Extending SWAP

Swap extension in linux can be done in two ways.

a) By creating a file

b) By creating a disk

We will see the steps for both the methods.

a) By creating a disk

a.1 Extend SWAP with the existing LVM

To extend an LVM2 swap logical volume (assuming /dev/VolGroup00/LogVol01 is the volume you want to extend):

(i) Disable swap for the associated logical volume:

# swapoff -v /dev/VolGroup00/LogVol01

(ii) Resize the LVM2 logical volume by 256 MB:

# lvresize /dev/VolGroup00/LogVol01 -L +256M

(iii) Format the new swap space:

# mkswap /dev/VolGroup00/LogVol01

(iv) Enable the extended logical volume:

# swapon -va

(v) Test that the logical volume has been extended properly:

# cat /proc/swaps # free

a.2  Extend SWAP by Creating a new LVM

To add a swap volume group (assuming /dev/VolGroup00/LogVol02 is the swap volume you want to add):

(i) Create the LVM2 logical volume of size 256 MB:

# lvm lvcreate VolGroup00 -n LogVol02 -L 256M

(ii) Format the new swap space:

# mkswap /dev/VolGroup00/LogVol02

(iii) Add the following entry to the /etc/fstab file:

/dev/VolGroup00/LogVol02   swap     swap    defaults     0 0

# swapon -va

Test that the logical volume has been extended properly. Above command will enable the extended logical volume:

# cat /proc/swaps # free

b) By creating a Swap File

Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 64 MB swap file is 65536.

(i) dd if=/dev/zero of=/swapfile bs=1024 count=65536

Setup the swap file with the command:

(ii) mkswap /swapfile

To enable the swap file immediately but not automatically at boot time:

(iii) swapon /swapfile

To enable it at boot time, edit /etc/fstab to include the following entry:

/swapfile          swap            swap    defaults        0 0