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Old 12-12-2004, 03:31 PM   #1
Registered: Sep 2004
Posts: 85

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Initrd Problems

Ive been trying to get my Debian laptop upgraded to kernel 2.6.5, but it seems that every time I attempt to do so I have a problem with my initrd.img file. I have been making one with:

mkinitrd -o initrd.img-2.6.5 2.6.5

from within my /boot directory, which creates initrd.img-2.6.5. I then point my grub boot loader to it, and set up the rest of grub, but whenever I reboot I get various problems, such as being unable to mount my root partition. Is this the correct command to make an initrd?

I am using Debian, on a reiserfs filesystem, with reiserfs built into my kernel. Is this the correct command needed to make a working initrd?
Old 12-12-2004, 05:10 PM   #2
Registered: Nov 2003
Distribution: slackware 14
Posts: 542

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Not sure this is what you're looking for...

Slackware initrd mini HOWTO
by Patrick Volkerding,
Sun Jun 20 01:38:41 PDT 2004

This document describes how to create and install an initrd, which may be
required to use the 2.6 kernel. Also see "man mkinitrd".

1. What is an initrd?
2. Why to I need an initrd?
3. How do I build the initrd?
4. Now that I've built an initrd, how do I use it?

1. What is an initrd?

Initrd stands for "initial ramdisk". An initial ramdisk is a very small
Linux filesystem that is loaded into RAM and mounted as the kernel boots,
and before the main root filesystem is mounted.

2. Why do I need an initrd?

The usual reason to use an initrd is because you need to load kernel
modules before mounting the root partition. Usually these modules are
required to support the filesystem used by the root partition (ext3,
reiserfs, xfs), or perhaps the controller that the hard drive is attached
to (SCSI, RAID, etc). Essentially, there are so many different options
available in modern Linux kernels that it isn't practical to try to ship
many different kernels to try to cover everyone's needs. It's a lot more
flexible to ship a generic kernel and a set of kernel modules for it. The
generic 2.6 kernel in Slackware supports the ext2 filesystem (which is
used by the initrd), and also supports most IDE controllers (much like the
old bare.i kernel). So, if you have an IDE based system that uses the
ext2 filesystem, then you will not need to use an initrd to boot.
Otherwise, read on.

3. How do I build the initrd?

The easiest way to make the initrd is to use the mkinitrd script included
in Slackware's mkinitrd package. We'll walk through the process of
upgrading to the 2.6.7 Linux kernel using the packages found in
Slackware's testing/packages/linux-2.6.7/ directory.

First, make sure the kernel, kernel modules, and mkinitrd package are
installed (the current version numbers might be a little different, so
this is just an example):

installpkg kernel-generic-2.6.7-i486-3.tgz
installpkg kernel-modules-2.6.7-i486-2.tgz
installpkg mkinitrd-1.0.1-i486-1.tgz

Change into the /boot directory:

cd /boot

Now you'll want to run "mkinitrd". I'm using reiserfs for my root
filesystem, and since it's an IDE system the reiserfs module will be
the only one I need to load:

mkinitrd -c -k 2.6.7 -m reiserfs

This should do two things. First, it will create a directory
/boot/initrd-tree containing the initrd's filesystem. Then it will
create an initrd (/boot/initrd.gz) from this tree. If you wanted to,
you could make some additional changes in /boot/initrd-tree/ and
then run mkinitrd again without options to rebuild the image. That's
optional, though, and only advanced users will need to think about that.

Here's another example: Build an initrd image using Linux 2.6.7 kernel
modules for a system with an ext3 root partition on /dev/hdb3. Note
that you need both the jbd and ext3 modules to use ext3:

mkinitrd -c -k 2.6.7 -m jbd:ext3 -f ext3 -r /dev/hdb3

4. Now that I've built an initrd, how do I use it?

Now that you've got an initrd (/boot/initrd.gz), you'll want to load
it along with the kernel at boot time. If you use LILO for your boot
loader you'll need to edit /etc/lilo.conf and add a line to load the
initrd. Here's an example section of lilo.conf showing how this is

# Linux bootable partition config begins
image = /boot/vmlinuz-generic-2.6.7
initrd = /boot/initrd.gz
root = /dev/hda6
label = Linux267
# Linux bootable partition config ends

The initrd is loaded by the "initrd = /boot/initrd.gz" line.
Just add the line right below the line for the kernel image you use.
Save the file, and then run LILO again ('lilo' at the command line).
You'll need to run lilo every time you edit lilo.conf or rebuild the

Other bootloaders such as syslinux also support the use of an initrd.
See the documentation for those programs for details on using an
initrd with them.


Have fun!
Old 12-13-2004, 06:41 AM   #3
Senior Member
Registered: Jul 2003
Location: Indiana
Distribution: Mandrake Slackware-current QNX4.25
Posts: 1,802

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mkinitrd is usually a script and it is distro specific. Most have help available with mkinitrd -h.

Since your root filesystem is reiserfs and you built reiserfs support into the kernel, the odds are you don't even need to make an initrd file.


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