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The Tuesday 2008-01-08 at 09:29 -0700, Bill Anderson wrote:
> % df -h
> Filesystem Size Used Available Capacity Mounted on
> /dev/disk/dsk0a 240M 208M 7666K 97% /
> /dev/disk/dsk0g 1923M 1335M 395M 78% /usr
Ok, question then.
What will happen during boot, if partition /usr fails the initial
filecheck? It can not be mounted, it has to be repaired first; but the
system can not drop you into a repair mode with a shell, because the shell
resides in /usr/bin/
Unix admins do not normally create a separate partition for /usr. In Unix, it
is a relatively static directory. Also, you need to kick the partition thing,
it is an x86ism. Under AIX, there is a root logical volume. One could create
separate LVs for /tmp, /var, and /home. Under Solaris, it is slices, and one
could create a separate slice for /usr and /home, under the default setup.
Ok, whatever you name them, the significance is that /usr is mounted
separately above, as 'df' shows :-)
If you cannot mount /usr, then you get a mount failure. Depending on the
machine, one could a console message, or one just get to read the numbers on
an RS6000. To correct problems, I can always boot into the firmware.
What does that unix do? Does it mount /usr readonly?
The boot halts.
Under ForPro (another version of Unix for those who remember Fortune
Systems), the solution was that /usr/bin had a minimum set of utilities. Of
course, the mount of another "partition" on /usr meant then overlaid those
utilities.
Aha. Which is precisely the point for having certain programs in Linux
residing in /bin, and it not being a symlink to /usr. Linux handles better
that situation, IMHO.
What is the advantage of having that symlink, then? There surely must be
something.
Anyway, discussion of Unix is OT.
But instructive for Linux, too. As it happens, I first installed Linux at
home because I wanted to practice a bit for the Unix I had at the job (and
Linux, too). That was a decade ago...
- --
Cheers,
Carlos E. R.
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