System Administration

System Administration

System administration maintains Linux systems for reliability, performance, and security.

Package Management

APT (Debian/Ubuntu): apt update/install/upgrade/remove. DNF (RHEL/Fedora): dnf install/update/remove. Snap and Flatpak for universal packages. Handle dependencies and repositories.

Service Management

systemd: systemctl start/stop/restart/status/enable/disable. Unit files in /etc/systemd/system/. journalctl views logs. Service dependencies and targets.

Scheduled Tasks

cron: minute hour day month weekday command. crontab -e. System crontabs in /etc/cron.d/. at for one-time tasks. systemd timers as modern alternative.

Logging

syslog/rsyslog collects logs. journald (systemd) provides structured logging. Key logs: /var/log/syslog, auth.log, kern.log. logrotate manages sizes.

Monitoring

top/htop (processes), vmstat (memory), iostat (disk I/O), free (memory), df/du (disk). Nagios, Zabbix, Prometheus + Grafana for production.

Performance Tuning

Identify bottlenecks: CPU (load average), memory (swap usage), disk I/O (iostat), network (iftop). Tune: sysctl parameters, optimise services, add resources, caching.

Summary

System administration — packages, services, scheduling, logging, monitoring, tuning — keeps Linux systems running reliably.