Logging Monitoring

How to Configure the Firewall on RHEL 9 with firewalld — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure the Firewall on RHEL 9 with firewalld

Red Hat Enterprise Linux 9 uses firewalld as its default firewall management daemon, backed by nftables as the kernel netfilter framework (replacing iptables which was the default in RHEL 7 and earlier). firewalld provides a zone-based model where each network interface is assigned to a trust zone — public, internal, dmz, trusted, and more — […]

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How to Set Up SSH Key-Based Authentication on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Set Up SSH Key-Based Authentication on RHEL 9

SSH key-based authentication is the gold standard for remote server access. Unlike passwords, SSH keys cannot be guessed by brute-force attacks. An Ed25519 private key is a 256-bit secret that would take longer than the age of the universe to crack by exhaustive search. When combined with a key passphrase, you have two-factor authentication: something […]

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How to Configure Fail2Ban to Protect SSH on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure Fail2Ban to Protect SSH on RHEL 9

Even with SSH key authentication enabled, a badly configured or temporarily accessible server with password auth still faces a constant barrage of brute-force login attempts. Fail2ban monitors log files for authentication failures, counts them per source IP, and when a configured threshold is crossed it issues a temporary ban by injecting a drop rule via […]

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How to Set a Hostname and FQDN on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Set a Hostname and FQDN on RHEL 9

A server’s hostname is its identity on the network. The fully qualified domain name (FQDN) combines the short hostname with the DNS domain, forming an address like web01.example.com. Many services depend on a correctly configured hostname and FQDN to function properly: email servers use the FQDN in SMTP HELO greetings (incorrect values cause delivery rejections), […]

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How to Sync Time with Chrony on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Sync Time with Chrony on RHEL 9

Accurate time synchronization is not optional on a server — it is a hard requirement. TLS certificate validation fails when the clock is wrong by more than a few minutes. Kerberos authentication rejects tickets with a clock skew over 5 minutes. Cron jobs fire at the wrong time. Log correlation across multiple servers becomes impossible […]

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How to Configure Automatic Security Updates on RHEL 9 — step-by-step RHEL 9 tutorial on Progressive Robot

How to Configure Automatic Security Updates on RHEL 9

Unpatched software is the leading cause of server compromise. The majority of publicly disclosed vulnerabilities already have patches available by the time attackers start actively exploiting them — the window between patch availability and active exploitation has shrunk from months to days. Manually patching servers is error-prone and inconsistent at scale. Automatic security updates ensure […]

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