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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
              Output version information and exit.

       -h, --help
              Display help 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