Friday, December 11, 2009

Creating a Swap File

To add a swap file:

  1. 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.

  2. At a shell prompt as root, type the following command with count being equal to the desired block size:

    dd if=/dev/zero of=/swapfile bs=1024 count=65536
  3. Setup the swap file with the command:

    mkswap /swapfile
  4. To enable the swap file immediately but not automatically at boot time:

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

    /swapfile          swap            swap    defaults        0 0

    The next time the system boots, it enables the new swap file.

  6. After adding the new swap file and enabling it, verify it is enabled by viewing the output of the command cat /proc/swaps or free.

Extending Swap on an LVM2 Logical Volume

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

1. Disable swapping for the associated logical volume:

# swapoff -v /dev/VolGroup00/LogVol01

2. Resize the LVM2 logical volume by 256 MB:

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

3. Format the new swap space:

# mkswap /dev/VolGroup00/LogVol01

4. Enable the extended logical volume:

# swapon -va

5. Test that the logical volume has been extended properly:

# cat /proc/swaps # free