Date: Thu, 19 Jul 2001 17:29:10 -0400 From: Garance A Drosihn <drosih@rpi.edu> To: freebsd-hackers@FreeBSD.ORG Cc: Bill Moran <wmoran@iowna.com> Subject: RE: Suggestions for sysinstall / disklabel Message-ID: <p0510100cb77ced816fa2@[128.113.24.47]> In-Reply-To: <59063B5B4D98D311BC0D0001FA7E452205FD9D73@l04.research.kpn.com> References: <59063B5B4D98D311BC0D0001FA7E452205FD9D73@l04.research.kpn.com>
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Here's an example where the current behavior of sysinstall and/or
disklabel got in the way of what I intended to do. Once I figured
out what exactly was happening, I understand why it happens and how
to get around it. Certainly I was doing a non-standard setup, but
it "seemed simple enough", and the installer made it much more
confusing.
I have a large disk. I want to break it up into DOS-style slices of:
s0: 1.87 gig - "not freebsd"
s1: 1.25 gig - "not freebsd"
s2: 2.75 gig - for booting into freebsd-stable
s3: 17.x gig - for booting into freebsd-current, & holding home
directories and the cvs repository.
The disk was initially formatted to be a freebsd disk, and after I
ran fdisk to pick new slice-sizes, every time freebsd boots it
complains that the partition table in slice 0 is larger than the
slice. (I have not actually installed anything in that slice yet).
While that's true, whatever is complaining about that should not
care about that because that partition IS NOT A FREEBSD SLICE, and
nothing in my fstab refers to it...
Anyway, back to the install. So I want to break up the two freebsd
slices to be:
s3: 2.75 gig - fbsd 4 2816m
a: 96 M = 4.3 /
e: 96 M = 5.x /x5/xRoot
b: 256 M = /swap
f: 96 M = 4.3 /xRoot
g: 128 M = 4.3 /var
h: 2.1 G = 4.3 /usr
s4: 17.x gig - fbsd 5
a: 96 M = 5.x /x5
f: 128 M = /tmp
g: 128 M = 5.x /x5/var
h: 2.0 G = 5.x /x5/usr
e: 512 M = /usr/home
b: 10.1 G = /usr/cvs
"/x5" is meant to be "/ for release 5", "/x5/var" is meant to be
"/var for release 5", and "/x5/usr" is meant to be "/usr for release 5".
Note that I do want to initialize both partitions at once, because both
my "stable" and "current" systems will reference partitions which are in
both slices. The "/xRoot" and "/x5/xRoot" partitions aren't particularly
interesting for this discussion. other than those are extra partitions
I do want to create there...
During the disklabel step in the install process (an install I'm doing
off the 4.3-release CD's), I go thru and create all the partitions on
slice 3 with no trouble. So far so good.
I go to create a "/x5" partition in slice 4, but it creates it as
"partition e" instead of "partition a". I don't want it as partition e.
Now, remember that during the boot-up process, the "boot0" code requires
that the "partition to boot from" be the first partition in the slice.
The "boot1" code assumes that the "partition to boot from" is labelled
"partition a". So, that partition which I will want to be "/ for
release 5" needs to be both the first partition in the slice, and it
needs to be labelled "partition a". (Mind you, I only know this due
to 20/20 hindsight. I couldn't have described it that clearly when I
was trying to do this...).
Why does disklabel make it "partition e"? Because it knows that it
should use "partition a" for the partition which will be mounted
as "/". Since I want to call this partition "/x5", it decides it
must make it partition 'e' so that the 'a' label will still be
available when (it assumes) I will later define that partition.
Okay, so I go to trick disklabel. I rename the "a" partition in
slice 3 to be something else, and go to create "/" is slice 4
(just so it will be partition a). But of course, disklabel knows
it's utterly bogus to create "/" in slice 4 if the first freebsd
slice is slice 3, so it won't let me do it. On the other hand,
it only tells me "you aren't permitted to do that", and I'm in
too stupid a mood to notice the obvious... I keep thinking that
maybe slice 4 is too far into the disk, and maybe there is still
a limit where you can only boot off the first 2 gig or 4 gig of
a disk. Eventually I give up and create /x5 in slice 3 (as
partition 'e' there).
For awhile I stumble along by always booting up from slice 3, and
then interrupting that boot process and typing in the commands to
boot from slice 3 partition e when I want freebsd-current. This
was interesting actually, as I learned a lot about what the new
loader can do and how it works. Pretty nice stuff there.
I tried booting from the first partition on slice 4 several times,
but initially it didn't occur to me that since the slice was still
labelled partition e, 'boot1' would not be able to work right. I
finally realized that, and ran 'disklabel -r -e ad0s4c' to just
rename partition 'a' to 'e' and visa-versa. I reboot into stable,
fix the /etc/fstab for current (slice 4), and now it's working
the way I wanted it. I can have slice 3 boot into release 4 and
slice 4 boot into release 5.
The problem for me here were all minor issues in disklabel during
the install process, but they ended up causing a lot of run-around
and man-page-reading before I sorted them out. Pretty much all
of what it was doing was "sensible" once I understood it, it just
happened to get in the way of what I personally wanted to do. And
when you're sitting there with an empty 20-gig disk and no operating
systems, you're not in much of a mood to go exploring into esoteric
details of how all these pieces fit together. Perhaps this is the
most frustrating thing about sysinstall, because when you run into a
problem you can't just do a "half-assed job now, and fix it later".
You have to figure it out right then or you're simply stuck.
Anyway, the above is a long-winded justification for the following
suggestions:
1) if disklabel has already been told about '/', then it
should not try and reserve partition 'a' of OTHER SLICES
to also be '/'. The first partition created in those
other slices should just be labelled partition 'a'.
2) similarly, if it already has swap space defined, then
it should not try to reserve partition 'b' of other
slices to be swap. The second partition defined in
those other slices should be labelled partition 'b'.
[I don't feel quite as strongly about that, though]
3) somewhat more informative error messages might be nice,
although I realize we also have the need to keep all
of this code as small as possible, so an install can
still be done via floppies. It would have been nice if
it had said "You can't put '/' in slice 4 when booting
from slice 3", for instance, instead of "You are not
permitted to do that" (without mentioning the reason
you're not permitted to do it). I came close to redoing
the fdisk-step just to get slice 4 under the 4-gig mark,
because I was guessing wrong as to the reason I was not
permitted to create '/' there.
Thinking about what people said about alpha installs, perhaps the
following is another strategy disklabel could take. On the other
hand, this may cause as many problems as it tries to solve.
4) never reserve 'a' or 'b'. Always create partitions in the
order people typed them in, except that WHEN someone says
they want to create '/', THEN both move that partition
to the front of the slice and name it 'a' (renaming other
partitions as needed). WHEN someone asks for swap, THEN
name that partition 'b' and rename other partitions to match.
I realize none of this is a crisis. I'm just trying to think up
suggestions of how the initial disk-partitioning steps could be
made a bit more user-friendly, even for deranged users like me.
I would also note that I have been doing installs since 2.2.7,
and I do also appreciate that this whole process has been getting
better and better with each release. I just think there are still
ways it could be made more flexible and "friendly", without getting
into the way of people who really do know what they are doing.
[btw, what is partition 'd' reserved for? why is it skipped over?
certainly that's not an important question, I was just curious...]
--
Garance Alistair Drosehn = gad@eclipse.acs.rpi.edu
Senior Systems Programmer or gad@freebsd.org
Rensselaer Polytechnic Institute or drosih@rpi.edu
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