[ts-7000] TS-7800: increasing size of ramdisk for initrd

["Theodore A. Roth" <>]

I have been trying unsuccessfully to create an initrd on a 2-GB sd
card that is larger than 4-MB.

First off I setup the partition table on the sd card using fdisk (on
Ubuntu Linux) to look like this:

Disk /dev/mmcblk0: 2032 MB, 2032664576 bytes
4 heads, 16 sectors/track, 62032 cylinders
Units = cylinders of 64 * 512 = 32768 bytes
Disk identifier: 0x00000000

        Device Boot      Start         End      Blocks   Id  System
/dev/mmcblk0p1               5        1028       32768   83  Linux
/dev/mmcblk0p2            1029        1540       16384   da  Non-FS data
/dev/mmcblk0p3            1541        2052       16384   da  Non-FS data
/dev/mmcblk0p4            2053       62032     1919360   83  Linux

I built a kernel from the linux-2.6.21-ts source and changed the
config to have a 16-MB ramdisk and modified the command line options:

CONFIG_BLK_DEV_RAM=y
CONFIG_BLK_DEV_RAM_COUNT=1
CONFIG_BLK_DEV_RAM_SIZE=16384
CONFIG_BLK_DEV_RAM_BLOCKSIZE=1024

CONFIG_CMDLINE="root=/dev/ram0 rw lpj=1662976 init=/linuxrc
console=ttyS0,115200n8 debug"

My kernel boots fine when installed into the 2nd partition and when I
have installed the initrd-busybox-rootfs-jun102008.dd file (downloaded
directly from TS ftp site) into partition 3. Both files are installed
using the dd utility.

Life is good up to this point.

Now I have created multiple new initrd files as such (all done as root):

======= begin  mk-initrd.sh ========
#!/bin/bash

set -e

## This one fails to run /linuxrc
#IMG="initrd-16MB.dd"
#CNT=16384

## This one works fine. [Same filesystem size as origin TS initrd file.]
#IMG="initrd-1.5MB.dd"
#CNT=1536

## This one works fine.
IMG="initrd-4MB.dd"
CNT=4096

dd if=/dev/zero of=${IMG} bs=1024 count=${CNT}
mkfs.ext2 ${IMG}
mkdir -p ts
mount -o loop initrd-busybox-rootfs-jun102008.dd ts
mkdir -p my
mount -o loop ${IMG} my
tar -C ts -cf - . | tar -C my -xf -
umount my
umount ts

echo "Now do this: dd if=${IMG} of=/dev/mmcblk0p3"
=========== end mk-initrd.sh ============

So:

* I can create a initrd image the same size as the one from TS and it
boots fine (runs /linuxrc)
* I can create a 4-MB image and it boots file.
* Any image over 4-MB fails to find the /linuxrc file, producing this
error message on the console:

... [bunch of kernel output removed]
RAMDISK: ext2 filesystem found at block 0
RAMDISK: Loading 16384KiB [1 disk] into ram disk... done.
VFS: Mounted root (ext2 filesystem).
Freeing init memory: 104K
Warning: unable to open an initial console.
Failed to execute /linuxrc.  Attempting defaults...
Kernel panic - not syncing: No init found.  Try passing init= option to kernel.

This leads me to suspect that the bootload from TS is possibly hard
coded to only load the first 4-MB from partition 3 of the SD card into
the ramdisk before starting the kernel.

So, now for my questions:

* Is my suspicion true?
* Is there a way to tell the bootloader the size of the image to load
into the ramdisk?
* Why doesn't the bootloader read the partition table and just copy
the entire partition in to the ramdisk?
* Is it even possible to use an initrd that is more than 4-MB?

Thanks.

Ted Roth

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