# Ubuntu – Is it normal for devices to change their device numbers

mountmountpoint

Last time I booted, my OS drive was sdc1 and my Data drive was sda1. Now they are reversed. Are they assigned randomly at boot?

It is normal. Usually it happens because devices get detected in a different order. They share the /dev/sd* device names, and they will change according to what you have plugged in at the time.

You can work around it in two ways:

1. Label the partitions then mount them by label

2. Mount them by UUID

Labelling a disk can be done with (for example)

tune2fs -L MyLabel /dev/sdxx


then use LABEL=Mylabel as the device name in /etc/fstab

Mounting can also be done by using UUID= in /etc/fstab

The UUID can be obtained by blkid, then you can put in /etc/fstab UUID=xxxxxxxxxx as device name. UUID is unique.