Posts Tagged ‘configuration file’

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How to automatically reboot (restart) Debian GNU Lenny / Squeeze Linux on kernel panic, some general CPU overload or system crash

Monday, June 21st, 2010

If you are a system administrator, you have probably wondered at least once ohw to configure your Linux server to automatically reboot itself if it crashes, is going through a mass CPU overload, e.g. the server load average “hits the sky”.
I just learned from a nice article found here that there is a kernel variable which when enabled takes care to automatically restart a crashed server with the terrible Kernel Panic message we all know.

The variable I’m taking about is kernel.panic for instance kernel.panic = 20 would instruct your GNU Linux kernel to automatically reboot if it experiences a kernel panic system crash within a time limit of 20 seconds.

To start using the auto-reboot linux capabilities on a kernel panic occurance just set the variable to /etc/sysctl.conf

debian-server:~# echo 'kernel.panic = 20' >> /etc/sysctl.conf

Now we will also have to enable the variable to start being use on the system, so execute:

debian-server:~# sysctl -p There you go automatic system reboots on kernel panics is now on.
Now to further assure yourself the linux server you’re responsible of will automatically restart itself on a emergency situation like a system overload I suggest you check Watchdog

You might consider checking out this auto reboot tutorial which explains in simple words how watchdog is installed and configured.
On Debian installing and maintaining watchdog is really simple and comes to installing and enabling the watchdog system service, right afteryou made two changes in it’s configuration file /etc/watchdog.conf

To do so execute:

debian-server:~# apt-get install watchdog
debian-server:~# echo "file = /var/log/messages" >> /etc/watchdog.conf
debian-server:~# echo "watchdog-device = /dev/watchdog" >> /etc/watchdog.conf

Well that should be it, you might also need to load some kernel module to monitor your watchdog.
On my system the kernel modules related to watchdog are located in:

/lib/modules/2.6.26-2-amd64/kernel/drivers/watchdog/
If not then you should certainly try the software watchdog linux kernel module called softdog , to do so issue:
debian-server:~# /sbin/modprobe softdog

It’s best if you load the module while the softdog daemon is disabled.
If you consider auto loadig the softdog software watchdog kernel driver you should exec:

debian-server:~# echo 'softdog' >> /etc/modules

Finally a start of the watchdog is necessery:

 


debian-server:~# /etc/init.d/watchdog start
Stopping watchdog keepalive daemon....
Starting watchdog daemon....

That should be all your automatic system reboots should be now on! 🙂

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Posted in Linux, System Administration | 6 Comments »

Installing qmailmrtg (qmail graph statistics on qmail activity) on Debian Lenny

Monday, April 19th, 2010

1. First it’s necessery to have the mrtg debian package installed.
If it’s not installed then we have to install it:

debian-server:~# apt-get install mrtg

2. Second download the qmailmrtg source binary
To download the latest current source release of qmailmrtg execute:

debian-server:~# wget http://www.inter7.com/qmailmrtg7/qmailmrtg7-4.2.tar.gz

It’s a pity qmailmrtg is not available for download via debian repositories.

3. Third download the qmail.mrtg.cfg configuration file

debian-server~# wget https://www.pc-freak.net/files/qmail.mrtg.cfg

Now you have to put the file somewhere, usually it’s best to put it in the /etc/ directory.
Make sure the file is existing in /etc/qmail.mrtg.cfg
4. Untar compile and install qmailmrtg binary


debian-server:~# tar -xzvvf qmailmrtg7-4.2.tar.gz
...
debian-server:~# make && make install

strip qmailmrtg7
cp qmailmrtg7 /usr/local/bin
rm -rf *.o qmailmrtg7 checkq core
cc checkq.c -o checkq
./checkq
cc -s -O qmailmrtg7.c -o qmailmrtg7
qmailmrtg7.c: In function ‘main’:
qmailmrtg7.c:69: warning: incompatible implicit declaration of
built-in function ‘exit’
qmailmrtg7.c:93: warning: incompatible implicit declaration of
built-in function ‘exit’
qmailmrtg7.c:131: warning: incompatible implicit declaration of
built-in function ‘exit’
qmailmrtg7.c:137: warning: incompatible implicit declaration of
built-in function ‘exit’

5. Set proper file permissions according to the user you indent to execute qmailmrtg as
I personally execute it as root user, if you intend to do so as well set a permissions to
/etc/qmail.mrtg.cfg of 700.
In order to do that issue the command:

debian-server:~# chmod 700 /etc/qmail.mrtg.cfg

6. You will now need to modify the qmail.mrtg.cfg according to your needs
There you have to set a proper location where the qmailmrtg shall generate it’s html data files.
I use the /var/www/qmailmrtg qmailmrtg log file location. If you will do so as wellyou have to create the directory.

7. Create qmailmrtg html log files directory

debian-server:~# mkdir /var/log/qmailmrtg

8. Now all left is to set a proper cron line to periodically invoke qmailmrtg in order to generate qmail activity statistics.

Before we add the desired root’s crontab instructions we have to open the crontab for edit, using the command.

debian-server:~# crontab -u root -e

I personally use and recommend the following line as a line to be added to root’s crontab.

0-55/5 * * * * env LANG=C /usr/bin/mrtg /etc/qmail.mrtg.cfg > /dev/null
9. Copy index.html from qmailmrtg source directory to /var/log/qmailmrtg


debian-server:/usr/local/src/qmailmrtg7-4.2# cp -rpf index.html /var/log/qmailmrtg

10. Last step is to make sure Apache’s configuration contains lines that will enable you to access the qmail activity statistics.

The quickest way to do that in Debian running Apache 2.2 is to edit /etc/apache2/apache2.conf and add a directory Alias as follows

Alias /qmailmrtg/ "/var/www/qmailmrtg/"

Now after Apache restart /etc/init.d/apache2 restart
You should be now able to access the qmail mrtg qmail log statistics through your Apache’s default configured host.
For instance, assuming your default configured Apache host is domain.com. You’ll be able to reach the qmailmrtg statistics through an url like:

http://domain.com/qmailmrtg/

After I verified and ensured myself qmail mrtg is working correctly after all the above explained steps partook I wasn’t happy with some headlines in the index.html and the html tile of qmailmrtg,
so as a last step I manually edited the /var/www/qmailmrtg/index.html to attune it to my likings.

Here is a screenshot of the qmailmrtg web statistics in action.

qmail mrtg on debian lenny

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Posted in System Administration | 6 Comments »

How to configure pine (alpine) console client to work with vpopmail pop3 and imap protocol

Monday, June 13th, 2011

I needed to check my mail via ssh connection, as my installed squirrelmail is curently broken and I’m away from my own personal computer.

I did some online research on how this can be achieved and thanksfully I finallyfound a way to check my pop3 and imap mailbox with a console client called alpine , better known in unix community under the name pine .

I installed pine on my Debian with apt:


debian:~# apt-get install alpine

Here is my pine configuration file .pinerc used to fetch my mail with pine:

a .pinerc conf file to check my pop3 mail

To use that file I placed it in my home directory ~/ , e.g.:


debian:~# wget https://www.pc-freak.net/files/.pinerc
...

To attune the pop3 server configuration in the sample .pinerc above one needs to change the value of:


inbox-path=
For example to configure pine to fetch mail from the pop3 server mail.www.pc-freak.net and store it locally in my home directory within a file called INBOX
I have configured the inbox-path .pinerc variable to look like so:


inbox-path={mail.www.pc-freak.net/pop3/user=hipo@www.pc-freak.net}INBOX

In above configuration’s inbox-path variable configuration the /pop3/ specifies I want to fetch my mail via the pop3 protocol , if one wants to use imap this has to be substituted with /imap/

The value user=hipo@www.pc-freak.net specifies my vpopmail created user which in my case is obviously hipo@www.pc-freak.net

The other variables which are good to be changed in .pinerc config are:


personal-name=

This variable has to be set to the name of the Email Sender which will be set, if pine is used to send email.

I also changed the user-domain variable as it’s used to set the domain name from which the pine client will send the emails from:

As my domain is www.pc-freak.net I’ve set the domain name variable to be:


user-domain=www.pc-freak.net

Now after launching pine it prompted me for my email password, putting in the pass did fetch all my new unread mails via pop3 protocol.

The only annoying thing was that each time I quit pine and start it up again, I’m now asked to enter the email password.

This behaviour is really shitty, but thanksfully one can easily workaround that by letting pine be constantly running detached in gni screen session.

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Posted in Linux, Various | No Comments »

How to solve “eAccelerator requires Zend Engine API version 220060519 , the Zend Engine API version 220090626 which is installed, is newer. Contact eAccelerator at http://eaccelerator.net for a later version of eAccelerator.” on FreeBSD

Monday, April 4th, 2011

I’ve recently upgraded my FreeBSD Apache server from port www/apache20 I had some issues before I tune up and recompile also the php5 port but eventually it worked out, however the Eaccelerator content caching module failed to load as it was outdated.

That’s a common inconvenient with eaccelerator that every system administrator out there has faced once or twice, especially on systems that has custom compiled Apache servers and does not use a specific precompiled version of the eaccelerator.

To solve the situation as you can expect I jumped on in the /usr/ports/www/eaccelerator and removed the current installed version of eaccelerator in order to compile and install the latest port version.:
To do that I first attempted to upgrade the eaccelerator port with portmaster but as there were some problems caused by autoconf initialization etc., I finally decided to abandon the idea of using portmaster and did it manually with the good old well known trivial commands:

freebsd# cd /usr/ports/www/eaccelerator
freebsd# make deinstall
freebsd# make install && make clean

I’ve continued further and restarted my Apache server to load the new eaccelerator version and made a small phpinfo php script to test if the eaccelerator is properly loaded, yet with zero success.

After checking out in my /var/log/httpd-error.log , I’ve determined the following error:

Failed loading /usr/local/lib/php/20060613/eaccelerator.so: Cannot open "/usr/local/lib/php/20060613/eaccelerator.so"

The error is quite obvious, to solve it I’ve opened my php configuration file /usr/local/etc/php.ini and placed in it:

and substituted the line:

zend_extension="/usr/local/lib/php/20060613/eaccelerator.so:"

with:

zend_extension="/usr/local/lib/php/20090626/eaccelerator.so"

Further on I gave Apache another restart with:

freebsd# /usr/local/etc/rc.d/apache2 restart
Performing sanity check on apache2 configuration:
Syntax OK
Stopping apache2.
Waiting for PIDS: 71140.
Performing sanity check on apache2 configuration:
Syntax OK
Starting apache2.

followed by another test if the eaccelerator is loaded with the phpinfo(); script.

Now even though the Failed loading /usr/local/lib/php/20060613/eaccelerator.so: Cannot open “/usr/local/lib/php/20060613/eaccelerator.so” was no more, the Eaccelerator was yet not loaded.

Another consult with /var/log/httpd-error.log now revealed me another eaccelerator error you read below:

eAccelerator requires Zend Engine API version 220060519.
The Zend Engine API version 220090626 which is installed, is newer.
Contact eAccelerator at http://eaccelerator.net for a later version of eAccelerator.

I did about 20 minutes of investigation on the internet looking for a possible fix which gave me some idea what might be the cause for error message, though it was finally my try/fail methodology that helped me solve the issue.

The solution to the issue appeared to be easy thanks God, to solve the error all you need to do is one more make clean right before installing the eaccelerator port.:
Here are the commands necessary to issue to solve the error and make the eaccelerator load properly:

freebsd# cd /usr/ports/www/eaccelerator
freebsd# make clean &&
freebsd# make install clean

Now after restarting the Apache server once again eaccelerator has properly been loaded once again.

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Posted in FreeBSD, System Administration | 2 Comments »

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