Security auditing is the practice of recording and reviewing system calls, file accesses, user actions, and configuration changes to detect policy violations, investigate incidents, and demonstrate compliance with standards like PCI DSS, HIPAA, and SOC 2. On RHEL 9, the Linux Audit Framework — provided by the auditd daemon — captures events at the kernel […]
Every Linux administrator needs at least one terminal text editor in their toolkit. When a remote server is accessible only via SSH with no GUI, when a configuration file needs editing before a service can start, or when you are recovering a broken system from a rescue shell, your text editor is your primary interface. […]
The Linux kernel’s systemd journal is a structured binary log that stores the output of every service, kernel message, boot sequence, and user session. Unlike traditional text-based syslog, the journal stores metadata alongside each log entry — the unit name, PID, UID, executable path, systemd unit state, and priority level — enabling far more precise […]
Running out of disk space is one of the most disruptive failures a server can experience. When a filesystem fills up, applications crash, log files stop writing (losing audit trails), databases corrupt transactions, and web servers return 500 errors. Proactive disk monitoring is essential — and RHEL 9 provides a full set of tools for […]
Automated task scheduling is the backbone of server maintenance: backups run at 3 AM, log cleanup happens daily, SSL certificates renew before they expire, and databases are vacuumed weekly. On RHEL 9, there are three scheduling mechanisms each suited to different scenarios. cron is the classic daemon that runs jobs on a schedule defined by […]
rsync is the Swiss Army knife of file synchronisation for Linux administrators. Unlike scp, which blindly copies every file every time, rsync computes a rolling checksum to identify changed file blocks and transfers only what has changed — making subsequent syncs dramatically faster and less bandwidth-intensive. It preserves file attributes (permissions, ownership, timestamps, ACLs, extended […]
DNS resolution on a Linux server is a multi-layered system. When an application calls getaddrinfo(“example.com”), the request passes through the Name Service Switch (NSS) framework, which consults sources in the order defined in /etc/nsswitch.conf — typically /etc/hosts first, then a DNS resolver. The DNS resolver reads its configuration from /etc/resolv.conf, which lists the DNS servers […]
While the earlier tutorial in this series covered the core useradd, usermod, and userdel tools for user lifecycle management, this guide goes deeper into the full toolkit for managing users and groups at scale on RHEL 9: bulk creation, password management with chpasswd, group administration with gpasswd, per-user resource limits with ulimit and /etc/security/limits.conf, user […]
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 […]
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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