Add swap space on a running system

I found a few systems that were setup with low swap [= to original RAM] on the system and now all my alerts for swap usage are going off.

On debian the steps to add a regular file for swapping were as follows:

1. make the swap file - create a contiguous file and label it as such



dd if=/dev/zero of=fourGfile count=4000000 bs=1024
chmod 0600 fourGfile
mkswap fourGfile



2. Mount it as a swap partition



swapon -v fourGfile



3. Add it to /etc/fstab



/var/cache/swapfile/fourGfile          none            swap    sw              0       0

This was it and now we have enough swap on the systems,

bash-3.1# free -l
           total       used       free     shared    buffers     cached
Mem:       8180284    7866476     313808          0      84660    7323408
Low:       8180284    7866476     313808
High:            0          0          0
-/+ buffers/cache:     458408    7721876
Swap:      7951784      95304    7856480

NOTE: Swapping on a system is not a good thing for performance but it adds to total virtual memory that a process can access on the system.