How to Open Ports on Ubuntu – A Beginner-Friendly Step-by-Step Guide

By 佐川 直弘 | Naohiro Sagawa (運営者)

※記事内に広告を含みます。Amazonアソシエイトとして適格販売により収入を得ています。　

1. Introduction

Opening ports is a necessary configuration that allows specific applications and services to be accessed from external sources. By default, most ports are closed in Ubuntu to enhance security. However, if you need to open specific ports, you can use the “ufw (Uncomplicated Firewall)” tool, which provides an easy way to manage firewall settings. This article explains how to open ports on Ubuntu in detail.

2. About Ubuntu’s Firewall (ufw)

Ubuntu comes with ufw, a built-in tool for easily configuring the firewall. This tool allows you to manage port opening and closing with a single command, making it convenient for both server administrators and desktop users. Opening ports is necessary for various purposes, such as running a web server or enabling SSH connections.

3. Preparation

You need administrative privileges to open ports. All commands introduced in this article should be executed using sudo. Also, ensure that ufw is installed on your system. Although ufw is usually pre-installed on Ubuntu, you can install it using the following command if needed:

sudo apt-get install ufw

4. Checking the Current Firewall Status

First, check the current status of the firewall. By running the following command, you can determine whether ufw is enabled and which ports are currently open:

sudo ufw status

The output of this command will display the current rules and port statuses. Here, you can verify which ports are already open and check the existing settings.

5. How to Open Ports Using ufw

To open a specific port, use the ufw allow command. For example, to open port 80, which is used by web servers, run the following command:

sudo ufw allow 80

Similarly, to open port 22 for SSH connections, use:

sudo ufw allow 22

Once the command is successfully executed, the specified port will be opened, allowing external access.

6. Reloading Firewall Settings

To apply the changes, you need to reload ufw. Run the following command:

sudo ufw reload

Executing this command will immediately apply the new settings, ensuring that the opened ports take effect.

7. Managing and Deleting Rules

To check existing rules, use the following command:

sudo ufw status verbose

To delete a specific rule, use the ufw delete command. For example, to remove the rule that allows port 22:

sudo ufw delete allow 22

You can also delete rules by specifying their number. First, list the rules with:

sudo ufw status numbered

Then, use the displayed rule number to delete it:

sudo ufw delete [rule number]

8. Testing the Configuration

To verify that the port has been successfully opened, you can test it using the following methods:

• Check the port status using the netstat command.
• Use an online tool to verify external accessibility.

If you encounter any issues, review your firewall rules and network settings.

9. Security Considerations

While opening ports is essential for running necessary applications and services, it also poses security risks. Open ports accept external connections, increasing the potential for unauthorized access. To maintain security, only open the minimum required ports and keep unnecessary ports closed.

10. Conclusion

This article explained how to open ports on Ubuntu using ufw. While port opening is a crucial configuration for network applications, it also comes with security risks. Proper management and periodic review of firewall settings are essential to maintaining a secure environment. We recommend regularly checking your firewall configurations and implementing the latest security measures.