After crash, / comes up mounted read-only, but in multiuser; mfs /tmp?

John Baldwin jhb at
Fri Dec 2 10:19:46 PST 2005

On Friday 02 December 2005 11:09 am, Maksim Yevmenkin wrote:
> John Baldwin wrote:
> > On Friday 02 December 2005 08:33 am, David Xu wrote:
> >>Robert Watson wrote:
> >>>While testing the new DRM update (went badly :-), I crashed my system
> >>>and had to power cycle it.  When it came back up, not surprisingly,
> >>>the file systems weren't clean.  When I reached a login prompt, I
> >>>logged in to modify /etc/rc.conf, and to my surprise, was told that
> >>>/etc/rc.conf wasn't writable.  Turns out it was because / was mounted
> >>>read-only:
> >>>
> >>>...
> >>>
> >>>/dev/ad0s3a on / (ufs, local, read-only)
> >>>devfs on /dev (devfs, local)
> >>>/dev/ad0s3e on /usr (ufs, local, soft-updates)
> >>>/dev/ad0s3d on /var (ufs, local, soft-updates)
> >>>/dev/md0 on /tmp (ufs, local)
> >>>
> >>>The rc scripts helpfully mounted an MFS /tmp for me, which while
> >>>friendly, succeeded in masking the problem and allowing the system to
> >>>come up in a rather undesirable state (from my perspective).  So it
> >>>sounds like maybe / wasn't remounted properly, and then the scripts
> >>>were too helpful thinking it was a diskless system.
> >>
> >>I have seen this for some days,  one machine I even have to reinstall
> >>the system because mount -u / does not work. :-(
> >
> > I've seen reports that mount -u -w / works whereas mount -u -o rw /
> > doesn't, so you might be able to mount -u -w / in single user mode after
> > running fsck as a way to recover.  Either that or boot single user, run
> > fsck, and then reboot before going into multiuser.
> this is all very nice as workaround, but does somebody actually working
> on the _real_ problem?
> it would be nice to have something in UPDATING saying this is broken
> now. all i can find in UPDATING is
> 20051129:
>   The nodev mount option was deprecated in RELENG_6 (where it
>   was a no-op), and is now unsupported.  If you have nodev or dev listed
>   in /etc/fstab, remove it, otherwise it will result in a mount error.
> sure that is not the problem, is it?

No, it's probably due to all the nmount changes in HEAD recently that have 
broken various mount options for other FS's such as smbfs and msdosfs as 
well.  Probably should bug crodig@ or just dig into the code to see how -o rw 
used to be handled and how it is not handled now.

John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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