In this video, you'll learn about labels and UUIDs.
We already talked about it, so you already know why.
It all has to do with device naming.
Device names are generated by systemd UDFD when the system is booting.
And changes to hardware topology may result in changed device names.
We have seen that.
When I added a couple of NVMe devices and rebooted my system, suddenly the disk previously
known as NVMe0n1 had become NVMe0n3.
So if you have hard-coded device names in your ETCFS step, it will fail dramatically
and you can start troubleshooting.
That's not a good idea.
And that is why you can use UUIDs and labels.
UUIDs are automatically assigned while creating the file system.
If at any time you don't see a UUID, well, the solution is simple.
You haven't created the file system in that case.
You can find block ID, BLKID to be pronounced as block ID to find currently existing UUIDs.
Labels are human understandable labels that are written to the file system.
And you need to create them yourself with the appropriate utilities.
The utility that you are going to use depends on the file system that you want to use.
You use mkfs.whatever.
It works for any file system with the uppercase L option to set a label while creating the
file system.
Or tune 2fs minus uppercase L to set a label on an existing exe file system.
And you can use xfs underscore admin minus uppercase L to set a label on an existing
XFS file system.
Now talking about XFS, you might get in a situation where you have duplicate UUIDs.
This will happen if you clone a device.
Because if you clone a device, you make an exact block-by-block copy of the contents
of your device.
And then the UUIDs are cloned as well.
And the result might be duplicated UUIDs.
And these prevent the file systems to be mounted properly.
Now if you want to deal with that situation, you use the mount option no UUID.
Or you just ignore the UUID and mount the device name by device name or label.
But that's a temporary situation.
The nice situation is to use xfs admin minus uppercase U generate.
That will generate a new UUID on an XFS file system.
Alternatively, there is UUID gen to generate a new UUID.
And tune 2fs minus uppercase U to work with the new generated UUID, which next can be
set on the device.
So UUIDs normally are generated automatically, but you can generate them manually as well,
which can be handy in some cases.