Summary of IT Troubleshooting and Technical Documentation

## Introduction System administration is the practice of keeping computer systems and services configured, running, and secure so users and applications can work reliably. A system administrator focuses on installing, configuring, and maintaining software and hardware, automating routine tasks, and responding to incidents. This guide covers core system administration concepts and tools to build practical skills for self-directed learners. ## Core responsibilities of a system administrator - Provisioning and installing systems and applications - Managing user accounts and permissions - Ensuring backups and recovery procedures work - Monitoring system health and performance - Applying updates and security patches - Automating routine tasks with scripts > Definition: System administration is the set of activities and practices that ensure computer systems and services operate reliably and securely for users and applications. ## Installation and configuration ### Installation guides and runbooks - An **installation guide** provides step-by-step instructions to set up a system or application. It lists prerequisites, configuration steps, verification checks, and rollback options. - A **runbook** documents routine operational procedures and incident response steps so staff can repeat tasks consistently. > Definition: Installation guide — A step-by-step document instructing how to set up a system or application. > Definition: Runbook — A documented procedure for a common IT operation or incident response. Practical example: 1. Read the installation guide for Database X to confirm supported OS and required packages. 2. Follow the guide to install dependencies, install the database, and apply initial configuration. 3. Run post-install checks from the runbook to verify that connections, authentication, and backups work. ## Network-related commands and tools (brief practical notes) Note: This section highlights tools a sysadmin often runs locally to inspect and troubleshoot host network settings and connectivity. > Definition: ipconfig — Windows command that displays IP configuration for all network interfaces. > Definition: ifconfig — Linux/macOS command that displays and configures network interface IP settings. > Definition: nslookup — Command-line tool for querying DNS servers to resolve hostnames to IP addresses. > Definition: ping — Command that sends ICMP echo requests to a host to test reachability and measure latency. > Definition: tracert / traceroute — Command that displays the sequence of routers a packet traverses to reach a destination. Real-world usage examples: - Run `ipconfig` on Windows or `ifconfig` on Linux/macOS to confirm the assigned IP address before registering a host in DNS. - Use `nslookup` to verify that a hostname resolves to the expected IP before updating a service configuration. - Use `ping` to verify basic reachability; combine with RTT (round-trip time) to judge latency. - Use `tracert`/`traceroute` to inspect the path to a remote host and identify intermediate hops. ## System addressing terms - **Default gateway**: the router address a device sends traffic to when the destination is outside the local network. > Definition: Default gateway — The router address a device sends traffic to when the destination is outside the local network. - **Hop**: one router along the path between source and destination. > Definition: Hop — One step in a network path — one router that forwards a packet toward its destination. - **TTL (Time To Live)**: a counter in IP packets that decrements at each hop; a packet is discarded when TTL reaches zero. > Definition: TTL — A counter in IP packets that decrements at each hop; the packet is discarded when TTL reaches zero. ## Memory and storage concepts - **RAM (Random Access Memory)**: fast, temporary memory used to store running programs and active data. > Definition: RAM — Fast, temporary computer memory used to store running programs and data. - **Swap /