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 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 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)