How to Increase the Size of Logical Volume (LVM) on Linux

Logical Volume Management (LVM) is a flexible and advanced option available to manage hard disks in most Linux distributions. It provides a higher level of storage management than traditional partitioning. One of the main advantages of LVM is the ability to resize logical volumes dynamically as storage needs increase.

In this tutorial, we will walk through the steps to increase the size of a logical volume on Linux. This can be particularly useful when you’re running out of space on a specific volume and have available unallocated space on your disk or a new disk.

Let’s get started.

Step 1: Check Current Disk Usage

Use the command `df -lh` to view the current disk usage.

df -lh

Example:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3             5.8G  4.3G  1.2G  79% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 506M     0  506M   0% /dev/shm
/dev/mapper/VolGroup00-datavol
                       13G  855M   12G   7% /data
/dev/mapper/VolGroup01-optvol
                       20G  173M   19G   1% /opt

Step 2: List All Partitions

To list all partitions on your system, use:

fdisk -lu

Example:

Disk /dev/sda: 21.4 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders, total 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *          63      208844      104391   83  Linux
/dev/sda2          208845     2313359     1052257+  82  Linux swap / Solaris
/dev/sda3         2313360    14667344     6176992+  8e  Linux LVM
/dev/sda4        14667345    41929649    13631152+  8e  Linux LVM

Disk /dev/sdb: 26.8 GB, 26843545600 bytes
255 heads, 63 sectors/track, 3263 cylinders, total 52428800 sectors
Units = sectors of 1 * 512 = 512 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1              63    41929649    20964793+  8e  Linux LVM

Step 3: Create a New Partition

If you have unallocated space on `/dev/sdb`, create a new partition:

fdisk /dev/sdb

Follow the on-screen instructions to create a new partition.

Example:

The number of cylinders for this disk is set to 3263.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (2611-3263, default 2611):
Using default value 2611
Last cylinder or +size or +sizeM or +sizeK (2611-3263, default 3263):
Using default value 3263

Command (m for help): t
Partition number (1-4): 2
Hex code (type L to list codes): 8e
Changed system type of partition 2 to 8e (Linux LVM)

Command (m for help): p

Disk /dev/sdb: 26.8 GB, 26843545600 bytes
255 heads, 63 sectors/track, 3263 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1        2610    20964793+  8e  Linux LVM
/dev/sdb2            2611        3263     5245222+  8e  Linux LVM

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.

Reboot the server:

reboot

Verify disk usage:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3             5.8G  4.3G  1.2G  79% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 506M     0  506M   0% /dev/shm
/dev/mapper/VolGroup00-datavol
                       13G  855M   12G   7% /data
/dev/mapper/VolGroup01-optvol
                       20G  173M   19G   1% /opt

Step 4: Format the New Partition

Once the partition is created, format it:

mke2fs -j /dev/sdb2

Example:

mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
656000 inodes, 1311305 blocks
65565 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1346371584
41 block groups
32768 blocks per group, 32768 fragments per group
16000 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736

Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 20 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

Step 5: Create a Physical Volume

Now, create a physical volume on the new partition:

pvcreate /dev/sdb2

Example:

  Physical volume "/dev/sdb2" successfully created

Step 6: Scan All Physical Volumes

To ensure the system recognizes the new PV, scan all physical volumes:

pvscan

Example:

  PV /dev/sdb1   VG VolGroup01      lvm2 [19.99 GB / 0    free]
  PV /dev/sda4   VG VolGroup00      lvm2 [13.00 GB / 0    free]
  PV /dev/sdb2                      lvm2 [5.00 GB]
  Total: 3 [37.99 GB] / in use: 2 [32.99 GB] / in no VG: 1 [5.00 GB]

Step 7: Extend the Volume Group

Extend your volume group (e.g., `VolGroup01`) to include the new PV:

vgextend VolGroup01 /dev/sdb2

Example:

  Volume group "VolGroup01" successfully extended

Step 8: Extend the Logical Volume

Now, increase the size of your logical volume:

lvextend -l +100%FREE /dev/VolGroup01/optvol

Example:

  Extending logical volume optvol to 24.99 GB
  Logical volume optvol successfully resized

Step 9: Resize the File System

After extending the logical volume, resize the file system:

resize2fs /dev/mapper/VolGroup01-optvol

Example:

resize2fs 1.39 (29-May-2006)
Filesystem at /dev/mapper/VolGroup01-optvol is mounted on /opt; on-line resizing required
Performing an on-line resize of /dev/mapper/VolGroup01-optvol to 6551552 (4k) blocks.
The filesystem on /dev/mapper/VolGroup01-optvol is now 6551552 blocks long.

Step 10: Verify the Changes

Finally, check the disk usage again to confirm the changes:

df -lh

Example:

Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3             5.8G  4.3G  1.2G  79% /
/dev/sda1              99M   12M   83M  13% /boot
tmpfs                 506M     0  506M   0% /dev/shm
/dev/mapper/VolGroup00-datavol
                       13G  855M   12G   7% /data
/dev/mapper/VolGroup01-optvol
                       25G  173M   24G   1% /opt

Commands Mentioned

• df -lh – Displays disk space usage
• fdisk -lu – Lists all partitions
• fdisk /dev/sdb – Creates a new partition on /dev/sdb
• mke2fs -j /dev/sdb2 – Formats the new partition
• pvcreate /dev/sdb2 – Creates a physical volume
• pvscan – Scans all physical volumes
• vgextend VolGroup01 /dev/sdb2 – Extends the volume group
• lvextend -l +100%FREE /dev/VolGroup01/optvol – Extends the logical volume
• resize2fs /dev/mapper/VolGroup01-optvol – Resizes the file system

FAQ

1. What is LVM in Linux?

   LVM stands for Logical Volume Management. It’s a method of allocating space on hard drives into virtual partitions that can be easily resized unlike traditional disk partitioning. This provides greater flexibility and efficiency in disk management.

2. Why would one need to resize a logical volume?

   Resizing a logical volume is often necessary when a particular volume is running out of space, and there’s available unallocated space on the disk or another disk. LVM provides the flexibility to resize volumes dynamically based on storage needs.

3. Is it safe to resize logical volumes?

   While LVM provides the tools to resize volumes, it’s essential to take precautions. Always backup critical data before making changes, and ensure you follow the correct procedures to avoid data loss or corruption.

4. Can I reduce the size of a logical volume?

   Yes, LVM allows both increasing and decreasing the size of logical volumes. However, reducing size requires extra caution to ensure data within the volume isn’t lost.

5. What’s the difference between a physical volume and a logical volume?

   In LVM, a physical volume (PV) refers to a storage device or a partition on a storage device, which can be used as part of LVM. It’s the foundational building block in the LVM hierarchy. On the other hand, a logical volume (LV) is a virtual partition created from space allocated from one or more physical volumes. It’s where your file systems can be created. Logical volumes offer the flexibility to be resized, moved, and modified as needed, unlike traditional partitions.

Conclusion

Increasing the size of a logical volume in Linux using LVM is a powerful feature that provides administrators with the flexibility to manage storage dynamically. This adaptability is especially beneficial in environments where storage needs can change, such as in cloud hosting or VPS server setups.

However, while LVM offers many advantages, it’s crucial to approach the process with caution. Always ensure that you have a backup of essential data before making any changes to your storage configurations. Mistakes or unforeseen issues can lead to data loss, so it’s better to be safe than sorry.

Furthermore, while this tutorial focused on increasing the size of a logical volume, LVM also supports other operations like reducing the size of a volume, migrating data between disks, and more. It’s a testament to the versatility and power of LVM in Linux.

For those who manage web servers or host multiple websites, understanding LVM can be a game-changer. It’s not just about adding more space; it’s about optimizing and making the most of the resources you have. Whether you’re on a dedicated server or a shared hosting environment, mastering LVM can significantly enhance your server management capabilities.

In conclusion, LVM is an indispensable tool for Linux administrators, offering a level of flexibility and control over storage that traditional partitioning methods can’t match. By following the steps outlined in this tutorial, you can efficiently manage and optimize your storage needs.