I have seen many people on the interwebs using dd and /dev/zero to create empty files. This is great if the file is small, but for a 50Gb file, it simply takes too long, particularly on EC2. The solution? Truncate!

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truncate -s 50G my-large-file

Boom – instant.

This is great for doing things like mounting /tmp on EC2 to the ephemeral storage so /tmp is not limited to 10Gb (or whatever your root image size is)

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cd /mnt
truncate -s 50G big-tmp
mkfs.xfs /mnt/big-tmp
mount -o loop /mnt/big-tmp /tmp