Linux on RAM

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I'm working on testing a Linux system on coldfire 5485.
I have the Freescale BSP, based on 2.6.10 kernel, and an evaluation
board for 5485.

until now, I have work with root filesystem on NFS or on Flash
Now, I need a system _exclusively_ on RAM (kernel and filesystem), but
I have some problems...

I work with a bootloader named Colilo (Coldfire Lilo).

In kernel compilation options, I have the choice between "cramfs" and
"ext2.gz Ramdisk" for a RAM root filesystem.

I have tried to use "ext2.gz Ramdisk". In this case, compilation
create kernel "vmlinux.bin" (2.6Mo) and the filesystem
"rootfs.ext2.gz" (3Mo, 9Mo unziped).

I have set following supports in kernel configuration :

<*> RAM disk support
(5) Default number of RAM disks
(12288) Default RAM disk size (kbytes)
[*] Initial RAM disk (initrd) support
<*> Second extended fs support
[*] Ext2 extended attributes
<*> ROM file system support
[*] /dev file system support
[*] Virtual memory file system support
[*] tmpfs Extended Attributes

Next, I have done :
- put "rootfs.ext2.gz" on RAM (0x02000000)
- put kernel "vmlinux.bin" on RAM (0x1000)
- command line of colilo :
"root=/dev/ram0 rootfstype=ext2.gz initrd=0x02000000
ramdisk_size12%288 load_ramdisk=1 keepinitrd"
- boot on kernel (g 0x2000)

"starting up linux rev 0.2: startmem 0xc022c000, size 125MB
Memory: 127848k/131072k available (1568k kernel code, 1384k data, 80k
devfs: 2004-01-31 Richard Gooch (
devfs: devfs_debug: 0x0
devfs: boot_options: 0x1
RAMDISK driver initialized: 5 RAM disks of 12288K size 1024 blocksize
VFS: Cannot open root device "ram0" or unknown-block(1,0)
Please append a correct "root=" boot option
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-

Please, could you explain me how can I have my system on RAM ? How
make kernel to see the rootfs ?

Thanks for help,

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