Linux Hostname Verification: FQDN, DNS Identity, and Reverse DNS Checks

Why Hostname Matters

A correctly configured hostname is essential for SSL certificate validation, email delivery (SPF/DKIM), service discovery, and cluster communication. Misconfigurations can cause subtle and hard-to-diagnose issues.

Checking Hostname

hostname
hostname -f  # FQDN
hostname -I  # IP addresses
hostnamectl

Verifying /etc/hosts

cat /etc/hosts
# Should contain:
# 127.0.0.1 localhost
# server-ip hostname.domain.com hostname

DNS Resolution Verification

dig +short $(hostname -f)
nslookup $(hostname -f)
getent hosts $(hostname -f)

Reverse DNS Check

dig -x $(hostname -I | awk "{print \$1}")
host $(hostname -I | awk "{print \$1}")
nslookup $(hostname -I | awk "{print \$1}")

Automated Verification with dargslan-hostname-check

pip install dargslan-hostname-check
dargslan-hostname-check
dargslan-hostname-check --dns
dargslan-hostname-check --reverse