Archive for the ‘Linux’ Category

How the SCP protocol works

That’s not my title but the one I stole from a fantastic Jan Pechanec’s blog post that describes how the SCP protocol works – I really encourage everyone to read it.

Posted on May 17, 2013 at 2:48 pm by sergeyt · Permalink · One Comment
In: FreeBSD, HP-UX, Linux, Solaris

Regression in pam_listfile module in RHEL5.9

Hot on the heels of the recent support ticket we opened with RedHat that has been finally resolved. For those who have RHN access below is the direct link: In a nutshell. After upgrading to RHEL 5.9 we lost the ability to ssh into any of our servers where pam_listfile was configured and the […]

Posted on March 26, 2013 at 8:50 pm by sergeyt · Permalink · Leave a comment
In: Linux

OpenLDAP with TLS, ppolicy and master-master replication on RHEL6.3

This post has been dusting on a draft shelf for too long. No reason to keep it there any loger. Below is the list of instructions which once followed would help anyone to end up with an OpenLDAP server on RHEL 6.1 (should work perfectly well with CentOS too). There is nothing special about it […]

Posted on February 23, 2013 at 1:25 pm by sergeyt · Permalink · 36 Comments
In: Linux

OpenGrok, Ubuntu and Linux source tree

After all, thanks to our very long New Year holidays, I had a chance to install OpenGrok search and cross reference engine. The main reason is to have a tool to be able to efficiently browse Linux kernel source code. I use OpenGrok quite frequently, especially when there is a need to dive into Solaris/OpenSolaris […]

Posted on January 7, 2013 at 12:31 am by sergeyt · Permalink · 7 Comments
In: Linux

Spacewalk, osad and jabberd miscommunication

Spacewalk is really a handy tool if you want to keep your Linux infrastructure up to date. Especially if you run Redhat based ditro, since essentially it’s community supported version of Redhat’s product called Satellite. But it has a nasty issue, at least in our case, when the clients stop responding to the commands from […]

Posted on December 24, 2012 at 11:05 am by sergeyt · Permalink · Leave a comment
In: Linux

DLM lock levels in OCFS2

Yesterday I had to get a bit deeper into OCFS2 details and come across this very helpful blog post about different DLM lock levels used in OCFS2. Gave me a chance to place all the ducks in a row. 

Posted on December 13, 2012 at 10:29 am by sergeyt · Permalink · Leave a comment
In: Linux

How to quickly fix osad failure to connect to the SpaceWalk server

If one day you noticed that you spacewalk client had started to spit at you with the following errors – just know that it’s very easy to fix. 2012/03/15 17:17:43 +04:00 29835 osad/jabber_lib.setup_connection(‘Connected to jabber server’, ‘spacewalk-server-name’) 2012/03/15 17:17:43 +04:00 29835 osad/jabber_lib.register(‘ERROR’, ‘Invalid password’) Stop spacewalk rhn-satellite stop rm -f /var/lib/jabberd/db/* Connect to […]

Posted on August 25, 2012 at 5:09 pm by sergeyt · Permalink · Leave a comment
In: Linux

NFSD panics on RHEL 5.8

If you as unlucky as I am and your RHEL 5.8 server has just spat the same call trace as you see on the picture I attached, then I’m here to make your problem less painful. If you have RHN account you could find a thorough explanation and the root case here and here If […]

Posted on June 21, 2012 at 9:22 pm by sergeyt · Permalink · Leave a comment
In: Linux

How to remove the last dead path in ESX

Feb 9 10:56:27 esx vmkernel: 47:18:55:03.308 cpu8:4225)WARNING: NMP: nmp_DeviceRetryCommand: Device “naa.60060e80056e030000006e030000004b”: awaiting fast path state update for failover with I/O blocked. No prior reservation exists on the device. Feb 9 10:56:27 esx vmkernel: 47:18:55:03.308 cpu8:4225)WARNING: NMP: nmp_DeviceStartLoop: NMP Device “naa.60060e80056e030000006e030000004b” is blocked. Not starting I/O from device. Feb 9 10:56:28 esx vmkernel: 47:18:55:04.323 cpu8:4264)WARNING: NMP: […]

Posted on April 12, 2012 at 11:59 pm by sergeyt · Permalink · Leave a comment
In: Linux, SAN

Linux solution for ARP flux

If for some reason you have to configure multiple network interfaces in the same subnet, e.g. eth0 –, eth1 –, eth2 –, etc., on Linux box you’d certainly face a so called ARP flux issue. To fix it (I assume you have kernel > 2.6.2) just set the following sysctl options as […]

Posted on April 12, 2012 at 11:49 pm by sergeyt · Permalink · Leave a comment
In: Linux