Extending a logical volume in a virtual machine running Red Hat or Cent OS

Purpose

This article provides steps for extending the root partition residing in a logical volume created with Logical Volume Manager (LVM) in a virtual machine running Red Hat/Cent OS.

Resolution

To extend the logical volume:

Note: These steps only apply to EXT3 file systems.

Caution: VMware recommends having a complete backup of the virtual machine prior making these changes.
  1. Power off the virtual machine.
  2. Edit the virtual machine settings and extend the virtual disk size. For more information, see Increasing the size of a virtual disk (1004047).
  3. Power on the virtual machine.
  4. Identify the device name, which is by default /dev/sda, and confirm the new size by running the command:

    # fdisk -l

  5. Create a new primary partition:
    1. Run the command:

      # fdisk /dev/sda (depending the results of the step 4)

    2. Press p to print the partition table to identify the number of partitions. By default there are 2: sda1 and sda2.
    3. Press n to create a new primary partition. 
    4. Press p for primary.
    5. Press 3 for the partition number, depending the output of the partition table print.
    6. Press Enter two times.
    7. Press t to change the system’s partition ID
    8. Press 3 to select the newly creation partition
    9. Type 8e to change the Hex Code of the partition for Linux LVM
    10. Press w to write the changes to the partition table.

  6. Restart the virtual machine.
  7. Run this command to verify that the changes were saved to the partition table and that the new partition has an 8e type:

    # fdisk -l

  8. Run this command to convert the new partition to a physical volume:

    Note: The number for the sda can change depending on system setup. Use the sda number that was created in step 5.

    # pvcreate /dev/sda3

  9. Run this command to extend the physical volume:

    # vgextend VolGroup00 /dev/sda3

    Note: To determine which volume group to extend, use the command vgdisplay.

  10. Run this command to verify how many physical extents are available to the Volume Group:

    # vgdisplay VolGroup00 | grep “Free”

  11. Run the following command to extend the Logical Volume:

    # lvextend -L+#G /dev/VolGroup00/LogVol00

    Where # is the number of Free space in GB available as per the previous command. Use the full number output from Step 10 including any decimals.

    Note: to determine which logical volume to extend, use the command lvdisplay.

  12. Run the following command to expand the ext3 filesystem online, inside of the Logical Volume:

    # ext2online /dev/VolGroup00/LogVol00

    Note: Use resize2fs instead of ext2online if it is not a Red Hat virtual machine.

  13. Run the following command to verify that the / filesystem has the new space available:

    # df -h /

Additional Information

For more information, see The Linux Logical Volume Manager from Redhat.
Note: The preceding link was correct as of Jan 29, 2014. If you find that the link is broken, please provide feedback and a VMware employee will update the link.

See Also

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