Diskless Linux Systems

Diskless Linux Systems

Post by Chris O'Reg » Fri, 28 Oct 1994 23:37:08



   I want to set up a Linux lab consisting of about four 386/486
computers.  The computers share a common drive located on one of
our lab's servers, otherwise, they do not have *any* local hard
disk space, so booting must be from floppy.

   Question #1:  The boot disk must mount "/" from a specific
                 directory on the NFS, and continue loading from
                 there.  How may I create such a boot disk?

   Question #2:  Can Linux use a swap "file" instead of a partition.
                 Repartitioning the drive is *NOT* an option.

Thanks for any help,

Chris O'Regan
Computer Engineering
Concordia University
Montreal, Canada.

 
 
 

Diskless Linux Systems

Post by Clint Hastin » Sun, 30 Oct 1994 01:54:14


|>    I want to set up a Linux lab consisting of about four 386/486
|> computers.  The computers share a common drive located on one of
|> our lab's servers, otherwise, they do not have *any* local hard
|> disk space, so booting must be from floppy.
|>
|>    Question #1:  The boot disk must mount "/" from a specific
|>            directory on the NFS, and continue loading from
|>                  there.  How may I create such a boot disk?
|>
|>    Question #2:  Can Linux use a swap "file" instead of a partition.
|>                  Repartitioning the drive is *NOT* an option.

Suggestion: go buy small hard drives (10, 20, 40MB should do -
maybe $20 apiece) for swap space and to boot from. I think having swap
mounted remotely would be painfully slow. Linux can use a swap "file",
but it's also probably slower. If you can't purchase drives, try to
get some donated.

You would have to have networking software up and running before you
could mount anything. Even if you could boot from a floppy, your root
would still remain on the floppy, would it not? And I would think that
mounting another disk on / would cause Linux to crash.

clint

 
 
 

Diskless Linux Systems

Post by Dave Bull » Wed, 02 Nov 1994 06:31:25


:    I want to set up a Linux lab consisting of about four 386/486
: computers.  The computers share a common drive located on one of
: our lab's servers, otherwise, they do not have *any* local hard
: disk space, so booting must be from floppy.

:    Question #1:  The boot disk must mount "/" from a specific
:                directory on the NFS, and continue loading from
:                  there.  How may I create such a boot disk?

:    Question #2:  Can Linux use a swap "file" instead of a partition.
:                  Repartitioning the drive is *NOT* an option.

: Thanks for any help,

: Chris O'Regan
: Computer Engineering
: Concordia University
: Montreal, Canada.

A#1:
Set up a file with an image of a minimal filesys (I got it down to 700 blocks ):
/, /dev, /etc, /sbin...  The exact contents are a exercise for the reader.
must be a minix filesys (I think).
(use loop device or create it on a floppy)
        mkfs /dev/fd0 700
        mount /dev/fd0 /mnt
        mkdir /mnt/bin /mnt/etc /mnt/lib /mnt/bin /mnt/sbin /mnt/usr ...
        cp -a /etc/init /etc/networks /etc/hosts ... /mnt/etc ...

Set up fstab to NFS-mount usr and anything else.
        server:/usr     /usr
        server:/bin     /bin1
        ...

Change rc to do 'mount -av' between rc.inet1 and rc.inet2
I also had /bin NFS mounted on /bin1 and then after it is mounted rename to /bin
        sh /etc/rc.inet1
        mount -av
        mv /bin /bin2; mv /bin1 /bin
        sh /etc/rc.inet2

Create a boot floppy (on fd1):
        cp /usr/src/linux/zImage /dev/fd1
        rdev /dev/fd1 /dev/fd0
        ramsize /dev/fd1 700
        umount /dev/fd0
        dd if=/dev/fd0 of=/dev/fd1 bs=1024 seek=512 count=700

Try booting.

But this wastes 700K of ram :-(, so I'm working on a init replacement that
implements rc.inet1, nfs-mounts /root, chroot /root, and exec the real init.

A#2
I don't think you can right now.  (But I'd like to hear otherwise).

--
Dave Bullis        Cognos, Inc     VOICE: (613) 738-1440 FAX: (613) 738-0002


"I didn't know the terminals were haunted.  The salesman didn't tell us."

 
 
 

Diskless Linux Systems

Post by Erik Mo » Fri, 04 Nov 1994 00:11:43




> :    I want to set up a Linux lab consisting of about four 386/486
> : computers.  The computers share a common drive located on one of
> : our lab's servers, otherwise, they do not have *any* local hard
> : disk space, so booting must be from floppy.

> :    Question #1:  The boot disk must mount "/" from a specific
> :           directory on the NFS, and continue loading from
> :                  there.  How may I create such a boot disk?

> :    Question #2:  Can Linux use a swap "file" instead of a partition.
> :                  Repartitioning the drive is *NOT* an option.

> : Thanks for any help,

> : Chris O'Regan
> : Computer Engineering
> : Concordia University
> : Montreal, Canada.

> A#1:
> Set up a file with an image of a minimal filesys (I got it down to 700 blocks ):
> /, /dev, /etc, /sbin...  The exact contents are a exercise for the reader.
> must be a minix filesys (I think).
> (use loop device or create it on a floppy)
>    mkfs /dev/fd0 700
>    mount /dev/fd0 /mnt
>    mkdir /mnt/bin /mnt/etc /mnt/lib /mnt/bin /mnt/sbin /mnt/usr ...
>    cp -a /etc/init /etc/networks /etc/hosts ... /mnt/etc ...

> Set up fstab to NFS-mount usr and anything else.
>    server:/usr     /usr
>    server:/bin     /bin1
>    ...

> Change rc to do 'mount -av' between rc.inet1 and rc.inet2
> I also had /bin NFS mounted on /bin1 and then after it is mounted rename to /bin
>    sh /etc/rc.inet1
>    mount -av
>    mv /bin /bin2; mv /bin1 /bin
>    sh /etc/rc.inet2

> Create a boot floppy (on fd1):
>    cp /usr/src/linux/zImage /dev/fd1
>    rdev /dev/fd1 /dev/fd0
>    ramsize /dev/fd1 700
>    umount /dev/fd0
>    dd if=/dev/fd0 of=/dev/fd1 bs=1024 seek=512 count=700

> Try booting.

> But this wastes 700K of ram :-(, so I'm working on a init replacement that
> implements rc.inet1, nfs-mounts /root, chroot /root, and exec the real init.

> A#2
> I don't think you can right now.  (But I'd like to hear otherwise).

Yes it can right now. I understand the systems do have a harddisk and
if you use an UMSDOS filesystem it works . Over here we use a Linux
bootdisk that nfs mounts the bin directories on a "full" Linux box
and swaps on the dos disk partition using UMSDOS.
This is in /etc/rc:

umssync /dos >/dev/null
mkswapfile /dos/swapfile 16384 &
echo "/dos/swapfile" >/etc/swapfile

Erik

> --
> Dave Bullis        Cognos, Inc     VOICE: (613) 738-1440 FAX: (613) 738-0002


> "I didn't know the terminals were haunted.  The salesman didn't tell us."

--------------------------------------------------
Erik Mouw, Department of Electrical Engineering,
Delft University of Technology, The Netherlands

        D  O  N  '  T     P  A  N  I  C  !

--------------------------------------------------

Justice is incidental to law and order -- J. Edgar Hoover

 
 
 

Diskless Linux Systems

Post by Alan C » Fri, 04 Nov 1994 21:07:29



>   Question #1:  The boot disk must mount "/" from a specific
>             directory on the NFS, and continue loading from
>                 there.  How may I create such a boot disk?

You can't do it directly. What you do is set up a boot disk that sets
up basic parameters and boots from a floppy disk root partition. This then
mounts the NFS disk , chroot's to it and kicks off the normal init. I've got
an experimental pair of disks for this(I've not made it into one disk yet).
It also uses a 1Mb ramdisk and points some config files, and things like
/etc/utmp that can't be shared into ramdisk - its still an experiment and
far from finished.

Quote:

>   Question #2:  Can Linux use a swap "file" instead of a partition.
>                 Repartitioning the drive is *NOT* an option.

Yep

Alan
--
  ..-----------,,----------------------------,,----------------------------,,

 ``----------'`----------------------------'`----------------------------''

 
 
 

Diskless Linux Systems

Post by Russell Mar » Sun, 06 Nov 1994 01:41:27


| :    Question #2:  Can Linux use a swap "file" instead of a partition.
| :                  Repartitioning the drive is *NOT* an option.
[...]
| A#2
| I don't think you can right now.  (But I'd like to hear otherwise).

You can certainly use a swapfile. I don't know if it has to be local
or not - I'd imagine it can be anywhere you want. It's just a matter
of dd'ing however much swap you want from /dev/zero and using mkswap -
then, swapon's your uncle! :-)

Obviously - assuming you can use remote swapfiles - you'd need a
different file for each machine, and I doubt it would be terribly
quick.

If you can't use remote swapfiles, you could always use the floppy as
swap. Actually, I just tried for the fun of it and, it works...
slowly. Interesting way to test for bad sectors. :-)

-Rus.

--


\ ::: "His world is under anaesthetic - subdivided and synthetic" - Rush ::: /

 
 
 

Diskless Linux Systems

Post by Dave Bull » Sun, 06 Nov 1994 00:25:42



: >   Question #1:  The boot disk must mount "/" from a specific
: >           directory on the NFS, and continue loading from
: >                 there.  How may I create such a boot disk?

: You can't do it directly. What you do is set up a boot disk that sets
: up basic parameters and boots from a floppy disk root partition. This then
: mounts the NFS disk , chroot's to it and kicks off the normal init. I've got

Hint: make sure you chdir("/") after the chroot to keep sh happy.

: an experimental pair of disks for this(I've not made it into one disk yet).
: It also uses a 1Mb ramdisk and points some config files, and things like
: /etc/utmp that can't be shared into ramdisk - its still an experiment and
: far from finished.

I'm done something similar.  Last night's problem is that syslogd tries
to create /dev/log (A UNIX domain socket) but fails because /dev is NFS-mounted
from my server.  I'm guessing that I can't have a UNIX domain socket on
a NFS filesys.  Is this true?  If so, are there any work arounds since
everything is NFS mounted.  Is there anything else that depends on
UNIX-domain sockets?  I've got the X server running ok.

: >
: >   Question #2:  Can Linux use a swap "file" instead of a partition.
: >                 Repartitioning the drive is *NOT* an option.

: Yep

I dimly recall that swap is not supported on NFS mounted files.
Is this not true anymore?  If so, this is good news.

: Alan
: --
:   ..-----------,,----------------------------,,----------------------------,,

:  ``----------'`----------------------------'`----------------------------''

PS: Thanks for all the fish^H^H^H^H^H code.

--
Dave Bullis        Cognos, Inc     VOICE: (613) 738-1440 FAX: (613) 738-0002


"I didn't know the terminals were haunted.  The salesman didn't tell us."

 
 
 

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