The fastd command is a VPN (Virtual Private Network) daemon that works on Layer 2 or Layer 3, supports different encryption methods, and is commonly used by the Freifunk community. It allows users to create secure and private connections over the internet. Here are several examples of how to use the fastd command:

Use case 1: Start fastd with a specific configuration file

fastd --config path/to/fastd.conf

Motivation: This use case is useful when you want to start the fastd daemon using a specific configuration file. The --config option specifies the path to the configuration file that contains the necessary settings for the VPN connection.

Explanation:

• fastd is the command itself.
• --config path/to/fastd.conf specifies the path to the configuration file. Replace path/to/fastd.conf with the actual path to your configuration file.

Example Output: The fastd daemon starts using the settings specified in the specified configuration file.

Use case 2: Start a Layer 3 VPN with an MTU of 1400, loading the rest of the configuration parameters from a file

fastd --mode tap --mtu 1400 --config path/to/fastd.conf

Motivation: This use case is helpful when you need to start a Layer 3 VPN connection with a specified maximum transmission unit (MTU) size. The --mtu option allows you to set the MTU size to 1400.

Explanation:

• fastd is the command itself.
• --mode tap sets the mode of the VPN connection to tap, which is a Layer 3 mode.
• --mtu 1400 specifies the maximum transmission unit (MTU) size to 1400. The MTU size determines the maximum size of packets that can be transmitted over the network.
• --config path/to/fastd.conf specifies the path to the configuration file. Replace path/to/fastd.conf with the actual path to your configuration file.

Example Output: The fastd daemon starts a Layer 3 VPN connection with an MTU size of 1400 using the settings specified in the configuration file.

Use case 3: Validate a configuration file

fastd --verify-config --config path/to/fastd.conf

Motivation: This use case allows you to validate the syntax and correctness of a configuration file before using it. This is useful to ensure that the configuration file does not contain any errors that could potentially cause issues with the VPN connection.

Explanation:

• fastd is the command itself.
• --verify-config option checks the syntax and correctness of the specified configuration file.
• --config path/to/fastd.conf specifies the path to the configuration file. Replace path/to/fastd.conf with the actual path to your configuration file.

Example Output: The fastd command verifies the syntax and correctness of the specified configuration file and provides feedback on whether it is valid or if there are any errors.

Use case 4: Generate a new key

fastd --generate-key

Motivation: This use case is useful when you need to generate a new key for authentication purposes in your VPN connection. A new key can be generated whenever you want to enhance security or when setting up a new VPN connection.

Explanation:

• fastd is the command itself.
• --generate-key option generates a new key.

Example Output: The fastd command generates a new key and displays it as output. The generated key can be used for authentication purposes in the VPN connection.

Use case 5: Show the public key corresponding to a private key in a configuration file

fastd --show-key --config path/to/fastd.conf

Motivation: This use case allows you to retrieve the public key corresponding to a private key that is specified in a configuration file. The public key can be used for authentication or identification purposes in the VPN connection.

Explanation:

• fastd is the command itself.
• --show-key option retrieves the public key corresponding to the private key specified in the configuration file.
• --config path/to/fastd.conf specifies the path to the configuration file. Replace path/to/fastd.conf with the actual path to your configuration file.

Example Output: The fastd command retrieves and displays the public key that corresponds to the private key specified in the configuration file.

Use case 6: Show the current version

fastd -v

Motivation: This use case allows you to quickly check the current version of the fastd command that is installed on your system. It is useful to verify that you are using the desired version and to check for any updates.

Explanation:

• fastd is the command itself.
• -v option displays the current version of the fastd command.

Example Output: The fastd command displays the current version of the fastd daemon, such as “fastd version 19.10-4”.

Conclusion:

The fastd command provides a versatile solution for setting up and managing VPN connections. With various options, it allows you to start the daemon using specific configuration files, validate configurations, generate keys, retrieve public keys, and check the current version. These examples provide a good starting point for using the fastd command and exploring its capabilities.