hosts centos7

The hosts file is a core component in Linux systems, including CentOS 7, enabling local domain name resolution by mapping hostnames to IP addresses. This guide explores its configuration for CentOS 7 users.

Understanding the hosts file

Linux systems use the hosts file to translate hostnames into IP addresses locally, often bypassing external DNS queries. Located at /etc/hosts, this plain text file improves performance for local network setups. CentOS 7 leverages this for quick name resolution, ideal for internal environments like development servers.

Accessing and editing the hosts file

Access requires root privileges. Open the file using a terminal editor. Run the command sudo nano /etc/hosts or sudo vi /etc/hosts to start editing. Ensure proper syntax to avoid system errors.

Entry syntax and examples

Each entry consists of an IP address, the hostname, and optional aliases, separated by spaces or tabs. A common example is:

127.0.0.1   localhost localhost.localdomain

To map a custom domain, add lines like 192.168.1.100 myserver.example.com myserver. This directs any request to "myserver" to the specified IP, useful for internal networks.

Practical applications

Use the hosts file to streamline local testing, such as mapping domains for web development. Prevent access to specific sites by redirecting them to 127.0.0.1. For instance, blocking an unwanted domain involves adding:

127.0.0.1   blocked-site.com

CentOS 7 prioritizes hosts file entries over DNS, making this approach efficient for custom network setups.

Verifying configuration changes

After saving the file, test entries using terminal commands. Ping the hostname with ping example.com to confirm resolution. Alternatively, employ nslookup or dig for detailed DNS lookup information. Changes take effect immediately.

Best practices and troubleshooting

Backup the hosts file before modifications using sudo cp /etc/hosts /etc/hosts.bak. Maintain file permissions at 644 with ownership as root. Syntax errors, such as incorrect IP formatting, cause resolution failures. Check entries thoroughly. Applications may require restarts to recognize new mappings.

The hosts file in CentOS 7 remains a straightforward tool for network management. Proper usage enhances system efficiency without complex dependencies.