On Wed, Oct 05, 2016 at 01:57:20PM -0000, Peter Larsen wrote:
> I never needed to reboot. I just keep working on my stuff, when
> done I turn the laptop off. Is there any reason to reboot right after
That's actually a very common misunderstanding. People think that "yum/dnf
update" leaves their system in a new updated stage. But it doesn't (completely).
It never has. Only after a reboot are all your patches applied and active.
Existing/running processes are rarely if ever reloaded. So when you update libraries,
kernels etc. your system will keep running with the old versions of those libraries
loaded. Remember, in Linux a inode is never deleted until the very last process has
released it. So any read file handles will keep a file, even one you cannot see with ls,
The only real complete update you can do is one that does a full reboot. We do have a few
tricks with DNF which will attempt to let you know what needs restarting. But you'll
find that a good part of our updates requires a restart of most if not all your system, in
order for the updates to become fully active.
What you write is mostly true, at least for "user" programs.
Various system services actually get restarted, e.g. all those that
are running as systemd units and are have %systemd_postun_with_restart in %post.
For servers that should be a majority of daemons (but not all, dbus-daemon
being a notable exception). Systemd also supports seamless restart of socket-activated
services, so it's even possible to restart daemons that are in live use without
For users programs we have nothing like that unfortunately.
But yeah, I'm nitpicking here, the general rule is what you say: one
has to restart the machine to make sure everything has bee restarted.
> This problem often shows itself on long running servers by a system not coming back
up/online after a reboot. And nobody understand why - but it's pretty simple. Nobody
tested that things worked after an update, and in most cases that requires a reboot. If
you kernel, glibc or network control system gets updated, you'll need to reboot to
reload them. Or of course take your network offline with everything running on your box
> So it may look like that "it works just fine" but it's a deception.
It's still running the older versions of libraries etc for most processes. If you
start looking at what's actually running after your update, you'll find that a
good part of your updated packages aren't running (yet) - and old versions are still
active. If you're attempting to apply security updates, this is an important
distinction and vital to be compliant. For us ordinary users, it's mostly an annoyance
as features we wanted, aren't there right after an update, or programs starts failing
after an update, as they attempt to dynamicly load in modules and find them
"changed", at times not even compatible with the running older version, and
things end up "strange". I've seen fonts go nuts, backgrounds disappear,
general themes not working etc. after an update on a workstation, simply because the
structure got changed - CSSes looking for files that no longer are there, etc.