Manpages - pivot_root.8

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 current working directory 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).

-V, –version

Display version information and exit.

-h, –help

Display help text and exit.

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

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

For bug reports, use the issue tracker at https://github.com/karelzak/util-linux/issues.

The pivot_root command is part of the util-linux package which can be downloaded from Linux Kernel Archive https://www.kernel.org/pub/linux/utils/util-linux/.