Notes of a Systems Administrator: 05/13/16

So you have run out of space on one of your LVM volumes, but there's another volume with too much space that's not being used. You need to shrink one and grow the other! First thing first! DO NOT SHRINK A (LVM) VOLUME WITHOUT resizing the FILESYSTEM first! Your data (filesystem) will be screwed! So let's have a go. Here will have a full volume /filetek/sth/sthdbs, and we have a volume being used as a mount point with too much space /filetek. We need to shrink /filetek and expand /filetek/sth/sthdbs.

root@server /
$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/volg0-root
                      969M  526M  394M  58% /
/dev/sda1             190M   85M   96M  47% /boot
/dev/mapper/volg0-home
                      4.7G  173M  4.3G   4% /home
/dev/mapper/volg0-usr
                      3.8G 1018M  2.6G  28% /usr
/dev/mapper/volg0-var
                      3.8G  470M  3.2G  13% /var
/dev/mapper/volg1-filetek
                      197G  9.4G  178G   6% /filetek
/dev/mapper/volg1-filetek--tmp
                       50G   52M   47G   1% /filetek/tmp
/dev/mapper/volg1-filetek--jrnl1
                       50G  885M   46G   2% /filetek/jrnl1
/dev/mapper/volg1-filetek--sthdbs
                      1.0T  970G  1.7G 100% /filetek/sth/sthdbs
/dev/mapper/volg1-filetek2
                      197G  1.6G  186G   1% /filetek2
/dev/mapper/volg1-filetek2--tmp2
                       50G   52M   47G   1% /filetek2/tmp2
/dev/mapper/volg1-filetek--jrnl2
                       50G  885M   46G   2% /filetek2/jrnl2

Let's umount all the volumes involved:

root@server ~
$ umount /filetek/tmp /filetek/jrnl1 /filetek/sth/sthdbs
root@server ~
$ umount /filetek

Let's resize (shrink) /filetek to 32GB by fsck'ing it first:

root@server ~
$ fsck -f /dev/mapper/volg1-filetek
fsck from util-linux-ng 2.17.2
e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
filetek: 2119/13107200 files (2.1% non-contiguous), 3307507/52428800 blocks

Using resize2fs:

root@server ~
$ resize2fs /dev/mapper/volg1-filetek 32G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/volg1-filetek to 8388608 (4k) blocks.
The filesystem on /dev/mapper/volg1-filetek is now 8388608 blocks long.

Now we can safely reduce the LVM volume size with the lvreduce command:

root@server ~
$ lvreduce -L 40G /dev/mapper/volg1-filetek
  WARNING: Reducing active logical volume to 40.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce filetek? [y/n]: y
  Size of logical volume volg1/filetek changed from 200.00 GiB (51200 extents) to 40.00 GiB (10240 extents).
  Logical volume filetek successfully resized

All, very good so let's expand our volume that has run out of space:

root@server ~
$ lvextend --size +200G /dev/mapper/volg1-filetek--sthdbs
  Size of logical volume volg1/filetek-sthdbs changed from 1.02 TiB (266240 extents) to 1.21 TiB (317440 extents).
  Logical volume filetek-sthdbs successfully resized

Now we need to grow the filesystem, but first let's fsck (e2fsck) it:

root@server ~
$ e2fsck -f /dev/mapper/volg1-filetek--sthdbs
e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
filetek-sthdbs: 1170/68157440 files (21.9% non-contiguous), 258555686/272629760 blocks

root@server ~
$ resize2fs /dev/mapper/volg1-filetek--sthdbs
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/volg1-filetek--sthdbs to 325058560 (4k) blocks.
The filesystem on /dev/mapper/volg1-filetek--sthdbs is now 325058560 blocks long.

Let's re-mount both filesystems to file all is good!

root@server ~
$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/volg0-root
                      969M  526M  394M  58% /
/dev/sda1             190M   85M   96M  47% /boot
/dev/mapper/volg0-home
                      4.7G  173M  4.3G   4% /home
/dev/mapper/volg0-usr
                      3.8G 1018M  2.6G  28% /usr
/dev/mapper/volg0-var
                      3.8G  470M  3.2G  13% /var
/dev/mapper/volg1-filetek2
                       32G  1.6G   29G   6% /filetek2
/dev/mapper/volg1-filetek--tmp
                       50G   52M   47G   1% /filetek/tmp
/dev/mapper/volg1-filetek--jrnl1
                       50G  885M   46G   2% /filetek/jrnl1
/dev/mapper/volg1-filetek2--tmp2
                       50G   52M   47G   1% /filetek2/tmp2
/dev/mapper/volg1-filetek--jrnl2
                       50G  885M   46G   2% /filetek2/jrnl2
/dev/mapper/volg1-filetek
                       32G  9.4G   21G  32% /filetek
/dev/mapper/volg1-filetek--sthdbs
                      1.2T  970G  189G  84% /filetek/sth/sthdbs

Notes of a Systems Administrator

Friday 13 May 2016

Shrinking filesystems with LVM - CentOS