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Much nicer, less confusing than the previous version.

OPENBSD_2_5
espie 25 years ago
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1 changed files with 335 additions and 258 deletions
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      src/etc/etc.i386/INSTALL.linux

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src/etc/etc.i386/INSTALL.linux View File

@ -1,134 +1,164 @@
$OpenBSD: INSTALL.linux,v 1.5 1999/01/09 17:18:20 espie Exp $
Warning: this document is currently being reviewed. It's not yet complete,
and probably contains loads of errors. As an example, I can't figure out
why Linux doesn't need mkswap as it shares the exact same blocks with
OpenBSD.
$OpenBSD: INSTALL.linux,v 1.6 1999/03/27 00:54:17 espie Exp $
Linux + OpenBSD: it's possible
by Marc Espie -- Marc.Espie@OpenBSD.org
by Marc Espie -- espie@cvs.OpenBSD.org
It is perfectly possible to have Linux and OpenBSD on the same disk.
As of this writing, OpenBSD can read and write Linux' partitions, whereas
Linux cannot access OpenBSD partitions (they differ from NetBSD partitions).
As of this writing (OpenBSD 2.5 & linux 2.2.3), both can read and write
other partitions, though Linux's support of BSD filesystems is still
experimental. Please note that 2.0 linux kernels, and most 2.1 kernels
don't know how to handle OpenBSD partitions (other BSD partitions are type
A5 and differ significantly from OpenBSD partitions--type A6).
You can even install OpenBSD from an ext2fs partition (choose install from
disk... ext2fs does not appear in the choices, but `default' it is).
First, make a bootable floppy of Linux. Then, you have to find some room
for OpenBSD. Don't worry about swap space: you can share Linux' swap
partition.
If you are starting from scratch, it is better to install Linux first.
Since you are going to use several OSes, you need a way to multi-boot, and
Linux's lilo fits the bill fine.
IMPORTANT: don't forget about lilo. You can't uninstall linux from this
disk without *first* restoring the MBR to an un-liloed state and making
*dead* sure OpenBSD boots as a default.
If you want to grab space from a Windows/DOS partition, use fips.
Fips20 knows all about FAT32, so windows 95 is no longer a problem.
Other sources of information, especially concerning other BSD systems,
must be taken with a healthy does of scepticism.
must be taken with a healthy does of scepticism. OpenBSD definitely
differs:
- disklabels can hold up to 16 partitions,
- type is A6, not A5,
- the `special' partitions in the disklabel are only a (root), b (swap),
and c (whole disk).
Planning & Good advice
----------------------
If you are starting on a new machine, be prepared to throw your
installation away. It is generally the case that you will install the
machine, play with it for a week/a month, and find out that you don't like
the setup, and then start over.
Write down any interesting information you find out during your first
installation. Don't do too many things to your box during the first month,
as you will lose these while reinstalling, unless you can do backups
conveniently.
Do you really need to have a dual-boot machines ? Most people don't need
both Linux and OpenBSD. Once you're satisfied with OpenBSD, you may find
out you just want to erase Linux...
Try to find out what your precise needs are, locate partitions whose size
may change next to each other, as far as possible... Put partitions whose
contents are unimportant (or whose backups are always up-to-date) next to
the frontier between OpenBSD and Linux. For instance, it's usually a good
idea to locate the swap area such that you can grow or shrink it. Keep in
mind that exceptional usage (very large, temporary swaps) can use a
temporary file instead of a partition, under both OpenBSD (snvd) and Linux.
First principles
----------------
OpenBSD does not use the DOS partitions for more than booting. You just
need a small DOS partition to put your OpenBSD root. Afterwards, OpenBSD
heeds some other information entirely, called the BSD disklabel. This
disklabel is another completely distinct description of your hard disk.
It does not even have to be consistent with the usual DOS partitions
information.
Throughout this document, we will distinguish between DOS partitions and
BSD partitions whenever this is necessary.
For consistency, it's better if all parts of the disks that
are actually used by OpenBSD are flagged as occupied, type A6, though it
is not necessary. The only part of the disk that should appear both as a BSD
partition and as a DOS partition is the root partition: it MUST begin on
the same sector for the boot process to work.
One way to visualize things is to picture OpenBSD embedded inside DOS
partitions: the DOS partitions used by OpenBSD may each contain several
OpenBSD partitions. As long as the DOS partition table has the right
start and length for each partition it will be kept happy.
The OpenBSD disklabel is just another mechanism that yield another
description of the disk. It is vitally important that the BSD root
partition start precisely where the corresponding DOS partition is supposed
to start, and it is better when all BSD partitions stay inside their
DOS partitions boundaries. Apart from OpenBSD partitions proper, the
BSD disklabel can contain a BSD description of other DOS partitions, but
this is not mandatory. If you don't have any constraints, having a correct
description of all partitions is better, but with bigger disks, keep in mind
that OpenBSD disklabels can't hold more than 16 partitions.
Contrarily to popular belief, OpenBSD does *NOT* need one contiguous chunk
of the disk (a `slice' in FreeBSD lingo). It is probably the simplest setup,
but other considerations (such as the need to boot several OS, and to have
several small primary partitions that all within the first 1024 BIOS
cylinders) may lead you to use two chunks for OpenBSD.
If you can, it is MUCH better to devote a full disk to OpenBSD: this limits
OpenBSD does only use the MBR partitions (the ones mapped in the Master
Boot Record) for booting. Afterwards, it trusts some bsd specific
information called the disklabel, which is another completely distinct
description of your hard disk. It does not even have to be consistent with
the usual DOS partitions information.
[OpenBSD requires a primary MBR partition for booting.]
Throughout this document, we will distinguish between MBR partitions and
disklabel partitions whenever this is necessary.
The safest way to deal with things is to allocate one primary MBR partition for
OpenBSD, type A6, that you will partition further with disklabel.
If you can, it is even safer to devote a full disk to OpenBSD: this limits
the number of mistakes you can do. Admittedly there are some cases where
this isn't a option (my machine is a laptop... I have to cope with the
hard disk I have).
hard disk I have), or where this can be slower (SCSI disk setups will
yield better throughput with swap interleaved among the disks).
Prime rule: *ALWAYS* use the disk partitioning tools that go with the OS.
They know more about its internal workings than you do. So use linux fdisk
for linux partitions, don't let it touch the OpenBSD disklabel, and
reciprocally.
DOS and BIOS and all the problems of the world
----------------------------------------------
Due to historical accident, your machine resident `Operating System',
also known as the BIOS, can only access hard-disks up to cylinder 1024.
Various lying tricks are used, so that your whole disk is usually
accessible to the BIOS, except for very large disks (>8Gb).
fdisk is usually going to give you reliable information: anything that is
before cylinder 1024 can be accessed through the BIOS.
When you first boot up OpenBSD, the kernel will detect your hardware,
and give you a message such as
wd0 at wdc0 drive 0: <TOSHIBA MK4006MAV>
wd0: 3909MB, 7944 cyl, 16 head, 63 sec, 512 bytes/sec, 8007552 sec total
wd0: using 16-sector 16-bit pio transfers, lba addressing
don't panic. This is just the real disk geometry. Trust fdisk on this one.
If fdisk shows you more than 1024 cylinders, you will have to cram OpenBSD
into that. Actually, it's enough that the disklabel partition used for
booting fits within the first 1024 cylinders (a:), so if you can get your
OpenBSD partition to start within 1024 cylinders, just get a small enough
a:, and you're in the clear. (You can get by with a: a bit under 20Mb,
BTW, just enough for /bin /sbin, a kernel and /etc).
Mapping your disk
-----------------
Starting from Linux, get a grasp of your partitions. Use df to check which
is what, then fdisk to get the actual setup of the disk.
Here is my disk:
--
is what, then fdisk to get the actual setup of the disk.
Write this down... in case you make a mistake further down, this can come
in handy.
Disk /dev/hda: 128 heads, 63 sectors, 993 cylinders
Units = cylinders of 8064 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 1 1 260 1048288+ 6 DOS 16-bit >=32M
/dev/hda2 261 261 273 52416 83 Linux native
/dev/hda4 287 287 601 1270080 5 Extended
/dev/hda5 287 287 303 68512 82 Linux swap
/dev/hda6 304 304 456 616864+ 83 Linux native
/dev/hda7 457 457 520 258016+ 83 Linux native
/dev/hda8 521 521 537 68512+ 83 Linux native
/dev/hda9 538 538 601 258016+ 83 Linux native
(In case you're wondering, yes this is a big disk. The Linux playground is
large, the OpenBSD area will be huge. As a developer, I usually have loads
of source & binaries lying around... a simple OpenBSD installation can fit
within 300 Mb with room to spare.)
In my setup hda2 is /, hda6 is /usr, hda7 is /usr/local, hda8 is /var, and
hda9 is /home.
Device Boot Start End Blocks Id System
/dev/hda1 1 211 850720+ 6 DOS 16-bit >=32M
/dev/hda2 212 273 249984 83 Linux native
/dev/hda3 274 992 2899008 a6 OpenBSD
The + at the end of the DOS line is because linux fdisk is brain-damaged
and wants to write output in 1024-sized chunks, so this stands for
`850720 blocks and a half'
Older flavors of linux fdisk won't recognize a6 as OpenBSD.
As you can see, my linux setup is very small. I have enough to check how
things such as gcc work on linux, but my machine is definitely an
OpenBSD developper's box.
Get the display to sectors with u, and jot down the corresponding
information as well:
--
Disk /dev/hda: 128 heads, 63 sectors, 993 cylinders
Units = sectors of 1 * 512 bytes
Device Boot Begin Start End Blocks Id System
/dev/hda1 63 63 2096639 1048288+ 6 DOS 16-bit >=32M
/dev/hda2 2096640 2096640 2201471 52416 83 Linux native
/dev/hda4 2306304 2306304 4846463 1270080 5 Extended
/dev/hda5 2306368 2306368 2443391 68512 82 Linux swap
/dev/hda6 2443455 2443455 3677183 616864+ 83 Linux native
/dev/hda7 3677247 3677247 4193279 258016+ 83 Linux native
/dev/hda8 4193343 4193343 4330367 68512+ 83 Linux native
/dev/hda9 4330431 4330431 4846463 258016+ 83 Linux native
Okay, finally switch to expert mode, and note the corresponding data.
Device Boot Start End Blocks Id System
/dev/hda1 63 1701503 850720+ 6 DOS 16-bit >=32M
/dev/hda2 1701504 2201471 249984 83 Linux native
/dev/hda3 2201472 7999487 2899008 a6 OpenBSD
--
Okay, finally switch to expert mode, and write the corresponding data.
Disk /dev/hda: 128 heads, 63 sectors, 993 cylinders
Nr AF Hd Sec Cyl Hd Sec Cyl Start Size ID
1 00 1 1 0 127 63 259 63 2096577 06
2 00 0 1 260 127 63 272 2096640 104832 83
3 00 0 0 0 0 0 0 0 0 00
4 00 0 1 286 127 63 600 2306304 2540160 05
5 00 1 2 286 127 63 302 64 137024 82
6 00 1 1 303 127 63 455 63 1233729 83
7 00 1 1 456 127 63 519 63 516033 83
8 00 1 1 520 127 63 536 63 137025 83
9 00 1 1 537 127 63 600 63 516033 83
1 00 1 1 0 127 63 210 63 1701441 06
2 00 0 1 211 127 63 272 1701504 499968 83
3 00 0 1 273 127 63 991 2201472 5798016 a6
4 00 0 0 0 0 0 0 0 0 00
Note that this is STILL the same data. The good point about this last
display is that it is almost what you're going to see in OpenBSD fdisk !
display is that it is almost what you're going to see in OpenBSD fdisk,
usually ! (I think there may be some very weird cases where this won't
match)
There are some differences though, mostly because Linux fdisk has made
some rather confusing choices:
@ -142,18 +172,8 @@ of the extended partition.
from cyl/hd/sec, in that order.
- it never shows and doesn't care about the real disk geometry.
You will notice that the 3rd primary partition is empty... this is where
I intend to stick my OpenBSD root partition (both DOS and BSD partitions),
and that I have left cylinders 601--992 empty... this is where I intend to
stick the rest of OpenBSD.
After OpenBSD is installed, partition 3 will show up as:
/dev/hda3 274 274 286 52416 a6 Unknown
/dev/hda3 2201472 2201472 2306303 52416 a6 Unknown
(recent Linux fdisk will display a6 as OpenBSD, but they still don't know
how to deal with the disklabel. Important: NEVER use Linux fdisk to fiddle
with OpenBSD disklabels.)
You will notice that I don't have a linux swap partition visible. My
linux setup currently uses the OpenBSD swap area.
Before starting to install OpenBSD, now would be a good time to check the
INSTALL.pt document... Especially note the alignment restriction of
@ -161,7 +181,7 @@ partitions (first sector of a partition must be at head 0, sector 1 of a
cylinder). This is enforced by Linux' fdisk.
The other point to note is that extended partitions are actually linked
lists. This will show up in OpenBSD' fdisk.
lists. This will show up in OpenBSD's fdisk.
Your clock and OpenBSD
----------------------
@ -172,29 +192,35 @@ system time from the hardware clock when booting... there is a --utc
option if your hardware clock is in universal time, but this is not
always what happens by default.
For instance, on a redhat 5.1 system, this happens in /etc/rc.d/rc.sysinit
which loads an /etc/sysconfig/clock that defines a variable called UTC, and
then proceeds calling hwclock.
For instance, on a redhat system, up to 5.2, this happens in
/etc/rc.d/rc.sysinit which loads an /etc/sysconfig/clock that defines a
variable called UTC, and then proceeds calling hwclock.
- ensure UTC is set to true,
- adjust your hardware clock from the system time if necessary, e.g.,
hwclock --systohc --utc.
Normally, this is one of the choices that the Linux installation program
lets you do: set your hardware clock to GMT.
The Linux partition table and OpenBSD
-------------------------------------
There is a problem with many Linux rc that do mount all file systems even
in single-user mode. After you've installed OpenBSD, if your Linux kernel
knows about BSD disklabels, it may insert lots of BSD partitions in its
list. Then, at the next reboot, you're in trouble. The simplest way around
this problem is probably to make sure you can boot from a Linux kernel
that doesn't know about disklabels. Otherwise, you may wish to check
your inittab and your rc to make deadly sure that single-user boot
will work.
There used to be a problem with many Linux rc that do mount all file systems
even in single-user mode. The 2.2 kernels fix that in a handy way: the
partition recorded in the MBR is scanned for a disklabel, and marked with
a ! if one is found. Then, the rest of the disk is scanned, before
coming back to the disklabel itself. That way, changes to the
OpenBSD disklabel won't affect the setup of the rest of the disk.
Anyhow, you may want to check that you can still boot from a Linux kernel
which doesn't know about disklabels. The long term solution is to fix your
inittab and rc scripts to make deadly sure thhat single-user boot will work
-- preferably by moving disk mounts to multi-user.
The OpenBSD installation
------------------------
If you've got the space, you can install from your ext2fs partitions. This
is what I did, as I have a slip connection to the rest of the world, and
the OpenBSD install floppy does not include slip.
is what I did, a long time in the past, as I had a slip connection to the
rest of the world, and the OpenBSD install floppy does not include slip.
REMEMBER TO BACKUP ALL IMPORTANT DATA ON YOUR DISK BEFORE DOING THE
INSTALLATION !!!
@ -202,112 +228,53 @@ INSTALLATION !!!
So you cp floppy*.fs /dev/fd0, then reboot...
First, the BSD kernel + ram disk loads, then there is a boot prompt, and
five seconds later, the boot proper starts.
five seconds later, the boot proper starts. After a while, you get to
fdisk and you enter the new partition into the MBR.
After a while, you will see your disk configuration scroll by. I got:
wd0 at wdc0 drive 0: <TOSHIBA MK4006MAV>
wd0: 3909MB, 7944 cyl, 16 head, 63 sec, 512 bytes/sec, 8007552 sec total
wd0: using 16-sector 16-bit pio transfers, lba addressing
at which point I got somewhat confused, especially as this is a configuration with
more than 1024 cylinders. In fact, this is the actual disk geometry, when
you inquire about it, but the geometry that the BIOS does see IS the fdisk
geometry, with 993 cylinders. As the 1024 cylinders is purely a BIOS
limitation, there is no actual trouble.
If you want to be sure, enquire at the boot prompt:
boot>machine diskconfig
before the automatic boot sequence continues.
Then I got into fdisk, and I proceeded to enter my new OpenBSD partition.
This is what the fdisk dump looked after my changes:
Disk: wd0 geometry: 992/128/63 [7999488 sectors]
Offset: 0 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 06 0 1 1 - 259 127 63 [ 63 - 2096577] DOS > 32MB
1: 83 260 0 1 - 272 127 63 [ 2096640 - 104832] Linux files*
2: A6 273 0 1 - 285 127 63 [ 2201472 - 104832] OpenBSD
3: 05 286 0 1 - 600 127 63 [ 2306304 - 2540160] Extended DOS
Selected extended partition 3
New MBR at offset 2306304.
Offset: 2306304 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 82 286 1 2 - 302 127 63 [ 2306368 - 137024] Linux swap
1: 05 303 0 1 - 455 127 63 [ 2443392 - 1233792] Extended DOS
2: 00 0 0 0 - 0 0 0 [ 2306304 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 2306304 - 0] unused
Selected extended partition 1
New MBR at offset 2443392.
Offset: 2443392 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 83 303 1 1 - 455 127 63 [ 2443455 - 1233729] Linux files*
1: 05 456 0 1 - 519 127 63 [ 3677184 - 516096] Extended DOS
2: 00 0 0 0 - 0 0 0 [ 2443392 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 2443392 - 0] unused
Selected extended partition 1
New MBR at offset 3677184.
Offset: 3677184 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 83 456 1 1 - 519 127 63 [ 3677247 - 516033] Linux files*
1: 05 520 0 1 - 536 127 63 [ 4193280 - 137088] Extended DOS
2: 00 0 0 0 - 0 0 0 [ 3677184 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 3677184 - 0] unused
Selected extended partition 1
New MBR at offset 4193280.
Offset: 4193280 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 83 520 1 1 - 536 127 63 [ 4193343 - 137025] Linux files*
1: 05 537 0 1 - 600 127 63 [ 4330368 - 516096] Extended DOS
2: 00 0 0 0 - 0 0 0 [ 4193280 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 4193280 - 0] unused
Selected extended partition 1
New MBR at offset 4330368.
Offset: 4330368 Signatures: 0xAA55,0x0
Starting Ending
#: id cyl hd sec - cyl hd sec [ start - size]
-------------------------------------------------------------------------
0: 83 537 1 1 - 600 127 63 [ 4330431 - 516033] Linux files*
1: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
2: 00 0 0 0 - 0 0 0 [ 4330368 - 0] unused
3: 00 0 0 0 - 0 0 0 [ 4330368 - 0] unused
0: 06 0 1 1 - 210 127 63 [ 63 - 1701441] DOS > 32MB
1: 83 211 0 1 - 272 127 63 [ 1701504 - 499968] Linux files*
2: A6 273 0 1 - 991 127 63 [ 2201472 - 5798016] OpenBSD
3: 00 0 0 0 - 0 0 0 [ 0 - 0] unused
fdisk geometry tells me that I needn't worry about cylinder 1024.
This matches very closely with what linux fdisk saw.
Nothing to it... you just follow the extended partition links using select,
jot down whatever you need, add the OpenBSD partition to look like you want
it to, and save everything.
If you had extended partitions, it would be a trifle bit harder:
you just follow the extended partition links using select, jot down
whatever you need, add the OpenBSD partition into the MBR to look like
you want it to, and save everything.
The * at the end of partition #1 means that the system normally boots under
Linux. In reality, lilo takes control and disregards this completely.
After you leave fdisk, you get to the interesting part: the disklabel
itself. If all goes well, OpenBSD synthesizes a nice disklabel out of what
it can deduce from the disk, including the ext2fs partitions.
There are only a few subtleties to take care of:
- initially, you can ONLY edit the disklabel part that matches the OpenBSD
DOS partition (a `slice' in FreeBSD lingo). You have to use b 0 * before
you can edit the whole disk.
- the real disk geometry becomes relevant. The Berkeley fast file system
- initially, you can ONLY edit the disklabel part that matches the
OpenBSD partition that was declared in the MBR (what you just entered in
fdisk, the `slice' from FreeBSD lingo). Most simple installation don't
need to edit more than that, but you can use b 0 * to unlock the whole
disk (this is a bad idea in most cases).
- your real disk geometry becomes more relevant. The Berkeley fast file system
can't use partial cylinder groups, hence BSD partitions should start
on cylinder boundaries, as any remaining sectors will be lost anyway.
(Actually, what's important is the disk geometry that disklabel gives you.
Trust it on that). In my case, sectors/cylinder=1008 and bytes/sector=512,
so the granularity of disklabel partitions is 504 Kb.
- units for size and offset can be given as sectors (default) or cylinders.
After edition, this is what my disklabel looks like:
# editing [Oh, oh, there is a ^# next... not mine.]
# using MBR partition 2: type A6 off 2201472 (0x219780) size 104832 (0x19980)
# using MBR partition 2: type A6 off 2201472 (0x219780) size 5798016 (0x587880)
# /dev/rwd0c:
type: ESDI
disk:
@ -330,94 +297,135 @@ drivedata: 0
16 partitions:
# size offset fstype [fsize bsize cpg]
a: 104832 2201472 4.2BSD 1024 8192 16 # (Cyl. 2184 - 2287)
b: 137024 2306368 swap # (Cyl. 2288 - 2423*)
b: 274176 2306304 swap # (Cyl. 2288 - 2559)
c: 8007552 0 unused 0 0 # (Cyl. 0 - 7943)
d: 409248 4846464 4.2BSD 1024 8192 16 # (Cyl. 4808 - 5213)
e: 511056 5255712 4.2BSD 1024 8192 16 # (Cyl. 5214 - 5720)
f: 204624 5766768 4.2BSD 1024 8192 16 # (Cyl. 5721 - 5923)
g: 1073520 5971392 4.2BSD 1024 8192 16 # (Cyl. 5924 - 6988)
h: 962640 7044912 4.2BSD 1024 8192 16 # (Cyl. 6989 - 7943)
i: 2096577 63 MSDOS # (Cyl. 0*- 2079*)
j: 104832 2096640 ext2fs # (Cyl. 2080 - 2183)
l: 1233729 2443455 ext2fs # (Cyl. 2424*- 3647*)
m: 516033 3677247 ext2fs # (Cyl. 3648*- 4159*)
n: 137025 4193343 ext2fs # (Cyl. 4160*- 4295*)
o: 516033 4330431 ext2fs # (Cyl. 4296*- 4807*)
Things to check:
- this disklabel is saved in MBR2 (basic DOS partition 2), as expected.
d: 613872 2580480 4.2BSD 1024 8192 16 # (Cyl. 2560 - 3168)
e: 920304 4846464 4.2BSD 1024 8192 16 # (Cyl. 4808 - 5720)
f: 628992 4217472 4.2BSD 1024 8192 16 # (Cyl. 4184 - 4807)
g: 204624 5766768 4.2BSD 1024 8192 16 # (Cyl. 5721 - 5923)
h: 1073520 5971392 4.2BSD 1024 8192 16 # (Cyl. 5924 - 6988)
i: 962640 7044912 4.2BSD 1024 8192 16 # (Cyl. 6989 - 7943)
j: 1701441 63 MSDOS # (Cyl. 0*- 1687)
k: 499968 1701504 ext2fs # (Cyl. 1688 - 2183)
l: 1023120 3194352 4.2BSD 1024 8192 16 # (Cyl. 3169 - 4183)
Things that check, more or less automatically:
- this disklabel is saved in MBR partition #2 (basic DOS partition 2),
as expected.
- all the BSD partitions proper are aligned on a cylinder boundary.
the root partition begins at the precise same offset the corresponding DOS
partition begins, and it extends for the same length.
Other BSD partitions don't show up in the DOS partition setup, hence they
begin precisely on cylinder 601/4808.
- the ext2fs partitions have the exact same layout under the OpenBSD
disklabel.
- the swap partition is very large. It gets used as mfs for my tmp
directories.
And here is the corresponding fstab:
/dev/wd0a / ffs rw 1 1
/dev/wd0d /usr ffs ro 1 2
/dev/wd0l /usr/local ffs ro 1 2
/dev/wd0e /home ffs rw 1 2
/dev/wd0g /var ffs rw 1 2
/dev/wd0h /big ffs ro 1 2
/dev/wd0f /usr/obj ffs rw 1 2
/dev/wd0i /vbig ffs rw 1 2
/dev/wd0j /dos msdos rw 1 2
/dev/wd0k /linux ext2fs rw
/dev/wd0b /tmp mfs rw
One point that is somewhat laborious is that the disklabel -E mode
(which you are currently using) tends to move partitions around to ensure
that ALL defined partitions are contiguous. Hence, you may need some fiddling
around and printing to ensure that Linux partitions do show up where they
should. In my case, disklabel moved the swap and all the ext2fs partitions
slightly, and I add to adjust them manually...
that ALL defined partitions are contiguous. For that reason, it is better
if you don't have to use b 0 *, as other partitions will be moved around to
remove holes, without regard for the rigid MBR partitionning.
ext2fs and DOS partitions should be recognized and positioned
automatically if all goes well.
Once the disklabel is written to disk, the installation proceeds as usual.
ext2fs partitions are perfectly usable from OpenBSD. My /home partition
is ext2fs, I have been using it for a week now without any trouble.
ext2fs partitions are perfectly usable from OpenBSD.
Booting
-------
First time I booted my system back, I did not get into OpenBSD as expected...
I plain forgot I had installed lilo in the master boot block, and lilo
does not heed the active partition flag. The fix was rather simple: from
the Linux system, I just had to edit lilo.conf to add the obsd entry:
the Linux system, I just had to edit lilo.conf to add the OpenBSD entry:
boot=/dev/hda
map=/boot/map
install=/boot/boot.b
prompt
timeout=50
image=/boot/myvmlinuz
label=linux
root=/dev/hda2
vga=4
read-only
image=/boot/vmlinuz-2.0.34-1
label=redhat
root=/dev/hda2
read-only
other=/dev/hda1
label=dos
table=/dev/hda
timeout=500
other=/dev/hda3
label=obsd
table=/dev/hda
label=bsd
table=/dev/hda
image=/boot/vmlinuz-2.2.3
label=linux
vga=4
root=/dev/hda2
read-only
image=/boot/vmlinuz-2.0.36-0.7
label=linux.orig
root=/dev/hda2
read-only
other=/dev/hda1
label=dos
table=/dev/hda
More details: I've kept the original redhat installation as
vmlinuz-2.0.36 because I'm paranoid, but the real setup uses only
bsd, linux, and dos.
rerun lilo, and voila, OpenBSD was able to boot !
Rerun lilo (DON'T FORGET THAT STEP), and voila, OpenBSD is able to boot!
Linux and OpenBSD partitions
----------------------------
As of pre4-2.2.0, the up-coming 2.2 linux kernel does incorporate my
patch to handle OpenBSD partitions, and remove duplicate partitions that
are referenced in both the disklabel for OpenBSD, and the MBR.
You also need a working ufs, which is also going to be in linux 2.2.
The 2.2 kernel does incorporate my patch for the correct handling of
OpenBSD partitions. You will probably need to reconfigure and rebuild
your linux kernel to recognize BSD disklabels... Here is how it shows up
on my box:
Partition check:
hda: hda1 hda2 hda3! < hda5 hda6 hda7 hda8 hda9 hda10 hda11 hda12 hda13 hda14
hda15 >
- the disklabel is detected early, but handled later.
- disklabel handling should remove duplicates: all partitions that are present
as both MBR and disklabel partition should get removed silently. (this does
not seem to work as advertized presently).
- the remaining partitions are checked for consistency.
and here is my linux fstab:
/dev/hda2 / ext2 defaults 1 1
/dev/hda6 swap swap defaults 0 0
/dev/hda5 /bsd ufs ufstype=44bsd 1 2
/dev/hda7 /bsd/usr ufs ufstype=44bsd 1 2
/dev/hda8 /home ufs ufstype=44bsd 1 2
/dev/hda9 /bsd/usr/obj ufs ufstype=44bsd 1 2
/dev/hda1 /dos vfat defaults 1 2
/dev/fd0 /mnt/floppy ext2 noauto 0 0
/dev/cdrom /mnt/cdrom iso9660 noauto,ro
2.2 kernels also include a working UFS, though you may run into Oops when
writing to ufs partitions. Note the ufstype=44bsd. If you forget that
in your mounts, it will fail. Depending upon your installation, you may
get a failure message, or you will have to dig through /var/log/ to find
it.
Running Linux binaries under OpenBSD
------------------------------------
You just have to recompile your BSD kernel with COMPAT_LINUX, and set up
/emul/linux as explained in compat_linux(1).
/emul/linux as explained in compat_linux(1). If you run GENERIC, you don't
have to recompile anything, as this is the default setup.
It's a good idea to mount your Linux file system under another point, then
make symbolic links so that you can control what gets used precisely.
Don't bother with the ports emul/linux_lib entry: it's only a set of Linux
libraries for people who don't have a Linux system running.
As of this writing, most applications work, apart from sound.
The Linux sound devices use differing ioctl from OpenBSD, hence anything that
needs to change the audio mode won't work, and produce audio garbage at best.
As you have a complete linux system, don't bother with the ports
emul/linux_lib entry: it's only a set of Linux libraries for people who
don't have a Linux system running.
A small detail that may cause problems: uname still says `OpenBSD', even
under Linux compatibility. The reason behind that is that we don't want
@ -435,3 +443,72 @@ suid can be coerced by using LD_PRELOAD.
As a rule, this should be achieved on a program-by-program basis.
The more networking programs that do tell they're running under OpenBSD,
the merrier !
A word of caution: brain-damaged linux installations
----------------------------------------------------
I just reinstalled the linux side of my laptop using redhat 5.2. This
CD does insist on having TWO linux partitions: one root partition, and one
swap partition (even though I have 32 Mb of memory, largely enough for
the installation). Since it uses a 2.0.36 kernel, it does NOT handle BSD
disklabels, so I couldn't tell it to use my swap area (I have this bad
feeling that distributed 2.2 boot kernels won't include BSD disklabel
handling anyway). Instead, I had to back my last OpenBSD partition up,
fiddle with my fdisk setup to feed the last cylinder as a swap partition
to their brain dead install CD. Then fetch the latest kernel source to the
linux side, and recompile to get a fully working linux setup. Finally,
reset the fdisk/disklabel to its normal state, and get the backed-up
partition to its normal location.
Another word of caution: getting enough rope to hang yourself
-------------------------------------------------------------
One previous version of this document got into much nastier details, and
gave installation instructions that were thoroughly dangerous.
- various tools may yield distinct views of your disk. These will match,
most often, but not always. Don't get confused if various fdisk, disklabel
utilities don't yield the same information. Generally, sector sizes and
offsets should match.
- try to keep various OSes segregated to their areas. Don't depend on
OpenBSD information to be correct for your linux setup and vice-versa.
Some weird problem with the brain-damaged PC architecture may force us to
tweak things so that OpenBSD will work seamlessly everywhere. Compatibility
with weird tricks is not a priority.
This being said, you will have noticed by now that the OpenBSD disklabel is
just another description of your hard-disk. It is almost completely
independent from the MBR description (it just has to be on the right sector
for the boot process to find it). You can get into trouble if things don't
match. Let it live within its MBR partition, unless you're completely sure
you know what you are doing, and don't expect there will always be someone
to get you of trouble. If your setup is really too weird, no-one can help.
As far as the boot process goes, I think lilo allows you to boot from ANY
partition recorded in the MBR, including extended partitions. The only
limitation is that the next stage bootstrap MUST take place entirely within
the first 1024 cylinders of the disk, as seen by the BIOS. OpenBSD
MBR partitions that extend beyond cylinder 1024 are no problem, as long as
the disklabel root (a) partition ends before cylinder 1024.
Since Windows, OpenBSD, and linux all have that limitation, the easiest way
is to start with Windows partitions (entirely within the first 1024
cylinders), follow with the linux boot partition (still within the first
1024 cylinders), then the OpenBSD area (which can span the 1024 cylinders
boundary, as long as a lives within the limit), and the remaining linux
partitions.
Weirder setups are unwarranted. Several bsd on the same disk MAY be
possible, but will be harder to manage:
- it is better if disklabels match,
- linux will obey the first disklabel it finds, try to ensure this is
OpenBSD disklabel, it can describe more partitions than the others,
- other BSD may get confused with each other data. Normally, the A5/A6
split ensures that Net/Free won't get mixed up with OpenBSD,
- FreeBSD and NetBSD will probably get confused with each other,
- if you have a 1024 cylinder limit, all boot areas must stay within the
1024 cylinder boundary, so only one of the BSD may span that limit, apart
from very, very nasty tricks.
Finally, how much disk space do you have anyway ? Do you really need to
cram that many OSes on the same disk ? Put them on separate disks rather.
If you reach that stage, you'd better be ready to hack at the linux kernel
to recognize several disklabels, for instance, or generally know what
you're doing.

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