Re: [Devil-Linux-discuss] Hack to install onto harddisk instead of memory (low memory solution)

[Heiko Z. <hz...@pr...>]

Hey,

thanks for the howto.

cu
   Heiko


On 05/15/2002 06:24:49 AM "Walter Haidinger" wrote:
>Hi!
>
>I've successfully installed Devil-Linux this weekend on an old machine=

>(486/66) with just 24 MB of RAM. I think that even 16 MB would be
>sufficient.
>However, in order to do that I had to make Devil-Linux boot onto a
>harddisk partition instead of a ramdisk. I was forced to do this
>because _both_ of my 32MB SIMMs turned out to be defective... :-(
>Well, here's what I did. Perhaps it helps somebody who has a similar
>problem. How about adding a docs section like "installing Devil-Linux
>on machines with less than 64 MB RAM" ?
>This may have been done already but I didn't search the mailing-list
>archives when I did it because I had no internet access at that time.
>
>Anyways, here goes:
>
>With my setup, I used three partitions (on an old 200+ MB IDE drive):
>* /dev/hda1 - DOS (C:), about 50 MB
>  Required because that old machine could not boot from CD-Rom and if
>  I have to use a harddisk anyways we can as well use it for booting
>too.
>  Please note that the floppy containing the config is still required
>  any may have to configure the BIOS to boot from HD first.
>* /dev/hda2 - Linux SWAP, 64 MB
>  I have free disk space so why not extend the already limited physica=
l
>  memory and set up a swap partition?
>* /dev/hda3 - Linux ext2, about 100 MB
>  Used as subsitute for the ramdisk. I've hacked the initrd to use
>  this partition instead of /dev/shm (see below).
>
>After setting up a DOS partition to boot from (C:), I copied the
>boot directory from the CD (to C:\boot). Next, I had to modify to
>linuxrc  script of initrd.gz.
>To do this, follow these steps (under Linux):
>1. Copy the initrd.gz from the CD-Rom somewhere, e.g.
>   > cp /cdrom/boot/initrd.gz /tmp
>2. Unpack it
>   > gunzip /tmp/initrd.gz
>3. Mount the file using the loopback-device:
>   > mount /tmp/initrd -o rw,loop=3D/dev/loop0 /mnt
>4. Modify /mnt/linuxrc with your favourite editor according to the
>   next section below.
>   > your-editor /mnt/linuxrc
>5. Copy your /sbin/swapon and /sbin/mkswap files to /mnt/sbin
>   Make sure that the binaries run on your Devil-Linux Version.
>   For me, binaries from SuSE-Linux 7.3 run on Devil-Linux 0.5.
>6. Unmount again
>   > umount /mnt
>7. Pack the modified image
>   > gzip initrd
>8. Copy the new initrd.gz to the boot directory of the DOS partition
>   (C:\boot)
>
>Now for the fun part: Howto modify linuxrc
>(I've modifed linuxrc v1.7 from the 0.5rc1 distribution)
>
>Here are the diffs in detail:
>
>28a29,32
>> SWAP_PART=3D/dev/hda2
>> echo "Adding swapspace on $SWAP_PART"
>> /sbin/swapon $SWAP_PART && print_status success || print_status
>failure
>>
>
>Add the swap partition. You might add a /sbin/mkswap $SWAP_PART right
>before swapon but I doubt that this is necessary. Well, of course you
>need to create the swap-space _once_ !
>31a36,43
>> DATA_PART=3D/dev/hda3
>> echo "Using $DATA_PART as ramdisk substitute:"
>> test -d /hd || mkdir /hd
>> echo -n "Creating ext2 filesystem on $DATA_PART"
>> /sbin/mke2fs -q $DATA_PART print_status success || print_status
>failure
>> echo -n "Mounting $DATA_PART"
>> mount -t ext2 -o rw $DATA_PART /hd && print_status success ||
>> print_status failure>
>
>Use partition set by DATA_PART as the ramdisk substitute.
>First create a mountpoint, then create the filesystem and mount it.
>*** WARNING:
>The partition is created _without_ question! Any previously stored
>data is lost! Actually, that is a good thing as it really simulates
>ramdisk behaviour and is therefore a security benefit.
>Also, you can simply turn off the machine without shutting down which
>is good if you have users power on/off the router without further
>knowledge.However, it can be *very* disastrous if you edit your
>partition table
>and forget to assign the correct partition in DATA_PART.
>33,35c45,49
>< test -d /dev/shm || mkdir /dev/shm
>< echo -n "Mounting SHM FS on /dev/shm"
>< mount -t shm -o size=3D40g shmfs /dev/shm && print_status success ||=

>print_status failure---
>> #test -d /dev/shm || mkdir /dev/shm
>> #echo -n "Mounting SHM FS on /dev/shm"
>> #mount -t shm -o size=3D40g shmfs /dev/shm && print_status success |=
|
>> print_status failure> rm -rf /dev/shm > /dev/null 2>&1
>> ln -s /hd /dev/shm
>39c53,54
>< ln -s /dev/shm /ram
>---
>> #ln -s /dev/shm /ram
>> ln -s /hd /ram
>
>Remove (comment) the shared memory stuff and replace it by symlinks.
>This allows transparent usage of the partition instead of /dev/shm,
>i.e. not subsequent scripts need to be modified.
>
>That are all changes made to linuxrc.
>I've attached a context diff with the changes.
>To apply it, run (replacing step 4 above) in /mnt after saving the
>attachment (to, say, /tmp):
>   patch < ../tmp/linuxrc.diff
>
>*** Security warning:
>If you store the boot files (kernel, initrd, ...) on the harddisk
>(i.e. if you do _not_ create a CD containing the new initrd.gz), that
>files _can_ be modified.Therefore, the integrity of the boot files
>_have_ to be verified!
>e.g.: Use MD5 hashes!
>
>1. Get md5sum.exe for DOS from http://etree.org/md5com.html
>   and put it on your config floppy.
>2. Create md5 checksums for all files that are on the harddisk,
>   e.g. (write on one line):
>     md5sum.exe C:\boot\initrd.gz C:\boot\loadlin.exe
>                C:\boot\vmlinuz > A:\boot.md5
>3. In autoexec.bat of your boot floppy, add the following 2 lines:
>     md5sum -vc boot.md5
>     if errorlevel 1 exit
>4. Don't forget to write-protect your floppy again!
>
>Now, if anyone modifies the files on the harddisk, md5sum fails the
>check and the autoexec.bat is aborted.
>That's finally it! I just hope that I forgot nothing as I wrote this
>mostly from memory...
>
>Anyways, comments *are* welcome!
>
>Regards, Walter
>
>PS: Yes, I know this is a (bad) hack and there are better ways
>    (that is, more configurable) to do this.
>    However, I had to get the system up and that is what did it.
>    You're free to do it any other way you desire! ;-)



=