(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
