Adding swap space

To add swap space on an already installed system:

1. Log in as root.

2. Use the dd(1M) command to create a file equivalent in size to the amount of swap space you are adding:
   
   dd if=/dev/zero of=file oseek=num bs=blocksize

   where file is the full pathname of the new file, and num is the number of MBs of swap space desired, and blocksize is the block size for both input and output. file must be in the root filesystem (``/''): if it is not, the swaptab will not be able to add it.

3. Use a text editor to edit the /etc/swaptab file and add information for device_name, start_offset, and size:
   
   file 0 -

   The device_name is the name of the file you created using the dd command, the start_offset is 0, and the minus sign indicates that the entire file is to be used as the size of the new swap space.

4. Reboot the system to make the new swap space available for use.

For example, the following sequence of commands configures 32MB of swap space (user input is in bold):

   # dd if=/dev/null of=swapfile oseek=32 bs=1024k
   0=0 records in
   0=0 records out
   # ls -l swapfile
   -rw-r---r--     1 root      sys      33554432 Jul 18 11:58 swapfile
   # swap -a swapfile
   # swap -l
   path                     dev     swaplo  blocks   free
   /dev/swap                38,2         0  819312   819312
   swapfile                 38,513       0   65536    65536

See swaptab(4) for more information about the /etc/swaptab file and dd(1M) for information about the data dump command.