ServerBuddies Support Blog

Quick way to add more SWAP space on your server

To check the swap space used you can use “free -m“.

If for some reason you have a server with too little SWAP then there is a quick way to create a swap file and then use it for additional swap space on the server.

And then we need to add the following to the /etc/fstab.

Instructions for deleting the swap file after import in Ensim

Eg. partition - /dev/hda3 mounted on /, swap file - /var/swapfile.

Turn off swapping for file “/var/swapfile” with the following command:

swapon, swapoff - enable/disable devices and files for paging and swapping

Swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices and files (as found in /proc/swaps or /etc/fstab)

Delete the file “/var/swapfile” with the following command:

Instructions to setup swap file

Select the partition where you want to create the swap file. This partition must have free disk space to create the swap file.

Create a file for swap with the following command (# is shell prompt):

where [count]= number of 1024 blocks required. If count=1024000 size of /var/swapfile will be 1024* 1024000 = 1 GB .

You can decide the size of “/var/swapfile” depending on the size of the backup tar file.

Setup an extra swap with the following command:

Enable “/var/swapfile” for swapping with the following command:

Verification: The file “/proc/swaps” must contain the entry for the swap file “/var/swapfile”. If this entry is not present, then swapping has not been enabled for the swap area.

Size of swap partition

Swap should equal 2x physical RAM for up to 2 GB of physical RAM, and then 1x physical RAM for any amount above 2 GB, but never less than 32 MB.

Using this formula, a system with 2 GB of physical RAM would have 4 GB of swap, while one with 3 GB of physical RAM would have 5 GB of swap.

Creating a large swap space partition can be especially helpful if you plan to upgrade your RAM at a later time.

If your partitioning scheme requires a swap partition that is larger than 2 GB, you should create an additional swap partition. For example, if you need 4 GB of swap, you should create two 2 GB swap partitions. If you have 4 GB of RAM, you should create three 2 GB swap partitions. Red Hat Enterprise Linux supports up to 32 swap files.

Change priority of swap files

You can check the current priority of the swap file from /proc/swaps.

Inorder to change the priority of the swap partitions, you need to edit the “fstab” and append the new priority. If you have the fstab entry for your swap file /swap1 as:

then append the following:

where x is the new priority you have set.

You can re-mount it by using ‘mount -a’ command.