Linux 🐧
Linux system administration, internals, and tooling for cloud-native engineering.
Start Here — Concepts Curriculum
The concepts section is a progressive curriculum from filesystem fundamentals to processes, services, and networking:
- 01 — Filesystem Hierarchy (
/etc,/var,/usr,/dev,/proc) - 02 — File Permissions (
rwx,chmod,chown,umask, ACLs) - 03 — Processes (PID, parent/child, zombies, daemons)
- 04 — Users & Groups (
/etc/passwd,/etc/shadow, sudo) - 05 — Package Management (
apt,pacman, repositories) - 06 — Services & systemd (
systemctl, service units) - 07 — Boot Process (BIOS/UEFI → GRUB → Kernel → systemd)
- 08 — Logging (
journalctl,/var/log, logrotate) - 09 — Networking Basics (IP, CIDR, gateway, DNS,
ss,curl) - 10 — Storage Basics (Disks, partitions, filesystems, LVM)
- 11 — Shell Basics (
bash, environment, PATH, pipes) - O Redirection (
stdin,stdout,stderr,tee,xargs)
Core Domains & Reference
1. Kernel Internals
Kernel architecture, cgroups v1 & v2, /proc and /sys virtual filesystems, signals, IPC, and process scheduling.
2. Networking & Firewalls
TCP/IP datapath, routing tables, iptables, nftables, firewalld, DNS resolution (systemd-resolved), netplan, and network tuning (sysctl).
3. Storage & Filesystems
Block storage, partition schemes (GPT/MBR), LVM (PV/VG/LV), RAID arrays, filesystems (ext4, xfs, btrfs), mount options, and /etc/fstab.
4. Identity, PAM & Permissions
User/group management, service accounts (nologin), sudoers policy, PAM authentication modules, and user namespaces.
5. Boot, Init & Scheduling
System initialization, GRUB2 configuration, systemd target units, systemd timers, cron & anacron, and ephemeral cleanup (systemd-tmpfiles).
6. Hardening & Sandboxing
Linux Capabilities (cap_net_admin, cap_sys_admin), seccomp syscall filtering, AppArmor profiles, auditd logging, immutable files (chattr +i), core dump restriction, and CIS benchmark baselines.
7. Containers & Virtualization
Container runtimes (runc, containerd), Linux namespaces (mount, PID, net, IPC, UTS, user), overlayfs storage driver, Podman rootless containers, and KVM/QEMU hypervisors. The Containers section builds on these: namespaces and cgroups, images and container networking.
8. Package Management
Package managers and repository infrastructure: apt (Debian/Ubuntu), pacman (Arch), yum/dnf (RHEL/Fedora), and low-level package tooling.
9. System Observability & Tracing
Performance monitoring and diagnostics: top, htop, vmstat, iostat, sar, strace, lsof, and eBPF tracing tools.
10. Shell Scripting & Productivity
Bash automation patterns, error handling (set -euo pipefail), traps, subshells, arrays, string manipulation, and terminal productivity with tmux.
11. Troubleshooting Methodology
Systematic root cause analysis playbooks for high CPU/load, OOM killer triggers, disk saturation, networking latency, and broken boot states.
Related Topics
- ☸️ Kubernetes — Node kubelets, cgroups, network namespaces, and container runtimes run on Linux.
- ☁️ AWS — EC2 Amazon Linux 2023, Ubuntu, and container hosts.
- 🚀 DevOps — CI/CD runner environments, shell scripting, and DevSecOps runtime hardening.
- 🔐 Security — Host IDS/IPS, Wazuh agent integration, and endpoint hardening.