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Karl_R
Tux's lil' helper
Joined: 21 Mar 2004
Posts: 118
Location: Sydney
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 Posted: Sun Mar 21, 2004 7:11 pm Post subject: Root block device unspecified or not detected |
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Hi,
I have read the previous posts on this subject but it dosn't help me.
I am using the gentoo-dev-sources (Kernel 2.6.3 r1) and used the latest genkernel to build the kernel and initrd
This is not a problem of not specifying "root=/dev/ram0 init=/linuxrc real_root=/dev/hda5"
(my root filesystem is on /dev/hda5) The problem seems to be with devfs or udev.
The problem is the the BusyBox ram disk created by genkernel has NOT created a /dev/hda5 device node. infact if I enter a shell in the ram disk and look through the /dev directory it hasn't created any device relating to my disk partitions. there is a device that relates to my disk at:
/dev/ide/host0/bus0/target0/lun0/disc which has a major number of 3 and a minor number of 0 but there is no part5 with a major number 3 and minor number 5.
Does anyone know how to fix this? do I have to edit the Busybox to add udev or devfs support and if so what's the best way to go about this?
Cheers
Karl |
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Karl_R
Tux's lil' helper
Joined: 21 Mar 2004
Posts: 118
Location: Sydney
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| Posted: Tue Apr 27, 2004 9:12 am Post subject: |
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 I have discovered what the real problem was and hence the solution.
The problem was that I was using lilo as my boot loader This problem does not occur when using grub (but I had to use lilo on my hardware, Toshiba Tecra M1 laptop).
As you are no doubt aware, when using lilo you have to write a lilo.conf file specifying
| Code: | boot=/dev/hda
prompt
timeout=50
message=/boot/message
default=linux
image=/boot/linux-2.6.5-gentoo-r1
label=linux
initrd=/boot/initrd-2.6.5-gentoo-r1
read-only
root=/dev/ram0
append="init=linuxrc real_root=/dev/hda5" |
Lilo reads this file and writes out the Map when the lilo command is ran. The file must be correct at the time lilo is ran hence the "/dev/hda" etc which are the discs and partitions of the "livecd"
The trouble is that when we come to boot up the ram disk (/dev/ram0) starts a udev daemon that manages /dev . This daemon creates device nodes that look like
| Code: | | /dev/ide/host0/bus0/target0/lun0/disk |
for the disk instead of /dev/hda and
| Code: | | /dev/ide/host0/bus0/target0/lun0/part5 |
for the /dev/hda5 partition.
The solution is to manually create these nodes before writting lilo.conf from within your livecd install.
To find out what these nodes should be called look in /proc/partitions. There will be entries like
| Code: |
/dev/ide/host0/bus0/target0/lun0/disk
/dev/ide/host0/bus0/target0/lun0/part5
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So find out the Major and Minor numbers for the bits you need. On my machine I ran:
| Code: |
$ ls -l /dev/hda
brwxr-x--- 1 root disk 3, 0 /dev/hda
$ ls -l /dev/hda5
brwxr-x--- 1 root disk 3, 5 /dev/hda5 |
so I need to create a node with Major number 3 Minor 0 and Major 3 Minor 5
| Code: | mknod /dev/ide/host0/bus0/target0/lun0/disk b 3 0
mknod /dev/ide/host0/bus0/target0/lun0/part5 b 3 5
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then write my lilo.conf as follows:
| Code: | boot=/dev/ide/host0/bus0/target0/lun0/disk
prompt
timeout=50
message=/boot/message
default=linux
image=/boot/linux-2.6.5-gentoo-r1
label=linux
initrd=/boot/initrd-2.6.5-gentoo-r1
read-only
root=/dev/ram0
append="init=linuxrc real_root=/dev/ide/host0/bus0/target0/lun0/part5"
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then run lilo. exit out of the chrooted enviroment unmount my partitions and reboot. Sorted
It would be nice if livecd created these udev device nodes by default to help out lilo users  |
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