sotware raid - don't forget to update your initramfs!
 

Just a quick tip to avoid a problem I just encountered. Yesterday I'd added a new drive to my software raid array but forgot to update the initramfs. While this isn't a problem for RAID 1, it probably is for most other RAID levels.

The end result was I could boot but not mount the root file system because Linux didn't seem to know about the extra drive. I'm running Debian so I got dropped into a busybox that didn't quite have enough features (namely no ability to create a mount point for my arrays) to resolve the problem.

I ended up downloading a Debian NetInst disk and using it in rescue mode. After starting my RAID arrays, I mounted and chrooted to the root array, mounted the /boot RAID 1 partition and updated the initramfs.

Problem resolved.

This general problem seems to have been more common in the past than it is these days. Don't know if that's because RAID is handled better automatically by most distros, or because fewer people are using RAID, or what. Still, good general advice...and I didn't know that about Debian's busybox tool set.