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’. From Wikipedia. Why it is required? If you want to set up your Linux box as a web hosting server for its users, you may need to give SFTP access. But they can get access to whole system Linux tree, just for reading but still very unsecure. So it is mandatory to lock them in their home directory. There are many other applications, it;s just a common example, so lets start its configuration.