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Linux, Sundry, Technical

HOWTO: Add a Swapfile at Boot

A while back I outfitted my personal workstation with 4GB of RAM. That’s plenty of memory and since disk space was tight I didn’t want to waste any on a swap partition, and I lived happily without swap for a very long time until I began using more virtualization. (I freed up space on my physical desk top by migrating my work environment from a laptop to a virtual machine on my personal workstation.)

I wrote a script to add a “temporary” swap file on demand but what I wanted was a swap file at boot. That actually turns out to be pretty simple. In this case, I just prepare the swap file:

FILE=/mnt/swapfile
SIZE=8388608 # 8 GB

dd if=/dev/zero of=$FILE bs=1024 count=$SIZE
mkswap $FILE $SIZE
swapon $FILE
swapon -s

Then, to make it stick, add this line to /etc/fstab just as you would for a swap partition:

/mnt/swapfile none swap sw 0 0

This is a win for the Unix everything-is-a-file philosophy.

See Also: Ubuntu Community Swap FAQ

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