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1996-11-17
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What is Diskless LINUX (DL-Linux)?
----------------------------------
Diskless Linux allows to have a Linux workstation on PCs without a hard
disk, provided that you have a "Linux server" which is a NFS server.
The Linux server exports the /home, /usr, /var, /sbin, and /bin
directories; you can choose to export /lib from the Linux server, but
this slows considerably the system.
What do you need?
-----------------
You need a BOOT disk and a ROOT disk. The BOOT disk is made with
these instructions:
dd if=/vmlinuz of=/dev/fd0
/sbin/vidmode /dev/fd0 0
/sbin/ramsize /dev/fd0 1440
/sbin/rdev /dev/fd0 /vmlinuz
I assume that the working kernel is named "vmlinuz". You can change
the video mode to whatever you want; 0 means the 80x50 mode, which I
prefer. You can also set the ramsize to 0 if you want to have
more free RAM; this slows things, but if you want to have more memory
for Xwindows, you can do that; remember that diskless workstations
can't use a swapfile and that a RAM disk uses part yof your RAM.
The ROOT disk has an ext2 filesystem with the basic things needed to
load a Linux session and to mount the remote filesystems described
above. A sample ROOT disk is included in the distribution. The base
of it is a root disk made by the SAR package, but it has been
pretty heavily modified. Some of the differences are:
- Some additional programs included.
- The /etc/inittab and the "rc" (system initialization) programs were
heavily modified. The /etc/inittab file is similar to the Slackware
distribution. The rc.S file calls the rc.bootp script for getting
the station's IP address and network configuration.
- The BOOTP program, bootpc and the rc.bootp script was made by
Charles Hawkins (ceh@eng.cam.ac.uk) and modified by Jon Peatfield
(J.S.Peatfield@amtp.cam.ac.uk) from from the U. of Cambridge, UK.
I made some further modifications to the script.
Installation
------------
1. Make a boot disk with or without RAMDISK. If your Linux station has
a hard disk, it's better to make a boot disk with RAMDISK, because
you can make a 8-16 MB swap partition. If your station is diskless,
it depends on how much RAM do you have. If you have only 4 MB, make
a boot disk without RAMDISK. If you have 8 MB, and want to load
Xwindows, use make also a boot disk without RAMDISK. For more than
8 MB or 8 MB without Xwindows, you can choose to make a boot disk
with RAMDISK.
I have two scripts, "make.boot.ram" and "make.boot.noram" for doing
a boot disk.
2. Download a root disk. Then get a formatted diskette and type:
dd if=<boot image> of=/dev/fd0
<boot image> can be "root.swapfile" for stations with a hard disk
(usually DOS machines with a Linux swap partition), or
"root.no.swapfile", usually for diskless stations; you can't make
a remote swapfile.....
3. If you need and to, make a swap partition or swap file. You will
need some 8-16 MB of free disk.
4. Now modify your
mount /dev/fd0 /mnt
After this, examine the mounted filesystems and modify whatever you
need, among them:
/etc/fstab - for mounting the right filesystems from the
Linux server and perhaps mounting other
filesystems from anywhere else
/etc/rc.d/rc.bootp - for the BOOTP configuration
/etc/rc.d/rc.S - you can modify it for setting up directly
your IP address without invoking rc.bootp
/etc/passwd and - you can, for example make these links to
/etc/group a directory where you have a copy of the
server original files
After modifying the root disk to your liking, type:
umount /mnt
5. Check that the Linux server has the correct configuration for
mounting the Linux filesystems:
- Check that the /etc/exports exports the /home, /var, /sbin,
/bin, /tmp and /usr filesystems. You can choose to export /lib,
also. WARNING: restrict the access of these filesystems to the
stations authorized to use Diskless Linux.
- Check that the /etc/rc.d/rc.inetd2 activates the rpc.portmap,
rpc.mountd and rpc.nfsd daemons. If not, uncomment the respective
parts of the rc.inet2 script.
6. Have your BOOTP server adequately configurated.
7. Go to a station, insert a boot disk and type CTRL-ALT-DEL. When
inserting a root disk or ramdisk is asked, insert your root
disk. After some seconds, the login prompt should appear. Login
as "root" and check that all is right.
Some possible scenarios
-----------------------
1. A diskless station with 4 MB RAM
--------------------------------
Use only a boot floppy WITHOUT a RAMDISK and a swapless root disk.
The first is needed because you can give away any single byte of RAM,
and the second because there is no such thing as a remote swap area....
2. A diskless station with 8 MB RAM
--------------------------------
You can use a boot floppy with or without a RAMDISK. It depends on
using or not Xwindows. If you wish to work with Xwindows, use a
boot disk without a RAMDISK. Otherwise, you won't have enough
RAM for running X. Use a swapless root disk.
3. A diskless station with 12-16 MB RAM
------------------------------------
I think you can use confidently a boot floppy WITH a RAMDISK unless
you want to run lots of X applications or memory-consuming programs.
Use always a swapless root disk.
4. A DOS station with any RAM and a 8+ MB swap partition or file
---------------------------------------------------------------
Use a boot floppy with RAMDISK and a root disk with a swapfile. Here
you can run any application depending on how much physical and
virtual (swap) RAM do you have. This is, of course, the best scenario.
To do
-----
Probably this same work on a little (about 5 MB) hard disk Linux partition.
Also, improvements on this work.
Comments
--------
Mail any comment, suggestion, etc. to Mario A. Guerra
(mguerra@cariari.ucr.ac.cr). I work at the University of Costa Rica.