Use jffs2-formatted initrd from RAM (not Flash)

Use jffs2-formatted initrd from RAM (not Flash)

[Sebastian Haag]

Hi,

I have a minimal linux system which consists of a bzImage (kernel 2.6.16.5) and
a rootfs (initrd). The rootfs is formatted with ext2. The kernel and initrd is
stored on a bootp server and is loaded at system startup into the system RAM.
Kernel gets extracted, mounts the rootfs and executes init.
Everything works fine.

To save memory in RAM, I want to compress the rootfs. I decided to use jffs2 as
filesystem, because its writable.

My kernel supports jffs2 filesystems and mtd devices (I hope so).

What I did:
- mkfs.jffs2 -l -o ../jffs_root.img
- test in qemu:

-----------------------------------
INITRD=jffs_root.img

qemu $INITRD -kernel bzImage -initrd $INITRD -net nic,vlan=0 -net
tap,vlan=0,ifname=tap0 -append "root=/dev/mtdblock0 rw blkmtd_device=/dev/ram0
rootfstype=jffs2"
-----------------------------------

I added the whole "-append thing", but I´m not absolutely sure what I did ;-)
But I´m sure, it doesn´t work...

I get the following messages:

RAMDISK driver initialized: 1 RAM disks of 4096K size 1024 blocksize
blkmtd: version $Revision: 1.27 $
blkmtd: mtd1: [/dev/ram0] erase_size = 128KiB
block2mtd: version $Revision: 1.30 $
...
RAMDISK: Couldn´t find valid RAM disk image starting at 0.
VFS: Mounted root (jffs2 filesystem).
Freeing unused kernel memory: 104k freed
Warning: unable to open an initial console.
Kernel panic - not syncing: No init found. Try passing init= option to kernel.



Do you have an idea which kernel parameters are needed to mount this
jffs2-rootfs properly?

Thanks,

Sebastian

Re: Use jffs2-formatted initrd from RAM (not Flash)

[Sebastian Haag]

sorry for the double post, had some problems with my mail client.


Nobody an idea? I can´t believe that...

Could you please give me some hints/links where I can find the solution
for this
problem? I googled too much the last days...

thanks

Re: Use jffs2-formatted initrd from RAM (not Flash)

[Nishanth Menon]

> Could you please give me some hints/links where I can find the solution 
> for this
> problem? I googled too much the last days...

Not an expert on this... my blind "googled" guess would be: mebbe try
mtdram?
here is a thread that might be of interest to you (mentions exactly how
this is done):
http://lists.infradead.org/pipermail/linux-mtd/2006-April/015285.html
and this one (for general info):
http://lists.infradead.org/pipermail/linux-mtd/2005-August/013390.html

Regards,
Nishanth Menon

Use jffs2-formatted initrd from RAM (not flash)

[Sebastian Haag]

Hi,

I have a minimal linux system which consists of a bzImage (kernel 2.6.16.5) and
a rootfs (initrd). The rootfs is formatted with ext2. The kernel and initrd is
stored on a bootp server and is loaded at system startup into the system RAM.
Kernel gets extracted, mounts the rootfs and executes init.
Everything works fine.

To save memory in RAM, I want to compress the rootfs. I decided to use jffs2 as
filesystem, because its writable.

My kernel supports jffs2 filesystems and mtd devices (I hope so).

What I did:
- mkfs.jffs2 -l -o ../jffs_root.img
- test in qemu:

-----------------------------------
INITRD=jffs_root.img

qemu $INITRD -kernel bzImage -initrd $INITRD -net nic,vlan=0 -net
tap,vlan=0,ifname=tap0 -append "root=/dev/mtdblock0 rw blkmtd_device=/dev/ram0
rootfstype=jffs2"
-----------------------------------

I added the whole "-append thing", but I´m not absolutely sure what I did ;-)
But I´m sure, it doesn´t work...

I get the following messages:

RAMDISK driver initialized: 1 RAM disks of 4096K size 1024 blocksize
blkmtd: version $Revision: 1.27 $
blkmtd: mtd1: [/dev/ram0] erase_size = 128KiB
block2mtd: version $Revision: 1.30 $
...
RAMDISK: Couldn´t find valid RAM disk image starting at 0.
VFS: Mounted root (jffs2 filesystem).
Freeing unused kernel memory: 104k freed
Warning: unable to open an initial console.
Kernel panic - not syncing: No init found. Try passing init= option to kernel.



Do you have an idea which kernel parameters are needed to mount this
jffs2-rootfs properly?

Thanks,

Sebastian