Sunday, 4 November 2012



In our previous post, we created the LVM. But what is the use of the lvm, if we can't resize the lvm. It is the useful utility provided by the lvm, that we can resize the volume while not halting the current service. Resizing includes both extending and reducing the size.

The main important point while extending or reducing the lvm is that we need to umount the device before resizing the partition.

# umount /dev/vg_name/lv_name

Extending LVM:

Suppose we have the lvm lv_name of size 9GB , But our requirement is of 10GB. So we need to extend our logical volume by 1GB. Now there may be two circumstances:

1. Your volume group has 1GB space.
2. Volume group doesn't have enough space.

1. If volume group has 1 GB of space then, we can simply extend the lvm as:

# e2fsck -f /dev/vg_name/lv_name

This command will check the file system for errors. It will repair the bad sectors in the filesystem.

#lvextend -L +1G lv_name
# lvextend -l +100 lv_name

this will increase the lvm by 100 physical extends. For more information refer to previous post of create lvm.

Now run following command for using the extended space. As we can't format the volume, because our data may be lost. So we run the following command to use the extended space.

# resize2fs -f /dev/vg_name/lv_name 10G

The lvm is created and ready to mount.
After mounting, you will be able to use the extra space you added.

2. Volume group doesn't have extra space.

If volume group doesn't have extra space, we will go through following procedure.
Create new partition and change the hex code for that partition, choose the size according to your need.
Create physical volume from that partition. This is illustrated in my post create lvm.
Add the physical volume created to the existing volume group as:

# vg_extend vg_name /dev/sda9

Where sda9 be your new created physical volume.
Now go through the procedure as in step one.

Reducing LVM:

After umounting the lvm we need to go through the following procedure:

Suppose we have 10GB of lvm space, but 5 GB of space is more than sufficient for us, so we will reduce the lvm as:

# e2fsck -f /dev/vg_name/lv_name

# resize2fs -f /dev/vg_name/lv_name 5G

#lvreduce -L 5G /dev/vg_name/lv_name

# e2fsck -f /dev/vg_name/lv_name

Now remount the lvm and use the space. e2fsck command is used to check filesystem for errors and resize2fs will format the filesystem to the size.

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