Set Default SSH User for Specific Host in Ubuntu

This article explains how to configure a default username for specific SSH connections in Ubuntu Linux by modifying your local SSH client configuration file. By setting up this configuration, you can connect to your remote servers using a simple alias without having to manually type your remote username or the full IP address every time.

To set a default user for a specific SSH connection, you need to edit or create the SSH config file in your user directory. Follow these steps to set it up:

Step 1: Open the SSH Config File

Open your terminal and open the SSH configuration file using a text editor like Nano. The file is located at ~/.ssh/config:

nano ~/.ssh/config

If the file or the ~/.ssh directory does not exist, this command will create the file once you save it.

Step 2: Add the Connection Details

Add a configuration block for your remote server. You need to define a nickname for the host, the actual IP address or domain name, and the default username.

Use the following format:

Host my-server-alias
    HostName example.com
    User your_remote_username

Replace the values as follows: * Host: The alias you want to type to initiate the connection (e.g., production, backup-server). * HostName: The actual domain name or IP address of the remote server. * User: The default username you want to use for this connection.

Step 3: Save and Exit

If you are using Nano, save the changes by pressing Ctrl + O, hit Enter to confirm, and then exit the editor by pressing Ctrl + X.

Step 4: Set the Correct Permissions

For security reasons, your SSH configuration file must have strict permissions so that other local users cannot read it. Run the following command to set the correct permissions:

chmod 600 ~/.ssh/config

Step 5: Connect to Your Server

Now you can connect to your remote server using only the alias you defined. You no longer need to type the username or the host’s IP address:

ssh my-server-alias

The SSH client will automatically read your configuration file, map my-server-alias to the correct IP address, and log you in using the specified default username.