, if you get error on qpdf runtime:
 

/usr/local/bin/qpdf: error while loading shared libraries: libqpdf.so.13: cannot open shared object file: No such file or directory

To solve the error find in your compile directory libqpdf.so.13 and copy it to /usr/lib or /usr/local/lib

 cp -rpf ./libqpdf/build/.libs/libqpdf.so.13 /usr/local/lib


3. Decrypt password encrypted (protected) PDF file

if you have time and you like reading be sure to check the extensive qpdf-manual.

To remove password from a PDF file protected with a password with qpdf

qpdf –password=SECRET-PASSWORD –decrypt input-file.pdf output-file.pdf

QPDF has a vast range of split and merge features. It can combine all the files in a folder (*.pdf), you can use it to try to recover damaged pdf files, extract individual pages from PDF, dump and reverse page range, make new created PDF with old PDF's reversed pages (pages 1,2,3,4 to become in order 4,3,2,1), apply some single pdf file metadata to multiple files.

4. Try to Recover damaged PDF file


To try to recover some damaged file with qpdf:
 

qpdf file-to-repair.pdf repaired-file.pdf

5. Extract certain pages or page range from PDF

It is recommended to use the version built from source to extract certain page range from PDF
 

/usr/local/bin/qpdf –empty –pages input-file.pdf 1-5 — outfile-file.pdf


If you wanted to take pages 1–5 from file1.pdf and pages 11–15 from file2.pdf in reverse, you would run
 

qpdf file1.pdf –pages file1.pdf 1-5 file2.pdf 15-11 — outfile.pdf

 

Make Apache webserver fix spelling mistyped URL errors and serve files case insensitive with mod_speling

Wednesday, July 16th, 2014

make_apache_fix_mistyped_spelling_urls_errors_and_serve_files_case_insensitive_mod_speling_logo
On most if not all modern GNU / Linux distributions, Apache webserver comes preinstalled with mod_speling.

What mod_speling does is it tries to find and serve files and directories for non-existing  (404 return code) urls with a similar name to passed URL. Other thing mod_speling does is it serves files case-insensitive, even though the UNIX / Linux filesystems are built to understand files case-sensitive.

mod_speling is a very useful module especially when files are being pushed (synchronized) to Apache visible from web document folder from operating systems like Windows whose filesystem doesn't store files case sensitive.

Let me give you a small example on M$ Windows a create file NewFile.html, NEWFILE.HTML, NeWfIlE.Html etc. are one and the same file newfile.html and not 3 different files like it is usually on UNIX / Linux filesystems.

If you happen to migrate old static Websites from Microsoft Internet Information Services (IIS) to UNIX / Linux based hosting. Often Html coders which create websites on Windows platform doesn't respect in website hyperlinks case-sensitive, because anyways Windows FS is case-insetive, thus moving the website to Linux host with Apache the website/s will end up with many 404 error pages, whose fixing for big static websites will be a real pain in the ass.

Also there might be need for mod_speling module enabled, for PHP / Python / Perl websites developed on MS Windows platform and tested on Windows host and then officially to be deployed on Linux.

Note that mod_speling name as a funny thing as actually the module is also converting mis-pelled / mis-typed Apache URLs:

If for example, someone tried to link to your website from a forum mistyping the URL address with mod_speling the mistyped URL could still be handled to open the real existing URL:

Lets say you have URL:
 

http://your-domain.com/files/what-Ever-fle.php


and the actual URL is:

http://your-domain.com/files/what-Ever-file.php

 

mod_speling will make Apache scan in /files/ for any files with similar name to what-Ever-fle.php and will open any similar matched file name, preventing you from the normal 404 error and therefore often serving exactly what it has to. Of course such a behavior could be unwanted in same cases for CMSes, which depend on 404 error code for proper operating, so be very sure when configuring mod_speling that this is exactly what you need.

mod_speling can be also useful sometimes for Search Engine Optimization – SEO, as it will show less 404 pages to Crawler search engine bots.

1. Enable mod_speling module on Debian GNU / Linux and Ubuntu

Enabling mod_speling in Apache in Debian / Ubuntu etc. debian based Linuxes is done with either creating symlink from /etc/apache2/mods-available/speling.load to /etc/apache2/mods-enabled/speling.load :
 

ln -sf /etc/apache2/mods-available/speling.load /etc/apache2/mods-enabled/speling.load

Or by using a2enmodDebian apache module enabling script:
 

a2ensite sitename


To enable mod_speling mis-speling resolve feature config directive is:

 

CheckSpelling on


To disable case sensitivity – as I said earlier helpful for migrations from Microsoft Windows hosts to Linux, use directive:

CheckCaseOnly on


To enable both use:

<IfModule mod_speling.c>
    CheckCaseOnly on
    CheckSpelling on
</IfModule>

Enabling mod_speling case-insensitivity and fixing mistypes in URL could be done from .htaccess, for any <Directory> (vhost) with enabled .htaccess with

AllowOverride All

To enable it for default set host in new Apache install place it in /etc/apache2/apache2.conf and /etc/apache2/sites-enabled/000-default

Then as usual to make the configuration changes take affect, restart Apache:
 

/etc/init.d/apache2 restart


2. Enablig mod_speling on CentOS, RHEL and Fedora Linux

 

Most of RPM based Linux distributions have already mod_speling by default in Apache, so there will be no need to explicitly enable the module within HTTPD.

To check whether mod_speling is already enabled in httpd issue:
 

/usr/sbin/httpd -M |grep -i mod_speling


If you don't get no output from command this means the module is not enabled. This is the case with CentOS Linux 6.5 for example …

To enable mod_speling on Apache level add in /etc/httpd/conf/httpd.conf

LoadModule speling_module modules/mod_speling.so

and restart webserver
 

/etc/init.d/httpd restart


If you get instead
 

/usr/sbin/httpd -M |grep -i mod_speling
speling_module (shared)

 

Then it is already loaded in HTTPD to enable the module for default domain add to /etc/httpd/conf/httpd.conf – within (<Directory "/var/www/html">),

<IfModule mod_speling.c>
    CheckCaseOnly on
    CheckSpelling on
</IfModule>

Or if you want to make it active for specific directories within /var/www/html/whatever-dir use either new <Directory ..> directive within Apache config, or enable .htaccess processing with AllowOverride All and place them in .htaccess . For complete mod_speling reference check on Apache's official website