[systemd-devel] Cannot mount anything after recovering and redoing boot mbr

[Richard Maw]

On Mon, Jul 27, 2015 at 01:18:55AM -0500, Christopher Cox wrote:
> I suspect that somebody here knows why, but all mounts now fail... well all but /.
> 
> Has anyone run across this before?  What did I miss?

I have seen this happen when I was using a kernel that was old and
didn't have CONFIG_FHANDLE turned on (there now exists a work-around
using /proc/self/fdinfo if your kernel is new enough), which may be worth
checking, but given your later comments about manually mounting failing,
this seems less likely to be the problem.

> I accidentally messed up my boot mbr. and I did a rescue cd and
> chroot in order to rerun grub2-mkconfig and do a grub2-install.
> 
> Now the system boots to a grub menu and tries to boot, root
> fileystem mounts but all other mounts fail so goes into "emergency"
> mode.  From that shell I cannot seem to mount anything, they all
> fail saying that whatever I'm trying to mount is already mounted or
> it's "in use".  I can't fsck umounted filesystems either.  They all
> say "in use".

This sounds like a udev malfunction to me, but I'm not familiar enough with how
it works to do any more than guess.

My best guess is that there's some locking going wrong, since
udevd will flock(…, LOCK_SH|LOCK_NB) device nodes, and fsck will
flock(…, LOCK_EX|LOCK_NB), so udev doesn't try to use a device while
it is being fsck'd.