This article is from the Frequently Asked Questions for Linux, the Free/Open Source UNIX-like operating system kernel that runs on many modern computer systems. Maintained by David C. Merrill with numerous contributions by others. (v1.0).
A: When you boot (or enable swapping manually) you should see
Adding Swap: NNNNk swap-space
If you don't see any messages at all you are probably missing
(the command to enable swapping) in your /etc/rc.local or /etc/rc.d/* (the system startup scripts), or have forgotten to make the right entry in /etc/ fstab:
/dev/hda2 none swap sw
If you see:
Unable to find swap-space signature
you have forgotten to run mkswap. See the manual page for details; it works much like mkfs.
Running the command free, in addition to showing free memory, should display:
total used free Swap: 10188 2960 7228
If typing cat /proc/swaps reveals only file or partition names, but no swap space information, then the swap file or partition needs re-initialization.
Use fdisk (as root) to determine which partition on a hard drive has been designated as the swap partition. The partition still needs to be initialized with mkswap before enabling it with swapon.
[Andy Jefferson, Steve Withers]