PIVOT_ROOT(8)                         System Administration                         PIVOT_ROOT(8)



NAME
       pivot_root - change the root filesystem

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).

OPTIONS
       -V, --version
              Display version information and exit.

       -h, --help
              Display help text and exit.

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), switch_root(8), umount(8)

AVAILABILITY
       The  pivot_root  command  is  part  of  the  util-linux  package  and  is  available  from
       ftp://ftp.kernel.org/pub/linux/utils/util-linux/.



util-linux                                 August 2011                              PIVOT_ROOT(8)