20
Strictly speaking, UUID is not addressing at all.
Addressing is very, very simple: read drive X sector Y - or else. Read memory address Z - or else. Addressing is simple, fast, leaves not much room for interpretation, and it's everywhere.
UUID is not addressing. Instead it's searching, finding, sometimes waiting for devices to appear, and also ...
13
The plain numbering scheme is not actually used in recent systems (with "recent" being Ubuntu 9 and later, other distributions may have adapted in that era, too).
You are correct in observing the root partition is set with the plain numbering scheme. But this only is a default or fall-back setting which is usually overridden with the very next command, such ...
5
Also do not forget labels. They aren't as unique as UUIDs, but much more informative, and make your fstab human readable. If it's your desktop, or a small company--in other words, you are managing a few to a few dozens drives, you may prefer labels to UUIDs.
Musing over @frostschutz's excellent answer to your question, one scenario when you would likely ...
3
Both schemes can be mixed and matched with most linux distributions.
The consequences can be desirable or undesirable depending on use case - for example, one might prefer the older scheme (and even disable udev-style persistence hacks) if hot replacement of (virtual hardware or actual hardware) drives without having to modify configuration files is wanted.
2
The answer to your second question ("why does this addressing scheme continue to be used?") is, I guess, inertia. Yes, it is totally possible to use only UUIDs on GPT partitioned disks. You can use UUIDs instead of /dev/xxx names in /etc/fstab. And now that we have the Discoverable Partitions Specification, in many cases you don't even have to specify the ...
1
In short, no.
If a device only needs to have one filesystem, Linux doesn't care whether the filesystem occupies the entire storage device or a partition on the device. For example, it's acceptable to mkfs.ext4 /dev/sdb; Linux can mount such a filesystem; Certainly from the command line.
BUT... be very careful with this. Not having a partition table may ...
1
It has been documented kernel behaviour for many years now that you can not rely on consistent device naming for drives even across reboots on the same server, let alone on different servers.
You will have to write your auto-RAID setup script to detect which drives are in the system and distinguish between the root SSD and the storage JBOD drives.
One ...
1
It would not have been necessary to reinstall Linux in this situation: Reinstalling grub2 with the help of a live distro would have been sufficient.
That does not help right now, but will save you trouble in the future.
Keep in mind that Windows always wants the first disk.
I have never had an EFI-Partition on any Linux-Disk, so I think you can safely use ...
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