The Debian Policy doesn't provide any guidance on when a package should use
reboot-required, only that that's the mechanism to be used:
9.12. Signaling that a reboot is required
Programs can signal that a reboot is required by
/run/reboot-required. It is conventional to add the name of the
package(s) requiring the reboot to
Programs should not add a package name to
if it is already present there.
/run/reboot-required mechanism is used when a reboot is needed
to fully apply the changes introduced by package installation or
upgrade. Typically it is the
postinst maintainer script that touches
/run/reboot-required, at the end of a successful configuration of
There are no guarantees provided by the
convention as to when or whether the requested reboot will occur.
So, I'd say any package maintainer can use it if they feel a reboot is required after the package is updated. Common examples include core libraries like glibc, which are used by so many things that rebooting is pretty much the only effective way to get everything to use the updated library.
One user checked the
postinsts of a few packages and came up with varied list: https://askubuntu.com/a/731993/158442. Other examples can be found in the bug report asking for documentation on this mechanism to be included in the Debian Policy (#919507).