Detailed Guide: How to Change the Hostname in Oracle Linux 8

Oracle Linux 8 (OL8) allows you to change the system’s hostname easily, which is helpful for identifying machines in a network. There are different types of hostnames in Linux, including:

• Static hostname: This is set by the user and remains consistent across reboots.
• Transient hostname: This is assigned dynamically by the system, often during network changes.
• Pretty hostname: A user-friendly, descriptive version of the hostname.

Here’s a step-by-step guide to change the hostname on Oracle Linux 8:

Prerequisites

• Ensure you have root or sudo access to perform these operations.

Step 1: Check the Current Hostname

Before changing the hostname, you might want to see the current hostname of the system.

1. Open a terminal.
2. Run the following command:

   hostnamectl status

This command will display the current hostname and other details about the system.

Step 2: Set the New Hostname

You can change the hostname using the hostnamectl command.

1. To set a new hostname, use the following syntax:

   sudo hostnamectl set-hostname <new-hostname>

For example, to change the hostname to server01:

   sudo hostnamectl set-hostname server01

2. Optionally, you can set a pretty hostname:

   sudo hostnamectl set-hostname "My Server" --pretty

Step 3: Verify the Change

After setting the hostname, verify that the new hostname is applied by using:

hostnamectl status

The output should reflect the new hostname.

Step 4: Update the /etc/hosts File

It’s a good practice to update the /etc/hosts file to reflect the new hostname, especially if you have static IP mappings. Follow these steps:

1. Open the /etc/hosts file using any text editor, such as vi or nano:

   sudo nano /etc/hosts

2. Find the line that maps the current hostname to the system’s IP, which might look something like this:

   127.0.0.1   localhost
   127.0.1.1   old-hostname

3. Replace old-hostname with the new hostname:

   127.0.0.1   localhost
   127.0.1.1   server01

4. Save the file and exit the editor.

Step 5: Reboot the System (Optional)

While this step is not mandatory, it ensures that all services are using the updated hostname. To reboot the system, use:

sudo reboot

Step 6: Verify After Reboot

Once the system is back online, verify the hostname change once more:

hostnamectl status

Alternative: Temporarily Change Hostname

If you need to change the hostname temporarily (which will not persist after reboot), you can simply use the hostname command:

sudo hostname <new-hostname>

To verify the temporary change:

hostname

Remember, this change will revert back to the original hostname after a reboot unless the hostnamectl command is used for a permanent change.

Troubleshooting

1. Hostname not updating after reboot: Ensure that the /etc/hostname file is correctly updated by the hostnamectl command. If necessary, manually edit the file:

   sudo nano /etc/hostname

Enter the desired hostname and save the file.

2. DNS conflicts: Ensure that the new hostname is properly configured in your DNS settings to avoid issues with network identification.

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This guide should help you successfully change the hostname on Oracle Linux 8. If you need further customization or have specific network settings, adjust accordingly.