Swap Space


Getting the Size Right

I've heard and read many arguments over the years about the correct amount of swap space on Linux. The requirement and reality has changed a lot for swap over time and this article is the best I've read summarising it all in a convincing manner.

The short conclusion from this article is:

swap = 2GB;

if (ram <= 1GB) {
  swap = ram;
}
else if (ram < 4GB) {
  swap = ram / 2;
}

Adding a Swap File

I love the simplicity with which you can add and remove swap files in runtime. This is how I added a 1GB swap file, adding an entry for it to/etc/fstab and activating it:

# dd if=/dev/zero of=/var/lib/swap.file bs=1024 count=1024000
# mkswap /var/lib/swap.file
# echo "/var/lib/swap.file swap swap defaults 0 0" >> /etc/fstab
# chmod 0600 /var/lib/swap.file
# swapon -a

That's it. Runningfree -m shows that I now have 1GB swap available. There's no greatness where there's no simplicity. And Linux is full of such simplicity :-)


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