A Productive Week – Cfengine and SSH-agent

Now that lack-of-sleep madness has passed I’ve managed to actually get some work done. In particular I’ve been chipping away at some of the tedious manual labour that comes with administering multiple machines.

To start off with I finally knuckled down to working out how to use ssh-agent. This nice article from SecurityFocus helped me get started. The most difficult bit was getting ssh-agent to run from fluxbox on start up. To fix that I added the following lines into .fluxbox/apps

[startup] {eval `ssh-agent -s`}
[startup] {ssh-add < /dev/null}

which pops up a dialog box for my passphrase on login.

I also started to get down to sorting out configuration management using cfengine. One of things that I've never been able to work out was how to make rules depend on one another. So if you have a rule that adds a line into the iptables config how do you then tell cfengine that iptables needs to be restarted. After hunting around on the web I found an example that does almost exactly what I need. A hacked up a quick example that would sort my root alias and then run the sendmail newaliases command.

{ /etc/aliases
BeginGroupIfNoSuchLine "root:           wescroot@wesc.ac.uk"
DeleteLinesStarting "#root"
Append "root:           wescroot@wesc.ac.uk"
DefineClasses "aliaseschanged"


Basically aliaseschanged is only set if the editfiles rule needs to be executed. So newaliases is only run if we actually update the aliases file. I have a more complicated set of rules that does the same thing for iptables. Next week globus4.