Posts Tagged ‘Stop’

How to start / Stop and Analyze system services and improve Linux system boot time performance

Friday, July 5th, 2019

systemd-components-systemd-utilities-targets-cores-libraries
This post is going to be a very short one and to walk through shortly to System V basic start / stop remove service old way and the new ways introduced over the last 10 years or so with the introduction of systemd on mass base across Linux distributions.
Finally I'll give you few hints on how to check (analyze) the boot time performance on a modern GNU / Linux system that is using systemd enabled services.
 

1. System V and the old days few classic used ways to stop / start / restart services (runlevels and common wrapper scripts)

 

The old fashioned days when Linux was using SystemV / e.g. no SystemD used way was to just go through all the running services with following the run script logic inside the runlevel the system was booting, e.g. to check runlevel and then potimize each and every run script via the respective location of the bash service init scripts:

 

root@noah:/home/hipo# /sbin/runlevel 
N 5

 

Or on some RPM based distros like Fedora / RHEL / SUSE Enterprise Linux to use chkconfig command, e.g. list services:

~]# chkconfig –list

etworkManager  0:off   1:off   2:on    3:on    4:on    5:on    6:off
abrtd           0:off   1:off   2:off   3:on    4:off   5:on    6:off
acpid           0:off   1:off   2:on    3:on    4:on    5:on    6:off
anamon          0:off   1:off   2:off   3:off   4:off   5:off   6:off
atd             0:off   1:off   2:off   3:on    4:on    5:on    6:off
auditd          0:off   1:off   2:on    3:on    4:on    5:on    6:off
avahi-daemon    0:off   1:off   2:off   3:on    4:on    5:on    6:off

And to start stop the service into (default runlevel) or respective runlevel:

 

~]#  chkconfig httpd on

~]# chkconfig –list httpd
httpd            0:off   1:off   2:on    3:on    4:on    5:on    6:off

 

 

~]# chkconfig service_name on –level runlevels

 


Debian / Ubuntu and other .deb based distributions with System V (which executes scripts without single order but one by one) are not having natively chkconfig but instead are famous for update-rc.d init script wrapper, here is few basic use  of it:

update-rc.d <service> defaults
update-rc.d <service> start 20 3 4 5
update-rc.d -f <service>  remove

Here defaults means default set boot runtime for system and numbers are just whether service is started or stopped for respective runlevels. To check what is your default one simply run /sbin/runlevel

Other useful tool to stop / start services and analyze what service is running and which not in real time (but without modifying boot time set for a service) – more universal nowadays is to use the service command.

root@noah:/home/hipo# service –status-all
 [ + ]  acpid
 [ – ]  alsa-utils
 [ – ]  anacron
 [ + ]  apache-htcacheclean
 [ – ]  apache2
 [ + ]  atd
 [ + ]  aumix

root@noah:/home/hipo# service cron restart/usr/sbin/service command is just a simple wrapper bash shell script that takes care about start / stop etc. operations of scripts found under /etc/init.d

For those who don't want to tamper with too much typing and manual configuration there is an all distribution system V compatible ncurses interface text itnerface sysv-rc-conf which could make your life easier on configuring services on non-systemd (old) Linux-es.

To install on Debian distros:

debian:~# apt-get install sysv-rc-conf

debian:~# sysv-rc-conf


SysV RC Conf desktop on GNU Linux using sysv-rc-conf systemV and systemd
 

2. SystemD basic use Start / stop check service and a little bit of information
for the novice

As most Linux kernel based distributions except some like Slackware and few others see the full list of Linux distributions without systemd (and aha yes slackw. users loves rc.local so much – we all do 🙂  migrated and are nowadays using actively SystemD, to start / stop analyze running system runnig services / processes

systemctl – Control the systemd system and service manager

To check whether a service is enabled

systemctl is-active application.service

To check whether a unit is in a failed state

systemctl is-failed application.service

To get a status of running application via systemctl messaging

# systemctl status sshd
● ssh.service – OpenBSD Secure Shell server Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled) Active: active (running) since Sat 2019-07-06 20:01:02 EEST; 2h 3min ago Main PID: 1335 (sshd) Tasks: 1 (limit: 4915) CGroup: /system.slice/ssh.service └─1335 /usr/sbin/sshd -D юли 06 20:01:00 noah systemd[1]: Starting OpenBSD Secure Shell server… юли 06 20:01:02 noah sshd[1335]: Server listening on 0.0.0.0 port 22. юли 06 20:01:02 noah sshd[1335]: Server listening on :: port 22. юли 06 20:01:02 noah systemd[1]: Started OpenBSD Secure Shell server.

To enable / disable application with systemctl systemctl enable application.service

systemctl disable application.service

To stop / start given application systemcl stop sshd

systemctl stop tor

To reload running application

systemctl reload sshd

Some applications does not have the right functionality in systemd script to reload configuration without fully restarting the app if this is the case use systemctl reload-or-restart application.service

systemctl list-unit-files

Then to view the content of a single service unit file:

:~# systemctl cat apache2.service
# /lib/systemd/system/apache2.service
[Unit]
Description=The Apache HTTP Server
After=network.target remote-fs.target nss-lookup.target

[Service]
Type=forking
Environment=APACHE_STARTED_BY_SYSTEMD=true
ExecStart=/usr/sbin/apachectl start
ExecStop=/usr/sbin/apachectl stop
ExecReload=/usr/sbin/apachectl graceful
PrivateTmp=true
Restart=on-abort

[Install]
WantedBy=multi-user.target


converting-traditional-init-scripts-to-systemd-graphical-diagram

systemd's advancement over normal SystemV services it is able to track and show dependencies
of a single run service for proper operation on other services

:~# systemctl list-dependencies sshd.service

 


● ├─system.slice
● └─sysinit.target
●   ├─dev-hugepages.mount
●   ├─dev-mqueue.mount
●   ├─keyboard-setup.service
●   ├─kmod-static-nodes.service
●   ├─proc-sys-fs-binfmt_misc.automount
●   ├─sys-fs-fuse-connections.mount
●   ├─sys-kernel-config.mount
●   ├─sys-kernel-debug.mount
●   ├─systemd-ask-password-console.path
●   ├─systemd-binfmt.service
….

.

 

You can also mask / unmask service e.g. make it temporary unavailable via systemd with

sudo systemctl mask nginx.service

it will then appear as masked if you do list-unit-files

If you want to change something on a systemd unit file this is done with

systemctl edit –full nginx.service

In case if some modificatgion was done to systemd service files e.g. lets say to
/etc/systemd/system/apache2.service or even you've made a Linux system Upgrade recently
that added extra systemd service config files it will be necessery to reload all files
present in /etc/systemd/system/* with:

systemctl daemon-reload


Systemd has a target states which are pretty similar to the runlevel concept (e.g. runlevel 5 means graphical etc.), for example to check the default target for a system:

One very helpful feature is to restart systemd but it seems this is not well documented as of now and though this might work after some system package upgrade roll-outs it is always better to reboot the system, but you can give it a try if restart can't be done due to application criticallity.

To restart systemd and its spawned subprocesses do:
 

systemctl daemon-reexec

 

root@noah:/home/hipo# systemctl get-default
graphical.target


 to check all targets possible targets

root@noah:/home/hipo# systemctl list-unit-files –type=target
UNIT FILE                 STATE   
basic.target              static  
bluetooth.target          static  
busnames.target           static  
cryptsetup-pre.target     static  
cryptsetup.target         static  
ctrl-alt-del.target       disabled
default.target            static  
emergency.target          static  
exit.target               disabled
final.target              static  
getty.target              static  
graphical.target          static  

you can put the system in Single user mode if you like without running the good old well known command:

/sbin/init 1 

command with

systemctl rescue

You can even shutdown / poweroff / reboot system via systemctl (though I never did that and I don't recommend) 🙂
To do so use:

systemctl halt
systemctl poweroff
systemctl reboot


For the lazy ones that don't want to type all the time like crazy to configure and manage simple systemctl set services take a look at chkservice – an ncurses text based menu systemctl management interface

As chkservice is relatively new it is still not present in stable Stretch Debian repositories but it is in current testing Debian unstable Buster / Sid – Testing / Unstable distribution and has installable package for Ubuntu / Arch Linux and Fedora

chkservice-Linux-systemctl-ncurses-text-menu-service-management-interface-start-chkservice
Picture Source Tecmint.com

chkservice linux help screen


3. Analyzing and fix performance boot slowness issues due to a service taking long to boot


The first very useful thing is to know how long exactly all daemons / services got booted
on your GNU / Linux OS.

linux-server:~# systemd-analyze 
Startup finished in 4.135s (kernel) + 3min 47.863s (userspace) = 3min 51.998s

As you can see it reports both the kernel boot time and userspace (surrounding services
that had to boot for the system to be considered fully booted).


Once you have the system properly booted you have a console or / ssh access

root@pcfreak:/home/hipo# systemd-analyze blame
    2min 14.172s tor@default.service
    1min 40.455s docker.service
     1min 3.649s fail2ban.service
         58.806s nmbd.service
         53.992s rc-local.service
         51.458s systemd-tmpfiles-setup.service
         50.495s mariadb.service
         46.348s snort.service
         34.910s ModemManager.service
         33.748s squid.service
         32.226s ejabberd.service
         28.207s certbot.service
         28.104s networking.service
         23.639s munin-node.service
         20.917s smbd.service
         20.261s tinyproxy.service
         19.981s accounts-daemon.service
         18.501s loadcpufreq.service
         16.756s stunnel4.service
         15.575s oidentd.service
         15.376s dev-sda1.device
         15.368s courier-authdaemon.service
         15.301s sysstat.service
         15.154s gpm.service
         13.276s systemd-logind.service
         13.251s rsyslog.service
         13.240s lpd.service
         13.237s pppd-dns.service
         12.904s NetworkManager-wait-online.service
         12.540s lm-sensors.service
         12.525s watchdog.service
         12.515s inetd.service


As you can see you get a list of services time took to boot in secs and you can
further debug each of it to find out why it boots so slow (netwok / DNS / configuration isssue whatever).

On a servers it is useful to look up for some processes slowing it down like gdm.service etc.

 

Close up words rant on SystemD vs SysemV

init-and-systemd-comparison-commands-linux-booting-1

A lot could be ranted on what is better systemd or systemV. I personally hated systemd since day since I saw it being introduced first in Fedora / CentOS linuxes and a bit later in my beloved desktop used Debian Linux.
I still remember the bugs and headaches with systemd's intruduction as it is with all new the early adoption of technology makes a lot of pain in the ass.
Eventually systemd has become a standard and with my employment as a contractor through Itelligence GmBH for SAP AG I now am forced to work with systemd daily on SLES 12 based Linuces and I was forced to get used to it. 
But still there is my personal preference to SystemV even though the critics of slow boot etc.but for managing a multitude of Linux preinstalled servers like Virtual Machines and trying to standardize a Data Center with Tens of Thousands of Linuxes running on different Hypervisors VMWare / OpenXen + physical hosts etc. systemd brings a bit of more standardization that makes it a winner.

* How to stop unattended upgrades on Debian / Ubuntu and other deb based Linux

Saturday, July 21st, 2018

If you wondered how to stop the annoying automatic upgrades that push unknown software in background loading the computer while you browse or work and Why here is how:

* 1. Stop Annoying Unattended Upgrades on Debian and Ubuntu Linux

As root you have to execute following command
linux:~# apt-get remove –yes unattended-upgrades

And TA DA DAAA DAA DAaM !!!
 

* From now if you like to upgrade to latest in order to upgrade you can do it manually with these 3 commands:

linux:~# apt-get update && apt-get upgrade && apt-get dist-upgrade dist-upgrade

Your thanks to me are very welcome

Stop contact form spam emails in Joomla, Disable “E-mail a copy of this message to your own address.” in Joomla

Friday, April 11th, 2014

email-copy-of-this-message-to-your-own-address_Contact_email_form
If you happen to have installed Joomla based website and setup a contact form and everything worked fine until recently but suddenly your server starts mysteriously acting as a spam relay – even though email server is perfectly secured against spam.
You probably have some issue with a website email contact form hacked or some vulnerability which allowed hackers to upload spammer php script.

I have a website based on Joomla and just until recently everything was okay until I noticed there are tons of spam flying out from my Qmail mail server (which is configured to check spam with Spamassassin has Bayesian Filtering, Distributed Checksum Claring House, Python Razor and plenty of custom anti-spam rules.

It was just yesterday I ended into that situation, then after evaluating all the hosted website, I've realized Spam issues are caused by an Old Joomla Website Contact form!

There were two issues in the form

in the contact form you have the field with a tick:

1. Well Known Joomla Form Vulnerability
Currently all Joomla (including 1.5.22 and 1.6 versions) are vulnerable to a serious spam relay problem as described in the official Joomla site.

There is a quick dirty workaround fix to contact form vulnerability –  disable a Joomla Comonent in ../joomla/components/com_mailto/

To disable it I had to:

cd /var/www/joomla/components
mv com_mailto com_mailtoNOT_USED

Above solution was described under a post resolve joomla spam relay earlier by Anatoliy Dimitrov (after checking closely the website it happened he is a colleague at HP 🙂 )

2. Second issue causing high amount of spam sent over the email server
was: "E-mail a copy of this message to your own address." contact form tick, which was practically enabling any Spammer with a list to inect emails and spam via the form sending copies to any email out on the internet!

You would definitely want to disable  "E-mail a copy of this message to your own address."
I wonder why ever any Joomla developer came up with this "spam form"?? 

joomla-disable-email-copy-of-this-message-to-your-own-address

Here is the solution to this:

1. Login to Joomla Admin with admin account
2. Goto Components -> Contacts -> Contacts
3. Click on the relevant Contact form
4. Under Contact Parameters go to Email Parameters
5. Change field E-mail Copy from Show to Hide and click Apply button

And Hooray the E-mail a copy of this message to your own address will be gone from contact form! 🙂

I've seen already plenty of problematic hacked servers and scripts before with Joomla in my last job in International University College – where joomla was heavy used, but I never experienced Joomla Security issues myself 'till know, in future I'm planning to never ever use joomla. Though it is an easy CMS system to setup a website its quite complicated to learn the menus – I remember when creating the problematic website it took me days until I properly setup all the menus and find all joomla components … besides these there is no easy way to migrate between different versions major releases in Joomla like in Wordperss, I guess this Mail Security Issue absolutely convinced me to quit using that piece of crap in future.

In mean Time another very serious Apache security flaw leaked on the Internet just few days ago – The OpenSSL Hearbleed Bug. Thanksfully I'm not running SSL anywhere on my website but many systems are affecting making most of your SSL communication with your Internet banking, E-mail etc. in danger. If you're running Apache with SSL make sure you test it for this vulnerability. Here is description of Heartbleed SSL Critical Vulnerability.

heartbleed_ssl_remote_vulnerability_logo

"The Heartbleed Bug is a serious vulnerability in the popular OpenSSL cryptographic software library. This weakness allows stealing the information protected, under normal conditions, by the SSL/TLS encryption used to secure the Internet. SSL/TLS provides communication security and privacy over the Internet for applications such as web, email, instant messaging (IM) and some virtual private networks (VPNs).

The Heartbleed bug allows anyone on the Internet to read the memory of the systems protected by the vulnerable versions of the OpenSSL software. This compromises the secret keys used to identify the service providers and to encrypt the traffic, the names and passwords of the users and the actual content. This allows attackers to eavesdrop on communications, steal data directly from the services and users and to impersonate services and users."

11

 

Make QMAIL with vpopmail vchkpw, courier-authlib and courier-imap auth work without MySQL on Debian Linux qmailrocks Thibs install

Friday, September 28th, 2012

How to make qmail vpopmail vchkpw courier-authlib and courier-imap work storing mails on hard disk with qmailrocks Thibs install

Recently installed a new QMAIL, following mostly Thibs Qmailrocks install guide. I didn’t followed literally Thibs good guide, cause in his guide in few of the sections like Install Vpopmail he recommends using MySQL as a Backend to store Vpopmail email data and passwords; I prefer storing all vpopmail data on the file system as I believe it is much better especially for tiny QMAIL mail servers with less than 500 mail box accounts.

In this little article I will explain, how I made Vpopmail courier-authlib and courier-imap play nice together without storing data in SQL backend.

1. Compile vpopmail with file system data storage support

So here is how I managed to make vpopmail + courier-authlib + courier-imap, work well together:

First its necessery to compile Vpopmailin store all its users data and mail data on file system. For this in Thibs Vpopmail Intsall step compiled Vpopmail without support for MySQL, e.g. instead of using his pointed compile time ./configure, arguments I used:


# cd /downloads/vpopmail-5.4.33
# ./configure \
--enable-qmaildir=/var/qmail/ \
--enable-qmail-newu=/var/qmail/bin/qmail-newu \
--enable-qmail-inject=/var/qmail/bin/qmail-inject \
--enable-qmail-newmrh=/var/qmail/bin/qmail-newmrh \
--enable-tcprules-prog=/usr/bin/tcprules \
--enable-tcpserver-file=/etc/tcp.smtp \
--enable-clear-passwd \
--enable-many-domains \
--enable-qmail-ext \
--enable-logging=y \
--enable-auth-logging \
--enable-libdir=/usr/lib/ \
--disable-roaming-users \
--disable-passwd \
--enable-domainquotas \
--enable-roaming-users
....
....
# make && make install-strip
# cat > ~vpopmail/etc/vusagec.conf < < __EOF__
Server:
Disable = True;
__EOF__
echo 'export PATH=$PATH:/var/qmail/bin/:/home/vpopmail/bin/' > /etc/profile.d/extrapath.sh
chmod +x /etc/profile.d/extrapath.sh
source /etc/profile

A tiny shell script with all above options to compile (qmail) vpopmail without MySQL / PostgreSQL support is here

For other steps concerning creation of vpopmail/vchkpw – user/group just follow as Thibs suggests.

2. Compile and install courier-authlib-0.59.1

I’ve made mirror of courier-authlib.0.59.1.tar.gz cause this version includes support for vchkpw without mysql, its a pity newer versions of courier-authlib not any more have support for vpopmail to store its data directly on the hard disk.

Then on downlaod, compile && install courier-authlib:

Download authlib courier-authlib.0.59.1.tar.gz – (I made mirror of courier-authlib.0.59.1.tar.gz you can use my mirror or download it somewhere else from the net):


# cd /usr/local/src
# wget -q http://www.pc-freak.net/files/courier-authlib.0.59.1.tar.gz
# tar -zxvvf courier-authlib.0.59.1.tar.gz

Compile courier-authlib

# ./configure --prefix=/usr/local --exec-prefix=/usr/local --with-authvchkpw --without-authldap --without-authmysql --disable-root-check --with-ssl --with-authchangepwdir=/usr/local/libexec/authlib
....
# make && make install && make install-strip && make install-configure
....

On Debian Squeeze, this version of courier-authlib compiles fine, on Debian Lenny I use it too and there it is okay.

Unless above commands returns a compile error authlib will be installed inside /usr/local/libexec. If you get any errors it is most likely due to some missing header files. The error should be self explanatory enough, but just in case you have troubles to find what deb is necessery to install, please check here the complete list of installed packages I have on the host . In case of problems the quickest way (if on Debian Squeeze) is to install same packages, type:


# wget -q http://www.pc-freak.net/files/list_of_all_deb_necessery_installed_packages_for_authlib.txt
# for i in $(cat list_of_all_deb_necessery_installed_packages_for_authlib.txt |awk '{ print $2 }'); do
apt-get install --yes $i;
done

This is for the lazy ones though it might install you some packs you don’t like to have on your host, so just install it in case you know what you’re doing 🙂

Next step is to set proper configuration for courier-authdaemon.

3. Configure courier-authlib in /usr/local/etc/authlib

Again for the lazy ones I have prepared a good config which is working 100% with vpopmail configured to store mails on the file system, to install the “good” configs, fetch mine and put them in proper location, e.g.:


# cd /usr/local/etc
# wget -q http://www.pc-freak.net/files/authlib-config-for-qmail-with-hdd-directory-stored-userdata.tar.gz
# tar -zxvvf authlib-config-for-qmail-with-hdd-directory-stored-userdata.tar.gz
....

For those who prefer not to use my configuration as pointed above, here is what you will need to change manually in configs:

Edit /usr/local/etc/authlib/authdaemonrc and make sure there variable authmodulelist and authmodulelist and daemons=5
equals to:


authmodulelist="authvchkpw"


authmodulelistorig="authuserdb authpgsql authldap authmysql authcustom authvchkpw authpipe"


daemons=10

Bear in mind here the setting daemons, will set how many maximum parallel connections should be possible to authdaemond on new IMAP fetch mail user requests. Setting it to 10 will allow your mail server to support up to 10 users to paralelly check your mail for a tiny mail server this setting is okay if you expect higher number of parallel mail users raise the setting to some setting fitting your needs.

P.S. On some qmail installations this value has created weird problems and took me hours to debug the whole mess is caused by this setting, make sure you plan it now unless you don’t to loose some time in future.

4. Stop debian courier-authdaemon and start custom compiled one

Now all is ready and authdaemond can be started, but before that if you have installed courier-authlib as a debian package you need to stop it via init script and only when completely sure old default Debian courier-authdaemon is stopped launch the new installed one:


# /etc/init.d/courier-authdaemon stop
# s ax |grep -i authdaemond |grep -v grep
#
# /usr/local/sbin/authdaemond start
#

To make the newly custom source installed courier-authdaemon to load itself on system boot instead of the debian installed package


# dpkg -l |grep -i courier-authdaemon
ii courier-authdaemon 0.63.0-3 Courier authentication daemon

open /etc/init.d/courier-authdaemond, after line:


. /lib/lsb/init-functions

add


/usr/local/sbin/authdaemond start
exit 0

This will make the script exit once launches cmd /usr/local/sbin/authdaemond start

5. Compile and Install courier-imap

You will also have to install from courier-imap archive source, I have tested it and know Qmail + Vpopmail + Courier-Imap works for sure with version courier-imap-4.1.2.tar.bz2

As of time of writing this post courier-imap-4.11.0.tar.bz2 is the latest available for download from Courier-imap download site unfortunately this version requires higher version of >= courier-authlib-0.63

In order install courier-imap-4.1.2.tar.bz2


# cd /usr/local/src
# wget -q http://www.pc-freak.net/files/courier-imap-4.1.2.tar.bz2
# tar -jxvvf courier-imap-4.1.2.tar.bz2
...
# chown -R hipo:hipo courier-imap-4.1.2
# su hipo
$ cd courier-imap-4.1.2/
$ export CFLAGS="-DHAVE_OPEN_SMTP_RELAY -DHAVE_VLOGAUTH"
$ export COURIERAUTHCONFIG=/usr/local/bin/courierauthconfig
$ export CPPFLAGS=-I/usr/local/courier-authlib/include
$ ./configure --prefix=/usr/local/courier-imap --disable-root-check
...
$ exit
# make
...
# make install
...
# make install configure

It is recommended courier-imap to be compiled with non root username. In above code I use my username hipo, other people have to use any non-root user.

6. Set proper configuration and new init script for courier-imap

In /usr/lib/courier-imap, download following working configs (for convenience I’ve made tar with my configs):


# cd /usr/lib/courier-imap
# rm -rf etc
# wget -q http://www.pc-freak.net/files/courier-imap-config-etc.tar.gz

Then you will have to overwrite default courier-imap init script in /etc/init.d/courier-imap with another one to start the custom compiled one instead of debian default installed courier-imap


# mv /etc/init.d/courier-imap /root
# cd /etc/init.d
# wget -q http://www.pc-freak.net/files/debian-courier-imap
# mv debian-courier-imap courier-imap
# chmod +x courier-imap

This init script is written use /var/lock/subsys/courier-imap, so you will have to also create /var/lock/subsys/


# mkdir -p /var/lock/subsys

7. Start custom installed courier-imap

The start/stop init script of newly installed courier-imap is /usr/lib/courier-imap/libexec/imapd.rc


/usr/lib/courier-imap/libexec/imapd.rc start

Since a new /etc/init.dcourier-imap is installed too, it can be also used to control courier-imap start/stop.

Well thats should be enough for Courier-authlib and Courier-Authlib to communicate fine between each other and be able to connect and fetch e-mail stored in file system by vpopmail.

8. Test if Qmail IMAP proto finally works


# telnet localhost 143
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE AUTH=CRAM-MD5 ACL ACL2=UNION STARTTLS] Courier-IMAP ready. Copyright 1998-2011 Double Precision, Inc. See COPYING for distribution information.
a login username@mail-domain.com my-username-password
a OK LOGIN Ok.
a LIST "" "*"
* LIST (\HasNoChildren) "." "INBOX.Sent"
* LIST (\Marked \HasChildren) "." "INBOX"
* LIST (\HasNoChildren) "." "INBOX.Drafts"
* LIST (\HasNoChildren) "." "INBOX.Trash"
a OK LIST completed
a EXAMINE Inbox
* FLAGS (\Draft \Answered \Flagged \Deleted \Seen \Recent)
* OK [PERMANENTFLAGS ()] No permanent flags permitted
* 6683 EXISTS
* 471 RECENT
* OK [UIDVALIDITY 1272460837] Ok
* OK [MYRIGHTS "acdilrsw"] ACL
a OK [READ-ONLY] Ok
* 1 FETCH (BODY[] {2619}
Return-Path:
Delivered-To: hipo@my-domain-name.com
Received: (qmail 22304 invoked by uid 1048); 24 Apr 2012 14:49:49 -0000
Received: from unknown (HELO localhost) (127.0.0.1)
by mail.my-domain-name.com with SMTP; 24 Apr 2012 14:49:49 -0000
Delivered-To: hipo@my-domain-name.com
Received: from localhost [127.0.0.1]
......
......

That’s all it works. Enjoy 🙂

How to completely disable Replication in MySQL server 5.1.61 on Debian GNU / Linux

Monday, July 16th, 2012

Replication_mysql_disable

Some time ago on one of the Database MySQL servers, I've configured replication as it was required to test somethings. Eventually it turned out replication will be not used (for some reason) it was too slow and not fitting our company needs hence we needed to disable it.

It seemed logical to me that, simply removing any replication related directives from my.cnf and a restart of the SQL server will be enough to turn replication off on the Debian Linux host. Therefore I proceeded removed all replication configs from /etc/my/my.cnf and issued MySQL restart i. e.:

sql-server:~# /etc/init.d/mysql restart
....

This however didn't turned off replication,as I thought and in phpmyadminweb frontend interface, replication was still appearing to be active in the replication tab.

Something was still making the SQL server still act as an Replication Slave Host, so after a bit of pondering and trying to remember, the exact steps I took to make the replication work on the host I remembered that actually I issued:

mysql> START SLAVE;

Onwards I run:

mysql> SHOW SLAVE STATUS;
....

and found in the database the server was still running in Slave Replication mode

Hence to turn off the db host run as a Slave, I had to issue in mysql cli:

mysql> STOP SLAVE;
Query OK, 0 rows affected, 1 warning (0.01 sec)
mysql> RESET SLAVE;
Query OK, 0 rows affected, 1 warning (0.01 sec)

Then after a reload of SQL server in memory, the host finally stopped working as a Slave Replication host, e.g.

sql-server:~# /etc/init.d/mysql restart
....

After the restart, to re-assure myself the SQL server is no more set to run as MySQL replication Slave host:

mysql> SHOW SLAVE STATUS;
Empty set (0.00 sec)

Cheers 😉

How to clear Squid Proxy Cache on Debian and Ubuntu

Saturday, July 16th, 2011

Squid proxy cache clear logo

It was necessery to clean up some squid cache for some proxy users on a Debian host. Until now I’ve used to run only custom build Squid server on Slackware Linux.

Thus I was curious if Debian guys were smart enough to implement a proxy cache cleaning option as an option to be passed on to squid’s init script.

Honestly I was quite suprised squid clear cache option is not there;

squid-cache:~# /etc/init.d/squid3
Usage: /etc/init.d/squid3 {start|stop|reload|force-reload|restart}
squid-cache:/#

As it was not embedded into init script I still hoped, there might be some Debian way to do the proxy cache clearing, so I spend some 10 minutes checking online as well as checked in squid3‘s manual just to find there is no specific command or Debian accepted way to clean squid’s cache.

Since I couldn’t find any Debian specific, way I did it the old fashioned way 😉 (deleted directory/file structures in /var/spool/squid3/* and used squid’s -z option, to recreate the swap directories.

Here is how:

squid-cache:~# /etc/init.d/squid3 stop;
squid-cache:~# rm -Rf /var/spool/squid3/*;
squid-cache:~# squid3 -z; /etc/init.d/squid3 start

Finally I was quite amazed to realize, there was not even a crontab script to periodically clear and re-create proxy cache.

My previous experience with maintaning an office Squid proxy cache has prooved, that periodic cache clean ups are very helpful, especially to resolve issues with cached unreslovable DNS entries in the server.
Clearing up squid cache every week or something, guarantees that failure to resolve certain hosts at certain times would not stay unresolvable like forever 😉

In that manner of thougths, I decided to put the following crontab which will twice a month clear up proxy’s cache, to possibly solve some failed squid DNS issues.

squid-cache:~# crontab -u root -l > file;
echo '00 04 12,26 * * /etc/init.d/squid3 stop; rm -Rf /var/spool/squid3/*; squid3 -z; /etc/init.d/squid3 start >/dev/null 2>&1'
>> file; crontab file

By the way, implementing the squid clear cache in Debian and Ubuntu ‘s init scripts and putting a periodic proxy clear up cron, seems like a feature worthy to be proposed to the distro developers and hopefully be embbed in some of the upcoming distro releases 😉