Renaming the root partition raid array

[Bruno Wolff III]

After a bit of a mishap today I tried renaming array associated with both
an f7 install and an f5 install. For the F5 install changing the grub.conf
and fstab files was good enough to do the job.
For the f7 install I got a kernel panic during the boot aftering doing
that. It wasn't able to set up /dev/root. The way I moved things around
was a bit different in the two cases, so that may be the underlying problem,
but I am wondering if f7 stores the name (or some other id) of the root
partition in another location that I missed.

What happened was that I installed f7 on md4 instead of m5 sort of overwriting
an fc5 install I wanted to keep. However, because of the software raid bug
(238353) the mirror was degraded during the install and I still had a copy
available, that I could relatively easily recover.
To try to move the f7 instance I added one of the md5 partitions to the
md4 array, let it sync, and than removed it. I then assembled md5 with
this removed partition. I then added back the other md5 partition and let
things sync back up. I then changed etc/fstab on md5 to have md5 be / and
changed grub.conf to have root=/dev/md4 changed to root=/dev/md5. However,
I couldn't get a reboot to run to successful completion using md5.

For the fc5 installion, I couldn't reuse md4, because I couldn't boot off of
md5 and hence md4 was pinned since it was used for the root filesystem on the
only os I could boot (and the f7 rescue version of mdadm refused to assemble
a new md4 for some reason I didn't figure out). So I assembled md7 using
the old md4 member that still had an intact copy of the fc5 install and
changed etc/fstab and added entry to grub.conf for it. Once I booted into
fc5 I was able to stop md4 and add the array element back into md7.