Linux Intermediate

What is Journalctl?

A command-line tool for querying and viewing logs collected by systemd's journal logging system.

Journalctl provides structured log access. Common usage: journalctl -u nginx (service logs), journalctl --since "1 hour ago" (time-based), journalctl -f (follow/tail), journalctl -p err (priority filtering).

The journal stores logs in a binary format, enabling fast querying, filtering by service/priority/time, and automatic log rotation. It replaces traditional text-based syslog for many use cases.

Related Terms

The modern Linux packet filtering framework that replaces iptables with a unified, more efficient rule-processing architecture.

The superuser account in Unix/Linux systems with unrestricted access to all commands and files.

A command-line tool that displays network connections, routing tables, and interface statistics on a system.

File Permissions

A security mechanism that controls who can read, write, or execute files and directories in Unix-like systems.

A powerful command for searching files and directories based on various criteria like name, size, type, and modification time.

The time specification format used in cron job scheduling, with five fields defining minute, hour, day of month, month, and day of week.

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