Important Hostname Files In Linux Explained With Examples

Important Hostname Files in Linux

In Linux, hostname configuration and resolution depend on a few important system files. These files control how your system identifies itself and how it resolves other hostnames on the network.

/etc/hostname

Purpose

Stores the static hostname of the system.

What It Contains

Only the system’s hostname (single line).

Example:

</> code

server01

or

</> code

prod-web01

How It Works

• Read during system boot
• Sets the permanent hostname
• Used by system services and the kernel

To view:

</> bash

cat /etc/hostname

To change permanently (recommended method):

</> bash

sudo hostnamectl set-hostname new-hostname

Modern distributions like Ubuntu, Debian, and CentOS manage this file automatically.

/etc/hosts

Purpose

Maps IP addresses to hostnames locally (before DNS lookup).

Example:

</> code

127.0.0.1   localhost
127.0.1.1   server01
192.168.1.10   web01

How It Works

• Checked before DNS (based on /etc/nsswitch.conf)
• Used for local resolution
• Helpful for development and testing

To edit:

</> bash

sudo nano /etc/hosts

Common use case:

</> code

127.0.0.1   myapp.local

This creates a local virtual hostname.

/etc/resolv.conf

Purpose

Defines DNS servers used for hostname resolution.

Example:

</> code

nameserver 8.8.8.8
nameserver 1.1.1.1
search example.com

How It Works

• Specifies DNS server IP addresses
• Used when resolving external hostnames
• May be managed automatically by NetworkManager or systemd-resolved

To view:

</> bash

cat /etc/resolv.conf

/etc/nsswitch.conf (Important for Resolution Order)

Purpose

Controls how hostname lookups are performed.

Example:

</> code

hosts: files dns

This means:

1. Check /etc/hosts
2. Then check DNS

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How Hostname Resolution Works in Linux

When you type:

</> bash

ping server01

Linux checks in this order:

• /etc/hosts
• DNS server from /etc/resolv.conf
• Returns IP address

File	Purpose	Scope
/etc/hostname	Stores system hostname	Local system
/etc/hosts	Maps IP to hostname	Local resolution
/etc/resolv.conf	DNS server configuration	Network resolution
/etc/nsswitch.conf	Lookup order configuration	System-wide

How to Create a Virtual Hostname in Linux

A virtual hostname usually refers to one of the following:

1. Creating an additional hostname mapped to your system (using /etc/hosts or DNS).
2. Creating a virtual host for a web server (like Apache or Nginx).
3. Setting a hostname inside a container or virtual machine.

The method depends on what you mean by “virtual hostname.” Below are the most common scenarios.

Create a Virtual Hostname Using /etc/hosts (Local Testing)

This method allows you to assign multiple hostnames to the same Linux machine without changing the main system hostname.

Step 1: Open /etc/hosts

bash

sudo nano /etc/hosts

Step 2: Add a New Virtual Hostname

Example:

lua

127.0.0.1   myapp.local
127.0.0.1   test.local

Or if using a server IP:

lua

192.168.1.100   myapp.local
192.168.1.100   api.local

Step 3: Save and Exit

Step 4: Test

bash

ping myapp.local

This creates a local virtual hostname used for development and testing.

Create a Virtual Host in Apache (Web Hosting)

If you’re hosting multiple websites on one server using Apache, you configure Virtual Hosts.

Step 1: Install Apache (if not installed)

bash

sudo apt install apache2

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Step 2: Create a Virtual Host Configuration File

bash

sudo nano /etc/apache2/sites-available/myapp.conf

Step 3: Add Configuration

apache

<VirtualHost *:80>
    ServerName myapp.local
    DocumentRoot /var/www/myapp

    <Directory /var/www/myapp>
        AllowOverride All
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/myapp_error.log
    CustomLog ${APACHE_LOG_DIR}/myapp_access.log combined
</VirtualHost>

Step 4: Create Website Directory

bash

sudo mkdir /var/www/myapp
sudo chown -R www-data:www-data /var/www/myapp

Step 5: Enable Virtual Host

bash

sudo a2ensite myapp.conf
sudo systemctl reload apache2

Step 6: Add Entry in /etc/hosts

lua

127.0.0.1 myapp.local

Now visit:

arduino

http://myapp.local

Create Virtual Host in Nginx

Step 1: Create Config File

bash

sudo nano /etc/nginx/sites-available/myapp

Step 2: Add Configuration

nginx

server {
    listen 80;
    server_name myapp.local;

    root /var/www/myapp;
    index index.html;

    location / {
        try_files $uri $uri/ =404;
    }
}

Step 3: Enable Site

bash

sudo ln -s /etc/nginx/sites-available/myapp /etc/nginx/sites-enabled/
sudo systemctl reload nginx

Add to /etc/hosts:

lua

127.0.0.1 myapp.local

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Create Virtual Hostname via DNS Server

In production environments:

• Add A record in DNS server.
• Point hostname to server IP.

Example:

myapp.example.com → 192.168.1.100

This method is used in enterprise environments.

Set Hostname Inside a Container (Docker Example)

bash

docker run --hostname mycontainer -it ubuntu bash

This creates a container with a custom hostname.

System Hostname and Virtual Hostname

Type	Purpose
System Hostname	Main name of Linux machine
Virtual Hostname	Additional domain mapped to same system
Web Virtual Host	Multiple websites on one server
DNS Hostname	Public domain pointing to server

Linux get hostname from IP

To find the hostname from an IP address in Linux, you can use reverse DNS lookup tools.

Using nslookup

</> bash

nslookup 192.168.1.10

If reverse DNS is configured, it will show:

</> code

name = server01.example.com

Using dig (Recommended)

</> bash

dig -x 192.168.1.10 +short

• -x → Reverse lookup
• +short → Displays only hostname

Using host Command

</> code

host 192.168.1.10

Example output:

</> code

10.1.168.192.in-addr.arpa domain name pointer server01.example.com.

Using getent (Checks System Resolver)

</> bash

getent hosts 192.168.1.10

This checks:

• /etc/hosts
• DNS
• System resolver configuration

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Hostname command in Linux with examples

The hostname command is a simple yet powerful utility in Linux used to view or temporarily change the system’s host name and domain name. It is part of the net-tools package and is one of the most frequently used commands by system administrators to identify machines in a network.

Basic Syntax

The basic syntax for the command is:

bash

hostname [options] [new_hostname]

Common Examples

A. View the Current Hostname

Simply typing the command without any arguments will display the name of your machine.

bash

hostname
# Output: my-linux-server

B. View the Fully Qualified Domain Name (FQDN)

If your system is part of a domain, this command shows the hostname followed by the domain name.

bash

hostname -f
# Output: my-linux-server.example.com

C. View the System’s IP Addresses

You can use hostname to quickly see the IP addresses associated with the host.

bash

hostname -I
# Output: 192.168.1.15 172.17.0.1

D. View the Domain Name

To see only the DNS domain name of the machine:

bash

hostname -d
# Output: example.com

E. Change the Hostname (Temporary)

You can change the hostname instantly. Note that this change is temporary and will revert to the original name after a reboot.

bash

sudo hostname new-server-name

Linux hostname examples

Professional Data Center (Structured)

In enterprise environments, hostnames follow a functional logic so any admin knows exactly what the server does.

• prod-us-web-01: Production environment, US region, Web server, instance 1.
• dev-eu-db-mstr: Development environment, Europe region, Database Master.
• stg-asia-app-04: Staging environment, Asia region, Application server 04.
• ops-mon-grafana: Operations team, Monitoring server, running Grafana.

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Home Lab & Small Office (Thematic

For smaller setups where you can remember each machine, “thematic” naming is common. It’s easier to remember than random strings of numbers.

• Planets: mercury, mars, jupiter, saturn.
• Scientists: tesla, curie, einstein, lovelace.
• Mythology: zeus, odin, thor, athena.
• Colors/Elements: carbon, cobalt, neon, argon.

Network & Infrastructure Devices

Devices that act as the “gateways” for your network usually have names that define their hardware position.

• gw-office-01: Gateway for the office.
• rt-edge-north: Edge Router for the northern segment.
• fw-external-primary: Primary external Firewall.
• sw-core-stack-a: Core Switch in Stack A.

Virtual Machines & Containers

Since these are often deleted and recreated (ephemeral), their names usually include a unique ID or the parent host’s name.

• docker-worker-8af2: A Docker worker node with a unique hex suffix.
• vm-101-ubuntu: Proxmox/ESXi VM with ID 101.
• k8s-node-worker-03: Kubernetes worker node.

Personal Devices

For your own computer, the name is usually simple and descriptive of the hardware.

• t480-laptop: Named after the ThinkPad model.
• main-desktop: Primary workstation.
• rpi-pihole: A Raspberry Pi running Pi-hole.
• gerrit-pc: Named after the owner.

Hostname Naming “Checklist”

Before you pick a name, check it against these rules:

Example	Valid?	Reason
web-server	Yes	Uses only letters and hyphens.
web_server	No	Underscores are technically illegal in many DNS configs.
1-server	No	Most systems dislike hostnames starting with a number.
Server-01	Maybe	Valid, but lowercase is the global standard to avoid issues.

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