Linux Speedrun

核心 · Key Idea

In one line: the Linux philosophy is "everything is a file + small composable tools". Master a few dozen commands plus redirection and pipes and you can do 90 % of day-to-day ops.

Directory layout (FHS)#

/etc       Global config (nginx.conf, systemd units)
/var       Variable data (logs in /var/log, DBs in /var/lib)
/usr       Distro programs and libraries
/opt       Third-party self-contained apps
/home      User home directories
/root      Root user's home
/tmp       Temp files, wiped on reboot
/proc /sys Kernel virtual filesystems (process info / kernel knobs)

Every file / device / network socket appears as a path — that's "everything is a file".

Analogy#

打个比方 · Analogy

Linux is a box of Lego bricks — each command (grep / sort / awk) is one brick; pipe them together with | to build any shape. Windows leans toward "one giant app solves everything".

Redirection and pipes#

cmd > file       # stdout to file (overwrite)
cmd >> file      # append
cmd 2> err.log   # redirect stderr
cmd > out 2>&1   # both into out
cmd1 | cmd2      # cmd1's stdout becomes cmd2's stdin
< file cmd       # stdin from file

| is Linux's most powerful idea:

ps aux | grep nginx | awk '{print $2}' | xargs kill -9

How it works#

Each command is a fork + exec'd process; stdin / stdout / stderr are its "three pipes".

Practical notes#

man cmd / tldr cmd — man is canonical; tldr is a quick cheatsheet of common usage.
Use xargs to convert stdin to arguments: find . -name '*.log' | xargs rm -f.
rm -rf cautiously — especially with variables. Echo first: echo rm -rf "$DIR"/*.
Env vars: export VAR=val for the current shell; persist in ~/.bashrc / ~/.zshrc.
Background: cmd & runs in background; nohup cmd > log 2>&1 & survives logout. In production use systemd.
History search: Ctrl+R reverse-searches your history — far faster than ↑.

Easy confusions#

bash

Default on nearly every distro.
Best script compatibility.

zsh

macOS default; oh-my-zsh is delightful.
Slight script-syntax drift from bash.