[CentOS] systemctl reboot -- server not accessible after reboot

Mon Oct 16 08:56:34 UTC 2017
James Hogarth <james.hogarth at gmail.com>

On 15 October 2017 at 12:20, Mike <1100100 at gmail.com> wrote:

> On Sat, Oct 14, 2017 at 2:29 PM, Vitalino Victor <vitalinobr at gmail.com>
> wrote:
> >
> > Try:
> >
> > # shutdown -r now
> >
> I'll have to try this late one evening.
> It's a production Samba Active Directory Domain Controller in
> production so it's difficult to do this without warning to users.
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Don't bother ... it makes no difference to how the shutdown happens, this
was nonsense "advice".

The shutdown 'command' is a symlink to systemctl which knows that it is
being called that way and will act on it ... the same as if you did
systemctl reboot

The issue surrounding remote syslog and gathering data on shutdown is that
depending on where the freeze you are experiencing occurs there may not be
any logs at all.

If it occurs before a sync to disk then any logs generated will be lost, if
it occurs after the pivot-root when /var/log is no longer mounted then
similarly any logs generated will be lost.

Of course if it is a *kernel* freeze issue then it is also likely that
whatever is occurring never gets to generate a log event ... as that's hard
to do with a frozen kernel ;)

I assume you've checked for BIOS/firmware updates and applied any pending?

Can you add IPMI (remote/out-of-band access) to that server? You may get
something through hardware event then ... this is why I prefer HP or Dell
kit over picking cheaper options when dealing with corporate needs ...
their iLO and iDRAC implementations are robust and can provide better
diagnosis on things like this with the built in hardware testing etc ...
and avoid a need to walk to a server and plug in a monitor ;)

If you can't set up remote syslog for some reason, or if there's no logs
found to help doing this, then I'd suggest removing rhgb and quiet from
your kernel command line, having a monitor attached at the time you do the
shutdown and monitor the console as you attempt the reboot.