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 neces
       sary 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 shells 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 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 2>&1

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



Linux				 Feb 23, 2000			 PIVOT_ROOT(8)