[CentOS] Controlling the order of /dev/sdX devices?

Fri Apr 1 14:19:13 UTC 2011
Lamar Owen <lowen at pari.edu>

On Friday, April 01, 2011 09:53:06 am Cal Sawyer wrote:
> Nope, no LVM on the RIAD array.  It just needs to load right after the main LVM so that something removable doesn't wiggle its way in and mess up the device order.

Ok, so the LVM line was for the previous filesystem; it wasn't completely clear from the post.  The LABEL line was clear, though.

> Yes, the suggestion from Robert H looks promising - working on it now.  Did i say i hate udev?  I thought there was going to be a replacement for it at some point?

udev *is* the replacement, and with C6 you're going to find it far earlier in the boot process, inside the initramfs courtesy of dracut.

Like it or not, fixed always-the-same device ids are going away for disk drives in Fedora-derived (and by extension, Red Hat derived) distributions.  udev might seem to be overkill, but it is what it is and it's here to stay, in CentOS-land at least, for as long as C6 is supported.  Might as well bite the bullet and learn how to do what needs to be done in udev.  Once figured out, you might find it more powerful than fixed ids ever were; I don't know, because I've not tried to do things like your situation.

Let us know if the suggeston works, and how well or not well it works.  Your 'read-only for all external drives' situation is unique; note that there are times that I've booted up a box with a removable plugged in, and the removable failed to enumerate at all.  It would only enumerate when it was hotplugged after the kernel systems were up; the particular case is with a USB3 drive and an ExpressCard USB 3 controller on Fedora 14, but I have had the issue with USB 2 devices on previous Fedoras, that might be reflected in C6.