Note that, depending on the implementation of pivot_root, root and cwd of the caller may or may not change. The following is a sequence for invoking pivot_root that works in either case, assuming that pivot_root and chroot are in the current PATH:
pivot_root . put_old
exec chroot . command
Note that chroot must be available under the old root and under the new root, because pivot_root may or may not have implicitly changed the root directory of the shell.
Note that exec chroot changes the running executable, which is necessary if the old root directory should be unmounted afterwards. Also note that standard input, output, and error may still point to a device on the old root file system, keeping it busy. They can easily be changed when invoking chroot (see below; note the absence of leading slashes to make it work whether pivot_root has changed the shell's root or not).
mount /dev/hda1 /new-root cd /new-root pivot_root . old-root exec chroot . sh <dev/console >dev/console 2>&1 umount /old-root
Mount the new root file system over NFS from 10.0.0.1:/my_root and run init:
ifconfig lo 127.0.0.1 up # for portmap # configure Ethernet or such portmap # for lockd (implicitly started by mount) mount -o ro 10.0.0.1:/my_root /mnt killall portmap # portmap keeps old root busy cd /mnt pivot_root . old_root exec chroot . sh -c 'umount /old_root; exec /sbin/init' \ <dev/console >dev/console 2>&1