 | | | why does one need an initrd if using LVM? | why does one need an initrd if using LVM? 2003-05-03 - By Robert P. J. Day
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(perhaps related to an earlier issue as to why one needs
an initrd when using ext3 ...)
earlier today, when demonstrating to a class how to rebuild
a kernel, i suggested that one could avoid having to deal with
creating an initrd.img if one built all necessary drivers into
the kernel.
since we were using ext3 filesystems and logical volumes,
i was very careful to tell everyone to add these features to
their kernel, and not leave them as modules. since they all
did that, i told them to skip building an initrd.img and
just reboot.
bad idea -- the boot hung at trying to mount the root
filesystem. i couldn 't figure out why since the kernel had
clearly loaded and started to run, so what was the problem?
one student just added the "initrd " line to her grub.conf
file for that kernel image, and it worked fine. puzzling.
so i ripped open that initrd.img and found just ext3.o,
jbd.o and lvm-mod.o. but why were these needed in the
initrd?
as a test, i ran "mkinitrd " against the new kernel,
got my new initrd.img, and opened it up to find ...
no module at all. not surprising since everything was
in the kernel, and "mkinitrd " was smart enough to figure
that out. but using that module-less initrd.img got the
boot to work.
what gives? i checked the /etc/fstab, and it turns
out that the /boot filesystem (a real primary partition,
not a logical volume) was listed with a LABEL field,
but even changing that back to a /dev entry didn 't
fix things.
so why is initrd.img necessary for LVs even when it has
no modules?
rday
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