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+# Linux – Administration
+
+Overview of common Linux administration tasks. Focus on day‑to‑day system management rather than distribution‑specific tools.
+
+For foundational concepts (kernel, filesystem, users, processes), see:
+
+- [Linux / Basics](./Basics.md)
+
+---
+
+## 1. User and Group Management
+
+Linux uses users and groups to control access to files, processes, and services.
+
+Typical administration tasks include:
+
+- Creating and removing users.
+- Adding users to groups (for example to grant `sudo` access).
+- Locking or disabling accounts.
+
+Key ideas:
+
+- Each user has a numeric user ID (UID) and a primary group ID (GID).
+- Additional group memberships are used to grant extra permissions (for example access to Docker or systemd‑journal).
+
+---
+
+## 2. Privileged Access and sudo
+
+Administrative operations are usually performed with elevated privileges.
+
+Approaches:
+
+- Direct `root` login (less common on modern systems for security reasons).
+- Using `sudo` to run specific commands as `root`.
+
+Principles:
+
+- Only trusted users should have `sudo` rights.
+- The set of allowed commands can be restricted via the sudoers configuration.
+
+In practice, administration is often done as an unprivileged user with `sudo` used only when needed.
+
+---
+
+## 3. Filesystem Permissions and Ownership
+
+Correct file and directory permissions are central to system security and stability.
+
+Key aspects:
+
+- Ownership (user and group) defines who primarily controls a resource.
+- Permission bits (read, write, execute) for user, group, and others control what can be done.
+- Special bits (setuid, setgid, sticky) influence execution and inheritance in specific cases.
+
+Administration tasks related to permissions include:
+
+- Adjusting ownership for application data directories.
+- Ensuring configuration files are restricted when they contain secrets.
+- Verifying that log and temporary directories have appropriate access.
+
+Additional reminders and command examples can be kept in:
+
+- [Linux / Cheat Sheet](./CheatSheet.md)
+
+---
+
+## 4. Services and systemd Units
+
+On many modern Linux distributions, **systemd** is used as the init system and service manager.
+
+Concepts:
+
+- A **unit** defines how a service, mount, timer, or other resource is started and managed.
+- Service units (for example `ssh.service`, `docker.service`) describe how to start and stop daemons.
+- Targets group units to represent boot states (for example `multi-user.target`).
+
+Typical administration actions:
+
+- Starting, stopping, and restarting services.
+- Enabling or disabling services at boot.
+- Checking service status and logs.
+
+Systemd units are usually stored under `/lib/systemd/system` or `/etc/systemd/system`. Local overrides can be created without modifying vendor files.
+
+---
+
+## 5. Logs and Troubleshooting
+
+System logs are essential for diagnosing issues.
+
+On systemd‑based systems, the journal stores logs from the kernel and many services.
+
+Common tasks:
+
+- Viewing recent logs for a specific service.
+- Filtering logs by priority or time range.
+- Inspecting boot logs to understand startup problems.
+
+In addition to the journal, many services also write to files under `/var/log`. Knowing where a service writes its logs is an important part of administration.
+
+---
+
+## 6. Software Installation and Updates
+
+Package management is used to install, update, and remove software.
+
+Administration concerns:
+
+- Keeping the system reasonably up to date for security fixes.
+- Avoiding unnecessary packages on minimal or security‑sensitive systems.
+- Understanding which repositories are enabled.
+
+The concrete commands differ per distribution (for example `apt` vs `dnf`), but the underlying tasks are similar.
+
+Distribution‑specific notes and examples can be recorded in a dedicated cheat sheet or in project‑specific documentation.
+
+---
+
+## 7. Scheduled Tasks and Automation
+
+Linux systems provide several mechanisms for scheduled or automated tasks.
+
+Common options:
+
+- `cron` jobs for periodic execution.
+- systemd timers for more structured scheduling tied to units.
+
+These mechanisms are used for activities such as log rotation, backups, or periodic health checks.
+
+---
+
+## 8. Backup and Recovery Considerations
+
+From an administrative perspective, backup and recovery planning includes:
+
+- Identifying which directories and data must be backed up.
+- Choosing backup tools and storage locations.
+- Testing restore procedures.
+
+Details are often project‑specific and can be documented alongside the systems that depend on them (for example in a home‑server or application‑specific section).
+
+---
+
+## 9. Relation to Other Documents
+
+- [Linux / Cheat Sheet](./CheatSheet.md)