Hello!

Not like it's a problem so far, but mostly my curiosity. I have 2 disks -- internal and external. The latter is connected via USB3 cable. My Ubuntu install is on the external drive. W10 is inside my laptop (it's a dual-boot system). So usually my internal drive is sda and my external one is sdb in Ubuntu (they're both SATA drives, of course). But today they switched their device names, so the internal became sdb and external became sda. After the reboot everything got back to normal. I personally haven't done anything in this regard. To me that's strange. Maybe someone could explain that to me, please.

I had the same thing happen to me also about two weeks ago on Xubuntu. Unfortunately for me it had happen after reboot into Xubuntu and then dd a slackware iso to sdb which end up b being my internal hard drive. The good out of all this is it only wrote over first part of the disk including part of my windows partition and was able to recover the MBR and partitions not written over using tesdisk amd windows from the recovery partition that wasn't written over niether. I had done a dd to sdb before the reboot without any problems. So beware with the ubuntu distros check you device naming every time before using DD.

Device names are not guaranteed, it just depends on the order they're detected on boot. That's why you don't use device names in fstab or other important areas, you use UUID or labels, something that is persistent.

I usually check the naming just to make sure before using DD and the one time I don't we'll there you go

Thank you all for your replies!

Have a look at https://help.ubuntu.com/community/UsingUUID

OK, I'll look into that, thanks!