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 right command

swapon -av

(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/sda2 none swap sw

(where sda2 is the swap partition. Check ‘gparted’ or ‘parted print all’ to locate your actual own swap partition)

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if the following error is displayed:
unable to find swap-space signature

you have forgotten to run mkswap. This works much like mkfs.
All you have to do is run it with your swap partition device ad an argument i.e.

mkswap /dev/sda2

then you have to copy the output string (which contains a long UUID hash) and paste it into your /etc/fstab file replacing the old swap line.

Running, free in addition to showing free memory, should display:

total used free
Swap: 10188 2960 7228

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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.

The swap partition always needs to be initialized with mkswap before enabling it with swapon!

Remember you always have to set a swap size equal or greater than your RAM in order to be able to use hibernation function!