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lvdisplay: shows information about Logical Volumes. 5.2.3. Extending Volume Groups

Continuing with srv as an LVM volume example, this section covers adding a second hard disk, creating a Physical Volume (PV), adding it to the volume group (VG), extending the logical volume srv and finally extending the filesystem. This example assumes a second hard disk has been added to the system. In this example, this hard disk will be named /dev/sdb and we will use the entire disk as a physical volume (you could choose to create partitions and use them as different physical volumes)


Make sure you don't already have an existing /dev/sdb before issuing the commands below. You could lose some data if you issue those commands on a non-empty disk.

1. First, create the physical volume, in a terminal execute:

sudo pvcreate /dev/sdb

2. Now extend the Volume Group (VG):

sudo vgextend vg01 /dev/sdb

3. Use vgdisplay to find out the free physical extents - Free PE / size (the size you can allocate). We will assume a free size of 511 PE (equivalent to 2GB with a PE size of 4MB) and we will use the whole free space available. Use your own PE and/or free space.

The Logical Volume (LV) can now be extended by different methods, we will only see how to use the PE to extend the LV:

sudo lvextend /dev/vg01/srv -l +511

The -l option allows the LV to be extended using PE. The -L option allows the LV to be extended using Meg, Gig, Tera, etc bytes.

4. Even though you are supposed to be able to expand an ext3 or ext4 filesystem without unmounting it first, it may be a good practice to unmount it anyway and check the filesystem, so that you don't mess up the day you want to reduce a logical volume (in that case unmounting first is compulsory).

The following commands are for an EXT3 or EXT4 filesystem. If you are using another filesystem there may be other utilities available.

sudo umount /srv

sudo e2fsck -f /dev/vg01/srv

The -f option of e2fsck forces checking even if the system seems clean.

5. Finally, resize the filesystem:

sudo resize2fs /dev/vg01/srv

6. Now mount the partition and check its size.

mount /dev/vg01/srv /srv && df -h /srv

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