NAME¶
pivot_root - change the root filesystem
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 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).
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)
AVAILABILITY¶
The pivot_root command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.