Cluster machines should call for help

[jdreed]

A cluster machine that is sad (i.e. because it downgraded itself to -workstation) should know enough to call for help.

A possible method is that the installer drops an unpackaged initscript somewhere that, if debathena-cluster is not installed, displays a single X window that says "This workstation is temporarily out of service, please contact hotline@…".

The window could also do more awesome things,like prompt the user to click a button to hackboot into PXE and reinstall, or something else.

But at the very least, it should advertise its brokenness.

[jdreed]

So, with new-gdm, we could probably do something with debathena-branding. Specifically, if it's running debathena-workstation, but has Hesiod CLUSTER=cluster, then something is horribly broken and it should scream loudly.

While Nagios will partially do what we want (and in fact already does, I believe), we may want to actually prevent users from using broken machines or inform them to go elsewhere.

[jdreed]

The installer has done this for a while now, and Nagios is sufficiently for cluster != workstation.