UFW development
The Linux kernel in Ubuntu provides a packet filtering system called `netfilter`, and the traditional interface for manipulating `netfilter` are the `iptables` suite of commands. iptables provide a complete firewall solution that is both highly configurable and highly flexible.
Becoming proficient in iptables takes time, and getting started with netfilter firewalling using only iptables can be a daunting task. As a result, many frontends for iptables have been created over the years, each trying to achieve a different result and targeting a different audience.
The Uncomplicated Firewall (UFW) is a frontend for iptables and is particularly well-suited for host-based firewalls. UFW provides a framework for managing netfilter, as well as a command-line interface for manipulating the firewall. UFW aims to provide an easy to use interface for people unfamiliar with firewall concepts, while at the same time simplifies complicated `iptables` commands to help an administrator who knows what he or she is doing. UFW is an upstream for other distributions and graphical frontends.
UFW in Ubuntu
Ubuntu 8.04 LTS introduced ufw, and it is available by default in all Ubuntu installations after 8.04 LTS.
Available Versions in supported versions of Ubuntu
- Ubuntu 14.04 LTS: 0.34~rc-0ubuntu2
- Ubuntu 16.04 LTS: 0.35-0ubuntu2
- Ubuntu 18.04 LTS: 0.36-0ubuntu0.18.04.1
- Ubuntu 20.04 LTS: 0.36-6
- Ubuntu 22.04 LTS: 0.36.1-4
- Ubuntu 24.04 LTS: 0.36.2-6
- Ubuntu 24.10: 0.36.2-6
- Ubuntu 25.04: 0.36.2-9
- Ubuntu 25.10: 0.36.2-9
- Ubuntu 26.04: 0.36.2-9build1
- Ubuntu Core: 0.36pre
Features
ufw has the following features:
| Feature | 0.31.1-1 | 0.34~rc-0ubuntu2 | 0.34-2 | 0.35 |
| default incoming policy (allow/deny) | yes | yes | yes | yes |
| allow/deny incoming rules | yes | yes | yes | yes |
| IPv6 (by default) | yes | yes | yes | yes |
| status | yes | yes | yes | yes |
| logging (on/off) | yes | yes | yes | yes |
| extensible framework | yes | yes | yes | yes |
| python 2.5 support | yes | no | no | no |
| application integration | yes | yes | yes | yes* |
| IPv4 rate limiting via 'limit' command | yes | yes | yes | yes |
| internationalization | yes | yes | yes | yes |
| multiport incoming rules | yes | yes | yes | yes |
| debconf/preseeding | yes | yes | yes | yes |
| default incoming policy (reject) | yes | yes | yes | yes |
| reject incoming rules | yes | yes | yes | yes |
| rule insertion | yes | yes | yes | yes |
| log levels | yes | yes | yes | yes |
| per rule logging | yes | yes | yes | yes |
| outgoing filtering (on par with incoming) | yes | yes | yes | yes |
| filtering by interface | yes | yes | yes | yes |
| bash completion | yes | yes | yes | yes |
| upstart support | yes | yes | yes | yes |
| improved reporting | yes | yes | yes | yes |
| reset command | yes | yes | yes | yes |
| rsyslog support | yes | yes | yes | yes |
| delete by rule number | yes | yes | yes | yes |
| python 2.6 support | yes | yes | yes | yes |
| 'show listening' report | yes | yes | yes | yes |
| python 2.7 support | yes | yes | yes | yes |
| increased protocol support (ah, esp) | yes | yes | yes | yes |
| IPv6 rate limiting via 'limit' command | -- | yes | yes | yes |
| python 3.2 support | -- | yes | yes | no |
| python 3.3 support | -- | yes | yes | yes |
| 'show added' report | -- | yes | yes | yes |
| python 3.4 support | -- | yes | yes | yes |
| before/after extensibility hooks | -- | yes | yes | yes |
| routed packet filtering (FORWARD) | -- | yes | yes | yes |
| systemd support | -- | -- | yes | yes |
| increased protocol support (igmp, gre) | -- | -- | yes | yes |
| python 3.5 support | -- | -- | yes | yes |
| Snappy for Ubuntu Core support | -- | -- | -- | yes |
| per rule comments | -- | -- | -- | yes |
Support for application integration is limited on Ubuntu Core at this time.
Basic Usage
Getting started with ufw is easy. For example, to enable firewall, allow ssh access, enable logging, and check the status of the firewall, run:
$ sudo ufw allow ssh/tcp $ sudo ufw logging on $ sudo ufw enable $ sudo ufw status Firewall loaded To Action From -- ------ ---- 22:tcp ALLOW Anywhere
This sets up a default deny (DROP) firewall for incoming connections, with all outbound connections allowed with state tracking.
On Ubuntu Core, simply replace ufw with ufw.cmd:
$ sudo ufw.cmd enable
Advanced Functionality
As mentioned, the ufw application is capable of doing anything that iptables can do. This is achieved by using several sets of rules files, which are nothing more than iptables-restore compatible text files. Fine-tuning ufw and/or adding additional iptables commands not offered via the ufw command is a matter of editing various text files.
- /etc/default/ufw: high level configuration, such as default policies, IPv6 support and kernel modules to use
- /etc/ufw/before[6].rules: rules in these files are evaluated before any rules added via the `ufw` command
- /etc/ufw/after[6].rules: rules in these files are evaluated after any rules added via the `ufw` command
- /etc/ufw/sysctl.conf: kernel network tunables
- /var/lib/ufw/user[6].rules or /lib/ufw/user[6].rules (0.28 and later): rules added via the `ufw` command (should not normally be edited by hand)
- /etc/ufw/ufw.conf: sets whether or not `ufw` is enabled on boot, and in 9.04 (ufw 0.27) and later, sets the LOGLEVEL
- /etc/ufw/after.init: initialization customization script run after ufw is initialized (ufw 0.34 and later)
- /etc/ufw/before.init: initialization customization script run before ufw is initialized (ufw 0.34 and later)
After modifying any of the above files, activate the new settings with:
$ sudo ufw disable $ sudo ufw enable
On Ubuntu Core, these files are located under
/var/lib/apps/ufw*/current. See ufw.doc ufw-on-snappy on an Ubuntu Core system for details.More information
- Ubuntu 16.04 LTS (Xenial Xerus)
- Ubuntu 18.04 LTS (Bionic Beaver)
- Ubuntu 20.04 LTS (Focal Fossa)
- Ubuntu 21.04 (Hirsute Hippo)
- Ubuntu 21.10 (Impish Indri)
- Ubuntu 22.04 LTS (Jammy Jellyfish)
- Ubuntu 24.04 LTS (Noble Numbat)
- Ubuntu 24.10 (Oracular Oriole)
- Ubuntu 25.04 (Plucky Puffin)
- Ubuntu 25.10 (Questing Quokka)
- Ubuntu 26.04 LTS (Resolute)
- Ubuntu Core
- See
ufw.docon your Ubuntu Core system, specificallyufw.doc ufw-on-snappy | lessto see how ufw differs on Ubuntu Core.
- See
- Specification: Ubuntu Firewall Spec
- Code: Launchpad
- Graphic User Interface for UFW: Gufw