Shell commands, files, permissions, processes, services, logs, SSH, cron and server maintenance.
- Start here: Learn what Linux is, why servers use it, and how the command line helps you control a machine.
- Core knowledge: Understand files, directories, permissions, users, package managers, and shell commands.
- Hands-on skill: Practice creating files, navigating systems, installing software, and fixing simple errors from the terminal.
- Applied understanding: Learn process management, service setup, SSH, logs, backups, and remote server administration.
- Advanced professional level: Explore scripting, system tuning, systemd, automation, security hardening, and enterprise Linux operations.
The Shell
The shell lets you control the system with commands. Common commands include ls to list files, cd to move folders, cp to copy, grep to search and sudo to run privileged actions.
Files and Permissions
Linux treats almost everything as a file. Permissions decide who can read, write or execute. For example, a web server should read website files but should not have permission to rewrite system files.
Processes and Services
A process is a running program. A service is a process managed by the operating system, often through systemd. You can check a service with systemctl status nginx and inspect logs with journalctl.
Real-World Example
An admin SSHs into the server, checks disk space, verifies the web service status, reviews recent logs and restarts only the failed service. Good Linux troubleshooting is calm, observable and reversible.
Automation
Cron runs scheduled jobs, such as backups or report generation. Shell scripts combine commands so repeatable work can be automated and reviewed.
Beginner Checklist
- Practice navigation and file editing.
- Learn permissions and ownership.
- Use SSH keys instead of passwords.
- Read logs before restarting services.
- Automate one repeated task with a script.
Linux is a predictable operating system for controlling files, processes, users and services.
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