[systemd-devel] /proc and /sys get unmounted during boot from NFS, which results in boot error

[Lennart Poettering]

On Tue, 03.02.15 23:00, Olaf Leidinger (oleid at mescharet.de) wrote:

> Dear systemd-devel list,
> 
> I'm trying to debug the following problem:
> 
> For some unknown reason, /proc and /sys get unmounted during boot
> from a NFS mounted rootfs. Booting to an emergency shell, I can observe
> them disappear by first calling mount (which reads from /proc due to /etc/mtab 
> being a symlink) and then calling "ls /proc". After calling ls, mount obviously
> complains about not being able to read mtab, instead of listing the mounts as 
> before.
> 
> A 2nd or 3rd call of mount before listing /proc works fine, too.

That's certainly weird. The log you pasted below doesn't show any
other commands running, which is particularly weird.

Maybe something from your initrd is acting weird?

systemd itself mounts /proc and /sys very early during boot, and then
never touches them anymore. They are excluded from the usual .mount
unit logic in order to ensure they never accidentally disappear...

> Booting with debug options yields no further information, no new
> messages appear while the debug shell is running and the messages
> before are not very interesting (as far as I can tell) [--> end of
> mail].

It might be interesting to strace PID 1 while you are doing this. And
if that doesn't help strace the other processes you run, to see if any
of them unmounts anything.

Lennart

-- 
Lennart Poettering, Red Hat