How to check if not clean shutdown?

[Warner Losh]

You can't, in general. By the time the boot loader starts, all knowledge of
past boots is gone, unless specific counter-measures were put in place.

However, if root is UFS and read/write in your box, it will be unclean on
anything but a clean shutdown/reboot. If it's read-only, ZFS or NFS
mounted, then you can't use this method.

If you have UEFI, you can set a UEFI variable on shutdown and clear it on
boot. If it's not there on boot, you had an unclean shutdown. You could do
the same with a file in a r/w filesystem that doesn't record clean/unclean
(like ZFS or NFS).

Locally, we have hacks to IPMI to record kernel crashes in the IPMI log,
but that's kinda specific to the BMC we have on our boards...

Warner


On Tue, May 22, 2018 at 7:57 AM, Johannes Lundberg <johalun0 at gmail.com>
wrote:

> Hi
>
> In the boot process on my test machines I'd like to do different things
> depending on the last run was a clean shutdown or kernel panic. Where/How
> can I get this information?
>
> Thanks!
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