hostname Command: Tutorial & Examples

Display and change the system hostname on Linux servers

The hostname command is a fundamental Linux utility used to display or set the system's hostname — the unique identifier assigned to a device on a network. The hostname plays an essential role in network communications, system identification, and service configuration. While the hostname command can temporarily change the hostname, making such changes permanent involves modifying system configuration files or using system tools.

This article explains how the hostname command works, common parameters, practical usage examples, making hostname changes persistent, and potential issues you might encounter on Linux servers and virtual machines.

What The hostname Command Does

The hostname command interacts with the Linux kernel and system configuration to retrieve or set the system's hostname. The hostname is a human-readable label that identifies the machine on a network and is used by various network protocols and services.

When run without arguments, hostname displays the current hostname. When given a new name as an argument, it sets the hostname temporarily until the next reboot or hostname change.

The hostname is stored in the kernel and can be queried or modified during runtime. However, to make the hostname persistent across reboots, system configuration files like /etc/hostname must be updated.

Why The hostname Is Important

The hostname uniquely identifies your server in a networked environment, which is critical for:

Network communications and routing
Logging and monitoring systems
Security and authentication mechanisms
Service configurations, such as web servers or databases that rely on hostname-based access control

Incorrect or inconsistent hostname configuration can lead to network failure, logging issues, or problems in distributed systems.

Common Parameters And Their Usage

The hostname command supports several useful command-line options:

-s, --short
Display the short hostname (up to the first dot).
-f, --fqdn, --long
Display the fully qualified domain name (FQDN).
-d, --domain
Display the DNS domain name.
-i, --ip-address
Display the IP address(es) associated with the hostname.
-I
Display all network addresses of the host.
-y, --yp
Display the NIS or YP domain name.
-F filename
Read the hostname from a specified file.
--help
Show help message.
--version
Show version information.

How To Use hostname: Basic And Advanced Examples

Here are some practical examples illustrating the usage of the hostname command.

Display the current hostname:

hostname


server01

Display the short hostname:

hostname -s


server01

Display the fully qualified domain name (FQDN):

hostname -f


server01.example.com

Display the domain name:

hostname -d


example.com

Display the IP address(es) associated with the hostname:

hostname -i


192.168.1.100

Set the hostname temporarily (effective until reboot):

sudo hostname new-hostname


# No output, but the hostname changes immediately

Verify the hostname change:

hostname


new-hostname

Set hostname permanently by modifying /etc/hostname:

echo "new-hostname" | sudo tee /etc/hostname


# You may need to reboot or restart hostname-related services for changes to take effect

Alternatively, on systemd-based systems, use hostnamectl:

sudo hostnamectl set-hostname new-hostname


# This modifies the persistent hostname and updates relevant services

Making Hostname Changes Persistent

While the hostname command modifies the hostname immediately, these changes are temporary and lost after a reboot. To make the hostname change permanent, update the appropriate system configuration files or use system-specific tools.

On most Linux distributions:
Edit the /etc/hostname file and replace the existing hostname with the new one.
On systemd-based systems (e.g., Ubuntu, CentOS 7+):
Use the hostnamectl command to set the hostname persistently.
Update /etc/hosts to reflect hostname changes:
It is often necessary to update the /etc/hosts file to map the hostname to the loopback address or the server's IP address to avoid resolution issues.

Example /etc/hosts entry:

127.0.0.1   localhost new-hostname

After making these changes, reboot the system or restart networking services to apply the new hostname fully.

Potential Problems And Pitfalls

Hostname Not Persisting After Reboot:
This occurs if the hostname change was made only via the hostname command without updating /etc/hostname or using hostnamectl.
Hostname Resolution Issues:
If /etc/hosts does not include the new hostname mapping, some services may fail to resolve the hostname, causing errors.
Inconsistent Hostname Across Network:
Ensure DNS records and DHCP configurations correspond to the hostname to avoid conflicts or dns-issue.
Permissions:
Changing the hostname requires superuser privileges. Use sudo to run commands that modify the hostname.
Effect on Running Services:
Some services may cache the hostname at startup; restarting these services or rebooting may be necessary after a hostname change.

Scripting And Automation With hostname

The hostname command is useful in scripts and automation tasks, such as configuration management or cloud-init scripts.

Example: Print the current hostname in a script

#!/bin/bash
current_hostname=$(hostname)
echo "Current hostname is: $current_hostname"

Example: Change hostname in a script with persistence

#!/bin/bash
new_hostname="webserver01"
sudo hostnamectl set-hostname "$new_hostname"
sudo sed -i "s/^127\.0\.1\.1.*$/127.0.1.1 $new_hostname/" /etc/hosts

This script sets a new hostname and updates /etc/hosts accordingly.

Related Commands And Tools

hostnamectl: A systemd utility for managing the hostname and related settings.
cat: View contents of files like /etc/hostname and /etc/hosts.
systemctl: Manage system services that may need restarting after hostname changes.
ip: Display network interfaces and addresses.
nslookup: Diagnose DNS resolution issues.