Add a switch_root utility (like kconfig's utils/run_init.c, although not
actuall using any of that code). This is needed because pivot_root doesn't
work right under initramfs. (See the menuconfig help.)
diff --git a/util-linux/Config.in b/util-linux/Config.in
index dc6d8fd..fe71dac 100644
--- a/util-linux/Config.in
+++ b/util-linux/Config.in
@@ -288,6 +288,28 @@
of wild and crazy things with your Linux system and is far more
powerful than 'chroot'.
+ Note: This is for initrd in linux 2.4. Under initramfs (introduced
+ in linux 2.6) use switch_root instead.
+
+config CONFIG_SWITCH_ROOT
+ bool "switch_root"
+ default n
+ help
+ The switch_root utility is used from initramfs to select a new
+ root device. Under initramfs, you have to use this instead of
+ pivot_root. (Stop reading here if you don't care why.)
+
+ Booting with initramfs extracts a gzipped cpio archive into rootfs
+ (which is a variant of ramfs/tmpfs). Because rootfs can't be moved
+ or unmounted*, pivot_root will not work from initramfs. Instead,
+ switch_root deletes everything out of rootfs (including itself),
+ does a mount --move that overmounts rootfs with the new root, and
+ then execs the specified init program.
+
+ * Because the Linux kernel uses rootfs internally as the starting
+ and ending point for searching through the kernel's doubly linked
+ list of active mount points. That's why.
+
config CONFIG_RDATE
bool "rdate"
default n
