/usr/sbin/chroot newroot command

The chroot utility causes command to be executed relative to newroot. The meaning of any initial slashes (\|/\|) in the path names is changed to newroot for command and any of its child processes. Upon execution, the initial working directory is newroot.

Notice that redirecting the output of command to a file,

chroot newroot \|command >x

will create the file x relative to the original root of command, not the new one.

The new root path name is always relative to the current root. Even if a chroot is currently in effect, the newroot argument is relative to the current root of the running process.

This command can be run only by the super-user.

The exit status of chroot is the return value of command.

Example 1 Using the chroot Utility

The chroot utility provides an easy way to extract tar files (see tar(1)) written with absolute filenames to a different location. It is necessary to copy the shared libraries used by tar (see ldd(1)) to the newroot filesystem.

example# mkdir /tmp/lib; cd /lib
example# cp ld.so.1 libc.so.1 libcmd.so.1 libdl.so.1 \e
 libsec.so.1 /tmp/lib
example# cp /usr/bin/tar /tmp
example# dd if=/dev/rmt/0 | chroot /tmp tar xvf -

cd(1), tar(1), chroot(2), ttyname(3C), attributes(5)

Exercise extreme caution when referencing device files in the new root file system.

References by routines such as ttyname(3C) to stdin, stdout, and stderr will find that the device associated with the file descriptor is unknown after chroot is run.