Re: Where do I find the definitive man page for mdadm?
On Saturday 13 November 2021 08:58:15 Andy Smith wrote:
> On Sat, Nov 13, 2021 at 08:39:15AM -0500, Gene Heskett wrote:
> > And I just found I didn't have an mdadm.conf, and I had figure a
> > new -C would have created it. But the last time I ran it, no
> > mdadm.conf was created.
> >
> > So I made a 2 liner from the --scan output. What else should it
> > have?
>
> It can be empty or missing. So the answer to your question is,
> "nothing". Mine have this:
>
> CREATE owner=root group=disk mode=0660 auto=yes
> HOMEHOST <system>
> MAILADDR root
>
> "man mdadm.conf" should tell you what each of those things does.
>
> > ARRAY /dev/md0 metadata=1.2 name=coyote:0
> > UUID=3d5a3621:c0e32c8a:e3f7ebb3:318edbfb ARRAY /dev/md1 metadata=1.2
> > name=coyote:1 UUID=ddb6ffa2:e068b701:f316cc5f:83938a13 You indicate
> > that these are not the UUID's to put in fstab, or do I
> > miss-understand?
>
> You've clearly read the email you are replying to which said "array
> UUIDs are not filesystem UUIDs and do not go in fstab", so I don't
> know why you are asking the same thing again.
>
> Array UUIDs are not filesystem UUIDs and do not go in fstab. What is
> unclear about this statement that you felt the need to do it anyway?
>
> > Experiment after putting those UUID's into fstab
>
> I still don't understand why, after reading me tell you that they
> don't go in fstab, you then put them in fstab.
>
> > @coyote:etc$ mount /home2
> > mount: can't find UUID=3d5a3621:c0e32c8a:e3f7ebb3:318edbfb
>
> Guess what - if you put arbitrary nonsense in /etc/fstab, it won't
> work.
>
> > root@coyote:etc$ mount /snapshot
> >
> > Which nicely demos why I don't trust UUID's.
>
> All you've demonstrated is that if you put garbage in your fstab
> then it won't work.
>
> But no one cares whether you "trust UUIDs" or not. You already said
> that you wanted to use fs labels, not UUIDs. Great. Do that then.
I just did. Works.
> > But, why didn't it work?
>
> I'm at a loss as to why you have to ask. You are replying to an
> email that tells you not to put nonsense in your fstab, you then
> show a transcript of you putting nonsense in your fstab, and then
> ask why it didn't work. You even, further down, quote me telling you
> not to put array UUIDs in your fstab. Is this performance art?
>
> > Why did I have to revert to md0/md1 names to remount them?
>
> 'cos given a choice between nonsense and a device node, mounting a
> device node is more likely to work.
So I've changed it. I guess the next question is why does
--scan even report it if its no good? blkid returns different UUID's.
Would those work?
Generally moot now, I just umounted them, LABEL'd them with mkfs.ext4 -L
and can mount by labels now.
> > > > And for the time being use that UUID in /etc/fstab to mount it
> > > > to /home2, right?
> > >
> > > No, because that is not a filesystem UUID. And you said you wanted
> > > to mount the filesystem by label anyway. So put whatever label you
> > > chose when you did mkfs (or when you did it from the installer).
> >
> > I didn't know mkfs can do labels.
>
> If only any of these tools had a man page.
>
> $ man mkfs.ext4
That is an alias to mkfs which covers all.
> […]
>
> -L new-volume-label
> Set the volume label for the filesystem to
> new-volume-label. The maximum length of the volume label
> is 16 bytes.
>
> Andy
Thanks Andy.
Cheers, Gene Heskett.
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
Reply to: