Linux

Start Here — Concepts Curriculum

The concepts section is a beginner curriculum — work through it in order if you’re starting out, or use it as a reference. It progresses from filesystem basics through to services, networking, and shell skills.

01-filesystem-hierarchy.md    — /etc, /var, /usr, /dev, /proc explained
02-file-permissions.md        — rwx, chmod, chown, umask, ACLs, special bits
03-processes.md              — PID, parent/child, zombies, daemons
04-users-and-groups.md        — /etc/passwd, /etc/shadow, /etc/group, sudo
05-package-management.md      — apt, pacman, dnf — packages and repositories
06-services.md               — systemd, systemctl, service files
07-boot-process.md           — BIOS/UEFI → GRUB → kernel → systemd
08-logging.md                — journalctl, /var/log, logrotate, binary logs
09-networking-basics.md       — IP, subnet, gateway, DNS, curl, ss
10-storage-basics.md          — disks, partitions, filesystems, mount, fstab, LVM
11-shell-basics.md           — bash, environment, PATH, aliases, history, pipes
12-io-redirection.md         — stdin/stdout/stderr, pipes, tee, xargs, here-docs

Sections

Concepts — Beginner curriculum

Fundamentals: filesystem hierarchy, permissions, processes, users/groups, packages, services, boot, logging, networking, storage, shell, I/O redirection. Also: hardlinks/softlinks, ulimit, TTY/PTY, tmpfs, sockets, spool directory.

Kernel — Kernel internals

cgroups, /proc & /sys, signals, process management. Reference material for after you’ve gone through the concepts curriculum.

Networking — TCP/IP, firewall, DNS

TCP/IP model, routing, iptables, firewalld, DNS resolution, ip command, dhcp, netplan, ss, network performance tuning.

Storage — Disks, LVM, filesystems

Disks and partitions, LVM, RAID, filesystems (ext4, xfs, btrfs), mount and fstab, storage performance tuning.

Users & Groups — Identity and PAM

User management, nologin accounts, sudo, /etc/passwd, /etc/shadow, /etc/group.

Boot & Init — Boot, systemd, scheduling

Boot process, systemd, cron and anacron, systemd timers, systemd-tmpfiles, nohup and disown.

Security — Hardening and access control

Capabilities, seccomp, AppArmor, auditd, chattr/lsattr, core dumps, device files, sysctl tuning, systemd service hardening, Linux CIS hardening, container security.

Virtualization — Containers and hypervisors

Container runtimes (runc, containerd), podman, namespaces (mount, user, network), overlayfs, systemd-nspawn, hypervisors, emulator vs virtualization.

Packaging — apt, pacman

apt, pacman — package management, repositories, AUR.

Observability — Monitoring and tracing

top, vmstat, iostat, sar, strace, journalctl, log management.

Shell Scripting — Bash scripting

bash cheatsheet, shell redirection, here-docs, process substitution, shell expansion, exit codes.

Troubleshooting — Debugging methodology

Systematic debugging, common issues, diagnosis framework.