Linux & the Command Line

You can open a terminal today and immediately move around, view files, and chain commands with pipes, before anything else on this path assumes you can.

Now that you can move around, learn where things actually live: config in /etc, logs in /var, binaries on your PATH, so a 'command not found' stops being a mystery.

This is where the permission model finally clicks: once chmod's octal math stops feeling arbitrary, every 'permission denied' becomes a two-second fix, though it's normal to come back and recheck this a few times.

A command that works today and vanishes tomorrow is almost always a PATH or .bashrc problem, and this step is what lets you fix that instead of just restarting your terminal and hoping.

Once you know where config lives, the next skill is finding anything else on disk in seconds with find and its filters, instead of scrolling through ls by hand.

This is the second click moment on this path: once regex stops looking like line noise, grep, sed, and awk turn any text file into data you can filter and reshape, and it's normal to reread this one more than once before it sticks.

Chain what grep, sed, and find just taught you into a script that runs itself on a schedule, turning a five-minute manual chore into a one-time five-minute build.

A frozen terminal or a runaway process is no longer a reason to reboot: you can see what's running, read its state, and send it the right signal instead of always reaching for kill -9.

Every process and permission you've touched so far traces back to a UID, so this step is where you start creating and managing the accounts and sudo rules behind them yourself.

Installing software stops being a copy-pasted command you don't understand once you know how apt, dnf, or pacman actually resolve dependencies and where they pull packages from.

The processes you learned to inspect two steps back are mostly started and supervised by systemd, so this is how you make a service survive a crash or a reboot instead of dying with your shell.

A full disk or a failed mount is now something you diagnose with df, lsblk, and fstab, rather than a mystery that ends with a support ticket.

Reach for this if you're heading toward managing real servers: LVM lets you resize a volume while it's still mounted, going deeper than the plain partitioning step 12 covered.

Whatever storage and services you've built so far are useless if you can't reach them, so this is how you read an interface, a route, and a socket with ip and ss.

The networking you just learned is how you reach a server; SSH is how you reach it securely, log in without a password, and tunnel a port through a bastion host.

An SSH port open to the whole internet is a liability, so this step is where you write the firewall rules that decide what's allowed to reach your services at all.

Take this if you're heading toward hardened production systems: SELinux and AppArmor stop a compromised service from touching files or ports even after the firewall rules from step 16 let its traffic through.

Pick this up if you want a faster daily driver: Oh My Zsh layers autocompletion, themes, and plugins on top of the shell configuration you set up back in step 4.

Every piece from user accounts to firewall rules finally comes together here as one sysadmin workflow you can run start to finish on a real box, from first login to hardened service.