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+.TH PIVOT_ROOT 8 "Feb 23, 2000" "Linux" "Maintenance Commands"
+.SH NAME
+pivot_root \- change the root file system
+.SH SYNOPSIS
+.B pivot_root
+.RB \fInew_root\fP
+.RB \fIput_old\fP
+.SH DESCRIPTION
+\fBpivot_root\fP moves the root file system of the current process to the
+directory \fIput_old\fP and makes \fInew_root\fP the new root file system.
+Since \fBpivot_root(8)\fP simply calls \fBpivot_root(2)\fP, we refer to
+the man page of the latter for further details.
+
+Note that, depending on the implementation of \fBpivot_root\fP, root and
+cwd of the caller may or may not change. The following is a sequence for
+invoking \fBpivot_root\fP that works in either case, assuming that
+\fBpivot_root\fP and \fBchroot\fP are in the current \fBPATH\fP:
+.sp
+cd \fInew_root\fP
+.br
+pivot_root . \fIput_old\fP
+.br
+exec chroot . \fIcommand\fP
+.sp
+Note that \fBchroot\fP must be available under the old root and under the new
+root, because \fBpivot_root\fP may or may not have implicitly changed the
+root directory of the shell.
+
+Note that \fBexec chroot\fP 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 \fBchroot\fP (see below; note the absence of
+leading slashes to make it work whether \fBpivot_root\fP has changed the
+shell's root or not).
+.SH EXAMPLES
+Change the root file system to /dev/hda1 from an interactive shell:
+.sp
+.nf
+mount /dev/hda1 /new-root
+cd /new-root
+pivot_root . old-root
+exec chroot . sh <dev/console >dev/console 2>&1
+umount /old-root
+.fi
+.sp
+Mount the new root file system over NFS from 10.0.0.1:/my_root and run
+\fBinit\fP:
+.sp
+.nf
+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
+.fi
+.SH "SEE ALSO"
+.BR chroot(1),
+.BR mount(8),
+.BR pivot_root(2),
+.BR umount(8)