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The system I am working with uses ssh to remotely connect to a Linux machine. It then executes a single shell command and analyses the output from the shell command.

If I run reboot, I get exit code -1, since rebooting of course kills the ssh connection. Any exit code other than 0 makes the system register a failure, thus I have been trying to write a single line command that will reboot and exit the ssh session gracefully.

The machines in question are very bare bones and the reboot utility does not allow any options so I can't just schedule a reboot for later.

After some thought I tried running

$ sleep 3 && reboot & exit

Which works when I call it manually: the connection closes with error code 0 and 3 seconds later the machine reboots. Great.

But the same command run through our system doesn't actually reboot. It just returns exit code 0 and the reboot never happens.

Why would this be?

  • I'm not certain why it's not working, but you could try ssh user@host "nohup init 6 < /dev/null > /dev/null 2>/dev/null". Alternatively, ssh user@host "nohup shutdown -r +1 > /dev/null 2>/dev/null" which will reboot the system one minute after the command is sent. – DopeGhoti Feb 22 '18 at 18:28
2

Use the shutdown command.

shutdown --reboot +1 "System is going down for reboot in 1 minute"

I suspect the reason reboot doesn't work is because it requires a tty. You could try running it with a background tty, but the shutdown command has everything you need, including cancelling -- as it says in response:

Shutdown scheduled for Thu 2018-02-22 15:19:33 MST, use 'shutdown -c' to cancel.
  • 1
    That explains it, one minute is a little long to wait but it does work thanks. – YetAnotherRCG Feb 26 '18 at 19:19
  • Say now instead of +1 and change the message to suit. There isn't a way to specify a shorter interval (e.g. +15s would mean "in fifteen seconds"), but you can specify the next minute, so if it's 10:57 now, you could say 10:58 as your time specification. – Rich Mar 8 '18 at 17:57

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