What is Chroot Jail and its Usecase on Linux

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While walking in your Linux journey, you might hit yourself with the term β€œchroot” (or β€œchroot jail”), and that’s what you’re about to learn today: what they are and their usage.

Tutorial Details

DescriptionChroot Jail
Difficulty LevelModerate
Root or Sudo PrivilegesYes
OS CompatibilityUbuntu, Manjaro, Fedora, etc.
Internet RequiredNo

What is Chroot Jail in Linux?

The chroot (a.k.a. β€œchange rootβ€œ) is a command used to push a user into a fake root directory (in jail) intentionally created by you with access to certain commands and permissions.

It works like this: first, you will create a fake replica of the root directory and move certain binary files (like bash and ls) from the β€œ/bin/” directory to your newly created root directory.

chroot jail

Lastly, you will use the chroot command to put/add the user into that isolated fake root directory (or environment) that contains limited command binaries (apart from binaries, anything else can also be added).

Since users are not allowed to read or write anything outside the fake root directory this way, this process is known as a β€œchroot jail” or β€œjailing user”.

Why Should You Use Chroot Jail?

The chroot jail is a process of creating a sandbox environment for a user or script with restricted permissions assigned by the jail creator that can come into use for various reasons, followed by

  • Restricting the user with specific permissions.
  • Creating a test environment for programs or scripts.
  • Execute old programs or scripts with incompatible binaries without crashing the application or system.
  • To recover the system or system password.
  • To reinstall the bootloader, like Grub or Lilo.
  • Virtual machine substitution.

Syntax of the Chroot Command

The chroot command takes three arguments: one is the option; another is the path of the fake root directory; and the last one is the command.


The following are the known options:

--groups=G_LISTIt describes the supplementary groups as g1, g2,…, gN.
--userspace=USER:GROUPSpecify the user or group (with their name or ID) to use.
--skip-chdirPrevent changing the working directory to β€œ/β€œ.
--helpDisplay the help section.
--versionGive version information.

Creating a Chroot Jail for the User

The first step for creating a chroot jail is to create a fake replica of the original root directory somewhere in your Linux filesystem.

1. Execute the following command to create a new directory with the name β€œjail” in your home directory that will be used as a fake root directory.

$ mkdir $HOME/jail


Creating a jail directory

2. Now create sub-directories (like β€œbinβ€œ, β€œlibβ€œ, and β€œlib64β€œ) that will store the program binaries and libraries in your β€œjail” (or fake root) directory.

$ mkdir -p $HOME/jail/{bin,lib,lib64}


Creating sub-directories within the jail directory

3. Let’s copy a few binaries like β€œ/bin/bash” and β€œ/bin/ls” into our fake β€œ$HOME/jail/bin” directory.

$ cp -v /bin/{bash,ls} $HOME/jail/bin/


Copying program binaries into the fake root directory

4. Execute the following β€œldd” command with a binary path to list the supporting libraries.

$ ldd /bin/bash
$ ldd /bin/ls


Listing supporting libraries for binaries

5. Copy the supporting libraries into the β€œlib” and β€œlib64” directories, starting with the bash libraries:

$ cp /lib/x86_64-linux-gnu/libtinfo.so.6 $HOME/jail/lib/
$ cp /lib/x86_64-linux-gnu/libc.so.6 $HOME/jail/lib/
$ cp /lib64/ld-linux-x86-64.so.2 $HOME/jail/lib64/


bash binary libraries

The following are the supporting libraries for ls binary:

$ cp /lib/x86_64-linux-gnu/libselinux.so.1 $HOME/jail/lib/
$ cp /lib/x86_64-linux-gnu/libc.so.6 $HOME/jail/lib/
$ cp /lib/x86_64-linux-gnu/libpcre2-8.so.0 $HOME/jail/lib/
$ cp /lib64/ld-linux-x86-64.so.2 $HOME/jail/lib64/


ls binary libraries

6. Lastly, enter into this mini-jail using the chroot command (it will start a new bash instance).

$ sudo chroot $HOME/jail/


Entering jail

If you execute any command outside of what is specified in the β€œ$HOME/jail/bin” directory, you will get β€œCommand not found” errors.

Testing the chroot jail

7. When you’re done, just execute the exit command to quit the chroot jail.

$ exit


Quitting the chroot jail

Final Tips

As you can see, if you want to have access to another command other than bash and ls, then you need to copy the binary and supporting libraries for that command into the chroot jail sub-directories.

After a while, this repetitive process will start getting boring, and you will lose interest in chroot. For that reason, I will suggest you use the restricted bash shell to limit user access and AppArmor or SELinux to restrict program or script access.

Chroot is better for system recovery and password resetting, but apart from that, you might rarely use it.

So, that was all a beginner should know about chroot jail.

If you have any questions related to this topic, feel free to ask them in the comment section.

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