I have an 8-core SuperMicro Xeon server with CentOS 6.3. The OS is installed on a 120 GB SSD connected by SATA, the machine also contains an Areca SAS controller with 24 drives connected. The motherboard is a SuperMicro X9DA7.
When I installed the OS, I used the default options, which creates an LVM volume group to contain / and /home, and keeps /boot and /boot/efi outside the volume group.
The machine is a couple of months old, and has been stable. While installing some new hardware, I decided to also clean up the cabling in the box, since it was a bit messy. In doing this, I probably moved the boot SSD disk to another port on the motherboard (it has a bunch, 2 SATA 6GBps and 6 SATA 3GBps).
When I booted the box after this, I got a kernel panic, the typical "Can't find root device".
I read some docs, and first tried to boot from a rescue disc and reinstal GRUB, but that didn't change anything. Further Googling got me the rdshell kernel parameter, and that dropped me to a shell when it failed to find the root device.
Reading https://fedoraproject.org/wiki/How_to_debug_Dracut_problems , I did the following:
# lvm vgscan # lvm vgchange -ay
And then
# ln -s /dev/mapper/<volumegroup>-<root_volume> /dev/root # exit
After this, the box boots up normally, and everything works as it should. However, when I reboot, it again fails to find the root device.
So, after all this, my question is, how do I make Dracut (I'm assuming) understand that this LVM volume is my root device and pick it up automatically?
And, is there a way to avoid this problem in the future, if I move drives around? Surely it can't be normal for this to happen just because I connect a drive to another port?