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04-02-2005 Alexandre Buisse

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This is a howto on how to get a working image of Hurd/L4 with qemu, on ia32 arch.

1. Floppy image

You will need the following :

  • automake 1.7 (or greater)
  • autoconf 2.53 (or greater)
  • grub
  • the CVS version of hurd-l4, which you can retrieve from the savannah server: cvs -z3 co hurd-l4
  • two flavours of Pistachio, the L4 kernel, which can be found at Take the demodisk for ia32 (pistachio-ia32-0.4-demodisk.bin.bz2), we'll checkout the CVS later (the 0.4 tarball isn't recent enough).

We will begin with the hurd itself (these steps are taken from the README).

$ cd hurd-l4
$ autoreconf -f -i -s

You shouldn't have any warnings with this autoreconf. If that is not the case, it probably hasn't used the good version of automake or autoconf. For instance, on Gentoo Linux, you must set WANT_AUTOCONF to 2.5 and WANT_AUTOMAKE to 1.7.

$ ./configure --enable-maintainer-mode --prefix=/l4
$ make
$ make install
$ mkdir /l4/boot
$ install -s laden/laden /l4/boot
$ install -s wortel/wortel /l4/boot
$ install -s physmem/physmem /l4/boot
$ install -s task/task /l4/boot
$ install -s deva/deva /l4/boot
$ install -s ruth/ruth /l4/boot

Now we'll prepare the Pistachio kernel :

$ cd ..
$ cvs login
$ cvs -z3 co pistachio
$ cd pistachio

We must apply some patchs for it to work properly with The Hurd. They are located in hurd-l4/README:

$ patch -p1 < ../hurd-l4/README

We will first compile sigma0 (and some other tools) :

$ cd user
$ autoreconf -f -i -s
$ mkdir BUILDDIR

We need to change the linkbase of sigma0 :

$ ../configure --with-s0-linkbase=0x40000 --prefix=/l4
$ make
$ make install

And now the kernel itself :

$ cd ../../kernel

You can use any builddir as long as the directory doesn't yet exist.

$ make BUILDDIR=/tmp/pistachio-build
$ cd /tmp/pistachio-build
$ vi Makeconf.local

You should modify the first three lines to :


now run:

$ make menuconfig

Set the options as they fit you but for qemu to work, you must have the following hardware :

IA32        Basic Architecture
Pentium1    Processor Type

You can now:

$ make

You should obtain a file named ia32-kernel into your build directory.

$ cp ia32-kernel /l4/boot
$ cp /l4/libexec/l4/sigma0 /l4/boot

We now have to modify a little bit the demodisk to use the kernel and servers we just obtained :

$ mkdir qemu
$ mkdir qemu/image
$ cd qemu
$ cp ~/pistachio-ia32-0.4-demodisk.bin.bz2 .
$ bunzip2 pistachio-ia32-0.4-demodisk.bin.bz2
$ mount -o loop pistachio-ia32-0.4-demodisk.bin image
$ cd image/boot
$ cp /l4/boot/* .
$ cd grub
$ vi menu.lst

Your should edit menu.lst to make it look like :

title  GNU Hurd on L4
kernel /boot/laden -D -o serial,uart1,speed=9600
module /boot/ia32-kernel
module /boot/sigma0
module /boot/wortel -D -o serial,uart1,speed=9600
module /boot/physmem
module /boot/task
module /boot/deva
module /boot/task
module /boot/ruth

The two -D are intended for debug, you can delete them if you want. It is possible that filenames are limited to 8 characters, check your image/boot directory for ia32-kernel. If it has been renamed into ia32-ker, modify the according line in menu.lst

When you start qemu, you will have two windows : the shell from which you launched it and a VGA window. You can interact with L4 in both windows (switching with the config/console command in the debugger). You can choose to have wortel and laden output to the serial device (the shell), which is default behaviour, or to VGA (change -o serial,urt1,speed=9600 by -o vga in your menu.lst).

The image is now ready :

$ cd ../../../
$ umount image

We can launch qemu:

$ qemu -dummy-net  -serial stdio -fda pistachio-ia32-0.4-demodisk.bin -boot a

Congratulations, you just booted Hurd/L4 ! To start the Kernel Debugger, press ESC. To switch the KDB mode from character (I find it unusable) to command line, type

> c
/conf> m

2. Disk Image

Everything went fine, and Hurd/L4 should have shown you a nice boot on our floppy image. Our next step will be to make banner run and show us its nice ASCII Art on this brand new OS.

However, there is one problem : banner linked with the libc weights about 6MB, and we only have a 1.44MB floppy. We will then begin with making an image of a whole hard disk instead of a simple floppy.

We still will work with qemu, of course, but we'll also use Bochs to install Grub on the image (I have not yet tried with qemu).

To begin with, some mathematics. We'll make a 30MB image but you can adapt this value to your need. A disk is made of heads, cylinders and sectors (we won't go in detail about what these really mean). A sector has a constant size of 512 bytes and there are at most 255 heads and 63 sectors. The total size of a disk is C * H * S * 512. We'll use the maximum capacity for S and 16 sectors and that will give us how much cylinders we need : C = E(30,000,000 / (16 * 63 * 512)) = 58. The exact size of our image will then be : 58 * 16 * 63 * 512 = 29,933,568 bytes and we will have 58 * 16 * 63 = 58464 pieces of 512 bytes.

Let's create it : we use the magic command dd on the special device which contain an infinity of 0.

$ dd if=/dev/zero of=hurd_l4.img bs=512 count=58464
  58464+0 records in
  58464+0 records out

We will mount it in loopback :

$ losetup /dev/loop0 hurd_l4.img

We need now to have it recognized as a hard disk :

$ fdisk -u -C58 -S63 -H16 /dev/loop0
  Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
  Building a new DOS disklabel. Changes will remain in memory only,
 until you decide to write them. After that, of course, the previous
 content won't be recoverable.

  Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

  Command (m for help):

We should create a new primary partition (press: 'n', 'p', '1', default, default) and toggle it bootable ('a', '1'). Now, if you press 'p', you should see something like :

  Command (m for help): p

  Disk /dev/loop0: 29 MB, 29933568 bytes
  16 heads, 63 sectors/track, 58 cylinders, total 58464 sectors
  Units = sectors of 1 * 512 = 512 bytes

        Device Boot      Start         End      Blocks   Id  System
  /dev/loop0p1   *          63       58463       29200+  83  Linux

If everything is fine (especially check the Start and End fields), you can press 'w' to write the table on the disk:

  Command (m for help): w
  The partition table has been altered!

  Calling ioctl() to re-read partition table.

  WARNING: Re-reading the partition table failed with error 22: Invalid argument.
  The kernel still uses the old table.
  The new table will be used at the next reboot.
  Syncing disks.

You will have noticed that the partition only starts at the 63rd sector. The beginning of the disk contains the MBR which is used for booting. We must then remount the disk making sure that this part is skipped before formating it. We know that a sector uses 512 bytes so we should begin at 63 * 512 = 32256 :

$ losetup -d /dev/loop0
$ losetup -o32256 /dev/loop0 hurd_l4.img

Now comes time to format it into a decent filesystem :

$ mke2fs /dev/loop0
  mke2fs 1.35 (28-Feb-2004)
  Filesystem label=
  OS type: Linux
  Block size=1024 (log=0)
  Fragment size=1024 (log=0)
  7328 inodes, 29200 blocks
  1460 blocks (5.00%) reserved for the super user
  First data block=1
  4 block groups
  8192 blocks per group, 8192 fragments per group
  1832 inodes per group
  Superblock backups stored on blocks:
          8193, 24577

  Writing inode tables: done
  Writing superblocks and filesystem accounting information: done

  This filesystem will be automatically checked every 22 mounts or
 180 days, whichever comes first.  Use tune2fs -c or -i to override.

We should now be able to mount it the right way :

$ mkdir mnt
$ losetup -d /dev/loop0
$ mount -o loop,offset=32256 hurd_l4.img mnt/

Here comes grub time (I assume you have the grub files in /boot/grub and the menu.lst we've obtained in the previous section is in ~/) :

$ mkdir -p mnt/boot/grub
$ cp /boot/grub/stage1 /boot/grub/stage2 /boot/grub/e2fs_stage1_5 mnt/boot/grub/
$ cp ~/menu.lst mnt/boot/grub

We will make a grub bootimage and boot it with bochs :

$ cat stage1 stage2 > grubboot.img

Copy the following into .bochsrc (replace the parts in caps by the right info) :

config_interface: textconfig
display_library: x
romimage: file=/usr/share/bochs/BIOS-bochs-latest, address=0xf0000
megs: 32
vgaromimage: /usr/share/bochs/VGABIOS-elpin-2.40
floppya: 1_44=PATH_TO_YOUR_GRUBBOOT_IMAGE, status=inserted
ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
ata1: enabled=0, ioaddr1=0x170, ioaddr2=0x370, irq=15
ata0-master: type=disk, path="PATH_TO_YOUR_DISK_IMAGE", cylinders=NUMBER_OF_CYLINDERS, heads=16, spt=63
newharddrivesupport: enabled=1
boot: a

log: /dev/stdout
panic: action=ask
error: action=report
info: action=report
debug: action=ignore
debugger_log: -
com1: enabled=1, dev=/dev/ttyS0
vga_update_interval: 300000
keyboard_serial_delay: 250
keyboard_paste_delay: 100000
floppy_command_delay: 500
ips: 1000000
mouse: enabled=0
private_colormap: enabled=0
fullscreen: enabled=0
screenmode: name="sample"
keyboard_mapping: enabled=0, map=/usr/share/bochs/keymaps/
i440fxsupport: enabled=0

And start Bochs with this configuration :

$ bochs -qf .bochsrc

When asked, choose 5. begin simulation. It is possible that you enter first into a debugger, answer 'c' to make it continue. You should see a grub commandline. Tell it to install grub on the disk :

grub> root (hd0,0)
  Filesystem type is ext2fs, partition type 0x83

grub> setup (hd0)
  Checking if "/boot/grub/stage1" exists... yes
  Checking if "/boot/grub/stage2" exists... yes
  Checking if "/boot/grub/e2fs_stage1_5" exists... yes
  Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded. succeeded
  Running "install /boot/grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/boot/grub/stage2/boot/grub/menu.lst"... succeeded.

Quit by pressing ^C q in the shell from which you launched bochs. Our image is now ready. Copy all the releving files in mnt/boot like for the floppy and then umount it and launch qemu :

$ cp /l4/boot/* mnt/boot/
$ umount mnt
$ qemu -serial stdio -dummy-net -hda hurd_l4.img -boot c

3. Running Banner

Still under construction but you should have no problems following hurd-l4/libc/README now that the hdd image works.

-- ?OgnyanKulev - 05 Feb 2005

I didn't bother to licence it as it is so small, but consider it is under some sort of creative commons that allows redistribution and modification.
-- Alexandre Buisse < >

-- ?JoachimNilsson - 05 Feb 2005

Comments from Marcus Brinkmann:

Thanks a lot for that. Some comments:

$ ../configure --with-s0-linkbase=0x40000 --prefix=/l4

I'd recommend to explain how to use --without-com0 here (or whatever it is called, don't remember) to choose VGA output, or how to configure the serial port. If you use vga, no -o option to laden and wortel should be used so you get all output on vga (but of course you can also mix it, whatever you want).

Serial 1 is currently going to be used for remote debugging of userland apps.

QEMU supports up to four serial ports, I use: -serial stdio and -serial pty and then I get the debugging output and kernel debugger in the terminal I started qemu in, and can use the pty for remote debugging with gdb (the latter doesn't work yet).


You should modify the first three lines to :

I never did that. I did change the menu item Processor Type to Pentium1 though. Maybe it has the same effect (and then your document would be a bit redundant here).

Somebody should at some point document all those menu options, some are quite useful for debugging!

Thanks, Marcus

-- ?OgnyanKulev - 05 Feb 2005

I've been doing this sort of thing (See also info grub for making bootable eltorito grub cd ISOs):

$ cd /usr/src/controlled/qemu-images
$ ls -R l4
ls -R l4
boot  deva  ia32-kernel  laden   physmem  sigma0  task  wortel


menu.lst  stage2_eltorito

$ cd /usr/src/controlled/qemu-images # dir above "l4" dir.
$ mkisofs -R -b boot/grub/stage2_eltorito -no-emul-boot \
  -boot-load-size 4 -boot-info-table \
  -o /usr/src/controlled/qemu-images/l4.iso l4

$ qemu -boot d -cdrom /usr/src/controlled/qemu-images/l4.iso

-- ?DerekDavies - 07 Feb 2005

You don't need a compiler targeting the Hurd. The above works with a compiler targeting Linux which are quite a bit easier to find. By adding "--target=i686-unknown-linux-gnu" to my configure line, I was able to cross compile hurd-l4 from Cygwin.

-- ?MichaelAdams - 22 Feb 2005

A bootable CD iso image is now available at

-- ?ChristopheDevine - 03 Mar 2005

Included the anonymous password in the CVSROOT for L4.

-- ?NowhereMan - 19 Mar 2005

I was able to use qemu instead of bochs to install grub on the new disk image. Just use:

qemu -dummy-net -serial stdio -fda grubboot.img -hda hurd_l4.img -boot a

and then the commands to type in the grub shell are the same.

-- ?MatteoSettenvini - 05 May 2005