This just happened to me: I installed Gentoo (using Gentoo Handbook) on single sata-disk ("1st disk") with 3 partitions. Used it some time, then I added one more hard-drive ("2nd disk"). And my system did not boot up! Reason? This second, new hard-disk got /dev/sda device which previously had my 1st hard-disk (the one I used for installation). Of course, info in /etc/fstab suddenly became wrong, as there were sda1/sda2/sda3 partitions which now have sdb1/sdb2/sdb3 device files. And this all despite of that the 1st disk is attached to port "sata1" and the 2nd disk to port "sata2" (according to motherboard-manual). Even in BIOS all seems to be correct, the 1st disk is detected as "First SATA Disk", the 2nd disk as "Second SATA Disk". I tried to switch cables and sata-ports, no change. The 2nd disk now always has /dev/sda, and the 1st disk is /dev/sdb (but was previously /dev/sda). I had to boot with live-cd, and correct fstab. Then system starts, but when I removed the 2nd disk, I had to edit fstab again and revert changes... Reproducible: Sometimes Steps to Reproduce: 1. Install Gentoo using Handbook on one hard-disk 2. Shutdown, attach the second hard-disk 3. turn-on. If you're lucky, the 2nd disk gets /dev/sdb device and system can boot-up as usual. If you're not, your 2nd disk gets /dev/sda device, and the system will not boot up because /etc/fstab gets broken Actual Results: System can not boot, as there is inconsistency between /dev and fstab Expected Results: System should boot-up as usual, even with the new hard-drive. Depending on how much time doc maintainers have, I see three solutions: 1. add short and simplified section about udev, and describe how to creade udev-rules so that a disk gets always the same dev-file, 2. rewrite the section 4 "Preparing the Disks" and 8 "Configuring your System" so that fstab uses UUID or LABEL instead of dev-files for the 1st field (fs_spec), 3. or at least issue big fat warning about what might happen, if user later attaches one more hard-disk.
We don't care about future installation of hardware in the handbook; we care about what's being used during the install process itself. Also, we do kind of already mention that drive designations are set by BIOS, so you should watch out for BIOS reordering: http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&chap=10§=2#doc_chap2
The point is, if you make mistake while installing gentoo (like using device-names in fstab) than in future adding hardware is very complicated if not impossible. With udev being stable long time, we should avoid using /dev in fstab, because they are dynamically (random, or maybe unpredictable) generated. In this case, bios does *not* play any role. I tried reordering too, but it does not change the way dev-names are generated by udev.
