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[vox-tech] initrd (was: Re: DEVFS and Redhat 7.2)
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[vox-tech] initrd (was: Re: DEVFS and Redhat 7.2)

On Mon, Dec 31, 2001 at 12:23:32PM -0800, R. Douglas Barbieri wrote:
> echo -en "Mounting dev filesystem: "
> /bin/mount --bind /dev /dev-state
> /bin/mount -n -t devfs none /dev
> echo
> /sbin/devfsd /dev
> The "mount --bind..." keeps a persistent state of the /dev
> filesystem--this allows one to change permissions and ownership of items
> in the /dev filesystem and have them preserved across reboots. The "mount
> -n -t..." command actually mounts the /dev filesystem. The "devfsd..." 
> line starts the DEVFS daemon.

Excellent! As you may recall, I asked if this was possible at Peter's devfs
talk but he did not know.

> I must admit that I'm in the dark as to the need for a boot image at
> all--what are the advantages? Why do we need it? On my RH7.1 system I have
> the image disabled (this is why I never ran into the DEVFS problem
> before). In fact, I can run my RH7.2 system just fine with the "initrd="
> line in /etc/lilo.conf remarked off. EXT3 and DEVFS seem to be happy in
> both instances.

The only use for an initrb is to load a driver needed to mount the root
filesystem (and the filesystemthat contains /lib/modules, in the odd case
that these are separate). Examples: /lib/modules is on a SCSI drive, but the
SCSI drivers are not compiled into your kernel; your root filesystem is in
reiserfs format but reiserfs is not compiled into your kernel.

It's a neat idea in principle, since it means that the stock distro kernel
need not be bloated with drivers that average folks don't need. (For some
reason most people don't use SCSI drives.) This can cut the kernel size in
half or more and reduces boot time. Red Hat uses an initrd; Debian compiles
common SCSI drivers into the stock kernels.

On the other hand, the initrd is arcane to set up and fragile once installed.
A better solution would be to let the bootloader find and install the
requisite driver modules. GRUB supports this for booting GNU HURD, but alas
the Linux module system is incompatible.

Henry House
The attached file is a digital signature. See <http://romana.hajhouse.org/pgp>
for information.  My OpenPGP key: <http://romana.hajhouse.org/hajhouse.asc>.

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