How to recover/reinitialize a trashed /var partition?

[Brooks Davis]

On Thu, Jul 29, 2004 at 01:43:29AM +0100, David Kreil wrote:
> 
> Hello,
> 
> I am writing in the hope that someone can give me a hint of how to either 
> recover or recreate a virgin FreeBSD /var partition in an otherwise 
> (apparently) functioning system.
> 
> Probably in the process of a drive failure in our hardware raid our /var 
> volume got corrupted (yeah, I know this should not happen... sigh. I now also 
> understand why it is recommended having /var on a separate partition...).
> 
> I tried running fsck -y on /var after umount-ing it, which gives a 
> segmentation fault (exit on signal 11) some way through the process after 
> displaying
> 
> ** Phase 2 - Check Pathnames
> ROOT INODE UNALLOCATED
> UNEXPECTED SOFT UPDATE INCONSISTENCY
> 
> ALLOCATE? yes
> 
> CG 0: BAD MAGIC FILE NUMBER
> UNEXPECTED SOFT UPDATE INCONSISTENCY
> 
> Now I wonder
>  - is this beyond repair? I should much like to recover /var,
>    just to be able to have a look at the /var/logs to get an idea what
>    went wrong when. About 3.6GB are reported to be in use by df.

I'm guessing it's beyond reasionable repair, but I'm not ufs expert.
Unless you've got data on there that you really need and didn't have
backed up, I'd just rebuild from acratch.

>  - If I cannot recover the /var partition, what is the canonical way of
>    recreating it? I suppose I can run newfs on it, but how do I create the
>    necessary subdir structure with the right file-permissions? Could
>    /stand/sysinstall do that?

The short version is:

# populate /var
/usr/sbin/mtree -deU -f /etc/mtree/BSD.var.dist -p /var
# add sendmail bits
/usr/sbin/mtree -deU -f /etc/mtree/BSD.sendmail.dist -p /
# create new syslog files
/usr/sbin/newsyslog -CC
# add a lastlog file
/usr/bin/touch /var/log/lastlog

I cribbed this from /etc/rc.d/var on current.

-- Brooks

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