Making a floppy system with PeeWeeLinux

[Adi Linden]

Hi,

Here are some instructions on how to create a floppy run system using
PeeWeeLinux.

1.  Use pwlconfig to pick the packages and files required.

2.  Use the custom files option to customize your system.

3.  Use the extract filesystem option to create a filesystem.

4.  Exit pwlconfig at this point.

5.  Create an empty ramdisk. Filling it with zero ensure optimal
    compression. Note that most Linux distributions include a kernel
    that allows 16 ramdisks of 4000kB each. I found the maximum
    uncompressed filesystem size on a floppy is about 3MB.
    Command to run for a 3MB filesystem:
        dd if=/dev/zero of=/dev/ram bs=1k count=3000

6.  Create a filesystem
        mke2fs -m0 -b 1024 /dev/ram 3000

7.  Mount the filesystem at a suitable location
        mount -t ext2 /dev/ram /mnt/flash

8.  Remove some unneeded stuff
        rm -rf /mnt/flash/lost+found

9.  Copy the extracted filesystem to the mounted ramdisk. Note that this
    filesystem does not require a kernel! The kernel will be put onto the
    floppy disk seperately. Nor will lilo be required in the package
    selection process.
    
    a. First option, use the 'cp' command:
        cp -a Embedded_Build/projects/<your project>/mnt/* /mnt/flash
        rm /mnt/flash/boot/bzImage

    b. Second option, use tar
        tar cp \
            --exclude=bzImage \
            --directory=Embedded_Build/projects/<your project>/mnt \
            ./ | tar xp --directory=/mnt/flash

10. ldconfig is a rather large binary which can be ommitted as long as it
    is run prior to compressing the ramdisk. We do it now.
        ldconfig -r /mnt/flash

11. Unmount the ramdisk
        umount /mnt/flash

12. Create a compressed image
        dd if=/dev/ram bs=1k count=3000 | gzip -v9 > ramdisk.img

13. Insert an empty floppy into the drive

14. Place the kernel on the floppy
        dd if=Embedded_Build/projects/<your project>/mnt/boot/bzImage \
            of=/dev/fd0

15. When dd finishes you will get a message similar to
        410+1 records in
        410+1 records out

    Record the number reported and add 1. The number indicated is the last
    1k block the kernel was written to. We want to start the compressed
    ramdisk image beyond the end of the kernel without overwriting the
    last block occupied by the kernel. So the number for our example would
    be 411

16. Place the ramdisk image on the floppy
        dd if=ramdisk.img of=/dev/fd0 bs=1k seek=411

17. Last we need to tell the kernel where our ramdisk can be found on the
    kernel. Calculate the sum of 16384 and the earlier recorded number of
    blocks. I.e 16384 + 411 = 16795

18. Tell the kernel what's up...
        rdev /dev/fd0 /dev/fd0
        rdev -r /dev/fd0 16795
        rdev -R /dev/fd0 0

    A quick explaination: 
        The first statement tells the kernel that it is booting from the
          floppy disk device.
        The second statement tells the kernel to load a compressed ramdisk
          starting at block 411 of the floppy device without prompting for
          a second disk. Details of the meaning of 16384 can be found in
          the kernel documentation.
        The third statement tells the kernel that it is starting at block
          0 of the floppy device (I might be wrong about this last rdev
          statement, though, but that's what I remember it was for).

19. That's it. Boot with the floppy and enjoy!

TTYL,
Adi

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