Linux Showroom

Execute command on every boot

Fabio — Sun, 13 Feb 2011 14:38:07 +0000

You want to execute a command on every boot but do not want to create an init script? Well, if your *nix system supports cron jobs which is very likely it is your lucky day.

Just open the cron file for the user who in whose name the command is supposed to run.

crontab -e

Add the following line to the open cron file and obviously replace YOUR COMMAND with whatever should be run on start-up.

@reboot YOUR COMMAND

Save the changes and now on every boot your command is executed once. Simple as that!

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Execute command on every boot

Memcache is not cacheing

Fabio — Tue, 18 Jan 2011 16:27:33 +0000

So you are using memcached to speed up your system. Than suddenly at some point you notice memcache is not helping anymore but is does not cache the part that has the worst impact on your system.

That´s what just has happened to me. Why is Memcache not cacheing I asked myself. Well, the default and highly recommend slabs size is 1 MB. Anything above just is not cached. Setting that limit higher with -I Xm (X being an integer) results in a warning which sounds really bad:

Starting memcached WARNING: Setting item max size above 1MB is not recommended!
Raising this limit increases the minimum memory requirements and will decrease your memory efficiency.

Hmm, not so good. Luckily I was able to downsize that particular item so that memcache stores it again.

I am still wondering if serving content from harddisk instead of RAM via memcached could be a good idea. I gotta try it one of these days. What do you think?

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Memcache is not cacheing

Use varnishlog to find hosts which cause most hits

Fabio — Tue, 14 Dec 2010 08:46:13 +0000

If your Varnish powered server is under constant load and you are wondering who causes that varnishlog is a helpful tool.

Start off by logging IP addresses for a while.

1	varnishlog -c -i RxHeader -I X-Forwarded-For > varnish.log

After you have collected enough information use the following line to find out which IP caused the most hits on your varnish.

1	cat varnish.log \| cut -d ' ' -f 12 \| sort \| uniq -c \| sort -n

Query the ripe database to find information on the IP addresses.

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Use varnishlog to find hosts which cause most hits

Library and WordPress plugin for Textbroker

Fabio — Mon, 08 Nov 2010 16:38:46 +0000

I created a library to access the API of the Textbroker marketplace more easily. The library is Open Source with a BSD licence. Feel free to grab a copy and play with it. Feedback is appreciated.

Based on that work I developed the Textbroker WordPress plug-in which makes it very easy and comfortable to place new orders and publish articles through your own WordPress installation.

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Library and WordPress plugin for Textbroker

Useful shell commands: last

Fabio — Sat, 06 Feb 2010 13:40:11 +0000

Today I will start a new series for linux/*nix newbies called Useful shell commands. Every now and then I will write about one of the powerful commands you’ll find on your shell. I will start the series with a command called last.

# last

Calling last on your commandline gives you a list of logins. You will see who is still logged in and who was logged in before from what adress.

You can shorten the list of results with last -n XX. XX being the number of results you want to have displayed, e.g. last -n 5 for 5 lines.

# last reboot

Calling last reboot lists the reboots since the log file which tracks all logins was created.

The manual page for last – man last – will show you more parameters.

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Useful shell commands: last

High available NFS4 server with drbd 0.8, pacemaker 1.0, heartbeat, openais on OpenSUSE 11.1

Fabio — Sat, 08 Aug 2009 14:07:42 +0000

For my podcast project I got five new root servers which are all connected internally through a switch. Two of the servers are connected directly over a crossover cable. Those two servers have 3 NICs, the other 2 servers have 2 NICs.

I share the website’s HTML, images and other resources through the NFS server to all five servers. All servers work as webservers with nginx and PHP-fpm. Each server also runs one more specific service: database master, solr master, cron jobs / crawler processes, Varnish / HAproxy.

The two directly connected servers share the static website resources over drbd. Pacemaker, heartbeat and openais secure the high availability of my NFS4 server. Setting this up took quiet a bit of fiddeling as there are how-tos for so many different (and outdated) versions are floating around the internet.

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High available NFS4 server with drbd 0.8, pacemaker 1.0, heartbeat, openais on OpenSUSE 11.1

php-fpm runlevel start script for OpenSuSE 11.1

Fabio — Thu, 30 Jul 2009 17:44:34 +0000

Nowadays OpenSUSE comes with almost all packages I need to run a fast and reliable webserver. As I have written before I use nginx and php-fpm for our podcast service.

You can get up-to-date packages of nginx through OpenSuSE’s build service. I have not yet found a RPM package of php-fpm though. Therefore I compile it myself. This works well and I have the advantage that I can customize by PHP package.

But there is also one disadvantage. There is no system runlevel script available this way. So you cannot make use of the rc stuff on OpenSuSE and start PHP at boot time. As I have quiet a few machines to administer I decided to write my own runlevel script to start php-fpm.

Looking closer into the stuff that is already delivered with the php-fpm package is a powerful start script. I took it as the basis of my script. I had to modify it only in a few places. Big thanks to the author(s)!

It will take a few easy steps to get php-fpm running after booting.

Download my modified php-fpm script to your server’s runlevel directory (/etc/rc.d).
Rename the file by removing the file extension (.txt)
Give your superuser (root) rights to execute it.
Open the file php-fpm in your favorite editor (Vim, emacs, joe, …).
Modify the three lines (php_fpm_BIN=, php_fpm_CONF=, php_fpm_PID=) on top to match your installation directory of php-fpm.
Save and close the file.
Start yast with yast runlevel and switch to expert mode with Alt+x
Activate php-fpm for runlevels 3 and 5 (or whatever suits you). Save your changes with Alt+o. That’s it!

Now your php-fpm installation starts on boot. If you ever have to reboot your machine you do not have to think about starting php-fpm manually as the system does it for you.

Let me know if this was helpful for you, if it works and if you have any questions!

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php-fpm runlevel start script for OpenSuSE 11.1

How to find out user id on linux system

Fabio — Fri, 03 Apr 2009 13:44:40 +0000

For a mount command I needed to find out what user id my user account had. There are several ways to find out. As root you could look into the passwd file (most likely /etc/passwd) or on OpenSuSE use the Yast user module. But I was looking for a way to find out my user id with my ordinary user account. The command I was looking for is id. Just open up a shell (konsole on KDE4) with your active user, type id and you get all the information about your user including groups and their ids. If you just want to know the user’s id, e.g. for a shell script use

id -u USERNAME

and you get back just the id of the user. Simple as that!

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How to find out user id on linux system

System upgrade openSUSE 11.0 to openSUSE 11.1 with zypper

Fabio — Sat, 20 Dec 2008 16:47:45 +0000

I had to set up a server. The hoster offers openSUSE 11.0 at the moment but no openSUSE 11.1 yet. As I like to go with the latest and greatest I decided to upgrade the system to openSUSE 11.1 after using the hoster’s installation image for openSUSE 11.0. I searched on the web how a system upgrade should be done this time. (It seems to differ all the time.) I found a zypper command chain. Change the installation reposotories in /etc/zypp/repos.d to the new version and type:

zypper refresh
zypper dist-upgrade

I did excatly that. It did refresh a few packages but as I guessed immediately not enough. I tried over. It did not help. Here is the solution. Delete all subdirectories in /var/cache/zypper and execute the commands above again.

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System upgrade openSUSE 11.0 to openSUSE 11.1 with zypper

New software packages bundled with OpenSuSE 11.1

Fabio — Thu, 18 Dec 2008 19:15:14 +0000

The newest version of OpenSuSE got released today. OpenSuSE 11.1 brings more than 230 new features the press release says. As I keep my systems up to date thanks to smart and all the repositories only a number of these new feature are missing on my OpenSuSE 11.0 installations. The most important reason I quickly upgrade my desktop system is KDE. As I am still using KDE version 3 and the version that comes with OpenSuSE 11.1 is the same I have installed (KDE 3.5.10) this does not convince me to upgrade.

I did however discover new software (packages) in OpenSuSE 11.1 I have not known before. These packages are Tasque, Tellico, Twinkle, Monsoon, PulseAudio and Derby. I googled these terms and came up with the following.

Tasque is a simple task management app (TODO list) for the Linux Desktop. The screenshots remind me of the todo app that comes with the KDE Kontact tool.
Tellico is a KDE application for organizing your collections. Tellico allows you to enter your collection in a catalogue database.
Twinkle is a free software/open source VoIP softphone application for Linux. It uses the SIP protocol. It also incorporates a GPL implementation of the ZRTP and SRTP security protocols and MD5 digest authentication.
Monsoon is a fully featured bittorrent GUI supporting many advanced features such as selective downloading, automatic port forwarding via uPnP and RSS integration.
PulseAudio is a sound server for POSIX and Win32 systems.
Apache Derby is an open source relational database implemented entirely in Java.

I’d like to say even before I tried it out openSUSE just got better!

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New software packages bundled with OpenSuSE 11.1