Chapter 23, the capstone of the track: the first-week work of a junior operator on server1. Read before changing (ls -l, cat, date -r), save evidence of what runs, what changed and what failed in files (the redirect, uname, id, tail, grep, awk, sort, uniq, diff, date -r, sudo -u, pgrep, ss, ssh-keygen), keep the original (cp, cmp), make bounded changes to a file, permissions and an archive (sed -i or nano, chmod, chgrp, export, gzip, tar, find -exec), verify them (diff and its exit status), trust a host key and deliver over SSH (ssh, scp to the deploy account) and hand over a record (script -c, a note). A 90-minute graded lab of 25 objectives in three tiers.