How do I know when a reboot is required?

[rnichols at interaccess.com]

On Mon, 12 Jan 2004, Simon Perreault <nomis80 at nomis80.org> wrote:
>
>On January 12, 2004 18:36, Don wrote:
>> But, how do I know what needs to be restarted/rebooted when updates to
>> things like cron or glibc are installed? To "be safe" I could always reboot
>> the machine after installing updates, but that seems unnecessary and
>> certainly unwanted.
>
>The only time you need to reboot the machine is when you install a new kernel. 
>All other rebooting is useless.

It's not quite that simple.  Let's say you update glibc to fix a
security hole or a memory leak.  That's great, and any program you start
after the update will be running with the new glibc.  But, all the
currently running programs will still be using the old, deleted version
of glibc, so services such as sendmail, cups, the X server, etc. don't
get the benefit of the change until they are restarted.  For something
as fundamental as glibc you basically have to bring the system down to
single-user mode in order to get rid of all the references to the old
version.

Offhand, I can't think of anything besides critical libraries and
perhaps the X server that would fall into the category of needing
special action to restart things after an update.  I believe Simon is
correct in his statement that only a kernel update actually _requires_ a
reboot (yes, there's even a way to restart 'init' without interfering
with the rest of the system), but for a few critical pieces rebooting
takes less time than figuring out how to avoid the reboot.

-- 
Bob Nichols         rnichols at interaccess.com