Tech@Sakana – A sysadmin’s blog

CFEngine can do wonders to keep a cluster in shape, but it can be very useful for a single server as well. Here is a configuration sample to monitor a few common services and restart them should they fail.

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A common problem when you deal with a pool of servers (clusters or server farms, you name it) is to execute the same command line on each server. It is usual to solve this with a “for” construct such as :

for i in server1 server2 ; do ssh $i "uname -a"; done

But this is basically re-inventing the wheel everytime. Here comes Distributed Shell (DSH).
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In this post we’ll install CFEngine on a Debian system. Debian make is really simple to install any packages, so let’s follow the “standard” package installation procedure (I’ll assume that apt is correctly setup on your system ! If you have troubles with it, let me know, I’ll write a post on this topic).
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CFEngine is a configuration management engine. I’m going to write a series of short posts as I’m going to use CFEngine in a current project. Let’s start with a short description of CFEngine purpose and main features.
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Cfengine is a tool which purpose is to describe what is a healthy system and how to bring it back to normal when something fails.

I won’t go into an explanation about how cfengine works, because the project webpage already has a neat tutorial and complete reference. Instead of that, I’ll explain how I used cfengine to build a fool proof Linux firewall.

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