OS
4 sub-sections
Operating Systems#
Quick-reference cheat sheets for the command-line tools and workflows used across Linux, Windows, z/OS, and macOS. Each section covers the core utilities, package managers, and scripting patterns specific to that platform.
What’s in this section#
| Platform | Key topics |
|---|---|
| Linux | grep · ripgrep · sed · awk · find · fd · git · curl · wget · apt-get · jq · ffmpeg |
| Windows | PowerShell · winget · WSL interop · beets · yt-dlp |
| z/OS | JCL · REXX · TSO/ISPF · FTP |
| macOS | macOS CLI · sips · Homebrew · launchctl |
Sections#
- Linux — Shell utilities, text processing, package management, and system tooling for Debian/Ubuntu-based systems.
- Windows — PowerShell scripting, the Windows Package Manager, WSL interoperability, and multimedia tools.
- z/OS — Mainframe essentials: JCL job control, REXX scripting, TSO/ISPF navigation, and dataset FTP transfers.
- macOS — Terminal productivity, built-in image tools, and macOS-specific CLI workflows.
[!TIP] Many Linux commands work identically inside WSL on Windows and in the macOS Terminal — start with the Linux section if you’re new to the command line.
Articles in this section (5)
Filesystems — Inodes, Links, Journaling, ext4/XFS/Btrfs/ZFS/APFS/NTFS
Core filesystem concepts every operator should know: inodes, directory structure, hard vs symbolic links, journaling, copy-on-write, and a head-to-head of ext4, XFS, Btrfs, ZFS, APFS, and NTFS with mount options and pitfalls.
Processes — Fork, Exec, Signals, Zombies, Cgroups
Process lifecycle on Unix: fork/exec/wait, PIDs, signals, zombies and orphans, parent/child trees, process groups, sessions, controlling terminals, and a tour of Linux cgroups.
Memory Management — Virtual Memory, Paging, Swap, OOM, mmap
How operating systems give every process its own address space: virtual memory and paging, swap, the OOM killer, mmap, copy-on-write, the page cache, allocator choices (glibc, jemalloc, mimalloc), and how to read memory counters in top, ps, and free.
Networking Stack — OSI/TCP-IP, Sockets, TCP/UDP, MTU, NAT, DNS
How packets actually move: the OSI and TCP/IP layer models, the BSD socket API, TCP vs UDP, the three-way handshake, MTU/MSS, NAT and port translation, basic IP routing, and the full DNS resolution flow.
Security Fundamentals — Users, Permissions, Capabilities, MAC, Sandboxing
OS-level security primitives every operator should know: users and groups, file permissions, Linux capabilities, SUID/SGID, mandatory access control (SELinux, AppArmor), sandboxing concepts, least privilege, and encryption at rest vs in transit.