[wplug] What is initrd and why is it necessary

[rkalaskar]

the kernel loads initrd (initial ram disk) as its root file system. initrd
inturn load the actual root file system (some thing like chain boot
loaders). On systems using initrd you would notice "umounting initrd"
console message while booting.

Its not absolutely required. The reason for this is that device support can
be added to initrd as module rather than being compiled as part of the
kernel. Most initrd will contain ext3 fs module.

If you want to know what your initrd contains, try this

#zcat initrd.img.gz > /dev/ram
#mount /dev/ram /mnt
#cd /mnt
#ls


Rahul

----- Original Message -----
From: "Paul Cantalupo" <lupey+ at pitt.edu>
To: <wplug at wplug.org>
Sent: Wednesday, December 18, 2002 2:51 PM
Subject: [wplug] What is initrd and why is it necessary


> In response to my email thread "kernel not loading after partitioning
> hard drive", Donald wrote:
>
> >>>snip
>         So the question for Paul is - do you have a valid initrd for
> each
> kernel, and does lilo.conf point to it?  If all looks OK - re-run lilo
> and
> you should be golden.
>
> To get an initrd is something like:
> mkinitrd -v -f --ifneeded <initrdimage-name>
> <kernel-version-to-build-against>
>         -this assumes that /etc/modules.conf has any required modules /
> aliases listed in it, otherwise you'll need to specify '--preload
> <module>'
> in the above syntax
>
> (ex: mkinitrd /boot/initrd-2.2.5-15.img 2.2.5-15)  and of course
> lilo.conf
> must reflect this image for this kernel.  the --ifneeded is nice because
> it
> will not build unnecessary initrd's - usually SCSI / exotic storage are
> the
> only reason for initrd's on PeeCees
> >>>snip
>
> I have never used initrd nor does initrd appear in my lilo.conf (see
> below). So, on my system, it seems that I can do without it. Is this
> something specific to different Linux distros? I am using Slackware 8.
>
> Thanks,
>
> Paul
>
>
>
>
> >>Contents of my lilo.conf file
>
> # LILO configuration file
> # generated by 'liloconfig'
> #
> # Start LILO global section
> lba32 # Allow booting past 1024th cylinder with a recent BIOS
> boot = /dev/hda
> prompt
> delay = 50
> timeout = 100
> change-rules
> reset
> # VESA framebuffer console @ 1024x768x64k
> vga = 791
> # End LILO global section
>
> # DOS bootable partition config begins
> other = /dev/hda1
> label = windows
> table = /dev/hda
> # DOS bootable partition config ends
>
> # Linux bootable partition config begins
> image = /vmlinuz_orig
> root = /dev/hda2
> label = working
> read-only # Non-UMSDOS filesystems should be mounted read-only for
> checking
>
> image = /vmlinuz_7.26.02
> root = /dev/hda2
> label = ntfs_7.26.02
> append="hdc=ide-scsi max_scsi_luns=1"
> read-only
>
> # Linux bootable partition config ends
>
>
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