RunLevels

Working on some servers recently has made me think about init.d and possibly creating a custom runlevel (e.g. 4), that shuts down everything, but SSH and networking (and its dependencies), and then disables login from anyone but a superuser or somone in a specified group - e.g. Staff,admin etc.

The default runlevel is 2/3 on most systems, with some systems using 5 for X11 and such, Level 1 is Single user, with Levels 0 and 6 being shutdown and reboot respectively.

The idea behind this would mean that maintanence could be conducted remotely on the server, without other daemons, or other users getting in the way - especially if you needed to conduct repairs to /home or /var say, which you can't do while it is in use.

Think of it as a remote users single user mode - but with minimal services like networking and ssh only, for use when you simply can't go to the datacenter and use init 1 (single user mode), and the task you need can be done remotely.

Not sure of the complete picture of how I would go about doing this yet, but it could prove useful for future use, possibly pushing this out via puppet to servers that are managed?

I'll probably look into this at some point, but for now it'll remain an idea.

Keith