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@ -1,29 +1,29 @@ |
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$OpenBSD: INSTALL.linux,v 1.11 2002/06/09 06:15:14 todd Exp $ |
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$OpenBSD: INSTALL.linux,v 1.12 2004/08/18 08:57:33 espie Exp $ |
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Linux + OpenBSD: it's possible |
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by Marc Espie -- espie@cvs.OpenBSD.org |
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by Marc Espie -- espie@OpenBSD.org |
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recent information by Tim Kornau -- opti@openbsd.de |
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It is perfectly possible to have Linux and OpenBSD on the same disk. |
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As of this writing (OpenBSD 2.5 & linux 2.2.3), both can read and write |
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other partitions, though Linux's support of BSD filesystems is still |
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experimental. Please note that 2.0 linux kernels, and most 2.1 kernels |
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don't know how to handle OpenBSD partitions (other BSD partitions are type |
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A5 and differ significantly from OpenBSD partitions--type A6). |
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Both can read and write other partitions. |
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You can even install OpenBSD from an ext2fs partition (choose install from |
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disk... ext2fs does not appear in the choices, but `default' it is). |
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If you are starting from scratch, it is better to install Linux first. |
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Since you are going to use several OSes, you need a way to multi-boot, and |
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Linux's lilo fits the bill fine. |
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Since you are going to use several OSes, you need a way to multi-boot. |
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If you keep Windows NT (or XP) on the disk, its multi-booter can deal |
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with OpenBSD (see the FAQ). Otherwise Linux's lilo fits the bill fine. |
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Recent versions of GRUB can also multiboot OpenBSD. |
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IMPORTANT: don't forget about lilo. You can't uninstall linux from this |
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disk without *first* restoring the MBR to an un-liloed state and making |
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*dead* sure OpenBSD boots as a default. |
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IMPORTANT: don't forget about lilo. If you use lilo, you can't uninstall |
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linux from this disk without *first* restoring the MBR to an |
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un-liloed state and making *dead* sure OpenBSD boots as a default. |
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If you want to grab space from a Windows/DOS partition, use fips. |
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If you want to grab space from an older Windows/DOS partition, use fips. |
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Fips20 knows all about FAT32, so windows 95 is no longer a problem. |
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Or use the commercial offering Partition Magic. |
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Other sources of information, especially concerning other BSD systems, |
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must be taken with a healthy dose of skepticism. OpenBSD definitely |
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@ -84,30 +84,6 @@ They know more about its internal workings than you do. So use linux fdisk |
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for linux partitions, don't let it touch the OpenBSD disklabel, and |
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reciprocally. |
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DOS and BIOS and all the problems of the world |
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---------------------------------------------- |
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Due to historical accident, your machine resident `Operating System', |
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also known as the BIOS, can only access hard-disks up to cylinder 1024. |
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Various lying tricks are used, so that your whole disk is usually |
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accessible to the BIOS, except for very large disks (>8Gb). |
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fdisk is usually going to give you reliable information: anything that is |
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before cylinder 1024 can be accessed through the BIOS. |
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When you first boot up OpenBSD, the kernel will detect your hardware, |
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and give you a message such as |
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wd0 at wdc0 drive 0: <TOSHIBA MK4006MAV> |
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wd0: 3909MB, 7944 cyl, 16 head, 63 sec, 512 bytes/sec, 8007552 sec total |
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wd0: using 16-sector 16-bit pio transfers, lba addressing |
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don't panic. This is just the real disk geometry. Trust fdisk on this one. |
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If fdisk shows you more than 1024 cylinders, you will have to cram OpenBSD |
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into that. Actually, it's enough that the disklabel partition used for |
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booting fits within the first 1024 cylinders (a:), so if you can get your |
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OpenBSD partition to start within 1024 cylinders, just get a small enough |
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a:, and you're in the clear. (You can get by with a: a bit under 20Mb, |
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BTW, just enough for /bin /sbin, a kernel and /etc). |
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Mapping your disk |
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----------------- |
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Starting from Linux, get a grasp of your partitions. Use df to check which |
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@ -128,8 +104,6 @@ The + at the end of the DOS line is because linux fdisk is brain-damaged |
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and wants to write output in 1024-sized chunks, so this stands for |
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`850720 blocks and a half' |
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Older flavors of linux fdisk won't recognize a6 as OpenBSD. |
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As you can see, my linux setup is very small. I have enough to check how |
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things such as gcc work on linux, but my machine is definitely an |
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OpenBSD developer's box. |
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@ -203,20 +177,6 @@ hwclock --systohc --utc. |
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Normally, this is one of the choices that the Linux installation program |
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lets you do: set your hardware clock to GMT. |
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The Linux partition table and OpenBSD |
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------------------------------------- |
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There used to be a problem with Linux's rc: it always mounts all file systems |
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even in single-user mode. The 2.2 kernels fix that in a handy way: the |
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partition recorded in the MBR is scanned for a disklabel, and marked with |
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a ! if one is found. Then, the rest of the disk is scanned, before |
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coming back to the disklabel itself. That way, changes to the |
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OpenBSD disklabel won't affect the setup of the rest of the disk. |
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Anyhow, you may want to check that you can still boot from a Linux kernel |
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which doesn't know about disklabels. The long term solution is to fix your |
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inittab and rc scripts to make deadly sure that single-user boot will work |
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-- preferably by moving disk mounts to multi-user. |
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The OpenBSD installation |
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------------------------ |
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If you've got the space, you can install from your ext2fs partitions. This |
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@ -347,8 +307,33 @@ Once the disklabel is written to disk, the installation proceeds as usual. |
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ext2fs partitions are perfectly usable from OpenBSD. |
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Booting |
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------- |
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Booting with GRUB |
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----------------- |
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Here is a sample configuration for a linux 2.4, linux 2.6, OpenBSD 3.6, |
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WindowsXP |
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timeout 30 |
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default 0 |
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fallback 1 |
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title OpenBSD |
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rootnoverify (hd0,3) |
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makeactive |
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chainloader +1 |
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title WinOS |
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rootnoverify (hd0,0) |
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chainloader +1 |
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title Debian GNU/Linux, kernel |
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root (hd0,2) |
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kernel /boot/vmlinuz root=/dev/ide/host0/bus0/target0/lun0/part3 ro |
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savedefault |
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boot |
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Booting with lilo |
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----------------- |
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First time I booted my system back, I did not get into OpenBSD as expected... |
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I plain forgot I had installed lilo in the master boot block, and lilo |
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does not heed the active partition flag. The fix was rather simple: from |
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@ -367,25 +352,16 @@ image=/boot/vmlinuz-2.2.3 |
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vga=4 |
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root=/dev/hda2 |
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read-only |
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image=/boot/vmlinuz-2.0.36-0.7 |
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label=linux.orig |
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root=/dev/hda2 |
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read-only |
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other=/dev/hda1 |
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label=dos |
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table=/dev/hda |
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More details: I've kept the original redhat installation as |
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vmlinuz-2.0.36 because I'm paranoid, but the real setup uses only |
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bsd, linux, and dos. |
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Rerun lilo (DON'T FORGET THAT STEP), and voila, OpenBSD is able to boot! |
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Linux and OpenBSD partitions |
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---------------------------- |
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The 2.2 kernel does incorporate my patch for the correct handling of |
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OpenBSD partitions. You will probably need to reconfigure and rebuild |
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your linux kernel to recognize BSD disklabels... Here is how it shows up |
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You will probably need to reconfigure and rebuild your linux kernel |
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to recognize BSD disklabels... Here is how it shows up |
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on my box: |
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Partition check: |
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@ -410,7 +386,7 @@ and here is my linux fstab: |
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/dev/fd0 /mnt/floppy ext2 noauto 0 0 |
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/dev/cdrom /mnt/cdrom iso9660 noauto,ro |
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2.2 kernels also include a working UFS, though you may run into problems when |
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linux kernels also include a working UFS, though you may run into problems when |
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writing to ufs partitions. Note the ufstype=44bsd. If you forget that |
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in your mounts, it will fail. Depending upon your installation, you may |
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get a failure message, or you will have to dig through /var/log/ to find |
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@ -484,30 +460,15 @@ you know what you are doing, and don't expect there will always be someone |
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to get you out of trouble. If your setup is really too weird, no-one can help. |
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As far as the boot process goes, I think lilo allows you to boot from ANY |
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partition recorded in the MBR, including extended partitions. The only |
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limitation is that the next stage bootstrap MUST take place entirely within |
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the first 1024 cylinders of the disk, as seen by the BIOS. OpenBSD |
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MBR partitions that extend beyond cylinder 1024 are no problem, as long as |
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the disklabel root (a) partition doesn't extend beyond cylinder 1024. |
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Since Windows, OpenBSD, and linux all have that limitation, the easiest way |
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is to start with Windows partitions (entirely within the first 1024 |
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cylinders), follow with the linux boot partition (still within the first |
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1024 cylinders), then the OpenBSD area (which can span the 1024 cylinders |
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boundary, as long as a lives within the limit), and the remaining linux |
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partitions. |
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Weirder setups are unwarranted. Several bsd on the same disk MAY be |
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possible, but will be harder to manage: |
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partition recorded in the MBR, including extended partitions. |
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Several bsd on the same disk MAY be possible, but will be harder to manage: |
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- it is better if disklabels match, |
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- linux will obey the first disklabel it finds, try to ensure this is |
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OpenBSD disklabel, it can describe more partitions than the others, |
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- other BSD may get confused with each other data. Normally, the A5/A6 |
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split ensures that Net/Free won't get mixed up with OpenBSD, |
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- FreeBSD and NetBSD will probably get confused with each other, |
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- if you have a 1024 cylinder limit, all boot areas must stay within the |
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1024 cylinder boundary, so only one of the BSD may span that limit, apart |
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from very, very nasty tricks. |
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Finally, how much disk space do you have anyway ? Do you really need to |
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cram that many OSes on the same disk ? Put them on separate disks rather. |
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espie
20 years ago