Turn on swap memory on Ubuntu

For some reason on my Ubuntu 9.04 desktop, swap memory is turned off. How can I turn it back on?

• Check that you have a swap partition defined in /etc/fstab.

  $ grep swap /etc/fstab
  UUID=14a0f7b9-dabb-4296-b0e7-013527a7d82d none swap sw 0 0

• Check that it is being used by the system

  $ swapon -s
  Filename Type Size Used Priority
  /dev/sda6 partition 1004020 215532 -1

• If it isn't, check that it is formatted as a swap partition.

  $ sudo fdisk -l /dev/sda
  [..snipped..]
  /dev/sda5 3842 6595 22121473+ 83 Linux
  /dev/sda6 6596 6720 1004031 82 Linux swap / Solaris
  

• If it is a swap partition, ready it for use and turn it on. At this point, you might see any errors that prevented its use.

  sudo mkswap /dev/sda6
  sudo swapon /dev/sda6
  

• Check that the partition is now being used using the swapon -s command from #2.

• Add an entry to /etc/fstab to have this swap partition loaded at bootup. You can replace the "UUID=xxx" part from above with "/dev/sda6" so the entry looks like this.

  /dev/sda6 none swap sw 0 0

If you didn't define a swap partition earlier, then you'd have to create one, or point swap to a regular file (less efficient).

If you have a swap partition defined in /etc/fstab already then sudo swapon -a

If you don't have the swap partition listed in /etc/fstab then sudo swapon device