Network configuration on RHEL 9 is managed by NetworkManager, and the primary tools for working with it are nmcli (NetworkManager Command-Line Interface) and the traditional ip command from the iproute2 package. Understanding both is essential: nmcli creates persistent network profiles that survive reboots and are managed by NetworkManager, while the ip command makes temporary changes […]
dnf (Dandified YUM) is the default package manager for RHEL 9 and the successor to yum. It handles installing, updating, removing, and querying RPM packages from local and remote repositories, resolving dependencies automatically using the libsolv library, and supporting transactions that can be rolled back if something goes wrong. For Red Hat Enterprise Linux, packages […]
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 […]
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 […]
Swap space acts as overflow memory. When the physical RAM is full, the Linux kernel moves the least-recently-used memory pages to swap on disk, freeing physical RAM for active processes. Without swap, when RAM is exhausted the Out of Memory (OOM) killer terminates processes — often the largest one, which is frequently your database or […]
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