Developer
dev- Git, build tools, and package managers from the CLI
- Process management for local dev servers
- Pipes, grep, sed, awk for log parsing
- Environment variables and shell scripting
man 1 universe
Master the Unix foundation
Every cloud VM, CI runner, container, and macOS terminal runs on ideas born at Bell Labs in 1969. Unix Core teaches the architecture, file system, processes, and commands that power modern infrastructure— with practical examples, not textbook theory.
UnixCore Terminal Playground
A simulated bash environment with realistic output and tips for every command. Type real Unix commands, use Tab completion, ↑↓ history, and Ctrl+L to clear. Open the full-screen terminal for distraction-free practice.
What is Unix?
Unix is a family of multitasking, multi-user operating systems built around a small kernel, a shell interface, and composable command-line tools. Linux, macOS, BSD, and most cloud infrastructure inherit its design: everything is a file, small programs do one thing well, and text streams connect them.
┌─────────────────────────────────────────────────────────┐ │ Applications git · nginx · python · docker · ssh │ ├─────────────────────────────────────────────────────────┤ │ Shell bash · zsh · sh (command interpreter) │ ├─────────────────────────────────────────────────────────┤ │ Kernel syscalls · scheduler · VFS · networking│ ├─────────────────────────────────────────────────────────┤ │ Hardware CPU · RAM · disk · NIC · devices │ └─────────────────────────────────────────────────────────┘
bash
# See the kernel version and architecture
uname -a
# List open files (everything is a file)
lsof -p $$
# Trace system calls made by ls
strace -e openat,read,write ls /etc 2>&1 | headA brief history
From a skunkworks project at Bell Labs to the backbone of the internet—understanding the lineage explains why macOS feels familiar to Linux admins and why POSIX still matters.
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1969
Bell Labs — Unix born
Ken Thompson and Dennis Ritchie create Unix on a PDP-7. The C language and pipe abstraction follow, shaping how we compose programs today.
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1977–1990s
BSD branch
Berkeley Software Distribution adds TCP/IP, vi, and the BSD socket API. FreeBSD, OpenBSD, and NetBSD carry this lineage; macOS/Darwin is BSD-derived.
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1991
Linux kernel
Linus Torvalds releases a free Unix-like kernel. GNU tools + Linux kernel = the Linux distros (Ubuntu, RHEL, Alpine) that run most servers and containers.
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2001–today
macOS & the cloud
Apple ships Darwin (BSD + Mach kernel) as macOS. AWS, GCP, and Azure run Linux at scale. Developers touch Unix daily—even on Windows via WSL.
Built for three personas
Every guide and command entry is tagged so you can focus on what matters for your role. Filter by persona on the Commands page.
System Administrator
sysadmin- Users, groups, permissions, and sudo
- systemd services, cron, and log rotation
- Package management across distros
- journalctl and /var/log troubleshooting
Infrastructure / DevOps
infra- Disk, mount points, and LVM basics
- Networking: ip, ss, curl, ssh, rsync
- Performance: vmstat, iostat, dmesg
- Containers share the host kernel—Unix matters
Explore the guide
Work top-down (architecture → file system → processes) or jump straight to the command reference.
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Unix Architecture
Kernel layers, subsystems, and the system call interface—open, read, write, fork, exec—with diagrams.
dev infra -
File System
FHS directory tree, inodes, links, permissions, and the "everything is a file" philosophy.
sysadmin dev -
Process Management
fork/exec lifecycle, process states, foreground vs background, and signals.
dev sysadmin -
Commands Reference
100+ commands with syntax, examples, pro tips, and persona filters. Searchable.
dev sysadmin infra -
Shell & Scripting
bash vs zsh, variables, pipes, redirection, and your first production-ready script.
dev -
Cheat Sheets
Printable, copyable quick references—one per persona with the most-used flags.
dev sysadmin infra
Warning: Commands like rm -rf / and dd if=/dev/zero of=/dev/sda can destroy systems. We call these out explicitly wherever they appear—always double-check paths and disks.