Linux – How to trigger a delayed system shutdown from in a shell script

bashlinuxshellshutdown

On my private network I have a backup server, which runs a bacula backup every night. To save energy I use a cron job to wake the server, but I haven't found out, how to properly shut it down after the backup is done.
By the means of the bacula-director configuration I can call a script during the processing of the last backup job (i.e. the backup of the file catalog). I tried to use this script: 

#!/bin/bash
# shutdown server in 10 minutes
#
# ps, 17.11.2013
bash -c "nohup /sbin/shutdown -h 10" &
exit 0

The script shuts down the server – but apparently it returns just during the shutdown,
and as a consequence that last backup job hangs just until the shutdown. How can I make the script to file the shutdown and return immediately?

Update: After an extensive search I came up with a (albeit pretty ugly) solution:
The script run by bacula looks like this: 

#!/bin/bash
at -f /root/scripts/shutdown_now.sh now + 10 minutes

And the second script (shutdown_now.sh) looks like this: 

#!/bin/bash
shutdown -h now

Actually I found no obvious method to add the required parameters of shutdown in the syntax of the 'at' command. Maybe someone can give me some advice here.

Best Solution

Depending on your backup server’s OS, the implementation of shutdown might behave differently. I have tested the following two solutions on Ubuntu 12.04 and they both worked for me:

As the root user I have created a shell script with the following content and called it in a bash shell:

shutdown -h 10 &
exit 0

The exit code of the script in the shell was correct (tested with echo $?). The shutdown was still in progress (tested with shutdown -c).

This bash function call in a second shell script worked equally well:

my_shutdown() {
  shutdown -h 10
}
my_shutdown &
exit 0
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