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Re: Shrink an XFS filesystem? (LVM)

Subject: Re: Shrink an XFS filesystem? (LVM)
From: Eric Sandeen <sandeen@xxxxxxx>
Date: 18 Jan 2002 14:24:26 -0600
Cc: linux-xfs@xxxxxxxxxxx
In-reply-to: <1011381555.2106.6.camel@stout.americas.sgi.com>
References: <871ygn8p71.fsf@juniper.intra.microsharp.com> <20020118200222.A26255@wotan.suse.de> <1011380895.23885.7.camel@jen.americas.sgi.com> <1011381555.2106.6.camel@stout.americas.sgi.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Fri, 2002-01-18 at 13:19, Eric Sandeen wrote:
> On Fri, 2002-01-18 at 13:08, Steve Lord wrote:
> > Might that in place filesystem converter work for this? 
> 
> Hm, maybe.  Convert from XFS to XFS, but make the loopback filesystem
> the size of your new, smaller filesystem.  And before you map the
> loopback filesystem down to the block device, shrink the block device
by
> removing a volume.

Actually, this will work!  (Except that convertfs seems to have trouble
converting _to_ xfs, let alone shrinking, I'll have to look at this...)

However, behold this example of using secret Russian technology* to
shrink an ext2 filesystem from 197 megs to 95 megs:

*http://tzukanov.narod. ru/convertfs/

-=BEFORE=-

[root@lite convertfs]# mke2fs -q /dev/sda1
mke2fs 1.23, 15-Aug-2001 for EXT2 FS 0.5b, 95/08/09
[root@lite convertfs]# mount /dev/sda1 /mnt/sda1/
[root@lite convertfs]# cp -aR /mnt/sda2/sda1/* /mnt/sda1/
[root@lite convertfs]# df -h /dev/sda1
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             197M   32M  155M  17% /mnt/sda1
[root@lite convertfs]# umount /dev/sda1


-=DURING=-

Run convertfs, with slight modifications:
(mkfs of new filesystem restricts size to new, smaller size)
(100000 blocks)

[root@lite convertfs]# ./shrinkfs 
== Creating clone of filesystem's device ==
===== Creating destination filesystem =====
mke2fs 1.23, 15-Aug-2001 for EXT2 FS 0.5b, 95/08/09
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
25064 inodes, 100000 blocks
5000 blocks (5.00%) reserved for the super user
First data block=1
13 block groups
8192 blocks per group, 8192 fragments per group
1928 inodes per group
Superblock backups stored on blocks: 
        8193, 24577, 40961, 57345, 73729

Writing inode tables: done                            
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 35 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
============== Copying files ==============
total 18
drwxr-xr-x    3 root     root         1024 Jan 16 10:35 foo
drwxr-xr-x    2 nfsnobod nfsnobod     1024 Jan 15 16:31 linktest
drwxr-xr-x    2 root     root        12288 Jan 18 13:26 lost+found
drwxr-xr-x   10 root     root         2048 Jan 17 14:10 root
drwxr-xr-x    3 root     root         1024 Jan 15 13:37 testing
drwxr-xr-x    2 root     root         1024 Jan 17 14:12 tmp
Filesystem            Size  Used Avail Use% Mounted on
/dev/loop7             95M   32M   58M  36% /usr/convertfs/fs2root
=== Preparing info for block relocation ===
0+1 records in
0+1 records out
============ Relocating blocks ============
Loading indexblocks... done.
Relocating blocks... done.
<etc>
<dies with an assert, but...>


-=AFTER=-

[root@lite convertfs]# e2fsck /dev/sda1
e2fsck 1.23, 15-Aug-2001 for EXT2 FS 0.5b, 95/08/09
/dev/sda1: clean, 1475/25064 files, 35350/100000 blocks
[root@lite convertfs]# mount /dev/sda1 /mnt/sda1/
[root@lite convertfs]# df -h /dev/sda1
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              95M   32M   58M  36% /mnt/sda1

Ta-Da!

Um, don't try this with data that _matters_ - ok?

-Eric
-- 
Eric Sandeen      XFS for Linux     http://oss.sgi.com/projects/xfs
sandeen@xxxxxxx   SGI, Inc.


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