LVM

What is LVM?

      LVM is Logical Volume management. In computer storage, lvm provides a method of allocating spaces on mass storage device that is more flexible than conventional partition schemes. One thing to keep in mind, we cannot bring /boot on LVM.

Following are the steps to create LVM on linux.

• Create physical volume
• Create volume group
• Create logical volume
  
• Make file system
•  Mount the file system

      1. Login with root user

2. Look for the unpartion slice or disk

# fdisk -l

Say for example we have /dev/sda4,/dev/sda5,etc

3. We will now create physical volume

# pvcreate /dev/sda4

We can also add two or more slice

# pvcreate /dev/sda4 /dev/sda5

To look for the details of physical volume, run the following command

# pvdisplay

4. Now create the volume group.

# vgcreate data /dev/sda4 /dev/sda5

where data is the name of volume group, by default 5mb volume group is created.

To make aroung 1gb we use the command,

# vgcreate -s 1G data /dev/sda4 /dev/sda5

# vgdisplay

Will display the  volume group details.

5. Next step is to create Logical volume

# lvcreate -l 50 -n datavol data

where datavol is the name of logical volume. If we want the logical volume in KB,MB,GB use -L

# lvcreate -L 20G -n datavol data

# lvdisplay

If will display teh details of Logical volume we created.

6. Next step is to create the file system on the logical volume we created.

# mke2fs -j /dev/data/datavol

7.Now create the mount point to use the file system

# mkdir /storage ( name of directory)

# mount /dev/data/datavol /storage

Logical volume /storage is created.

If we need to resize the volume, we need to follow the step

# unmount /storage

# e2fsadm -L -1G /dev/data/datavol ( 1G is the extended volume)

# mount  /storage

OR

# umount /storage

# resize2fs /dev/data/datavol 1G

# lvreduce -L -1G /dev/data/datavol

# mount /storage