lvreduce ext4 example

lvreduce ext4 example

 

An lvreduce ext4 example to show you how to shrink an ext4 filesystem? The example below is a quick guide with a basic safe approach to reducing the size of an logical volume. Hopefully the raw disk was used with pvcreate and not a partition. Doing so would defeat the purpose of having LVM, which is to use the “logical” portion of the volume manager. Growing and shrinking. When you are shrinking a filesystem under control of LVM, you have to tell the filesystem first that you want it to be smaller. And then you have to reduce the size of the logical volume. So below are the basic steps to reducing the size of an ext4 filesystem.

In this example, the /var/lib/mysql-data filesystem is too big. I need to take some of this space on that volume group and give to another lv. it is 170GB, and I want to shrink it to 100GB.

# df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/vg-root-root_lv

2.0G  398M  1.5G  22% /

tmpfs                 2.0G     0  2.0G   0% /dev/shm

/dev/sda1             194M   48M  137M  26% /boot

/dev/mapper/vg-root-home_lv

                      485M   11M  449M   3% /home

/dev/mapper/vg-opt_lv

                      9.9G  611M  8.8G   7% /opt

/dev/mapper/vg-root-tmp_lv

                      2.9G  171M  2.6G   7% /tmp

/dev/mapper/vg-root-usr_lv

                      4.9G  2.8G  1.9G  61% /usr

/dev/mapper/vg-root-var_lv

                      2.0G  773M  1.1G  42% /var

/dev/mapper/vg-data-mysql-data_lv

                      183G  3.3G  170G   2% /var/lib/mysql-data

Unmount the filesystem

I use the unmount command to unmount the filesystem. Remember I sai safe way :)

# umount /var/lib/mysql-data

# e2fsck -f /dev/mapper/vg-data-mysql-data_lv

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

/dev/mapper/vg-data-mysql-data_lv: 68666/12124160 files (5.4% non-contiguous), 1623264/48496640 blocks

Resize the ext4 filesystem

Resize or shrink the ext4 filesystem

# resize2fs -p /dev/mapper/vg-data-mysql-data_lv 100G

resize2fs 1.41.12 (17-May-2010)

Resizing the filesystem on /dev/mapper/vg-data-mysql-data_lv to 26214400 (4k) blocks.

Begin pass 2 (max = 5713)

Relocating blocks             XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Begin pass 3 (max = 1480)

Scanning inode table          XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Begin pass 4 (max = 1547)

Updating inode references     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

The filesystem on /dev/mapper/vg-data-mysql-data_lv is now 26214400 blocks long.

Shrink the Logical Volume

Resize or shrink the logical volume using the lvreduce command, which is part of the LVM suite of commands. We give the lvreduce command the size argument is Gigabits.

# lvreduce -L 100G /dev/mapper/vg-data-mysql-data_lv

WARNING: Reducing active logical volume to 100.00 GiB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce mysql-data_lv? [y/n]: y

Reducing logical volume mysql-data_lv to 100.00 GiB

Logical volume mysql-data_lv successfully resized

Remount the logical volume

# mount /var/lib/mysql-data

And now that the filesystem is remounted and no errors were seen, you can run the df comnand and see that the logical volume is now 100GB.

# df -h  /var/lib/mysql-data

Filesystem            Size  Used Avail Use% Mounted on

/dev/mapper/vg-data-mysql-data_lv

99G  3.3G   91G   4% /var/lib/mysql-data

It’s that easy. The only LVM on the market that is easier is ZFS which is a combination filesystem and LVM. A 2 for 1 type of deal. ZFS is king in my world. End of tangent.