Re: fsck in background?

Andreas Dilger wrote:

> On Mar 31, 2003  21:14 +0400, Hans Reiser wrote:
>  
>
> > Oleg Drokin wrote:
> >
> >    
> >
> > > On Mon, Mar 31, 2003 at 12:30:37PM +0200, myciel wrote:
> > >      
> > >
> > > > so I'm curious if maybe fscking in background is planned? - idea is not new
> > > > and bsd guys say that they have it  for freebsd 5.0 in ffs.
> > > >   
> > > >
> > > >        
> > > This is not possible for reiserfs, I think.
> > > reiserfs have non-constant metadata location , so while you can certainly
> > > check fs consistency of some snapshot, you cannot fix it because all the
> > > real data might have ben shifted to other blocks, old blocks might have
> > > been already freed and so on.
> > >      
> > It can be done, but I don't have the funding/staff for it.
> >    
>
> I wrote a script to do this once, using LVM snapshots.  Attached here.
> I haven't used it in a long time, and didn't do much other than write
> it and test it out a bit, but it likely works OK.
>
> It obviously doesn't actually fix any problems that it detects, but
> for systems that run a long time it avoids the need to do a shutdown
> to verify large filesystems are intact.  For ext2/3 it also resets the
> "last checked" count/time so that ext3 will not do gratuitous full fscks
> if the system has been up over 6 months (assuming you run the script
> periodically while the system is running).
>
> Cheers, Andreas
> ============================= lvm-fsck =============================
> #!/bin/sh
> # Automatically checks ext2/ext3 filesystems that are currently mounted
> # and also residing on LVM logical volumes, so that we can snapshot them.
> # You need to have the LVM VFS locking patch applied for this to work.
> #
> # (C) Andreas Dilger, 2001
> #
> # Licensed under the GNU General Public License, version 2 or later
>
> #set -vx
>
> # Use the PATH to find any installed fsck programs
> PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin
> PROG=`basename $0`
>
> FSCKLV=lvfsck
> lvscan | grep ACTIVE | while read LVSCAN DASH ACTIVE LV LV2 SIZE; do
>         [ "$LV" = "Snapshot" ] && continue
>         if [ "$LV" = "Original" ]; then
>                 LV=`echo $LV2 | tr -d \"`
>         else
>                 LV=`echo $LV | tr -d \"`
>         fi
>         VG="`dirname $LV`"
>         LVS="$VG/$FSCKLV"
>         # This could be smarter (i.e. removing old snapshot after checking if
>         # another lvm-fsck is running, but we don't want to do concurrent fscks
>         # if it takes a really long time to run, or if the script has problems.
>         # Sadly, lvdisplay does not return an error code if $LVS doesn't exist
>         if [ "`lvdisplay $LVS 2> /dev/null`" ]; then
>                 echo "$LVS exists!  Unable to check $LV"
>                 continue
>         fi
>
>         # Check if this LV is mounted and has a fsck-able filesystem on it
>         AWKLV="`echo $LV | tr / .`"
>         FSTYPE=`mount | awk "/^$AWKLV/ { print \\$5 }"`
>         FSCK="`which fsck.$FSTYPE 2> /dev/null`"
>         [ "$FSCK" ] || continue
>
>         echo "$PROG: running read-only $FSCK on $LV"
>         # Just a guess at how much snapshot space we need
>         SIZE="`df -P $LV | tail +2 | awk '{ print $2 / 500 }'`"
>         lvcreate -s -L ${SIZE}k -n $FSCKLV $LV > /dev/null
>         rc=$?
>         if [ $rc -ne 0 ]; then
>                 echo "Creating snapshot of $LV at $LVS failed with rc=$rc" 1>&2
>                 continue
>         fi
>         case $FSTYPE in
>         ext2|ext3) $FSCK -f -n $LVS; rc=$?
>                 if [ $rc -eq 0 ]; then
>                         tune2fs -C 0 $LV > /dev/null
>                         tune2fs -T now $LV > /dev/null 2>&1
>                         ;;
>         reiserfs) echo Yes | $FSCK --check $LVS; rc=$? ;;
>         *) echo "Don't know how to check $FSTYPE filesystems passively"; rc=$1;;
>         esac
>         [ $rc -ne 0 ] && echo "$FSCK of $LV failed with rc=$rc" 1>&2
>         lvremove -f $LVS > /dev/null
>         rc=$?
>         [ $rc -ne 0 ] && echo "lvremove of $LVS failed with rc=$rc" 1>&2
> done
> --
> Andreas Dilger
> http://sourceforge.net/projects/ext2resize/
> http://www-mddsp.enel.ucalgary.ca/People/adilger/
>
>
>
>  
Oleg, consider putting a link to this on our web site.....

--
Hans