Cryptswap and Linux assigning different devices letters to disk

I had this weird issue recently: I had a simple Ubuntu setup with cryptesetup and swap, and the crypt swap device (say /dev/mapper/mycryptoswap1) keept disappearing.
Caution: fiddling with cryptsetup and disk devices is dangerous for data and OS. I personally made a full backup on a separate disk and then umplugged it to be sure it wouldn’t be involved in any mishap.

Turns out is a little worse that that: Linux is changing the drive devices assignations (eg /dev/sdb /dev/sdg) at every boot under my nose. I did not notice at first because I am using UUIDs, so everything looked fine. Unfortunately my raw partition did not have any UUID.  Probably there’s a way to assign an UUID to a general partition, but I didn’t address this issue.
Having the disk changing its letter any time was the reason why the crypttab device wasn’t created a boot.  I was lucky: would a partition with valuable data be present in the other disk, it would be overwritten with encrypted swap data.

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A quick and dirty udevadm script

This script (very dirty) was handful to me to discover some parameters (e.g KERNELS) to differentiate on udev/rules.d rules similar devices on a physical usb port basis. It’s relased under the GNU General Public License and with no guaranties. Please read the Disclaimer. It needs of course udevadm and less. Syntax is: showdevicedetails.sh #!/bin/bash # … Leggi tutto