UFW Essentials: Common Firewall Rules and Commands for Linux Security

• UFW Simplifies Firewall Management: UFW is a user-friendly interface for managing iptables, designed to simplify firewall configuration on Ubuntu-based systems.

• Default Policies Are Secure by Design: By default, UFW denies all incoming connections and allows all outgoing connections, creating a secure baseline for most servers.

• Always Allow SSH Before Enabling UFW: If you’re connected via SSH, enable SSH access with sudo ufw allow OpenSSH before activating UFW to avoid losing remote access.

• Use Application Profiles When Available: UFW integrates with application profiles (e.g., Nginx Full, OpenSSH), allowing easier rule creation without specifying port numbers manually.

• Support for IP-Based Rules: You can allow or block traffic from specific IP addresses or subnets using simple commands like ufw allow from IP or ufw deny from subnet.

• Interface-Specific Rules Offer Granular Control: UFW allows rule targeting per network interface, which is useful for multi-interface systems and virtualized environments.

• UFW Integrates with Both IPv4 and IPv6: Rules apply to both IP versions unless explicitly disabled. You’ll see (v6) entries in the status output for IPv6 rules.

• Docker Can Conflict with UFW: Docker modifies iptables directly, potentially bypassing UFW rules unless additional configuration is applied.

• UFW Rules Can Be Reset or Deleted Easily: Use ufw reset to wipe all rules or ufw delete to remove specific ones, including by rule number for precision.

• Best Practices Enhance Security and Maintainability: The guide emphasizes clear practices: setting default policies early, backing up rule sets, using logging, and avoiding use of firewalld alongside UFW. <$>

• This guide is in cheat sheet format with self-contained command-line snippets.
• Jump to any section that is relevant to the task you are trying to complete.
• When you see highlighted text in this guide’s commands, keep in mind that this text should refer to IP addresses from your network.

Remember that you can check your current UFW ruleset with sudo ufw status or sudo ufw status verbose.

To check if ufw is enabled, run:

sudo ufw status

Status: inactive

The output will indicate if your firewall is active or not.

If you get a Status: inactive message when running ufw status, it means the firewall is not yet enabled on the system. You’ll need to run a command to enable it.

To enable UFW on your system, run:

sudo ufw enable

You’ll see output like this:

Firewall is active and enabled on system startup

UFW Default Policies

When you enable UFW for the first time, it applies a set of default policies that define how the firewall handles incoming and outgoing connections. By default, UFW is configured to:

• Deny all incoming connections
• Allow all outgoing connections

You can verify the current default policy settings with the following command:

sudo ufw status verbose

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), deny (routed)
New profiles: skip

If you want to change the default behavior, you can update the default policies using the following commands:

• To deny all incoming connections (recommended for most servers):

  sudo ufw default deny incoming
  
  

• To allow all outgoing connections (the default):

  sudo ufw default allow outgoing
  
  

• To deny all forwarded traffic (relevant for routers and gateways):

  sudo ufw default deny routed
  
  

These default rules act as a baseline. Once set, you can explicitly allow trusted connections using ufw allow rules, as described in the other sections of this guide.

You can always reapply or reset your default policies as needed, depending on how restrictive or open you want your firewall to be.

If, for some reason, you need to disable UFW, you can do so with the following command:

sudo ufw disable

Be aware that this command will fully disable the firewall service on your system.

UFW is a user-friendly front-end for managing iptables, the underlying packet filtering framework used by most Linux systems. When you configure firewall rules using UFW, it translates those rules into iptables syntax behind the scenes.

This means that:

• You don’t need to write iptables rules manually.
• Changes made through UFW are automatically applied via iptables.
• Both IPv4 and IPv6 rules are managed unless IPv6 support is explicitly disabled in UFW’s configuration.

To check whether UFW is managing your iptables rules, you can inspect the raw iptables output:

sudo iptables -L

You’ll see chains like ufw-before-input, ufw-user-input, and others, which are automatically created and managed by UFW to enforce its policies.

UFW stores its persistent rule definitions in configuration files, typically under:

/etc/ufw/

Most users never need to edit these files directly. However, if you also manage iptables rules manually or through other tools (like Docker or custom scripts), you should be aware that UFW might overwrite or conflict with those rules.

While UFW simplifies rule management, iptables still does the actual packet filtering at the kernel level. Think of UFW as a command-line assistant that speaks iptables fluently, so you don’t have to.

To block all network connections that originate from a specific IP address, run the following command, replacing the highlighted IP address with the IP address that you want to block:

sudo ufw deny from 203.0.113.100

Rule added

In this example, from 203.0.113.100 specifies a source IP address of “203.0.113.100”.

If you run sudo ufw status now, you’ll see the specified IP address listed as denied:

Status: active

To                         Action      From
--                         ------      ----
Anywhere                   DENY        203.0.113.100         

All connections, coming in or going out, are blocked for the specified IP address.

How to Block a Subnet

If you need to block a full subnet, you can use the subnet address with the from parameter in the ufw deny command. This would block all IP addresses in the example subnet 203.0.113.0/24:

sudo ufw deny from 203.0.113.0/24

Rule added

To block incoming connections from a specific IP address to a specific network interface, run the following command, replacing the highlighted IP address with the IP address you want to block:

sudo ufw deny in on eth0 from 203.0.113.100

Rule added

The in parameter tells ufw to apply the rule only for incoming connections, and the on eth0 parameter specifies that the rule applies only for the eth0 interface. This might be useful if you have a system with several network interfaces (including virtual ones) and you need to block external access to some of these interfaces, but not all.

To allow all network connections that originate from a specific IP address, run the following command, replacing the highlighted IP address with the IP address that you want to allow access:

sudo ufw allow from 203.0.113.101

Rule added

If you run sudo ufw status now, you’ll see output similar to this, showing the word ALLOW next to the IP address you just added.

Status: active

To                         Action      From
--                         ------      ----
...          
Anywhere                   ALLOW       203.0.113.101 

You can also allow connections from a whole subnet by providing the corresponding subnet mask for a host, such as 203.0.113.0/24.

To allow incoming connections from a specific IP address to a specific network interface, run the following command, replacing the highlighted IP address with the IP address you want to allow:

sudo ufw allow in on eth0 from 203.0.113.102

Rule added

The in parameter tells ufw to apply the rule only for incoming connections, and the on eth0 parameter specifies that the rule applies only for the eth0 interface.

If you run sudo ufw status now, you’ll see output similar to this:

Status: active

To                         Action      From
--                         ------      ----
...         
Anywhere on eth0           ALLOW       203.0.113.102            

To delete a rule that you previously set up within UFW, use ufw delete followed by the rule (allow or deny) and the target specification. The following example would delete a rule previously set to allow all connections from an IP address of 203.0.113.101:

sudo ufw delete allow from 203.0.113.101

Rule deleted

Another way to specify which rule you want to delete is by providing the rule ID. This information can be obtained with the following command:

sudo ufw status numbered

Status: active

     To                         Action      From
     --                         ------      ----
[ 1] Anywhere                   DENY IN     203.0.113.100             
[ 2] Anywhere on eth0           ALLOW IN    203.0.113.102             

From the output, you can see that there are two active rules. The first rule, with highlighted values, denies all connections coming from the IP address 203.0.113.100. The second rule allows connections on the eth0 interface coming in from the IP address 203.0.113.102.

Because UFW’s default policy denies all incoming traffic, a specific DENY rule is only necessary to override a more permissive ALLOW rule. You can remove this rule if you don’t have any conflicting ALLOW rules for that source.

To delete a rule by its ID, run:

sudo ufw delete 1

You will be prompted to confirm the operation and to make sure the ID you’re providing refers to the correct rule you want to delete.

Deleting:
 deny from 203.0.113.100
Proceed with operation (y|n)? y
Rule deleted

If you list your rules again with sudo ufw status, you’ll see that the rule was removed.

Upon installation, applications that rely on network communications will typically set up a UFW profile that you can use to allow connections from external addresses. This is often the same as running ufw allow from, with the advantage of providing a shortcut that abstracts the specific port numbers a service uses and provides a user-friendly nomenclature to referenced services.

To list which profiles are currently available, run the following:

sudo ufw app list

If you installed a service such as a web server or other network-dependent software and a profile was not made available within UFW, first make sure the service is enabled. For remote servers, you’ll typically have OpenSSH readily available:

Available applications:
  OpenSSH

To enable a UFW application profile, run ufw allow followed by the name of the application profile you want to enable, which you can obtain with a sudo ufw app list command. In the following example, we’re enabling the OpenSSH profile, which will allow all incoming SSH connections on the default SSH port.

sudo ufw allow "OpenSSH"

Rule added
Rule added (v6)

Remember to quote profile names that consist of multiple words, such as Nginx HTTPS.

To disable an application profile that you had previously set up within UFW, you’ll need to remove its corresponding rule. For example, consider the following output from sudo ufw status:

sudo ufw status

Status: active

To                         Action      From
--                         ------      ----
OpenSSH                    ALLOW       Anywhere                               
Nginx Full                 ALLOW       Anywhere                  
OpenSSH (v6)               ALLOW       Anywhere (v6)                   
Nginx Full (v6)            ALLOW       Anywhere (v6)        

This output indicates that the Nginx Full application profile is currently enabled, allowing any and all connections to the web server both via HTTP and via HTTPS. If you want to allow only HTTPS requests from and to your web server, you must first enable the most restrictive rule, which in this case would be Nginx HTTPS, and then disable the currently active Nginx Full rule:

sudo ufw allow "Nginx HTTPS"
sudo ufw delete allow "Nginx Full"

Remember, you can list all available application profiles with sudo ufw app list.

When working with remote servers, you’ll want to make sure that the SSH port is open to connections so that you are able to log in to your server remotely.

The following command will enable the OpenSSH UFW application profile and allow all connections to the default SSH port on the server:

sudo ufw allow OpenSSH

Rule added
Rule added (v6)

Although less user-friendly, an alternative syntax is to specify the exact port number of the SSH service, which is typically set to 22 by default:

sudo ufw allow 22

Rule added
Rule added (v6)

To allow incoming connections from a specific IP address or subnet, use a from directive to define the source of the connection. This will require that you also specify the destination address with a to parameter. To lock this rule to SSH only, you’ll limit the proto (protocol) to tcp and then use the port parameter and set it to 22, SSH’s default port.

The following command will allow only SSH connections coming from the IP address 203.0.113.103:

sudo ufw allow from 203.0.113.103 proto tcp to any port 22

Rule added

You can also use a subnet address as from parameter to allow incoming SSH connections from an entire network:

sudo ufw allow from 203.0.113.0/24 proto tcp to any port 22

Rule added

The Rsync program, which runs on port 873, can be used to transfer files from one computer to another.

To allow incoming rsync connections from a specific IP address or subnet, use the from parameter to specify the source IP address and the port parameter to set the destination port 873.

The following command will allow only Rsync connections coming from the IP address 203.0.113.103:

sudo ufw allow from 203.0.113.103 to any port 873

Rule added

To allow the entire 203.0.113.0/24 subnet to connect to your server via rsync:

sudo ufw allow from 203.0.113.0/24 to any port 873

Rule added

Upon installation, the Nginx web server sets up a few different UFW profiles within the server. Once you have Nginx installed and enabled as a service, run the following command to identify which profiles are available:

sudo ufw app list | grep Nginx

  Nginx Full
  Nginx HTTP
  Nginx HTTPS

To enable both HTTP and HTTPS traffic, choose Nginx Full. Otherwise, choose either Nginx HTTP to allow only HTTP or Nginx HTTPS to allow only HTTPS.

The following command will allow both HTTP and HTTPS traffic on the server (ports 80 and 443):

sudo ufw allow "Nginx Full"

Rule added
Rule added (v6)

Upon installation, the Apache web server sets up a few different UFW profiles within the server. Once you have Apache installed and enabled as a service, run the following command to identify which profiles are available:

sudo ufw app list | grep Apache

  Apache
  Apache Full
  Apache Secure

To enable both HTTP and HTTPS traffic, choose Apache Full. Otherwise, choose either Apache for HTTP or Apache Secure for HTTPS.

The following command will allow both HTTP and HTTPS traffic on the server (ports 80 and 443):

sudo ufw allow "Apache Full"

Rule added
Rule added (v6)

Web servers, such as Apache and Nginx, typically listen for HTTP requests on port 80. If your default policy for incoming traffic is set to drop or deny, you’ll need to create a UFW rule to allow external access on port 80. You can use either the port number or the service name (http) as a parameter to this command.

To allow all incoming HTTP (port 80) connections, run:

sudo ufw allow http

Rule added
Rule added (v6)

An alternative syntax is to specify the port number of the HTTP service:

sudo ufw allow 80

Rule added
Rule added (v6)

How to Allow All Incoming HTTPS (port 443)

HTTPS typically runs on port 443. If your default policy for incoming traffic is set to drop or deny, you’ll need to create a UFW rule to allow external access on port 443. You can use either the port number or the service name (https) as a parameter to this command.

To allow all incoming HTTPS (port 443) connections, run:

sudo ufw allow https

Rule added
Rule added (v6)

An alternative syntax is to specify the port number of the HTTPS service:

sudo ufw allow 443

Rule added
Rule added (v6)

If you want to allow both HTTP and HTTPS traffic, you can create a single rule to allow traffic on both ports simultaneously. This usage requires that you also define the protocol with the proto parameter, which in this case should be set to tcp.

To allow all incoming HTTP and HTTPS (ports 80 and 443) connections, run:

sudo ufw allow proto tcp from any to any port 80,443

Rule added
Rule added (v6)

MySQL listens for client connections on port 3306. If your MySQL database server is being used by a client on a remote server, you’ll need to create a UFW rule to allow that access.

To allow incoming MySQL connections from a specific IP address or subnet, use the from parameter to specify the source IP address and the port parameter to set the destination port 3306.

The following command will allow the IP address 203.0.113.103 to connect to the server’s MySQL port:

sudo ufw allow from 203.0.113.103 to any port 3306

Rule added

To allow the entire 203.0.113.0/24 subnet to be able to connect to your MySQL server, run:

sudo ufw allow from 203.0.113.0/24 to any port 3306

Rule added

PostgreSQL listens for client connections on port 5432. If your PostgreSQL database server is being used by a client on a remote server, you must explicitly allow this traffic.

To allow incoming PostgreSQL connections from a specific IP address or subnet, specify the source with the from parameter, and set the port to 5432:

sudo ufw allow from 203.0.113.103 to any port 5432

Rule added

To allow the entire 203.0.113.0/24 subnet to be able to connect to your PostgreSQL server, run:

sudo ufw allow from 203.0.113.0/24 to any port 5432

Rule added

Mail servers, such as Sendmail and Postfix, typically use port 25 for SMTP traffic. If your server shouldn’t be sending outgoing mail, you may want to block that kind of traffic. To block outgoing SMTP connections, run:

sudo ufw deny out 25

Rule added
Rule added (v6)

This configures your firewall to drop all outgoing traffic on port 25. If you need to reject outgoing connections on a different port number, you can repeat this command and replace 25 with the port number you want to block.

Over time, your UFW rule set may grow cluttered with test rules, duplicate entries, or outdated configurations. If you need a clean slate, UFW provides a built-in command to reset its configuration back to the default state.

Resetting UFW will:

• Disable the firewall (UFW will no longer be active)
• Delete all existing rules; both allow and deny
• Reset default policies to:
  • deny for all incoming traffic
  • allow for all outgoing traffic
• Clear application profile rules (e.g., OpenSSH, Nginx, Apache)
• Remove all numbered rule references used for deletion

To perform a full reset of UFW, run the following command:

sudo ufw reset

Resetting all rules to installed defaults. This may disrupt existing ssh connections. Proceed with operation (y|n)? 

Type y to confirm.

This action is useful when:

• Your firewall is behaving unexpectedly
• You’ve misconfigured multiple rules and want to start fresh
• You’re switching server roles (e.g., from a web server to a database node)
• You want to standardize your configuration across systems

Once you’ve reset UFW, you’ll need to reconfigure essential access rules. For example, to re-allow SSH and activate the firewall again:

sudo ufw allow OpenSSH
sudo ufw enable

You can then rebuild your rule set from scratch based on your current needs.

While UFW is the default firewall manager on Ubuntu-based systems, other Linux distributions, especially Red Hat-based ones, use a different tool: firewalld. Both tools serve the same purpose of managing firewall rules, but they take different approaches and are designed with different priorities in mind.

What is firewalld?

firewalld is a firewall management tool that provides a dynamic interface for managing rules. It utilizes the concept of zones, which lets you define different trust levels for network interfaces (for example: public, internal, dmz). This makes it ideal for more complex environments where different parts of the system or network require different firewall behavior.

firewalld supports both runtime and permanent rules. Runtime changes take effect immediately without restarting the service, making it suitable for on-the-fly updates. Permanent rules persist across reboots and are typically used for long-term configuration.

It also includes rich rule support (such as service-based access, ICMP types, interface filtering, and source/destination address control) and is often managed through graphical tools like firewall-config or Cockpit.

UFW versus firewalld

How to Choose Between UFW and firewalld

• Choose UFW if you’re running a single-purpose server, need quick rule setup, or prefer a minimal interface.
• Choose firewalld if you’re dealing with multi-interface setups, virtual networks, or enterprise-grade configurations where zone-based configurations and live rule updates are important.

How to Check and Manage firewalld Status

To check if firewalld is running on your system:

sudo systemctl status firewalld

To stop and disable it if you are using UFW, use the following commands:

sudo systemctl stop firewalld
sudo systemctl disable firewalld

To get the most out of UFW while minimizing misconfigurations and downtime, consider following these recommended best practices when setting up and maintaining your firewall.

Always Allow SSH Before Enabling the Firewall

If you’re connected to a server over SSH, make sure to allow SSH before enabling UFW to avoid being locked out:

sudo ufw allow OpenSSH
sudo ufw enable

Failing to do this will block your remote access the moment UFW is enabled.

How to Set Default Policies Before Adding Rules

Set your default incoming and outgoing policies early in your configuration so you’re starting with a secure baseline:

sudo ufw default deny incoming
sudo ufw default allow outgoing

Only then should you begin explicitly allowing the services you need.

How to Use Application Profiles When Available

Instead of manually allowing ports, use predefined application profiles:

sudo ufw allow "Nginx Full"

To see what profiles are available:

sudo ufw app list

This makes rule management easier and reduces the chance of human error when typing port numbers or protocols.

How to Be Specific With IPs, Ports, and Protocols

Limit exposure by tightening rules as much as possible. For example, instead of opening SSH to the world:

sudo ufw allow from 203.0.113.0/24 to any port 22 proto tcp

This approach minimizes your server’s attack surface by only allowing trusted sources.

How to Use Numbered Rules for Easier Management

When you need to remove or audit specific rules, use:

sudo ufw status numbered

This makes it easier to delete rules precisely without needing to retype full command strings:

sudo ufw delete 2

How to Test Changes in a Maintenance Window (if possible)

Firewall misconfigurations can disrupt services. If you’re modifying rules on a production server, test during off-peak hours or schedule a short maintenance window to reduce risk.

Use Logging to Monitor Activity

Enable logging to capture dropped connections and debug firewall behavior:

sudo ufw logging on

Logs are typically stored in:

/var/log/ufw.log

You can control verbosity with:

sudo ufw logging low  # or medium / high / full

How to Back Up Rules Before Making Major Changes

Before resetting or reworking your UFW configuration, save the current ruleset:

sudo ufw status numbered > ufw-backup.txt

This lets you recreate or review past configurations if something goes wrong.

Don’t Use UFW and firewalld Together

Stick to one firewall management system. Running both UFW and firewalld simultaneously can cause rule conflicts and unpredictable behavior.

Disable the one you’re not using:

sudo systemctl disable firewalld

Or:

sudo ufw disable

Following these best practices will help ensure your firewall is secure, maintainable, and doesn’t interrupt your server’s connectivity.

1. What is the default UFW policy?

By default, UFW is configured to deny all incoming connections and allow all outgoing connections. This means no external device can initiate a connection to your system unless explicitly allowed, while your system is free to access external resources.

You can view the current default policies by running:

sudo ufw status verbose

To change the defaults, use:

sudo ufw default deny incoming
sudo ufw default allow outgoing

2. How do I allow a specific IP address in UFW?

To allow all traffic from a specific IP address, use the allow from syntax. Replace the IP with the address you want to permit:

sudo ufw allow from 203.0.113.101

This creates a rule that permits all types of connections from that IP to your server. If you want to restrict it to a specific port or protocol, you can add more parameters:

sudo ufw allow from 203.0.113.101 to any port 22 proto tcp

This allows only SSH (TCP port 22) traffic from the given IP.

3. How can I check which rules are currently active?

To view your active UFW rules, run:

sudo ufw status

For more detailed output, including default policies and logging status, use the verbose flag:

sudo ufw status verbose

If you want to view rules with line numbers (helpful for deleting specific rules), run:

sudo ufw status numbered

4. Can UFW block outgoing traffic?

Yes, UFW can be used to block outgoing connections. While UFW allows all outbound traffic by default, you can add rules to deny specific ports or destinations.

To block all outgoing SMTP traffic on port 25, for example:

sudo ufw deny out 25

You can also block outgoing traffic to specific IP addresses or ranges:

sudo ufw deny out to 203.0.113.0/24

To change the default policy for all outbound traffic:

sudo ufw default deny outgoing

Be cautious with outbound rules, especially on servers that require external access for updates, backups, or package installations.

5. Does UFW work with IPv6?

Yes, UFW supports both IPv4 and IPv6 by default. When you enable a rule like sudo ufw allow ssh, it creates rules for both IPv4 and IPv6 unless configured otherwise.

You can verify IPv6 rules are active by checking the output of:

sudo ufw status

You’ll see entries like:

OpenSSH (v6)             ALLOW       Anywhere (v6)

To disable IPv6 support in UFW, edit the configuration file:

sudo nano /etc/default/ufw

Set:

IPV6=no

Then reload UFW:

sudo ufw disable && sudo ufw enable

6. Can I use UFW with Docker?

UFW and Docker can conflict because Docker bypasses the default iptables rules UFW sets up. As a result, Docker containers may be exposed to the network even if UFW appears to block traffic.

If you’re running Docker and need strict firewall control, you’ll need to:

• Use Docker’s own firewall rules
• Or reconfigure iptables policies to work correctly with UFW

To secure your system while running Docker, consider using Docker’s --iptables=false option and managing container traffic manually, or use advanced UFW/Docker integration scripts.

7. How do I delete a specific UFW rule?

There are two main ways to delete a UFW rule:

1. By repeating the exact rule:

   sudo ufw delete allow from 203.0.113.101
   
   

2. By rule number:

   First, list rules with numbers:

   sudo ufw status numbered
   
   

   Then delete a rule by its number:

   sudo ufw delete 2
   
   

   You’ll be prompted to confirm the deletion before the rule is removed.

8. How do I list available application profiles in UFW?

Many networked applications (like Nginx, Apache, or OpenSSH) register UFW profiles when installed. You can view all available profiles with:

sudo ufw app list

To see what ports a profile covers, run:

sudo ufw app info "Nginx Full"

This will show which ports the profile opens and any associated protocols. Using application profiles simplifies rule management and abstracts away the need to remember specific port numbers.

UFW is a powerful yet approachable tool for managing firewall rules on Ubuntu systems. With its simple syntax and built-in support for both IPv4 and IPv6, UFW makes it easy to enforce access controls without needing to write complex iptables rules by hand.

This guide has covered the most common UFW commands and use cases, including how to allow or deny traffic by port, IP address, and network interface, as well as how to manage application profiles and reset the firewall configuration. Most of these examples can be adapted to fit your own network needs by modifying parameters like IP addresses or port numbers.

For more in-depth details on UFW command options and advanced usage, consult the manual using man ufw or explore Ubuntu’s official documentation.

To explore and learn more about firewall configuration and Linux networking, check out these helpful resources:

• How to Set Up a Firewall with UFW on Ubuntu
• Linux Open Port: Step-by-Step Guide to Managing Firewall Ports
• 50+ Essential Linux Commands: A Comprehensive Guide