How to add swap to and Amazon EC2 instance running Ubuntu 12.04 LTS?

Question

default Ubuntu 12.04 LTS doesn\'t create swap for some reason. Is there \"proper\" way to add it after install?

root@aux3:/root# df -h
Filesystem      Size  Used Avai         


        

Answer 1

I set up swapspace first (had to build one from sources), but then decided to fall back to a manual solution since I prefer more control over memory in production environment.

I assume that mounting of 2 instance block devices is already configured in /etc/fstab as /.inst0 and /.inst1.

Add something like this in /etc/rc.local:

setup_swap()
{
  for D in /.inst0 /.inst1; do
    findmnt $D || continue
    cd $D || continue
    test -r swapfile || dd if=/dev/zero of=swapfile bs=1M count=12292
    chmod 600 swapfile
    mkswap swapfile
    swapon swapfile
  done
}

setup_swap

The code is fully compatible with EC2 instance storage (aka SSD, aka "ephemeral", which is destroyed every time you stop the instance), and is reboot-friendly.

Please keep in mind it takes a while to create and/or enable the swapfiles, so give it a little time once you reboot to see if it worked. :)