Sent: Fri Dec 10 2010 14:58:59 GMT-0700 (Mountain Standard Time)
From: Neil Brown <redacted>
To: Patrick H. <redacted> linux-raid@vger.kernel.org
Subject: Re: disable creation of md127

On Fri, 10 Dec 2010 14:38:30 -0700 "Patrick H." [off-list ref]
wrote:

  

quoted

How can I prevent the MD driver from auto-creating md127 on boot?
I have a server which is exporting /dev/sdb1 via iSCSI. The remote 
client for this device is using it in a raid device so it has raid 
metadata on it. However because of this, when the target server boots 
up, the md driver shoves it into md127. And because of this, the iSCSI 
target daemon (tgtd) wont export the device as its now part of a raid 
device.
The partition type is 0x83, not 0xfd.

RHEL6 2.6.32-71
    

The md driver isn't auto-creating this.  
mdadm is being run and being asked to create this, possibly implicitly.

Exactly how you stop this from happening depends on where it is an initrd
script or a boot script that is doing it, and which version of mdadm you have.

If you have 3.0 or later, then putting
   AUTO -all

in mdadm.conf might be enough.
If you have a 2.x, you probably need to tell the init script not to run
mdadm, maybe edit the script, maybe set some default variable.  I know little
about RHEL and so cannot suggest specifics.

NeilBrown

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Youre right. I removed every single md-related init script so I didnt 
think mdadm was doing it. But apparently I forgot about udev. I replaced 
mdadm with a script to dump out a bunch of info and found that udev is 
calling `mdadm -I /dev/sdb1`. Any idea where this might be configured 
at? I did a recursive grep for 'mdadm' in the entire /etc and found 
nothing but init scripts and a little selinux stuff  (nothing in /etc/udev).

-Patrick