Re: Where do I find the definitive man page for mdadm?

[Dan Ritter <dsr@randomstring.org>]

Gene Heskett wrote: 
> The man page we have goes on and on for megabytes without ever giving an 
> example.
> 
> I thought maybe it could scan for devices so that I could build an 
> mdadm.conf but it wont do a --scan by itself.

You are looking for

mdadm --detail  --scan

It is in that man page, as an example under --detail.


> But I don't see an option (or recognize it if it is there) to give it a 
> controller id and let it make a raid10 out of the 4 identical drives it 
> could find there.
> 
> If there is such a critter, point me at it please.

You have to feed mdadm the drives you want specifically; there's
no scattershot approach.

Let's say that the drives are /dev/sdf, /dev/sdg, /dev/sdh and
/dev/sdi.

(You can re-confirm what drive is what via hdparm -i, or
smartctl.)

If you have data on them, it will be wiped out. You should copy
off anything important, and then run wipefs on each of them.

Then, creation is

# mdadm -C /dev/md0 --level=10 --raid-devices=4 /dev/sdf /dev/sdg /dev/sdh /dev/sdi

(assuming you want it named /dev/md0 and there isn't one
already)

Then you can make a filesystem on /dev/md0 and put it in your
fstab, mount it, and copy data over to it.

> What I'd like to do when I install bullseye, is use this raid10 for 
> the /home partition in the bullseye install.

The installer will recognize it as an md RAID and can be told that you
want to use it as-is, or you can destroy it and re-create it without
data.

-dsr-