Administration

The ongoing-maintenance side of running a Linux system, once it's installed, configured, and online.

• Backups

  A backup that's never been tested to restore isn't a backup - the 3-2-1 rule as a baseline strategy, and the standard Linux tools (rsync, tar) for actually implementing it.

• Cron and Scheduled Tasks

  Two ways to run something on a schedule on Linux - the traditional cron daemon with its terse five-field syntax, and systemd timers as the newer systemd-native alternative.

• Kernel and System Updates

  The kernel updates separately from installed applications, as its own package - and unlike most updates, doesn't take effect until a reboot, because the running kernel stays loaded in memory regardless of what gets installed on disk.

• Logs and journald

  Where Linux logs actually live and how to read them - journald's structured, queryable log on systemd systems, alongside the traditional plain-text files under /var/log that many tools still expect.

• Monitoring and Performance

  The core commands for understanding what a Linux system is doing right now - CPU load, memory use, disk space, and which specific process is responsible.

• Time Synchronization (NTP/chrony)

  Clock drift silently breaks TLS certificate validation, cron scheduling, log correlation across machines, and time-based auth tokens - chrony (or the lighter systemd-timesyncd) keeps a machine's clock synced to a reliable external source automatically.