Let me start with another Wikipedia quote:

A chroot on Unix operating systems is an operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot name (and therefore normally not access) files outside the designated directory tree. The term chroot may refer to the chroot(2) system call or the chroot(8) wrapper program. The modified environment is called a chroot jail.

What this means is that you can create a directory (for example /opt/root), copy necessary program there and execute this program. For such program /opt/root/ will be the root directory /. To understand why you would want that, read Wikipedia chroot article.

It is practice time. You will do now create a minimal chroot environment with bash. To do this you will create a directory structure and copy bash and its dependencies into it.

Now you will learn how to create a chroot environment and enter into it.

 1: sudo -s
 2: ldd /bin/bash
 3: mkdir -vp /opt/root/bin
 4: mkdir -v /opt/root/lib
 5: mkdir -v /opt/root/lib64
 6: cp -v /bin/bash /opt/root/bin/
 7: cp -v /lib/libncurses.so.5 /opt/root/lib/
 8: cp -v /lib/libdl.so.2 /opt/root/lib
 9: cp -v /lib/libc.so.6 /opt/root/lib
10: cp -v /lib64/ld-linux-x86-64.so.2 /opt/root/lib64
11: chroot /opt/root/

Wohoo, you just created yourself a Linux! Sort of.

user1@vm1:/opt~ sudo -s
root@vm1:/opt# ldd /bin/bash
        linux-vdso.so.1 =>  (0x00007fff17bff000)
        libncurses.so.5 => /lib/libncurses.so.5 (0x00007f4b1edc6000)
        libdl.so.2 => /lib/libdl.so.2 (0x00007f4b1ebc2000)
        libc.so.6 => /lib/libc.so.6 (0x00007f4b1e85f000)
        /lib64/ld-linux-x86-64.so.2 (0x00007f4b1f012000)
root@vm1:/opt# mkdir -vp /opt/root/bin
mkdir: created directory `/opt/root'
mkdir: created directory `/opt/root/bin'
root@vm1:/opt# mkdir -v /opt/root/lib
mkdir: created directory `/opt/root/lib'
root@vm1:/opt# mkdir -v /opt/root/lib64
mkdir: created directory `/opt/root/lib64'
root@vm1:/opt# cp -v /bin/bash /opt/root/bin/
`/bin/bash' -> `/opt/root/bin/bash'
root@vm1:/opt# cp -v /lib/libncurses.so.5 /opt/root/lib/
`/lib/libncurses.so.5' -> `/opt/root/lib/libncurses.so.5'
root@vm1:/opt# cp -v /lib/libdl.so.2 /opt/root/lib
`/lib/libdl.so.2' -> `/opt/root/lib/libdl.so.2'
root@vm1:/opt# cp -v /lib/libc.so.6 /opt/root/lib
`/lib/libc.so.6' -> `/opt/root/lib/libc.so.6'
root@vm1:/opt# cp -v /lib64/ld-linux-x86-64.so.2 /opt/root/lib64
`/lib64/ld-linux-x86-64.so.2' -> `/opt/root/lib64/ld-linux-x86-64.so.2'
root@vm1:/opt# chroot /opt/root/

1. Executes bash as superuser (root).
2. Prints out libraries which bash needs to run.
3. Creates /opt/root/ and /opt/root/bin/ directories in one command. Neat, eh?
4. Creates /opt/root/lib directory.
5. Creates /opt/root/lib64 directory.
6. Copies /bin/bash to /opt/root/bin/.
7. Copies /lib/libncurses.so.5 to /opt/root/lib/.
8. Copies /lib/libdl.so.2 to /opt/root/lib/.
9. Copies /lib/libc.so.6 to /opt/root/lib/.
10. Copies /lib64/ld-linux-x86-64.so.2 to /opt/root/lib64/.
11. Changes root directory to /opt/root/.

1. Read man chroot, man ldd.
2. Copy ls command to your chroot and make it work.
3. A hard one: copy vim to your chroot and make it work.