Linux Fundamentals & Shell Mastery covers: How Linux Works, Linux Basics, Hands-on DevOps with Linux. Understand how Linux works at the level of processes, filesystems, users, permissions, and systemd. Write shell scripts that automate real tasks. Become comfortable living in the terminal.
Rails runs on Linux. Understanding processes, file descriptors, and signals helps you debug Puma and Sidekiq in production. When Puma's worker gets killed by the OOM killer, you need to understand /proc/<pid>/oom_score. When Sidekiq stops processing jobs, you need ps aux | grep sidekiq and kill -USR1. When disk fills up because of log rotation failure, you need to understand /var/log and logrotate. Module 0 gives you these skills.
| Rails Situation | Linux Skill |
|----------------|-------------|
| Puma memory bloat | ps aux, /proc/pid/status, OOM killer |
| Sidekiq stuck jobs | kill -USR1, strace -p |
| Disk full | df -h, du -sh, logrotate |
| Permission denied | chmod, chown, ls -la |
| App won't start on boot | systemd, journalctl -u myapp |
| SSH key issues | ~/.ssh/authorized_keys, sshd_config |
You have been SSH-ing into servers for years. You have restarted Puma, tailed logs, killed runaway processes, and grepped through production output at 2 AM. But here is the thing …
There is a machine in Helsinki, or Virginia, or Frankfurt, and your Rails app lives on it. Not metaphorically — a Linux kernel on that machine is scheduling your Puma workers onto…
Here is an uncomfortable exercise. Without looking anything up: make a file readable by your deploy user but writable only by root. Extract the fifth column from a log file, count…
Somewhere in your history there is a server-setup ritual you have performed by hand more than once: install Ruby, create the deploy user, configure PostgreSQL, set up Nginx, wire …
Work through each item before the checkpoint.
Provision an Ubuntu box by hand — no Docker, no Capistrano — and understand every step: the deploy user, file permissions, systemd services, log rotation, and firewall rules. You …
6 lessons. Read in order; spiral back when you need to. By the end you'll have used the core ideas twice — once on the abstract, once on something you'll meet at work next week.