This FAQ is maintained by Alistair Riddoch, based on the origonal by Brian Candler; please send all updates to ajr@ecs.soton.ac.uk. The latest version of this document is available at http://www.ecs.soton.ac.uk/elks. Note that ELKS is in the very early stages of development and this information is likely to become out of date rapidly.
Additional information can be found at the ELKS home page at http://www.uk.linux.org/ELKS-Home.
There is a mailing list. To subscribe, send a message to majordomo@vger.rutgers.edu containing the words subscribe linux-8086 in the body. Archives of the mailing list can be found at http://epocha.pd.mcs.net/Linux8086/. At the moment this archive doesn't seem to be working. There was an unofficial linux-8086 mailing list archive at http://www.cyberpass.net/~dummy/robert/archives/linux-8086/ which seems to be down at the moment.
Note that ELKS is not Linux, and the mailing list is not a suitable place for posting questions about Linux (despite its name). These would be better sent to one of the Linux-specific newsgroups such as comp.os.linux.misc
More information on the background, goals and current status of the project can be found at the ELKS home page.
ftp://ftp.ecs.soton.ac.uk/pub/elks/
ftp://cam053212.student.utwente.nl/pub/8086-nix/ELKS/
ftp://tsx-11.mit.edu/pub/linux/ALPHA/linux-16/
ftp://src.doc.ic.ac.uk/packages/linux/tsx-11-mirror/ALPHA/linux-16/
ftp://ftp.amscons.com/pubi/mirrors/ELKS
If you know of any others or wish to set one up, please contact the maintainer.
Recent releases contain a conmpiled binary kernel which most people whould be able to use for initial testing. You should only need to compile your own if you wish to modify the kernel, or change the configuration options. The file boot in images.zip can be written to floppy with dd or RAWRITE.EXE to make a kernel boot disk.
If you want to compile your own kernel, download dev86/Dev86-0.0.13.4.tar.gz and kernel/elks-0.0.67/elks-0.0.67.tar.gz (or the latest versions) from linux.mit.edu, or one of the other sites. Unpack Dev86 them into /usr/src (or any other convenient directory), and elks into /usr/src/linux-86
tar -xvzf Dev86-0.0.13.tar.gz -C /usr/src
tar -xvzf elks-0.0.67.tar.gz -C /usr/src
The development environment will be created in /usr/src/linux-86, and
the kernel source in /usr/src/elks. Next you have to build the
development tools, which include the bcc compiler:
cd /usr/src/linux-86
make install
Next, compile the kernel.
cd /usr/src/elks
# Build kernel
make config
make dep
make
Make config works in the same way as the main Linux kernel. The default
configuration will work on almost all systems. Don't change any of the
options unless you know what you are doing.(If you're used to building Linux kernels with gcc, you'll be amazed at how quick this is! :-) The result is a floppy disk image called "Image", which you can copy to a formatted floppy and boot from.
dd if=Image of=/dev/fd0
or
make disk
You should now be able to boot with this disk, but you won't get much
further without a root floppy disk for it to mount. You can either use
the image file root provided in images.zip, or make your own.
You'll need to use bcc to compile an 'init' program and make a root minix
filesystem. This is explained further down.
A real version of 'init' is being prepared for inclusion in the tiny-utils package, also on linux.mit.edu. A very basic init and login is included in the sysutils part of the elkscmd package which is distributed with each release. The kernel code has recently been changed so that it loads /bin/init instead of /bin/sh.
To install init and login compile them both with
bcc -0 -O -s init.c -o init
bcc -0 -O -s login.c -o login
and copy them into the /bin directory of your root disk. login requires an
/etc/passwd and a /etc/group file, and a /bin/sh (or other depending on the
entry in /etc/passwd.
-0 selects 8086 code generation,
-O enables optimisation,
-ansi enables ansi-style function prototypes (only), and
-s strips symbols out of the binary.
As of kernel 0.0.56 sash now works and is being used as /bin/sh by most people. It can be found in elkscmd.tar.gz. For best results copy /etc/passwd and /etc/group from a standard linux distribution onto your root disk so that ls -l works okay, and /usr/lib/liberror.txt so that sash error reporting works.
A version of ash is also included which does work under ELKS, but is much larger, and may not work at all on machines with <640K of memory.
dd if=root of=/dev/fd0 bs=8192
or under DOS, RAWRITE.EXE can be used.
You need to create a minix floppy containing the appropriate bits and
pieces. This file should contain init, login, and sh in /bin/ and passwd and
group in /etc/, as well as three ttys for init in /dev/.
Note: /dev/tty is different to normal Linux which uses (5,0)
fdformat /dev/fd0H1440 # if floppy not yet formatted
mkdir /usr/src/root86 # make a directory
cd /usr/src/root86
mkdir dev # create directorys in it
cd dev
mknod tty c 4 0 # creatye the required devices
mknod tty2 c 4 1
mknod tty3 c 4 2
mknod fd0 b 3 128
cd ..
mkdir bin
cd bin
cp <path-to-elkscmd-init> init # copy in essential binaries
cp <path-to-elkscmd-login> login
cp <path-to-elkscmd-sash> sh
cd ..
mkdir etc
cd etc
cp <path-to-skeleton-passwd> passwd # add required files for login
cp <path-to-skeleton-group> group
cd ..
fdformat /dev/fd0H1440 # if floppy not yet formatted
mkfs -t minix -n14 /dev/fd0 1440
mount -t minix /dev/fd0 /a # need a mount point "/a"
cp -pR /usr/src/root86/* /a
umount /a
Some distributions use /dev/fd0u1440 instead of /dev/fd0H1440.You should removed passwords from the passwd file as they are not yet suported, and make sure the shell entry for each user is /bin/sh for future compatability.
Alternatively, if you have a 2.0.x kernel and mount-2.5k, you can use the loopback filesystem to create a disk image on your hard disk, and then dump it to floppy
dd if=/dev/zero of=root.image bs=18k count=80
losetup /dev/loop0 root.image
mkfs -t minix /dev/loop0 1440
mount -t minix /dev/loop0 /a
...
umount /a
dd if=root.image of=/dev/fd0
As of ELKS 0.0.53 floppy sizes other than 1.44M now work. Just follow the
above intructions substituting the appropriate sizes in where required.
However, because of the way 360K disks are written by 1.2Meg drives, the
instructions below must be followed if you are trying to boot a machine with
a 360K drive.
One solution is to fit a 360K drive as the second drive in your Linux PC - you can then format 360K disks with fdformat /dev/fd1d360 and create filesystems as usual.
Otherwise, you will need to create a floppy disk image file, transfer it to the PC which has the 360K drive (e.g. using a serial cable), then use "rawrite" under DOS to recreate the disk from the image file.
Root disks are now autodetected so you no longer have to re-compile for disk sizes other than 1.44Mb.
dd if=/dev/fd0 of=root.image bs=1k count=360
This image can then be transferred to the target and written out using
'rawrite' as before. If you use the loopback filesystem this step is
not necessary.
If you get an error about root disk mount failing on device 03c0, load the boot image into a hex editor and look for c003h somewhere near the start of the image and change it to 8003h. (c003h is 03c0 in Intel's backwards byte ordering). This should work for any version, but it is not clear whether the address of the byte to edit varies between version. jose@cnct.com reports that in 0.0.62 boot image, the two bytes are at 0adf - oade.
First create a partition with fdisk. Any version of fdisk will be able to do this, but the current root disk only supports hd?1-4, which are primary partitions, and if you already have a DOS primary partition you will not be able to make a second primary partition with DOS fdisk. The version of fdisk included on the ELKS 0.0.67 root disk is still young code, but seems to work fine on my system.
Having created the partition, boot ELKS from boot and root floppies, and create a filesystem using mkfs. It is safe to use ELKS fdisk to check you know the correct device name for the partition you want to create the filesystem on. To create the filesystem type
mkfs /dev/hd?? <size>
where hd?? is the correct partition, and size is the size of the partition
in Kbyte blocks. <size> cannot be more than 32M. E.g. To make a filesystem on
the first partition on the slave disk, which is a 20M partition type:
mkfs /dev/hdb1 20000
Now mount the partition on the /mnt mount point by typing
mount /dev/hd?? /mnt
where hd?? is the correct partition. The root directory of the new partition
may look a bit corrupted and it may not be possibly to use ls from /mnt. I
am not sure why mkfs is generating slightly corrupt filesystems, but I am
working on it.Create the essential directories on the new filesystem as follows:
mkdir /mnt/bin
mkdir /mnt/dev
mkdir /mnt/usr
mkdir /mnt/usr/lib
mkdir /mnt/mnt
mkdir /mnt/etc
mkdir /mnt/root
mkdir /mnt/home
mkdir /mnt/home/user?....
Now copy essential files. You will need many more than these for a decent system but here are the essentials and some of the more useful ones.
cp /bin/init /mnt/bin/init
cp /bin/login /mnt/bin/login
cp /bin/sh /mnt/bin/sh
cp /bin/ls /mnt/bin/ls
cp /bin/pwd /mnt/bin/pwd
cp /bin/mount /mnt/bin/mount
cp /bin/umount /mnt/bin/umount
cp /bin/cp /mnt/bin/cp
cp /etc/passwd /mnt/etc/passwd
cp /etc/group /mnt/etc/group
cp /usr/lib/liberror.txt /mnt/usr/lib/liberror.txt
Finally create the essentail devices:
mknod /mnt/dev/tty c 4 0
mknod /mnt/dev/tty2 c 4 1
mknod /mnt/dev/tty3 c 4 2
mknod /mnt/dev/fd0 b 3 128
mknod /mnt/dev/fd1 b 3 192
mknod /mnt/dev/hda b 3 0
mknod /mnt/dev/hda1 b 3 1
mknod /mnt/dev/hda2 b 3 2
mknod /mnt/dev/hda3 b 3 3
mknod /mnt/dev/hda4 b 3 4
mknod /mnt/dev/hdb b 3 64
mknod /mnt/dev/hdb1 b 3 65
mknod /mnt/dev/hdb2 b 3 66
mknod /mnt/dev/hdb3 b 3 67
mknod /mnt/dev/hdb4 b 3 68
Now unmount the new partition with
umount /dev/hd??
You will now need to re-compile a new kernel with the correct root device selected. To do this edit include/linuxmt/conmfig.h in the ELKS kernel sources, and changed the ROOT_DEV from 0x380 to the device number of the partition. The last two digits must be the minor number of the partition in hex. The minor number can be found from the list above in the far right column. E.g. The minor number for hdb3 is 67, which is 43 in hex, so the ROOT_DEV value is 0x343.
Type
make disk
to build a new kernel floppy, and reboot the ELKS machine with this new boot
disk. The new root should mount, but may give a warning, and the system come
up as normal, but much faster than from floppy. As before the root directory
may be corrupted, but it should be possible to change to other directories
normally, and the system should work otherwise normally.
cd /usr/src/linux-86/elksemu
make module
insmod binfmt_elks.o
Note that you will need to rerun the 'insmod' each time you reboot. There
are some sample bcc programs you can try in /usr/src/linux-86/tests
(such as a version of 'wc')
If when making the module you get an error saying "modversions.h: no such file or directory" then you need to edit the Makefile to remove the reference to this file, i.e.:
MODCFLAGS=-D__KERNEL__ -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer \
-fno-strength-reduce -pipe -m486 -DCPU=486 -DMODULE -DMODVERSIONS
floppy { device /dev/fd0 threeinch }