PIVOT_ROOT(8) System Administration PIVOT_ROOT(8)NAME
pivot_root - change the root filesystem
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:
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
Display version information and exit.
Display help text and exit.
Change the root file system to /dev/hda1 from an interactive shell:
mount /dev/hda1 /new-root
pivot_root . old-root
exec chroot . sh <dev/console >dev/console 2>&1
Mount the new root file system over NFS from 10.0.0.1:/my_root and run
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
pivot_root . old_root
exec chroot . sh -c 'umount /old_root; exec /sbin/init' \
<dev/console >dev/console 2>&1
SEE ALSOchroot(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 avail‐
able from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
util-linux August 2011 PIVOT_ROOT(8)