Before reducing the size of a file system, take a full backup of it!!!!

You must reduce in two parts:

- Reduce the ext3 file system
- Reduce the logical volume

You must ensure that when you reduce the logical volume, the logical volume size is not less that the file system size or you can loss the data, so you can reduce the file system size and then reduce the logical volume to a size a little bigger than the file system size, to ensure that you won't break the file system.

Procedure to reduce a 6 GB file system/logical volume to 5 GB, in this case, is /dev/rhel4vg/lvrhel4:

*** Check the current size:

# df -h /mnt/rhel4
S.ficheros          Tamaño Usado  Disp Uso% Montado en
/dev/mapper/rhel4vg-lvrhel4
                      6,0G  141M  5,8G   3% /mnt/rhel4

# lvdisplay /dev/rhel4vg/lvrhel4
  --- Logical volume ---
  LV Name                /dev/rhel4vg/lvrhel4
  VG Name                rhel4vg
  LV UUID                HcD4Es-Ar4s-0GaI-e3GS-29bI-8uuV-EE9NJH
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                6,00 GB
  Current LE             1536
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2

*** Umount the file system an run fsck:

# umount /mnt/rhel4/

# e2fsck -f /dev/mapper/rhel4vg-lvrhel4
e2fsck 1.39 (29-May-2006)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
/lost+found not found.  Create<y>? yes

Pass 4: Checking reference counts
Pass 5: Checking group summary information

/dev/mapper/rhel4vg-lvrhel4: ***** FILE SYSTEM WAS MODIFIED *****
/dev/mapper/rhel4vg-lvrhel4: 11/786432 files (18.2% non-contiguous), 60567/1572864 blocks

*** Resize the file sytem to 5 GB

# resize2fs  /dev/rhel4vg/lvrhel4 5G
resize2fs 1.39 (29-May-2006)
Resizing the filesystem on /dev/rhel4vg/lvrhel4 to 1310720 (4k) blocks.
The filesystem on /dev/rhel4vg/lvrhel4 is now 1310720 blocks long.

*** Resize the logical volume to a value a little bigger than 5 GB (Here you can see in the warning that will be reduced to 5,18 GB)

# lvreduce /dev/rhel4vg/lvrhel4 -L 5300M
  /dev/cdrom: open failed: Sistema de ficheros de sólo lectura
  Attempt to close device '/dev/cdrom' which is not open.
  WARNING: Reducing active logical volume to 5,18 GB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lvrhel4? [y/n]: y
  Reducing logical volume lvrhel4 to 5,18 GB
  Logical volume lvrhel4 successfully resized

*** Verify the new sizes

# lvdisplay /dev/rhel4vg/lvrhel4
  --- Logical volume ---
  LV Name                /dev/rhel4vg/lvrhel4
  VG Name                rhel4vg
  LV UUID                HcD4Es-Ar4s-0GaI-e3GS-29bI-8uuV-EE9NJH
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                5,18 GB
  Current LE             1325
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:2

# mount /mnt/rhel4/

# df -h /mnt/rhel4/
S.ficheros          Tamaño Usado  Disp Uso% Montado en
/dev/mapper/rhel4vg-lvrhel4
                      5,0G  141M  4,8G   3% /mnt/rhel4


Pretty cool!!, isn't it??