Re: Where do I find the definitive man page for mdadm?
On Sat, Nov 13, 2021 at 01:14:56PM -0500, Gene Heskett wrote:
> I wouldn't argue near as loud if it hadn't already been proven to me that
> what you call filesystem UUID's are volatile.
What I and everyone else call filesystem UUIDs do not change unless
you force them to change, because they only exist inside the
filesystem. It seems far more likely that you are confused, in the
same way you have been confused throughout this whole thread. If
you've got something outside of your control scribbling in your
filesystems then that is a very serious bug.
I think you are and have been confused between different things that
have UUIDs. Filesystems, MD arrays, GPT partitions and lots of other
things all can have UUIDs.
In this thread you have repeatedly shown that you don't understand
the difference between those UUIDs and have tried to use them in
your fstab, so it seems far more likely that any prior issue you
have had with filesystem UUIDs is going to be down to similar
confusions and not some serious bug.
> It happened when I moved a drive from sda to sdd several years
> ago.
Barring some strange bug that only you have ever seen, it is not
possible, so I believe you are mistaken. This is going to be
another one of those things where you swear software behaved in
incredibly improbable ways, you are asked to reproduce it and can't.
I will gladly eat humble pie if you can reproduce this one and show
us. I will be excited for the bug report we can make together,
because that would be a real doozy.
Like that time you said that having an IPv6 address configured
prevented you from compiling some software, a claim you kept
repeating in multiple unrelated threads any time IPv6 was mentioned,
until you were asked to reproduce the issue and couldn't.
We all make mistakes from time to time but filling the archives with
bold assertions like "filesystem UUIDs are volatile" I think would
come under the category of an extraordinary claim that would require
extraordinary proof.
> Getting ready to switch to the next version of debian because I
> always install to a new drive, which I installed wheezy on, then
> put the old drive back in on a different sata port to get my data
> copied to the new drive. No boot but single. It took me 3 days to
> build an fstab that mounted everything by Labels. When I finally
> had a working system again, I ran blkid again, and with the same
> drives except the boot drive re-arranged, every UUID blkid
> reported was different from what it was in the now commented out
> lines in fstab.
"blkid" also reports things called PARTUUIDs, so I think this is
explained by it doing that, and you being confused. Nothing you have
described could cause a filesystem UUID to change.
> The downside of now using mkfs to install a label, I didn't use it then
> but something else, but mkfs also wipes the drive, so in this case I
> hadn't moved anything to it, so I lost nothing reformating to install
> the label. The utility, if it wasn't journal-something or other I don't
> recall, but it could label a partition that already had content, without
> losing that data.
You have not once in this thread asked how to label an existing
filesystem without re-creating it. Although you don't even need to
ask us, because:
https://lmgtfy.app/?q=how+do+I+label+an+ext4+filesystem
So instead of doing a trivial search, or even asking, you just
assume that it can't be done and have a nice old rant. Weird flex,
but OK.
The above is for ext* filesystems; other filesystems have their own
tools for changing the label. A similar search will find them, too.
People have been putting and changing labels on filesystem in Linux
for decades. It's well understood and well documented. If you look.
First you complain that fs UUIDs are volatile, now you complain that
fs labelling is hard without even doing the most basic research. At
least these topics have been adequately covered, so unwary searchers
are unlikely to stumble upon this thread in future and be led down a
very long garden path by the bizarre claims within.
> Its simply too big a risk to do UUID mounts with something that
> important.
For you, maybe, but I guarantee this is down to some confusion on
your part. Confusion is still a valid reason to shy away from
something, especially when there is an alternate approach (mount by
label) that works much better for you, but blaming it on
mysteriously changing UUIDs and/or the mdadm man pages is not
helping.
Andy
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