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       pivot_root - change the root file system


       pivot_root new_root put_old


       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).


       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 and run

       ifconfig lo up   # for portmap
       # configure Ethernet or such
       portmap   # for lockd (implicitly started by mount)
       mount -o ro /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


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


       The pivot_root command is part of  the  util-linux-ng  package  and  is
       available from