/dev/home -> /dev/sda5
/dev/group1 -> /dev/sdb1
/dev/group2 -> /dev/sdc1
And before you get all worked up because people can mount on /disk1/usr
and /disk2/usr, add something like /dev/disk1!usr -> /dev/whatever,
much like you suggested. In my 15+ years of Unix experience, there
aren't a lot of name space conflicts on the basename of mount points.
It's not an issue since you can support both basename and full pathname
with "/"s translated to "!".
: I don't see how this could possibly work. If I haven't yet mounted
: /usr, how can the system know what /dev/usr is (in your naming
: scheme)?
The system probes each block device. It can just as easily read the super
block (if there is one) on each block device. Most (all?) super blocks
store the mount point that this file system was last mounted on. So you
could just as easily have the boot up messages print out:
SCSI device sda: hdwr sector= 512 bytes. Sectors= 2110812 [1030 MB] [1.0 GB]
sda: sda1 (/) sda2 (/usr)
SCSI device sdb: hdwr sector= 512 bytes. Sectors= 4194058 [2047 MB] [2.0 GB]
sdb: sdb1 (/home) sdb2 (swap) sdb3 (/u)
: > As far as I know, no other Unix system (or VMS/NT for that matter) has
: > such a system. IRIX did something like this (has a /dev/root symlink)
: > but I don't think it is used to mount the file system, it is made after
: > booting up.
:
: That's because you have a chicken and egg problem :-)
No, I don't.
: Er, hold on. I think I see more what you're trying to do. You want to
: move /etc/fstab elsewhere, essentially. So each FS/partition will
: record where it should be mounted?
Kind of, yes. The physical device names in fstab /may/ be replaced
with logical names. The logical names are stored in the data and the
system figures out the logical to physical mapping for you. The mapping
is stashed in /dev by devfs (or something) and the system can happily
use them /no matter where the partition happens to be today/. So the
physical name part of fstab is indeed moved - to the devices themselves.
Think of it as a distributed database of sorts.
Just to beat a dead horse: The location of the data is stored in the data.
Think of each disk partition as a "volume". Each volume has a type
(file system, swap, unknown). Each volume of type "filesystem" has a
superblock. Each superblock has a field, sb_lastmounted, which is the
location where this partition was last mounted. When the system probes,
it remembers all the block devices that were there, and then goes through
another, higher level probe, where each file system is called to identify
the block device's location. So this is a new fs operation, something
like fs_mountpoint().