Re: Can't figure out how to use mdadm in initrd

[Ken Causey <ken@ineffable.com>]

On Fri, 2002-06-28 at 09:58, Neil Brown wrote:
> On  June 28, ken@ineffable.com wrote:
> > I don't get it.  I cannot seem to get mdadm to handle a degraded array
> > no matter what I do.  I'm setting up a system with all filesystems
> > including boot and root on software RAID.  I initially tried to use
> > raidstart in my initrd but ran into a bug that prevents reinstating
> > missing array members in some circumstances, so I was directed to use
> > mdadm instead.  Here's my current setup:
> > 
> > root is on /dev/md2 (RAID5)
> > 
> > The /etc/mdadm/mdadm.conf file in the initrd contains:
> > 
> > DEVICE /dev/sd*
> > ARRAY /dev/md2 devices="/dev/sda3,/dev/sdb3,/dev/sdc3"
> 
> the "devices=" is not the best way to say what devices to use.
> It works OK for IDE which has stable names but not so good for
> SCSI which doesn't.
> 
> What you are saying is "Please assemble an array from precisely
>  /dev/sda3, /dev/sdb3, and /dev/sdc3", and mdadm is saying,
> "Sorry, those three devices do not make an array".
> 
> You should use either "uuid=" (preferred) or "super-minor=" 
> (easier to manage in some ways).
> 

Ah, OK.  Thank you.  I will try that.


> > 
> > The modules loaded are
> > 
> > modprobe -k aic7xxx
> > modprobe -k raid1
> > modprobe -k raid5
> > modprobe -k ext3
> > modprobe -k ext2
> > 
> > mdadm is run as
> > 
> > set "/dev/md2"
> > [ -b "$1" ] || set "/dev/md/2"
> > mdadm --assemble --run --scan "$1"
> 
> This bit of code is silly.  If it chooses "/dev/md/2", then it
> won't find a match in /etc/mdadm/mdadm.conf and wont do anything
> useful. 
> Why not just:
>    mdadm --assemble --scan

I understand that it may seem silly, but it makes plenty of sense when
you consider that it is generated by mkinitrd which is ended to be of
general use.  Unfortunately you are seeing this out of context as this
script is told whether or not devfs is in use or not.

I don't need --run?  The man page seems to imply that --run is needed if
you want to start a degraded array.

> 
> It will then start everything listed in mdadm.conf.
> 
> NeilBrown
>