udev and mkraid

udev and mkraid

[Andreas Jellinghaus]

Hi,

how to mkraid on an udev system?
/dev is a tmpfs and has only inodes found via /sys
(created by udevstart).

Now there is no md0, so there is no md0 device in /dev,
so I can't make an md0 with mkraid. But if I could, 
udev would create an md0 device.

Oh well. 

Either the mkraid tool should know how to create an md
device without /dev/mdX existing, or the kernel md driver
should always export all possible md via sysfs, even if
they don't exist, so mkraid can create them.

Did I miss anything?

As a hack, I'm running mknod before mkraid.
But it would be nice, if some day that would
no longer be necessary. It defeats the whole purpose
of mkraid in my opinion.

So if you know a better way, please let me know.

Regards, Andreas



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Re: udev and mkraid

[Kevin P. Fleming]

Andreas Jellinghaus wrote:

> how to mkraid on an udev system?
> /dev is a tmpfs and has only inodes found via /sys
> (created by udevstart).

First, you should be using mdadm instead of mkraid.

Second, /dev/md0 _does_ get created by default on a system running udev, 
at least it does on my systems. That doesn't help if you need /dev/md1 
or anything higher, though.



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Re: udev and mkraid

[John L Fjellstad]

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On Tue, Jun 22, 2004 at 05:57:47AM -0700, Kevin P. Fleming wrote:
 
> Second, /dev/md0 _does_ get created by default on a system running udev, 
> at least it does on my systems. That doesn't help if you need /dev/md1 
> or anything higher, though.

Both md0 and md1 get created at my place since I have two raid
partitions. On the system that doesn't have raid, I don't get any, like
expected.

-- 
John L. Fjellstad
web: http://www.fjellstad.org/          Quis custodiet ipsos custodes

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Re: udev and mkraid

[Kevin P. Fleming]

John L Fjellstad wrote:

> Both md0 and md1 get created at my place since I have two raid
> partitions. On the system that doesn't have raid, I don't get any, like
> expected.

There is (ugly) code in the kernel to automatically create /dev/md0 
regardless of whether any RAID-autodetect partitions are found. If 
that's not happening on your system, it would be interesting to find out 
why. It certainly happens on mine, and I rely on that behavior to boot 
my machines.


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Re: udev and mkraid

[John L Fjellstad]

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On Wed, Jun 23, 2004 at 05:59:08AM -0700, Kevin P. Fleming wrote:
> that's not happening on your system, it would be interesting to find out 
> why. It certainly happens on mine, and I rely on that behavior to boot 
> my machines.

I just upgraded to 2.6.7, but this was true for 2.6.5 too. I'm using
Linus' original kernel...

On my server, which has RAID1, I have the raid code compiled into the
kernel.  AFAIK, it gets created by udev.  Using udevinfo, I can see that
md0 is a /block/md0, with these SYSFS information:
    SYSFS{dev}="9:0"
    SYSFS{range}="1"
    SYSFS{size}="690560"
    SYSFS{stat}="    1636        0    34472        0
		600583        0  4804664        0        0        0
		0"

For md1, I see these information:
  looking at class device '/sys/block/md1':
      SYSFS{dev}="9:1"
      SYSFS{range}="1"
      SYSFS{size}="267257088"
      SYSFS{stat}="   20071        0   261188        0
		  458504        0  3676670        0        0        0
		  0"

So the information does look like it is exported to sysfs.

On the workstation, I don't have raid code compiled in, and get no mdX
nodes created.

-- 
John L. Fjellstad
web: http://www.fjellstad.org/          Quis custodiet ipsos custodes

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