root=/dev/ram0

root=/dev/ram0

[Andrew Dixon]

Hi All,
I'm trying to mount a compressed ramdisk image on /dev/ram0 and run my
root filesystem from there.  My problem is that when I try to boot I get
the following error:

    VFS: Cannot open root device "ram0" or 01:00
    Please append a correct "root=" boot option

earlier in the boot process the ram disks are recognized:

    RAMDISK driver initialized: 16 RAM disks of 4096K size 1024
blocksize

I'm using kernel 2.4.5-pre3 from Ben H's source.

Anyone know why the kernel isn't able to open /dev/ram0?

Thanks,
Andy

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Re: root=/dev/ram0

[Paul Ruhland]

Andrew,

First make sure you are passing the correct boot args to the kernel:

   root=/dev/ram0

Is this echoed by the kernel during boot?

Also, make sure you have 'Second extended filesystem' support
('CONFIG_EXT2_FS=y' in .config) compiled into your kernel.

That's really all I can suggest without more information.


On Thursday 26 July 2001 04:02 pm, you wrote:
> Hi All,
> I'm trying to mount a compressed ramdisk image on /dev/ram0 and run my
> root filesystem from there.  My problem is that when I try to boot I get
> the following error:
>
>     VFS: Cannot open root device "ram0" or 01:00
>     Please append a correct "root=" boot option
>
> earlier in the boot process the ram disks are recognized:
>
>     RAMDISK driver initialized: 16 RAM disks of 4096K size 1024
> blocksize
>
> I'm using kernel 2.4.5-pre3 from Ben H's source.
>
> Anyone know why the kernel isn't able to open /dev/ram0?
>
> Thanks,
> Andy
>

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Re: root=/dev/ram0

[Andrew Dixon]

Paul Ruhland wrote:
>
> Andrew,
>
> First make sure you are passing the correct boot args to the kernel:
>
>    root=/dev/ram0
>
> Is this echoed by the kernel during boot?

Yup.

>
> Also, make sure you have 'Second extended filesystem' support
> ('CONFIG_EXT2_FS=y' in .config) compiled into your kernel.
>

I definitely do

> That's really all I can suggest without more information.
>

What other informatin would be useful?  This has got me stumped.  The
ramdisk support in the kernel seems to be working OK.  I booted the
system up with an nfs mounted root partition and did the following:

	#dd if=/dev/zero of=/dev/ram0 bs=1k count=4096
	#dd if=/fs of=/dev/ram0    (fs is my filesystem image)

This went off without a hitch so I tried mounting /dev/ram0:

	#mount /dev/ram0 /mnt

also fine and when I look in /mnt the filesystem looks OK too.

Thanks,
Andy

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RE: root=/dev/ram0

[Rey Estrada]

You might want to try setting ramdisk_size too.  It's been a while since I
played with this stuff and the argument may be called something else.

Rey Estrada
Motorola Computer Group
2900 S Diablo Way
Tempe, AZ  85282


-----Original Message-----
From: owner-linuxppc-embedded@lists.linuxppc.org
[mailto:owner-linuxppc-embedded@lists.linuxppc.org]On Behalf Of Andrew Dixon
Sent: Thursday, July 26, 2001 2:33 PM
To: 'linuxppc-embedded@lists.linuxppc.org'
Subject: Re: root=/dev/ram0


Paul Ruhland wrote:
>
> Andrew,
>
> First make sure you are passing the correct boot args to the kernel:
>
>    root=/dev/ram0
>
> Is this echoed by the kernel during boot?

Yup.

>
> Also, make sure you have 'Second extended filesystem' support
> ('CONFIG_EXT2_FS=y' in .config) compiled into your kernel.
>

I definitely do

> That's really all I can suggest without more information.
>

What other informatin would be useful?  This has got me stumped.  The
ramdisk support in the kernel seems to be working OK.  I booted the
system up with an nfs mounted root partition and did the following:

        #dd if=/dev/zero of=/dev/ram0 bs=1k count=4096
        #dd if=/fs of=/dev/ram0    (fs is my filesystem image)

This went off without a hitch so I tried mounting /dev/ram0:

        #mount /dev/ram0 /mnt

also fine and when I look in /mnt the filesystem looks OK too.

Thanks,
Andy


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Re: root=/dev/ram0

[Amit D Chaudhary]

Hi,


Can you give the following details,
Are you trying to load it as initrd? Not I assume, else confirm that
CONFIG_BLK_DEV_INITRD=y

Incase you are setting /dev/ram0 as the rootfs using rdev or equivalent,
how does the rootfs end up on the ramdisk when the kernel starts up?

Amit

ps - Did not mean to skip the list.

Andrew Dixon wrote:

> Paul Ruhland wrote:
>
>>Andrew,
>>
>>First make sure you are passing the correct boot args to the kernel:
>>
>>   root=/dev/ram0
>>
>>Is this echoed by the kernel during boot?
>>
>
> Yup.
>
>
>>Also, make sure you have 'Second extended filesystem' support
>>('CONFIG_EXT2_FS=y' in .config) compiled into your kernel.
>>
>>
>
> I definitely do
>
>
>>That's really all I can suggest without more information.
>>
>>
>
> What other informatin would be useful?  This has got me stumped.  The
> ramdisk support in the kernel seems to be working OK.  I booted the
> system up with an nfs mounted root partition and did the following:
>
> 	#dd if=/dev/zero of=/dev/ram0 bs=1k count=4096
> 	#dd if=/fs of=/dev/ram0    (fs is my filesystem image)
>
> This went off without a hitch so I tried mounting /dev/ram0:
>
> 	#mount /dev/ram0 /mnt
>
> also fine and when I look in /mnt the filesystem looks OK too.
>
> Thanks,
> Andy
>
>
>
>


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Re: root=/dev/ram0

[Andrew Dixon]

Amit D Chaudhary wrote:
>
> Hi,
>
> Can you give the following details,
> Are you trying to load it as initrd? Not I assume, else confirm that
> CONFIG_BLK_DEV_INITRD=y

I am trying to load it as initrd.

andrew.dixon@pig2:/usr/src/linux$ cat .config |grep
CONFIG_BLK_DEV_INITRD
CONFIG_BLK_DEV_INITRD=y

And this is set up correctly in the kernel.  Just to make sure that my
configuration was a workable solution I recompiled everything for an i86
architecture and I tried it out on my laptop.  I put my compressed
ramdisk image and kernel onto a floppy and used ldlinux.sys as a boot
loader passing it the command:

	root=/dev/ram0 initrd=fs.gz

and it works fine.  This prompted me to do a little searching through
the ramdisk source (/usr/src/linux/drivers/block/rd.c) and I found that
the ramdisk expects to find the ramdisk image on the floppy drive:

	if (MAJOR(ROOT_DEV) != FLOPPY_MAJOR
#ifdef CONFIG_BLK_DEV_INITRD
		&& MAJOR(real_root_dev) != FLOPPY_MAJOR
#endif
	)
	  //ADD
	  //we don't want to return here because our real_root_dev is not the
	  //floppy but the disk or flash device.  Right?  Right!
	  //		return;


It still doesn't work but I've got that feeling that I'm getting
closer.  I'm going to make sure that the hard disk is detected before
the ramdisk tries to load the image

later,
Andy

P.S. Do people on the list like to be cc'd on responses or should I keep
all mail to the list only?

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Re: root=/dev/ram0

[Amit D Chaudhary]

Interesting, try the following,
Don't specify root= anywhere including kernel cmdline

in your initrd, ensure thet there is a symlink /linuxrc to /bin/sh(or
equivalent).

Amit

Andrew Dixon wrote:

> Amit D Chaudhary wrote:
>
>>Hi,
>>
>>Can you give the following details,
>>Are you trying to load it as initrd? Not I assume, else confirm that
>>CONFIG_BLK_DEV_INITRD=y
>>
>
> I am trying to load it as initrd.
>
> andrew.dixon@pig2:/usr/src/linux$ cat .config |grep
> CONFIG_BLK_DEV_INITRD
> CONFIG_BLK_DEV_INITRD=y
>
> And this is set up correctly in the kernel.  Just to make sure that my
> configuration was a workable solution I recompiled everything for an i86
> architecture and I tried it out on my laptop.  I put my compressed
> ramdisk image and kernel onto a floppy and used ldlinux.sys as a boot
> loader passing it the command:
>
> 	root=/dev/ram0 initrd=fs.gz
>
> and it works fine.  This prompted me to do a little searching through
> the ramdisk source (/usr/src/linux/drivers/block/rd.c) and I found that
> the ramdisk expects to find the ramdisk image on the floppy drive:
>
> 	if (MAJOR(ROOT_DEV) != FLOPPY_MAJOR
> #ifdef CONFIG_BLK_DEV_INITRD
> 		&& MAJOR(real_root_dev) != FLOPPY_MAJOR
> #endif
> 	)
> 	  //ADD
> 	  //we don't want to return here because our real_root_dev is not the
> 	  //floppy but the disk or flash device.  Right?  Right!
> 	  //		return;
>
>
> It still doesn't work but I've got that feeling that I'm getting
> closer.  I'm going to make sure that the hard disk is detected before
> the ramdisk tries to load the image
>
> later,
> Andy
>
> P.S. Do people on the list like to be cc'd on responses or should I keep
> all mail to the list only?
>
>
>
>


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Re: root=/dev/ram0

[Peter Ryser]

Hi Andy,

configure your kernel with
- ramdisk support
- ramdisk support as boot device
- extended fs 2 support


make a minimal ramdisk consisting of the files/directories
/linuxrc
/dev/console
where
/linuxrc is a copy of sash
/dev/console is created with: mknod /dev/console c 5 1

compress the ramdisk and move it to
linux/arch/ppc/boot/tree/ramdisk.image.gz

There are two different ways to set the kernel command line (eventually in
linux/arch/ppc/boot/tree/main.c)
- leave it empty (do it this way for a start)
- set it to: root=/dev/ram0 init=/linuxrc rw

Build the kernel: make zImage.initrd

Download the image and boot.

I hope this helps

- Peter

Andrew Dixon wrote:

> Hi All,
> I'm trying to mount a compressed ramdisk image on /dev/ram0 and run my
> root filesystem from there.  My problem is that when I try to boot I get
> the following error:
>
>     VFS: Cannot open root device "ram0" or 01:00
>     Please append a correct "root=" boot option
>
> earlier in the boot process the ram disks are recognized:
>
>     RAMDISK driver initialized: 16 RAM disks of 4096K size 1024
> blocksize
>
> I'm using kernel 2.4.5-pre3 from Ben H's source.
>
> Anyone know why the kernel isn't able to open /dev/ram0?
>
> Thanks,
> Andy
>


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