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Re: freezeing the ext3 filesystem



On Apr 29, 2003  11:49 +0200, Per Andreas Buer wrote:
> I discovered that SGI XFS for Linux har a utility called xfs_freeze,
> which freezes the filsystem and makes sure that the filesystem is
> consistant. It is a bit like a mount -o remount,ro but it does not fail
> when applications have open files.
> 
> When we take snapshots of our XFS volume, we do "xfs_freeze -f /mnt/foo;
> lvcreate -s /dev/vg_foo/bar /dev/vg_foo/bar-snapshot;xfs_freeze -u
> /mnt/foo".
> 
> Is such a utility available for Ext3?

If you have the VFS lock patch from the LVM sources applied (STILL! not
part of the stock kernel), then it does the equivalent of the xfs_freeze
command inside the kernel as part of the LVM snapshot.

The problem with a command like xfs_freeze from user-space is that it
can cause the whole system to lock up if used incorrectly.  However,
in the *nix tradition, we have never prevented root from getting enough
rope to shoot themselves in the foot, so having "tune2fs -z/-Z" or
something wouldn't be a bad idea (for backups without LVM, etc).

Cheers, Andreas
--
Andreas Dilger
http://sourceforge.net/projects/ext2resize/
http://www-mddsp.enel.ucalgary.ca/People/adilger/





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