Chapter 2: Using Essential Tools

Mastering the fundamental tools every RHEL administrator needs: documentation, editing, and shell operations.

Key Concepts

Getting Help

Tool Purpose Example

man

Manual pages

man passwd, man 5 passwd

info

GNU documentation

info coreutils

--help

Quick reference

ls --help

/usr/share/doc

Package documentation

ls /usr/share/doc/bash

pinfo

Better info reader

pinfo coreutils

Man Page Sections

Section Content Example

1

User commands

man 1 passwd (command)

5

File formats

man 5 passwd (file)

8

Admin commands

man 8 useradd

Hands-On Exercises

Exercise 2.1: Man Page Navigation

# Open man page for passwd command
man passwd

# Navigation:
# /pattern  - search forward
# ?pattern  - search backward
# n         - next match
# N         - previous match
# g         - go to beginning
# G         - go to end
# q         - quit

# Search for password-related pages
man -k password
apropos password

# Find the configuration file section
man 5 passwd

Exercise 2.2: Vim Essentials

# Create practice file
vim /tmp/practice.txt

Vim Modes:

Mode Enter Purpose

Normal

Esc

Navigation, commands

Insert

i, a, o

Text entry

Visual

v, V, Ctrl+v

Selection

Command

:

File operations

Essential Commands:

# Movement
h, j, k, l  - left, down, up, right
w, b        - word forward/back
0, $        - line start/end
gg, G       - file start/end
:n          - go to line n

# Editing
i           - insert before cursor
a           - append after cursor
o           - open line below
O           - open line above
x           - delete character
dd          - delete line
yy          - yank (copy) line
p           - paste after
P           - paste before
u           - undo
Ctrl+r      - redo

# Search/Replace
/pattern    - search forward
?pattern    - search backward
n, N        - next/prev match
:%s/old/new/g - replace all

# File operations
:w          - save
:q          - quit
:wq         - save and quit
:q!         - quit without saving
:w filename - save as

Exercise 2.3: I/O Redirection

# tag::io-redirect[]
# Redirect stdout to file
ls -la > files.txt

# Append stdout to file
echo "new line" >> files.txt

# Redirect stderr to file
find / -name "*.conf" 2> errors.txt

# Redirect both stdout and stderr
find / -name "*.conf" > results.txt 2>&1

# Modern syntax (bash 4+)
find / -name "*.conf" &> all.txt

# Discard output
command > /dev/null 2>&1

# Pipe stdout to another command
ls -la | grep "^d"

# Pipe and tee (split output)
ls -la | tee listing.txt | grep "^d"
# tag::io-redirect[]

Exercise 2.4: Shell Variables

# Set variable
MYVAR="hello world"

# Use variable
echo $MYVAR
echo ${MYVAR}

# Export for child processes
export MYVAR

# Unset variable
unset MYVAR

# Environment variables
env             # list all
printenv HOME   # specific variable

# Important variables
echo $HOME      # home directory
echo $PATH      # executable search path
echo $USER      # current user
echo $SHELL     # current shell
echo $PS1       # prompt string

Exercise 2.5: History and Shortcuts

# History operations
history         # show history
!n              # execute command n
!!              # execute last command
!string         # execute last command starting with string

# Keyboard shortcuts
Ctrl+a          # beginning of line
Ctrl+e          # end of line
Ctrl+u          # delete to beginning
Ctrl+k          # delete to end
Ctrl+w          # delete word backward
Ctrl+r          # reverse search history
Ctrl+l          # clear screen
Ctrl+c          # cancel current command
Ctrl+d          # exit shell

Diagram: I/O Streams

D2 Source (render with Kroki or d2 CLI)
# I/O Streams in Linux
# Edit this D2 diagram as you learn

direction: right

title: Standard I/O Streams {
  shape: text
  style.font-size: 24
}

# Input/Output model
process: Process {
  shape: rectangle
  style.fill: "#e3f2fd"
  style.stroke: "#1565c0"
  style.stroke-width: 2
}

stdin: stdin (0) {
  shape: parallelogram
  style.fill: "#c8e6c9"
}

stdout: stdout (1) {
  shape: parallelogram
  style.fill: "#fff9c4"
}

stderr: stderr (2) {
  shape: parallelogram
  style.fill: "#ffcdd2"
}

keyboard: Keyboard {
  shape: cylinder
  style.fill: "#e0e0e0"
}

terminal: Terminal {
  shape: cylinder
  style.fill: "#e0e0e0"
}

file: File {
  shape: document
  style.fill: "#f3e5f5"
}

pipe: "| (pipe)" {
  shape: hexagon
  style.fill: "#b3e5fc"
}

# Connections
keyboard -> stdin: "default input"
stdin -> process
process -> stdout
process -> stderr
stdout -> terminal: "default output"
stderr -> terminal: "default errors"

# Redirection examples
stdout -> file: "> redirect"
stdin <- file: "< redirect"
stdout -> pipe: "to next command"

# Legend
legend: {
  label: File Descriptors
  style.fill: "#fafafa"

  fd0: "0 = stdin  (input)"
  fd1: "1 = stdout (output)"
  fd2: "2 = stderr (errors)"
}

Notes

Add your personal notes here as you work through the chapter.

What Worked

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What Broke

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Key Takeaways

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