Re: Specify devices manually in exotic environment

From: linux-os (Dick Johnson)
Date: Wed Aug 23 2006 - 07:57:58 EST

On Wed, 23 Aug 2006, Milan Hauth wrote:

> On Wed, 23 Aug 2006 12:10:27 +0200, Denis Vlasenko
> <vda.linux@xxxxxxxxxxxxxx> wrote:
>>>> mknod /dev/root b "$ROOTMAJ" "$ROOTMIN"
>>> This also did not help -- 'cat: /dev/root: No such device or address'.
>>> Major/minor is 4/0, as recommended in the kernel docs for /dev/root.
>> What cat? Where did I say to cat anything? I said "create new node,
>> namely, 'root', in the /dev, with the following major/minor#".
> I did create the root node (b4/0). Just used cat for testing, since I
> didn't have dd available yet on the initrd. But obviously it did not
> work.. :-\
>> If it doesn't work, maybe your initrd is mounted ro.
>> Remount it rw first. Or mount a ramfs somewhere,
>> it will give you writable place to play.
>>> So where can I find my flash memory..? Again, with GRUB I just had to
>>> specify the device address (0x80) and the kernel/initrd positions in
>>> sector syntax, which works fine. Maybe I can do the same in Linux with
>>> my
>>> ext2 partition, to specify the start and end sectors ('Specify drives
>>> manually..'). But where to start?
>> Start by reading boot messages. They ought to say
>> what devices are found.
> Ah, excellent: A IDE controller is found:
> CS5530: IDE controller at PCI slot 0000:00:12.2
> The according line in lspci:
> 00:12.2 0101: 1078:0102
> And there are also two IDE interfaces:
> PCI: Setting latency timer iof devvice 0000:00:12.0 to 64
> ide0: BM-DMA at 0xfb00-0xfb07, BIOS settings: hda: pio, hdb: pio
> ide1: BM-DMA at 0xfb08-0xfb0f, BIOS settings: hdc: pio, hdd: pio
> Probing IDE interface ide0...
> Probing IDE interface ide1...
> ..but no devices, which is logical: If there would be devices, I could use
> them via /dev/hd*.
> But why is the IDE controller being recognized, while no devices are
> found..?
>> Try hexdump'ing your sd devices:
>> # dd if=/dev/sda bs=1024 count=1 | hexdump
>> and see whether they give something like boot sector.
> 'No such device or address'.. I already tried special devices before,
> forgot to mention.
> Maybe I just gonna try to get some more information about my hardware and
> recheck my Kernel configuration..
> Cheers, milahu
> -

A lot of flash devices emulate a IDE hard disk. With an IDE driver
__installed__, the first one should be /dev/hda, the first partition
should be /dev/hda1, etc. You can use the attached MAKEDEV to
see what the major/minor numbers should be, and make a few in
your initial RAM disk to exeriment.

Dick Johnson
Penguin : Linux version on an i686 machine (5592.62 BogoMips).
New book:

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Attachment: MAKEDEV
Description: MAKEDEV