Re: Where do I find the definitive man page for mdadm?
Hello,
On Fri, Nov 12, 2021 at 11:42:32AM -0500, Gene Heskett wrote:
> On Friday 12 November 2021 10:18:07 Dan Ritter wrote:
> > After you have set them up, mdadm.conf has things like this:
> >
> > ARRAY /dev/md/0 metadata=1.2 name=debian:0
> > UUID=aeac6271:676b1852:04f077d6:fcd285d6 ARRAY /dev/md/1 metadata=1.2
> > name=debian:1 UUID=d74ff881:2e966c37:ec6ef1ec:75b8cdce ARRAY /dev/md/2
> > metadata=1.2 name=debian:2 UUID=7c56166b:0d5aed8b:a9d03c45:e9b8080c
> That doesn't appear to be true. I have run the create which seemed to be
> ok, then mkfs -text4 /dev/md0, then mounted it at /home2.
>
> But /etc/mdadm/mdadm.conf doesn't yet have any of that, only this:
You don't need to list the arrays in /etc/mdadm/mdadm.conf since
udev assembles arrays based on the metadata that exists on each
device. It's fine for there to be no ARRAY lines in there. These
days it's only really useful in recovery situations or for setting
some special options per array.
You can still do the
# mdadm --detail --scan
to find the lines to put in the mdadm.conf yourself.
> And again, I don't trust UUID's as moving a drive cable to a different
> socket has invalidated the whole lot of them once before. I would much
> rather LABEL the array, and mount it in /etc/fstab by that label.
There may be some conceptual error here. The UUIDs you would put in
/etc/fstab are FILESYSTEM UUIDs, not array UUIDs. Lots of things in
computing have UUIDs.
After you put a filesystem on each array you can refer to the
FILESYSTEM label in /etc/fstab. These labels are internal to each
filesystem and nothing to do with any layer below, such as md.
> LABEL as I recall is a journalctl function? Does it work on raid10's?
Filesystem labels have nothing to do with journalctl. And I don't
know what you mean by them being "a function".
Again, filesystems (can) have labels, these are a filesystem detail,
RAID doesn't know nor care.
> Humm, now:
> gene@coyote:~/AppImages$ sudo mdadm --detail --scan
> [sudo] password for gene:
> ARRAY /dev/md0 metadata=1.2 name=coyote:0
> UUID=8ad67ef1:a14d63ab:c684ec2b:42a0c011
>
> So I should add that last line to which category in mdadm.conf?
mdamd.conf doesn't have categories. You would just append that line
at the end, ensuring it is all on one line.
> 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 form the installer).
In a later email you did this:
# mkfs -Text4 …
and got an obscure error.
That's because you did "-T" instead of "-t", which means something
completely different. You may want to get into the habit of doing:
# mkfs.ext4 …
instead as it's clearer and easier to remember.
Cheers,
Andy
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https://bitfolk.com/ -- No-nonsense VPS hosting
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