redhat man page for pivot_root

PIVOT_ROOT(8)						       Maintenance Commands						     PIVOT_ROOT(8)

NAME
       pivot_root - change the root file system

SYNOPSIS
       pivot_root new_root put_old

DESCRIPTION
       pivot_root  moves  the root file system of the current process to the directory put_old and makes new_root the new root file system.  Since
       pivot_root(8) simply calls pivot_root(2), we refer to the man page of the latter for further details.

       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:

       cd new_root
       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).

EXAMPLES
       Change the root file system to /dev/hda1 from an interactive shell:

       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

SEE ALSO
       chroot(1), mount(8), pivot_root(2), umount(8)

Linux								   Feb 23, 2000 						     PIVOT_ROOT(8)