Table of Contents

Firejail creates a restricted environment for untrusted applications. It’s written in C and it’s lightweight and easy to use.

Installation

Firejail is available on most Linux-based operating systems (Debian, Arch Linux, etc.). Install firejail using your system package manager.

Creating sandboxes

firejail <options> <command>
# e.g.: firejail firefox
  • Without arguments, executes user preferred shell (specified in $SHELL). In this case, exit from sandbox by typing exit (or press Ctrl + D).
  • Firejail does not work with Flatpak or Snap packages.

Some of the available options are:

  • --name=<name>: set a sanbox name.
  • --net=none: no network access.
  • --nosound: disable sound.
  • --novideo: disable video devices such as the webcam.
  • --private: mount new /root and /home/user directories in temporary filesystems.
  • --appimage <appimage file>: sandbox an AppImage.
  • --disable-mnt: blacklist /mnt, /media, /run/mount and /run/media access.
  • --blacklist=<folder or file path>: blacklist a folder or file.
  • --private-bin=<file>, --private-etc=<file,directory>, --private-home=<file,directory>, --private-opt=<file,directory>, --private-srv=<file,directory>: create a new /bin, /etc, /home or /opt with only the files and folders specified.
  • --private-tmp: create an empty /tmp.
  • --read-only=<folder or file path>: set directory or file read-only.

Run man firejail for more info.

Monitoring and management

  • firejail --list: list sandboxes.
  • firejail --top: top-like statistics.
  • firejail --tree: print a tree of all sandboxed processes.
  • firejail --shutdown=<name|pid>: shutdown a sandbox.
  • firemon <pid>

Desktop integration

A symbolic link to /usr/bin/firejail under the name of a program, will start the program in Firejail sandbox. The symbolic link should be placed in the first $PATH position. On most systems, a good place is /usr/local/bin directory. For example (run as root or with ‘sudo’):

ln -s /usr/bin/firejail /usr/local/bin/firefox

Verify the right path for your app is the newly created:

$ which firefox
/usr/bin/firefox
$ sudo ln -s /usr/bin/firejail /usr/local/bin/firefox
$ which firefox
/usr/local/bin/firefox

When you don’t need to sandbox the application anymore, just delete the symbolic link (run as root or with ‘sudo’):

rm /usr/local/bin/firefox

If you have any suggestion, feel free to contact me via social media or email.