On 09/12/12 05:03, Khoa Nguyen wrote: > Can you tell me more about busybox ? > What do you mean "busybox in an initramfs" ? > > I understand that due to failed boot process because the kernel can't > mount the root file system to read /etc/inittab. > So we use busybox to mount manually . Right ? > When the kernel boots, it mounts the root file system and executes /sbin/init from there. /sbin/init becomes process number one, and is responsible for system initialization (eg. running rc.d scripts and more).
But the kernel does not understand boot=<uuid>, only boot=<path-to-device>, and if for some reason the kernel can not mount the root file system, you are stuck. Initramfs is a compressed archive of files. The initramfs file is read from disk by grub and passed to the kernel. The kernel is then mounting this (as a ramfs ) as the root filesystem and executes /sbin/init. See http://www.linuxfordevices.com/c/a/Linux-For-Devices-Articles/Introducing-initramfs-a-new-model-for-initial-RAM-disks/ http://lugatgt.org/content/booting.inittools/downloads/presentation.pdf http://kaarpux.kaarposoft.dk/packages/l/linux.html The /sbin/init in the initramfs can then do whatever is necessary to mount the real root filesystem from disk, and finally run /sbin/init on the real root file system. Or it can run a whole system directly from the initramfs, never touching your disk. My init file in the initramfs looks like this: http://sourceforge.net/p/kaarpux/code/ci/HEAD/tree/master/packages/l/linux.files/init?force=True It basically mounts the /proc /sys and /dev special directories, finds the real root file system and mounts it, and finally executes /sbin/init on the real root file system. However, if something goes wrong (or if you specify busybox on the command line) it will drop into a /bin/sh shell from busybox. BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides replacements for most of the utilities you usually find in GNU fileutils, shellutils, etc. See http://busybox.net/ http://kaarpux.kaarposoft.dk/packages/b/busybox.html My way of building the initramfs: http://kaarpux.kaarposoft.dk/packages/l/linux.html http://sourceforge.net/p/kaarpux/code/ci/HEAD/tree/master/packages/l/linux.yaml (line 128-145) Good luck... /Henrik -- http://linuxfromscratch.org/mailman/listinfo/lfs-support FAQ: http://www.linuxfromscratch.org/lfs/faq.html Unsubscribe: See the above information page
