Restoring server images

While backups are usually often considered when designing high-availability server parks, doing an actual restore is often overlooked. You simply don't want to pull a plug and rather wait for the actual disaster to happen.
Having a full file system image of a server, while space and time consuming can be the fastest way to get a server back online after a failure. If you have a SAN available, it can clone LUNs for your transparently and you can swap them back in when a machine fails or burn down. However, not everyone has one.

Using clonezilla, you can easily pull images off of Linux or even Windows servers and restore them (even using multicast!) in minutes. As it only copies used blocks, that 300 GB local disk can result in a 5 GB image. For a restore, Clonezilla restores the appropriate image based on MAC address.

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Preventing PuTTY timeouts

Just found a great tip to prevent timeouts of PuTTY sessions. I'm fine with timeouts by the host, but in our case the firewall kills sessions after 30 minutes of inactivity... When using PuTTY to ssh to your Linux/Unix servers, be sure to use the feature to send NULL packets to prevent a timeout. I've set it to once every 900 seconds, i.e. 15 minutes... See screenshot on the right.

Tuning the nscd name cache daemon

I've been playing a bit with the nscd now and want to share some tips related to tuning the nscd.conf file. To see how the DNS cache is doing, use nscd -g. nscd configuration: 0 server debug level 26m 57s server runtime 5 current number of threads 32 maximum number of threads 0 number of times clients had to wait yes paranoia mode enabled 3600 restart internal passwd cache: no cache is enabled [other zero output removed] group cache: no cache is enabled [other zero output removed] hosts cache: yes cache is enabled yes cache is persistent yes cache is shared 211 suggested size 216064 total data pool size 1144 used data pool size 3600 seconds time to live for positive entries 20 seconds time to live for negative entries 66254 cache hi...

Dell Linux - OMSA Hardware Monitoring

Just getting started using Dell's OpenManage Server Administrator (OMSA) on our Oracle Linux platform. There are some confusing instructions going around so it's not immediately clear what to do, hence my blogging here. :) There is a site on Dell - Hardware Monitoring , as well as a wiki with instruction on how to setup their OMSA tooling using yum or up2date. [update]My first update for their instructions: be sure your server has Internet access, as most servers will use a proxy or so. use export http_proxy=http://yourproxy.example.com:port to configure it just for the session, and setup up2date to use an HTTP proxy by editing the settings in /etc/sysconfig/rhn/up2date .

Oracle: Unbreak my Linux Heart

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