[lfs-dev] Issue with /dev/shm on host system.

John Joganic john at joganic.com
Thu Dec 20 13:59:40 PST 2012


On my Ubuntu 12 installation the only virtual file system listed in
/etc/fstab is /proc.  Everything else is a physical volume or swap. 
That said, this install is running in a VM.  I don't recall if I
installed it from media or downloaded it.  It seems worthwhile to have a
look at other installations.

-John

> Bruce Dubbs <mailto:bruce.dubbs at gmail.com>
> December 20, 2012 2:53 PM
>
> Both /run and /dev are in fstab. Also look at the mountvirtfs and
> mountfs boot scripts to put in context.
>
> -- Bruce
>
> John Joganic <mailto:john at joganic.com>
> December 20, 2012 2:36 PM
> Mount indicates that /dev is devtmpfs and /run is tmpfs, so you are
> correct; they must be getting regenerated on boot.
>
> Thank you,
> -John
>
> Matt Burgess <mailto:matthew at linuxfromscratch.org>
> December 20, 2012 1:25 PM
>
> I've just created a ticket in our Trac system
> (http://wiki.linuxfromscratch.org/lfs/ticket/3258) to make sure this
> isn't forgotten about.
>
> Thanks for the report, and thanks to Pierre for the quick fix.
>
> John, I think that /run should be a tmpfs on your Ubuntu host, but could
> you confirm please? If it is, then your /run/shm directory will be
> recreated on a reboot.
>
> Could you also confirm that /dev is also a tmpfs (or devtmpfs) please?
> That should mean that the /dev/shm symlink will also be recreated on a
> reboot (I'm assuming here that there's a udev rule or
> a /lib/udev/devices/shm node around that will achieve this. Therefore I
> don't think any permanent damage will have been done to your host.
>
> Regards,
>
> Matt.
>
> John Joganic <mailto:john at joganic.com>
> December 20, 2012 12:49 PM
> I have put that in place, and it does appear to resolve the issue.
>
> Is there a process in the LFS community to update the instructions?
> Given that, as written, the process can break the host, it seems
> appropriate to at least include a warning.
>
> Thank you for the quick reply.
>
> -John
>
> Pierre Labastie <mailto:pierre.labastie at neuf.fr>
> December 20, 2012 11:40 AM
> Why not create the $LFS/run dir at this stage and mount a tmpfs on it,
> then mkdir $LFS/run/shm and mount a tmpfs on it.
> Something like:
> if [ -h $LFS/dev/shm ]; then
> mkdir -p $/LFS/run/shm
> mount -vt tmpfs shm $LFS/run/shm
> fi
>
> Perhaps with a readlink to assess that the link is really /run/shm.
>
> Of course, there would be something similar when exiting chroot:
> if [ -h $LFS/dev/shm ]; then
> umount $LFS/run/shm
> fi
> Pierre



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