Recently, I came across Ubuntu Server install. During install, it asked me whether or not to allow booting system from degraded RAID array (probably because I installed system onto RAID1 /dev/md0 device). This is mighty-useful option for unattended servers which just have to come online, whether or not their RAID array is degraded (as long as it didn't completely fail).
After quick lookup, I found that it works by either reading /etc/initramfs-tools/conf.d/mdadm configuration file (BOOT_DEGRADED=true option), or by reading kernel boot line argument (bootdegraded=true).
Question: Is there something similar (a way to boot system with degraded array) that would work for Debian? I'm not sure if this exact method is applicable, or even that it has this specific functionality.
I'm asking this because I used to have RAID5 array in some system, and upon improper shutdown, it could not boot, until I manually "fixed" the array, which proved to be major PITA, since server was unattended at remote location, there was no UPS, and power failures did happen. So, I'm asking so I could prevent this kind of issue in future.
Best Answer
You want start_dirty_degraded. Try specifying md-mod.start_dirty_degraded=1 as a boot argument to the kernel image.