Resize a logical volume

From Crashcourse Wiki

If you're using LVM for your filesystem partitioning, you might need to occasionally resize a logical volume (and its corresponding filesystem, of course). As an example, consider my (ext3-format) 1G /opt filesystem, which isn't doing much useful at the moment, so we can resize it to 5G as an utterly pointless exercise.

NOTE: Apparently, you don't need to unmount the filesystem to resize it, so I'll be fixing up this page shortly.

Examining the logical volume

First, check the current filesystem properties:

# mount
...
/dev/mapper/f8-opt on /opt type ext3 (rw)
...
# df /opt
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/f8-opt     1015704     60124    903152   7% /opt

So that filesystem is obviously 1G in size, and 7% full. In addition, given that my volume group name is clearly "f8", I can refer to that particular logical volume using one of two filenames:

# ls -l /dev/mapper/f8-opt
brw-rw---- 1 root disk 253, 1 2007-12-24 05:23 /dev/mapper/f8-opt
# ls -l /dev/f8/opt
lrwxrwxrwx 1 root root 18 2007-12-24 05:23 /dev/f8/opt -> /dev/mapper/f8-opt

Check the current properties of that logical volume:

# lvdisplay /dev/f8/opt
  --- Logical volume ---
  LV Name                /dev/f8/opt
  VG Name                f8
  LV UUID                7EbBEo-mwzB-y4bS-kyuC-H9f9-oEmW-1COYOx
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                1.00 GB            <---- Before the resize, of course.
  Current LE             32
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1
#

Extending the /opt logical volume and filesystem

The steps:

• Unmount the filesystem.
• Extend the logical volume.
• Extend the (ext3) filesystem to match the size of the logical volume.

# umount /opt
# lvextend -L +4G /dev/f8/opt        [Make the logical volume 4G larger.]
  Extending logical volume opt to 5.00 GB
  Logical volume opt successfully resized
# lvdisplay /dev/f8/opt
  --- Logical volume ---
  LV Name                /dev/f8/opt
  VG Name                f8
  LV UUID                7EbBEo-mwzB-y4bS-kyuC-H9f9-oEmW-1COYOx
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                5.00 GB        <------ Excellent.
  Current LE             160
  Segments               2
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1
# e2fsck -f /dev/f8/opt              [Check the filesystem for safety's sake.]
...
# resize2fs /dev/f8/opt              [By default, resize FS to new logical volume size.]
resize2fs 1.40.2 (12-Jul-2007)
Resizing the filesystem on /dev/f8/opt to 1310720 (4k) blocks.
The filesystem on /dev/f8/opt is now 1310720 blocks long.
#

And let's check the results:

# mount /opt
# df /opt
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/f8-opt     5078656     60880   4808064   2% /opt
# find /opt
... should see old content here, of course ...
#

Looks good, and we're done. Decreasing the size of a filesystem and logical volume, as well as working with other filesystem formats, is left as an exercise for the reader:

# man lvreduce

Feedback to rpjday@crashcourse.ca.

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