ufw
Networking
Usage
sudo ufw <allow|deny|status> ...A friendly wrapper around iptables on Debian and Ubuntu; allow SSH before you `enable` it or you cut the session you are sitting in, and Docker publishes ports straight into iptables where ufw rules do not cover them.
Common flags
| Flag | Meaning |
|---|---|
| allow 22/tcp | Open a port; allow OpenSSH uses the named application profile instead. |
| allow from 10.0.0.0/8 to any port 5432 | Open a port to one network only. |
| deny <port> | Block it explicitly. |
| default deny incoming | The usual starting point, set before you enable. |
| status numbered | List the rules with the numbers that delete needs. |
| delete <n> | Remove rule number n. |
| enable / disable | Turn the firewall on or off, persistently. |
Examples
sudo ufw allow OpenSSH && sudo ufw enableAllow SSH first, then switch the firewall on.
sudo ufw status numberedSee what is open and get the rule numbers.
sudo ufw delete 3Remove the third rule.
When a connection fails, these narrow down how far it got — name not resolving, no route, or a blocked port.
How to read this
- Square brackets [ ] mark a part you may leave out.
- An ellipsis … means you can list more than one.
- Flags are case-sensitive — in some commands -r and -R do different things.
Questions
Q. What does ufw do?
A friendly wrapper around iptables on Debian and Ubuntu; allow SSH before you `enable` it or you cut the session you are sitting in, and Docker publishes ports straight into iptables where ufw rules do not cover them.
Q. How do I type it?
sudo ufw <allow|deny|status> ... — square brackets mark the parts you can leave out.
Q. How many flags are worth knowing?
7 are listed here; the full set is in man ufw. This command sits under Networking.
Related commands
man page: man ufw