/etc/hostname and /etc/HOSTNAME

The files /etc/hostname and /etc/HOSTNAME are used to configure the system's hostname in Unix-like operating systems. The location and usage of these files can vary between different Linux distributions. Here's an overview of these files and how they are used:

/etc/hostname

This file is commonly used in Debian-based distributions (such as Debian, Ubuntu, and their derivatives) to set the system's hostname.

Contents of /etc/hostname

The /etc/hostname file typically contains a single line with the hostname of the system. For example:

myhostname

In this example, myhostname is the name of the system.

Setting the Hostname

1. Edit the /etc/hostname File:

   sudo nano /etc/hostname

   Enter the desired hostname and save the file.

2. Apply the New Hostname: To apply the new hostname without rebooting, use the hostname command:

   sudo hostname -F /etc/hostname

3. Verify the Hostname:

   hostname

Additional Configuration

It is also good practice to update the /etc/hosts file to map the new hostname to 127.0.1.1. For example:

127.0.0.1   localhost
127.0.1.1   myhostname

/etc/HOSTNAME

This file is typically used in Red Hat-based distributions (such as RHEL, CentOS, Fedora, and their derivatives) to set the system's hostname.

Contents of /etc/HOSTNAME

The /etc/HOSTNAME file also contains a single line with the hostname of the system. For example:

myhostname

Setting the Hostname

1. Edit the /etc/HOSTNAME File:

   sudo nano /etc/HOSTNAME

   Enter the desired hostname and save the file.

2. Apply the New Hostname: To apply the new hostname without rebooting, use the hostnamectl command:

   sudo hostnamectl set-hostname myhostname

3. Verify the Hostname:

   hostname

Additional Configuration

It is also good practice to update the /etc/hosts file to map the new hostname to 127.0.0.1 or 127.0.1.1. For example:

127.0.0.1   localhost
127.0.1.1   myhostname

Key Differences and Usage

1. File Locations:

   • Debian-based systems: /etc/hostname.

   • Red Hat-based systems: /etc/HOSTNAME.

2. Hostname Commands:

   • Debian-based systems: hostname -F /etc/hostname.

   • Red Hat-based systems: hostnamectl set-hostname <hostname>.

3. Configuration Syntax:

   • Both files use a single line to specify the hostname.

Conclusion

The /etc/hostname and /etc/HOSTNAME files are essential for setting the system's hostname in Unix-like operating systems. Understanding their locations and usage in different Linux distributions helps in managing and configuring hostnames effectively. Remember to update the /etc/hosts file to ensure proper hostname resolution.