Date: Sat, 29 Dec 2001 03:36:04 +0100 (CET) From: BOUWSMA Beery <freebsd-user@netscum.dyndns.dk> To: freebsd-current@freebsd.org Subject: Re: nullfs and unionfs Message-ID: <200112290236.fBT2a4800748@beerswilling.netscum.dyndns.dk>
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[replies sent directly to me may timeout and bounce, since I'm not
online as often as I should be, but I'll check the list archives]
I wrote a while back to freebsd-hackers:
> Is it safe (relatively speaking) to use the null and the union
> filesystems?
Well, so far I have had no serious problems with -stable, though
a few apparent bugs seem to be obvious; however, it seems that
the unionfs mount in -current is a great way for me to readily
and reliably panic the system, with a couple mutex panics that I
didn't make notes of.
Apart from the failure of getcwd() on my particular unionfs mount
atop a nullfs mount in both -stable and -current, I seem to see a
few other oddities only in -current. To wit:
[01:48:09]root@dastardly.newsbastards.org:~{507}# mount_unionfs /usr/local/sour
ce-hacks/ /usr/src
[01:48:33]root@dastardly.newsbastards.org:~{508}# ls -la !$
ls -la /usr/src
total 127
drwxr-xr-x 42 root wheel 512 Dec 27 02:43 .
drwxr-xr-x 42 root wheel 512 Dec 27 02:43 .
drwxr-xr-x 24 root wheel 512 Dec 27 06:31 ..
drwxr-xr-x 24 root wheel 512 Dec 27 06:31 ..
-rw-r--r-- 1 root wheel 4735 Sep 5 1999 COPYRIGHT
-rw-r--r-- 1 root wheel 7494 Mar 27 2001 Makefile
-rw-r--r-- 1 root wheel 25954 Dec 24 02:46 Makefile.inc1
-rw-r--r-- 1 root wheel 9761 Aug 28 1999 Makefile.upgrade
-rw-r--r-- 1 root wheel 2678 Aug 31 2000 README
-rw-r--r-- 1 root wheel 32930 Dec 27 23:45 UPDATING
drwxr-xr-x 36 root wheel 512 Dec 27 02:43 bin
drwxr-xr-x 36 root wheel 512 Dec 27 02:43 bin
drwxr-xr-x 53 root wheel 512 Dec 27 03:17 contrib
drwxr-xr-x 53 root wheel 512 Dec 27 03:17 contrib
drwxr-xr-x 9 root wheel 512 Dec 27 02:43 crypto
drwxr-xr-x 9 root wheel 512 Dec 27 02:43 crypto
drwxr-xr-x 19 root wheel 512 Dec 27 02:43 etc
etc. Trust me, I am not making this up.
> mount -t union -a fail to do anything, like
> /usr/local/system/src /usr/src null ro
> /usr/local/source-hacks /usr/src/ union rw )
> ^
I just noticed that NetBSD's `mount' man page says that an `-a' mount
will not work if the same *type* of mount on the mountpoint already
exists; perhaps FreeBSD needs to check the type in addition to the
mountpoint in ismounted() and allow certain types of filesystems,
such as unionfs, to pile up atop existing mountpoints, in order for
the above fstab lines to work without the ugly trailing directory slash...
thanks
barry bouwsma
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