crypttab for swap points at /dev/sdXX

[Michał Sawicz]

Installing Ubuntu 15.04 with the console installer (I used netboot) allows you to set up full-disk encryption, and almost forces you to encrypt swap, too. Unfortunately if your installation media is a USB stick, for example, /dev/sda is applied to it, target hard drive ends up being /dev/sdb or even, as in my case, /dev/sdc:

$ cat /etc/crypttab
sdc3_crypt /dev/sdc3 /dev/urandom cipher=aes-xts-plain64,size=256,swap,discard
sdc4_crypt UUID=b76d7592-ae0d-4b04-93d3-f18f3acfd20e none luks,discard

Upon reboot, /dev/sdc3 does not exist any more, and the system waits (fortunately there's a timeout) for it to appear. This results in at least prolonged boot and no swap.

The line should point at /dev/disk/by-id/ or similar instead, since UUID and labels are lost on reboot. Or maybe we can have the crypt process apply a known UUID/label after opening the device?

Second thing is whether the map should even mention sdX? Could it instead default to some user-friendlier string?