Increasing a Logical Volume

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This article contains instructions for increasing the size of a Logical Volume using a Debian Linux VMware Virtual Machine (VM). This how-to information should be similar with other distributions of Linux.

Initial Position

As the screenshot above shows, the entire hard disk area that has been allocated to a VM is assigned for the boot partition, for one thing, and for the LVM, for another.

The LVM configuration is as follows for this example. 

vm208:~# pvs
  PV         VG    Fmt  Attr PSize  PFree
  /dev/sda2  vm208 lvm2 a-   19,75G    0 
vm208:~# vgs
  VG    #PV #LV #SN Attr   VSize  VFree
  vm208   1   6   0 wz--n- 19,75G    0 
vm208:~# lvs
  LV     VG    Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  home   vm208 -wi-ao  10,54G                                      
  root   vm208 -wi-ao 332,00M                                      
  swap_1 vm208 -wi-ao   1,07G                                      
  tmp    vm208 -wi-ao 380,00M                                      
  usr    vm208 -wi-ao   4,66G                                      
  var    vm208 -wi-ao   2,79G                                      
vm208:~# df -h
File System          Size Used  Avail Used% Shared as
/dev/mapper/vm208-root
                      322M  175M  131M  58% /
tmpfs                 187M     0  187M   0% /lib/init/rw
udev                   10M  612K  9,5M   6% /dev
tmpfs                 187M     0  187M   0% /dev/shm
/dev/sda1             228M   28M  189M  13% /boot
/dev/mapper/vm208-home
                       11G  155M  9,7G   2% /home
/dev/mapper/vm208-tmp
                      368M   11M  339M   3% /tmp
/dev/mapper/vm208-usr
                      4,6G  332M  4,1G   8% /usr
/dev/mapper/vm208-var
                      2,8G  280M  2,4G  11% /var
vm208:~#

The size of the "root" logical volume for the "vm208" (/dev/mapper/vm208-root) volume group should be increased.

Step-by-step Instructions

Increasing the Size of the Hard Disk Area at the VMware Level

The VM dialog for configuring the settings will be opened by right-clicking the VM from the vSphere Client and then clicking "Edit Settings". From there, select the hard disk and increase its size to the desired value, from 20 gigabytes to 25 gigabytes for our example.

Once the VM has been re-booted, the following image should then appear.

Creating an Additional Partition

To be able to use this additional hard disk space, an additional partition must be created (such as by using the cfdisk utility). To do that, the free memory will be selected using the arrow keys and New > Primary > completely available memory selected (if desired). Afterwards, the area will be partitioned.

Afterwards, the new partition table must be written using the "Write" command and the partitioning utility closed using the "Quit" command. To continue with this example, the partition table must be re-read. To avoid another reboot, the partition table can be re-read by the "partprobe" command (a component in the "parted" package).

Initializing the New Partition as a Physical Volume

So that this additional partition can be used for LVM and a volume group assigned, it must next be initialized as a Physical Volume (PV). 

vm208:~# pvs
  PV         VG    Fmt  Attr PSize  PFree
  /dev/sda2  vm208 lvm2 a-   19,75G    0 
vm208:~# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created
vm208:~# pvs
  PV         VG    Fmt  Attr PSize  PFree
  /dev/sda2  vm208 lvm2 a-   19,75G    0 
  /dev/sda3        lvm2 --    5,00G 5,00G
vm208:~#

Increasing the Size of the Volume Group

So that the size of the logical volume "root" can be increased, the size of the corresponding volume group must first be increased. 

vm208:~# vgs
  VG    #PV #LV #SN Attr   VSize  VFree
  vm208   1   6   0 wz--n- 19,75G    0 
vm208:~# vgextend vm208 /dev/sda3
  Volume group "vm208" successfully extended
vm208:~# vgs
  VG    #PV #LV #SN Attr   VSize  VFree
  vm208   2   6   0 wz--n- 24,75G 5,00G
vm208:~#

Increasing the Size of the Logical Volume

Next, the size of the logical "root" volume can be increased. 

vm208:~# lvs
  LV     VG    Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  home   vm208 -wi-ao  10,54G                                      
  root   vm208 -wi-ao 332,00M                                      
  swap_1 vm208 -wi-ao   1,07G                                      
  tmp    vm208 -wi-ao 380,00M                                      
  usr    vm208 -wi-ao   4,66G                                      
  var    vm208 -wi-ao   2,79G                                      
vm208:~# lvextend -L 1G /dev/mapper/vm208-root 
  Extending logical volume root to 1,00 GB
  Logical volume root successfully resized
vm208:~# lvs
  LV     VG    Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  home   vm208 -wi-ao  10,54G                                      
  root   vm208 -wi-ao   1,00G                                      
  swap_1 vm208 -wi-ao   1,07G                                      
  tmp    vm208 -wi-ao 380,00M                                      
  usr    vm208 -wi-ao   4,66G                                      
  var    vm208 -wi-ao   2,79G                                      
vm208:~#

In this example, we will increase the size of the logical root volume to roughly 1 gigabyte. We will reserve the remaining free memory for the vm208 volume group for later use for another logical volume, for example.

Note: The lvextend command will not indicate the amount by which the logical volume should been increased, but rather the final size to which it should be increased. Alternatively, the + symbol can be used before setting the size and the logical volume will then be increased about the specified size.

Increasing the Size of the File System

To be able to use the additional storage area, the size of the file system must finally be increased. ext3, which will support such increases without problems (even in the mounted state), has been used as the file system in our example. 

vm208:~# df -h
File System          Size Used  Avail Used% Shared as
/dev/mapper/vm208-root
                      322M  175M  131M  58% /
tmpfs                 187M     0  187M   0% /lib/init/rw
udev                   10M  616K  9,4M   7% /dev
tmpfs                 187M     0  187M   0% /dev/shm
/dev/sda1             228M   28M  189M  13% /boot
/dev/mapper/vm208-home
                       11G  155M  9,7G   2% /home
/dev/mapper/vm208-tmp
                      368M   11M  339M   3% /tmp
/dev/mapper/vm208-usr
                      4,6G  332M  4,1G   8% /usr
/dev/mapper/vm208-var
                      2,8G  281M  2,4G  11% /var
vm208:~# resize2fs -p /dev/mapper/vm208-root 
resize2fs 1.41.3 (12-Oct-2008)
The file system under /dev/mapper/vm208-root will be mounted as /, and online size changes will be necessary.
old desc_blocks = 2, new_desc_blocks = 4
Execute an online size change to /dev/mapper/vm208-root to 1048576 (1k) blocks.
The file system under /dev/mapper/vm208-root will now be 1048576 block large.

vm208:~# df -h
File System          Size Used  Avail Used% Shared as
/dev/mapper/vm208-root
                      993M  176M  766M  19% /
tmpfs                 187M     0  187M   0% /lib/init/rw
udev                   10M  616K  9,4M   7% /dev
tmpfs                 187M     0  187M   0% /dev/shm
/dev/sda1             228M   28M  189M  13% /boot
/dev/mapper/vm208-home
                       11G  155M  9,7G   2% /home
/dev/mapper/vm208-tmp
                      368M   11M  339M   3% /tmp
/dev/mapper/vm208-usr
                      4,6G  332M  4,1G   8% /usr
/dev/mapper/vm208-var
                      2,8G  281M  2,4G  11% /var
vm208:~#

Summarization of the Steps

  1. Increase the size of the hard disk area (at the physical or VMware level)
  2. Reboot the machine so that the additional hard disk space will be detected
  3. Create an additional partition, for example, by using cfdisk
  4. Re-read the partition table, such as, by re-booting or using the partprobe command
  5. Initialize a new physical volume using the pvcreate command
  6. Increase the size of the volume group using the vgextend command
  7. Increase the size of the logical volume using the lvextend command
  8. Increase the size of the file system, such as, by using the resize2fs command

Additional Information

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