man(1) firejail man page man(1)
Firejail - Linux namespaces sandbox program
firejail [options] [program and arguments]
Firejail is a SUID sandbox program that reduces the risk of security
breaches by restricting the running environment of untrusted applica‐
tions using Linux namespaces. It includes a sandbox profile for Mozilla
Firejail also expands the restricted shell facility found in bash by
adding Linux namespace support. It supports sandboxing specific users
Without any options, the sandbox consists of a filesystem chroot build
from the current system directories mounted read-only, and new PID and
IPC namespaces. If no program is specified as an argument, /bin/bash
is started by default in the sandbox.
-c Execute command and exit.
Chroot into dirname directory.
--csh Use /bin/csh as default user shell.
Print debug messages.
Use this address as default gateway in the new network names‐
Print options end exit.
Use this IP address in the new network namespace.
Join the sandbox of the specified process.
--list List all sandboxed processes.
Set sandbox hostname.
Enable a new network namespace and connect it to this bridge
device. Unless specified with option --ip and --defaultgw, an
IP address and a default gateway will be assigned automatically
to the sandbox. The IP address is checked using ARP before
assignment. The IP address assigned as default gateway is the
bridge device IP address. Up to four --net bridge devices can be
--noip No IP address and no default gateway are configured in the new
network namespace. Use this option in case you intend to start a
DHCP client in the sandbox.
Enable a new, unconnected network namespace.
Mount a filesystem overlay on top of the current filesystem.
OverlayFS support is required in Linux kernel for this option to
Mount new /tmp, /root and /home/user directories.
Use a custom profile, see below.
Enable seccomp filter.
--top Monitor the most CPU-intensive sandboxes.
Print program version and exit.
--zsh Use /usr/bin/zsh as default user shell.
Option --list prints the tree of processes running in the sandbox. The
format for each process entry is as follows:
Option --top is simillar to the UNIX top command, however it applies
only to sandboxes. Listed below are the available fields (columns) in
Command used to start the sandbox.
CPU% CPU usage, the sandbox share of the elapsed CPU time since the
last screen update
PID Unique process ID for the task controlling the sandbox.
Prcs Number of processes running in sandbox, including the control‐
RES Resident Memory Size (KiB), sandbox non-swapped physical memory.
It is a sum of the RES values for all processes running in the
SHR Shared Memory Size (KiB), it reflects memory shared with other
processes. It is a sum of the SHR values for all processes run‐
ning in the sandbox, including the controlling process.
Uptime Sandbox running time in hours:minutes:seconds format.
User The owner of the sandbox.
The profile files define a chroot filesystem built on top of the exist‐
ing host filesystem. Each line describes a file element that is removed
from the filesystem (blacklist), a read-only file or directory (read-
only), or a tmpfs mounted on top of an existing directory (tmpfs).
# this is a comment
Remove /usr/bin directory.
Remove /etc/password file.
Read-only /etc/password file.
Mount an empty tmpfs filesystem on top of /etc directory.
File globbing is supported, and PATH and HOME directories are searched:
Remove all gcc files in /usr/bin (file globbing).
Remove ifconfig from the regular path directories.
Remove .ssh directory from user home directory.
Default Firejail profile files are stored in /etc/firejail directory,
user profile files are stored in ~/.config/firejail directory. See
/etc/firejail/firefox.profile for more examples.
To configure a restricted shell, replace /bin/bash with /usr/bin/fire‐
jail in /etc/password file for each user that needs to be restricted.
Alternatively, you can specify /usr/bin/firejail in adduser command:
adduser --shell /usr/bin/firejail username
Additional arguments passed to firejail executable upon login are
declared in /etc/firejail/login.users file.
Start a regular /bin/bash session in sandbox.
Start Mozilla Firefox.
firejail --debug firefox
Debug Firefox sandbox.
Start a /bin/bash session with a new tmpfs home directory.
firejail --net=br0 ip=10.10.20.10
Start a /bin/bash session in a new network namespace. The ses‐
sion is connected to the main network using br0 bridge device.
An IP address of 10.10.20.10 is assigned to the sandbox.
firejail --net=br0 --net=br1 --net=br2
Start a /bin/bash session in a new network namespace and connect
it to br0, br1, and br2 host bridge devices.
List all sandboxed processes.
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
0.9.8 Jul 2014 man(1)
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