How do you add swap to an EC2 instance?

You can add a 1 GB swap to your instance with these commands:

sudo dd if=/dev/zero of=/swapfile bs=1M count=1024
sudo mkswap /swapfile
sudo swapon /swapfile

To enable it by default after reboot, add this line to /etc/fstab:

/swapfile swap swap defaults 0 0

A fix for this problem is to add swap (i.e. paging) space to the instance.

Paging works by creating an area on your hard drive and using it for extra memory, this memory is much slower than normal memory however much more of it is available.

To add this extra space to your instance you type:

sudo /bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024
sudo /sbin/mkswap /var/swap.1
sudo chmod 600 /var/swap.1
sudo /sbin/swapon /var/swap.1

If you need more than 1024 then change that to something higher.

To enable it by default after reboot, add this line to /etc/fstab:

/var/swap.1   swap    swap    defaults        0   0

Swap should take place on the Instance Storage (ephemeral) disk and not an EBS device. Swapping will cause a lot of IO and will increase cost on EBS. EBS is also slower than the Instance Store and the Instance Store comes free with certain types of EC2 Instances.

It will usually be mounted to /mnt but if not run

sudo mount /dev/xvda2 /mnt

To then create a swap file on this device do the following for a 4GB swapfile

sudo dd if=/dev/zero of=/mnt/swapfile bs=1M count=4096

Make sure no other user can view the swap file

sudo chown root:root /mnt/swapfile
sudo chmod 600 /mnt/swapfile

Make and Flag as swap

sudo mkswap /mnt/swapfile
sudo swapon /mnt/swapfile

Add/Make sure the following are in your /etc/fstab

/dev/xvda2      /mnt    auto    defaults,nobootwait,comment=cloudconfig 0   2
/mnt/swapfile swap swap defaults 0 0

lastly enable swap

sudo swapon -a