I have an external USB drive that I use for rsnapshot backups. Under 16.04.x it was detected as a USB drive and automatically mounted at /media/usb0, so I configured rsnapshot to use that as its backup target.
After upgrading to 18.04.1, the USB drive has magically become /dev/sda (which had been the internal hard disk in 16.04.x) and is no longer mounted automatically at boot, resulting in rsnapshot failures. I "fixed" the problem by adding the UUID for /dev/sda1 to /etc/fstab and having it mounted at /media/usb0, but this doesn't "feel" like a correct solution.
Can anyone help/explain why 18.04.1 now (a) finds the USB drive before the internal drive and most importantly (b) no longer automatically mounts the USB drive at /media/usb0 as 16.04.5 had been doing?
FWIW, I have found that this happened on 2 of the three machines I have that boot with a USB drive attached. On the third machine, it works exactly as it did in 16.04.5. The 2 that show this behavior are both physically tiny (500GB) Seagate drives that are powered by the USB port. The other has two La Cie external drives with their own external power. All three computers are different hardware, one custom built, one dell server, and one gateway -- the gateway is working normally.
In reality, I don't expect to ever find out why this behavior changed, but I can always hope.