How can I tell, from the command line, whether the machine requires a reboot?

Question

When you install certain updates (e.g. a new kernel) in Ubuntu Desktop, you get an indication that a reboot is required (in Lucid, the logout icon turns red).

How can I check, from the command line, whether an Ubuntu server requires a reboot?

I could grep for 'System restart required' in /etc/motd, but I'd like a solution that's more elegant. Also, I want a solution that works in older releases, e.g. Hardy (8.04 LTS).

Answer 1

You can simply check if the file /var/run/reboot-required exists or not.

For example, any of these would tell you "no such file" or "file not found" if you do not need to reboot, otherwise they will show information about the file:

file /var/run/reboot-required
stat /var/run/reboot-required
ls /var/run/reboot-required

In a bash script, you can use:

#!/bin/bash
if [ -f /var/run/reboot-required ]; then
  echo 'reboot required'
fi

Answer 2

Normally if the file

/var/run/reboot-required 

exists you should reboot. You can see if this file is there by using this simple command in gnome-terminal.

ls /var/run/reboot-required

Answer 3

Aswell as the most direct methods written by others there is a handy indication if you use byobu - a set of scripts to make GNU screen a little more user friendly. It shows a set of information at the bottom of the screen, and that can include whether a reboot is required - along with whether updates are available, the time, uptime, memory used ...

In this screenshot you can see from the 199! on the bottom line with the red background that there are 199 updates available, and the ! means that some are security updates. The menu in the foreground is selecting which status notifications should be displayed.

If a reboot is required then this will be indicated by the symbol (R) displayed in the lower bar with white text on a blue background. More details and other indicators can be read about in the byobu man page.

Answer 4

In the package debian-goodies is a command named checkrestart which is quite useful. Its output can help you avoid a full reboot.

Answer 5

The /etc/motd file gets its information about whether a reboot is required from /var/run/reboot-required file.

You can check the content of this file in terminal by using cat /etc/motd command