Re: Where do I find the definitive man page for mdadm?
On Sat, Nov 13, 2021 at 07:26:11PM -0500, Gene Heskett wrote:
> Is not me thats confused
Yes, it still is.
> but both lsblk and blkid spitting out 4 sets of identical UUID's as all drives are identical.
Like I have told you many many times in this thread, the *context*
of the UUID matters. Both blkid and lsblk are showing you UUIDs for
RAID array members, so that's the UUID of the array *not* an fs
UUID.
So again, as I have said multiple times, lots of things have UUIDs;
just because you see the term "UUID" doesn't mean that it is the
UUID of a filesystem. It is the UUID of whatever it is you're
looking at. If you are working with filesystems only take
the UUID of filesystems.
Using a different tool isn't going to make the other UUIDs go away!
You have to ask only for the type of thing you're interested in
(filesystems)!
I'll annotate each one to show you where you are confused:
> Example:
> root@coyote:etc$ lsblk -o +UUID
> NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT UUID
[…]
> sde 8:64 0 931.5G 0 disk
> ├─sde1 8:65 0 878.9G 0 part 3d5a3621-c0e3-2c8a-e3f7-ebb3318edbfb
^ UUID of a RAID array. So We know sde1 belongs to an array with
UUID 3d5a3621-c0e3-2c8a-e3f7-ebb3318edbfb.
> │ └─md0 9:0 0 1.7T 0 raid10 /home2 708320b3-10af-4c15-b5b1-a9ff7be06d99
^ UUID of the *filesystem* on /dev/md0.
> sdf 8:80 0 931.5G 0 disk
> ├─sdf1 8:81 0 878.9G 0 part 3d5a3621-c0e3-2c8a-e3f7-ebb3318edbfb
^ UUID of a RAID array. So we know that sdf1 belongs to RAID array
3d5a3621-c0e3-2c8a-e3f7-ebb3318edbfb. We already saw this array UUID
before, so we know that both sde1 and sdf1 are part of the same
array. This is BTW how udev knows which arrays to assemble.
> │ └─md0 9:0 0 1.7T 0 raid10 /home2 708320b3-10af-4c15-b5b1-a9ff7be06d99
^ UUID of filesystem on md0. md0 mentioned again because sde1 and
sf1 are both part of md0.
And so on.
All of your problems with UUIDs can be explained by you simply
reading and trying to use the UUID of things that aren't
filesystems.
I think part of the problem is you being overwhelmed with data. You
keep using blkid (and now lsblk) to look at every single block
device on your system. That can be a really large amount of things
that are all inter-related.
$ sudo lsblk | wc -l
481
Do I want to look at 481 lines of output just to find something
specific?
You can get the device nodes of all your RAID arrays from:
$ cat /proc/mdstat
and then just focus on those, not all of their constituent member
devices.
Andy
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