Mastering man Pages Part 2: Sections and Advanced Usage for LFCS

# Task 1: Section 8 user commands
man -k user | grep "(8)"
# Output shows: useradd, userdel, usermod, etc.

# Task 2: /etc/group man page
man -k group | grep "(5)"
# Or directly:
man 5 group

# Task 3: Compare crontab sections
man 1 crontab
# Press q

man 5 crontab
# Press q

cat << 'EOF'
Comparison:
- man 1 crontab: How to use the crontab command
  - crontab -e (edit)
  - crontab -l (list)
  - crontab -r (remove)

- man 5 crontab: Format of crontab files
  - Field 1: Minute (0-59)
  - Field 2: Hour (0-23)
  - Field 3: Day of month (1-31)
  - Field 4: Month (1-12)
  - Field 5: Day of week (0-7)
  - Field 6: Command to execute
EOF

# Task 4: Find all section 5 man pages
man -k . | grep "(5)" | wc -l
# Shows count

man -k . | grep "(5)" | head -20
# Shows first 20

# Task 5: Document findings
cat << 'EOF'
Key Differences by Section:
- Section 1: Commands you RUN
- Section 5: Files you EDIT
- Section 8: Admin commands (require sudo)

Always use section 5 for configuration files!
EOF

# Task 1: Archive commands
man -k archive
# Finds: tar, zip, gzip, bzip2, ar, etc.

man -k compress
# Alternative search

# Task 2: Network configuration
man -k network | grep "(8)"
# Shows network admin commands

man -k "network config"
# More specific search

# Task 3: Password-related pages
man -k password
# Lists all password-related man pages

man -k password | wc -l
# Count them

# Task 4: Count all man pages
man -k . | wc -l
# Note: . matches everything

# Alternative:
man -k "" | wc -l

# Task 5: Find dates (requires looking at man page files)
ls -lt /usr/share/man/man1 | head
# Newest in section 1

ls -ltr /usr/share/man/man1 | head
# Oldest in section 1

# Find specific man page modification date
stat /usr/share/man/man1/ls.1.gz

# Task 1: Check database status
# Try a search first
man -k test_command_that_does_not_exist
# If you see "nothing appropriate", database may need update

# Task 2: Update database
sudo mandb
# Wait for completion (may take 30 seconds to 2 minutes)

# Output shows:
# Processing manual pages under /usr/share/man...
# Updating index cache...

# Task 3: Verify update
man -k ls | grep "^ls "
# Should show: ls (1) - list directory contents

# Task 4: Find database location
sudo find /var -name "index.db" 2>/dev/null
# Or:
sudo find /var/cache/man -type f 2>/dev/null

# Common locations:
ls /var/cache/man/index.db  # Debian/Ubuntu
ls /var/cache/man/*/index.db  # RHEL/CentOS

# Task 5: Test before/after
# Simulate "before" by using stale search
man -k very_specific_command_xyz
# Should show "nothing appropriate" or relevant results

# After mandb:
sudo mandb
man -k ls
# Should show results

# Task 1: Section 5 config pages
man -k config | grep "(5)"
# Or more specific:
man -k configuration | grep "(5)"
man -k . | grep "(5)" | grep -i config

# Task 2: Disk management (section 8)
man -k disk | grep "(8)"
# Common results: fdisk, mkfs, parted, lsblk

man -k partition | grep "(8)"
# Alternative search

# Task 3: Text processing (section 1)
man -k text | grep "(1)"
man -k process | grep "(1)"
# Results: sed, awk, grep, cut, sort, etc.

# Task 4: Exclude results
man -k file | grep -v "filesystem"
# Show file-related, but exclude filesystem

man -k user | grep "(8)" | grep -v "group"
# User commands, but not group-related

# Task 5: Create aliases
cat << 'EOF' >> ~/.bashrc

# Custom man search aliases
alias mans1='man -k $1 | grep "(1)"'   # Section 1
alias mans5='man -k $1 | grep "(5)"'   # Section 5
alias mans8='man -k $1 | grep "(8)"'   # Section 8
alias manconfig='man -k . | grep "(5)"'  # All config files

EOF

# Reload bashrc
source ~/.bashrc

# Test aliases
mans8 user    # Shows section 8 user commands
manconfig     # Shows all section 5 pages

# Task 1: Find /etc file man pages
man -k . | grep "(5)" | grep -E "fstab|passwd|group|hosts|resolv"

# Or check specifically
man 5 fstab
man 5 passwd
man 5 group
man 5 hosts
man 5 resolv.conf

# Task 2: Read fstab man page
man 5 fstab
# Learn about 6 fields:
# device, mountpoint, type, options, dump, pass

# Task 3: Read hosts man page
man 5 hosts
# Learn format: IP_address canonical_hostname [aliases...]

# Task 4: resolv.conf man page
man 5 resolv.conf
# Learn about: nameserver, search, domain directives

# Task 5: Create reference list
cat << 'EOF' > ~/config-files-man-pages.txt
Important Config Files and Their man Pages

System Users and Groups:
- /etc/passwd       (man 5 passwd)    - User accounts
- /etc/group        (man 5 group)     - Group definitions
- /etc/shadow       (man 5 shadow)    - Shadow passwords
- /etc/gshadow      (man 5 gshadow)   - Shadow group passwords

Filesystem and Mount:
- /etc/fstab        (man 5 fstab)     - Filesystem table
- /etc/mtab         (man 5 fstab)     - Mounted filesystems

Network Configuration:
- /etc/hosts        (man 5 hosts)     - Static hostname lookup
- /etc/resolv.conf  (man 5 resolv.conf) - DNS resolver config
- /etc/nsswitch.conf (man 5 nsswitch.conf) - Name service switch
- /etc/networks     (man 5 networks)  - Network names

Scheduling:
- /etc/crontab      (man 5 crontab)   - System cron jobs
- /etc/at.deny      (man 5 at)        - At command access

Login and Security:
- /etc/login.defs   (man 5 login.defs) - Login defaults
- /etc/sudoers      (man 5 sudoers)   - Sudo configuration

Usage: man 5 <filename>
EOF

cat ~/config-files-man-pages.txt

# Task 1: Create users
man -k "create user" | grep "(8)"
# Or:
man -k "add user" | grep "(8)"
# Finds: useradd(8), adduser(8)

man 8 useradd

# Task 2: Check disk space
man -k "disk space"
# Or:
man -k disk | grep -E "space|usage"
# Finds: df(1), du(1)

man 1 df    # Disk free
man 1 du    # Disk usage

# Task 3: Change file ownership
man -k owner
# Or:
man -k "change owner"
# Finds: chown(1), chgrp(1)

man 1 chown

# Task 4: Compress files
man -k compress
# Finds: gzip(1), bzip2(1), xz(1), zip(1), tar(1)

man 1 gzip

# Task 5: Process tree
man -k "process tree"
# Or:
man -k process | grep -i tree
# Finds: pstree(1)

man 1 pstree

# Create discovery cheat sheet
cat << 'EOF'
Command Discovery Patterns:

Task → Search Keywords:
- Create/add users → "add user", "create user"
- Disk space → "disk space", "disk usage"
- File ownership → "owner", "change owner"
- Compress → "compress", "archive"
- Process info → "process", combined with specific term

Strategy:
1. Think of keywords related to task
2. Use man -k with keywords
3. Filter by section if needed
4. Read man page of likely candidate
EOF

# Task 1: Find user creation command
man -k "create user" | grep "(8)"
# Find: useradd(8)

# Task 2-4: Read useradd man page for options
man 8 useradd
# Search within man page:
/-d        # Home directory option
/-s        # Shell option
/-G        # Groups option

# Or search from command line:
man -k useradd
man 8 useradd | grep -A 5 "home-dir"

# Task 5: Construct command
cat << 'EOF'
Create user 'jdoe' with:
- Home directory: /home/jdoe
- Shell: /bin/bash
- Groups: wheel, developers

Command:
sudo useradd -d /home/jdoe -s /bin/bash -G wheel,developers jdoe

Breakdown (from man 8 useradd):
-d /home/jdoe      : Home directory
-s /bin/bash       : Login shell
-G wheel,developers: Supplementary groups
jdoe               : Username

Set password:
sudo passwd jdoe

Verify:
id jdoe
grep jdoe /etc/passwd
EOF

# Task 1: Find fstab man page
man -k fstab
# Finds: fstab(5)

# Task 2-3: Read the man page
man 5 fstab
# Take notes on 6 fields

# Document findings:
cat << 'EOF'
/etc/fstab format (from man 5 fstab):

Field 1: Device (what to mount)
  - /dev/sda1
  - UUID=xxxx-xxxx
  - LABEL=mylabel

Field 2: Mount point (where to mount)
  - /home
  - /boot
  - /mnt/data

Field 3: Filesystem type
  - ext4
  - xfs
  - nfs
  - swap

Field 4: Mount options
  - defaults
  - rw, ro
  - noexec
  - user

Field 5: Dump (backup)
  - 0 = don't dump
  - 1 = dump this filesystem

Field 6: Pass (fsck order)
  - 0 = don't check
  - 1 = check first (root filesystem)
  - 2 = check after root
EOF

# Task 4: Create valid entry
cat << 'EOF'
Example /etc/fstab entry:

/dev/sdb1  /mnt/data  ext4  defaults  0  2

Breakdown:
/dev/sdb1    : Device to mount
/mnt/data    : Mount point
ext4         : Filesystem type
defaults     : Use default options
0            : Don't dump
2            : Check after root filesystem
EOF

# Task 5: Verify syntax
# Before editing /etc/fstab, test mount:
sudo mkdir -p /mnt/data
sudo mount -t ext4 /dev/sdb1 /mnt/data
# If successful, entry is valid

# Check current fstab:
cat /etc/fstab

# Start timer
start=$(date +%s)

# Task 1: List processes
man -k "list process" | grep "(1)"
# Or quick:
man -k process | grep "(1)" | head -5
# Find: ps(1)

# Task 2: Kill processes
man -k kill | grep "(1)"
# Find: kill(1), killall(1), pkill(1)

# Task 3: Check network interfaces
man -k "network interface"
# Or:
man -k interface | grep -i network
# Find: ip(8), ifconfig(8)

# Task 4: Download files
man -k download
# Or:
man -k "download files"
# Find: wget(1), curl(1)

# Task 5: Change permissions
man -k permission
# Or:
man -k "change permission"
# Find: chmod(1)

# End timer
end=$(date +%s)
duration=$((end - start))

echo "Time taken: $duration seconds"
echo "Target: 180 seconds (3 minutes)"

if [ $duration -lt 180 ]; then
    echo "✅ Excellent! Under 3 minutes!"
else
    echo "⏱️ Practice more to improve speed"
fi

# Quick reference:
cat << 'EOF'
Answers:
1. ps - Process status
2. kill, killall, pkill - Terminate processes
3. ip, ifconfig - Network interface info
4. wget, curl - Download files
5. chmod - Change file permissions
EOF

# Task 1: Search for fake command
man -k this_command_absolutely_does_not_exist

# Task 2: Diagnose error
# If you see:
# "nothing appropriate"
# Or:
# "man: nothing appropriate"

# This means:
cat << 'EOF'
Possible causes:
1. Man database not initialized
2. Man database outdated
3. No man pages match search
EOF

# Check database status:
ls -lh /var/cache/man/index.db 2>/dev/null || echo "Database may not exist"

# Task 3: Fix the error
echo "Updating man page database..."
sudo mandb

# This rebuilds the entire database
# Wait for completion (30 seconds to 2 minutes)

# Task 4: Verify fix
man -k test
# Should show results

man -k ls | grep "^ls "
# Should show: ls (1) - list directory contents

# Task 5: Document steps
cat << 'EOF' > ~/man-troubleshooting.txt
man -k Troubleshooting Guide

Problem: "nothing appropriate" error
Symptoms:
- man -k returns no results
- Gets "nothing appropriate" message
- man -k worked before but stopped

Solutions:
1. Update database:
   sudo mandb

2. Check database exists:
   ls /var/cache/man/index.db

3. If database missing:
   sudo mandb -c    # Create from scratch

4. Verify after update:
   man -k ls

Prevention:
- Run mandb after installing software
- Some systems auto-update (check cron)
- Manual update if needed

Emergency (if mandb fails):
- Reinstall man-db package
- Check disk space (df -h)
- Check /var/cache/man permissions
EOF

cat ~/man-troubleshooting.txt

# Task 1: User account management
man -k "user account"
man -k user | grep account

# Task 2: Network interface
man -k "network interface"
man -k network | grep interface

# Task 3: File system
man -k "file system"
man -k filesystem

# Task 4: Compare quoted vs unquoted
man -k user account    # Searches for "user" OR "account"
man -k "user account"  # Searches for exact phrase

# Task 5: Best strategy
cat << 'EOF'
Multi-word search tips:
- Quotes for exact phrases
- No quotes for broader search (OR)
- Try both approaches
- Filter with grep for precision
EOF

# Bash scripting
man bash
man -k bash | grep -i script

# Shell built-ins
man bash
# Search for "SHELL BUILTIN COMMANDS"

# Regular expressions
man 7 regex
man -k regex | grep "(7)"

# Section 7 pages
man -k . | grep "(7)" | head -20

man ls
man dir
# Note: dir is similar to ls

man cat
man more
man less
# Compare paging features

man grep
man egrep
man fgrep
# Note: egrep = grep -E, fgrep = grep -F

# Section 2: System calls
man -k . | grep "(2)" | head -10
man 2 open
man 2 read
man 2 write

# Section 3: Library functions
man -k . | grep "(3)" | head -10
man 3 printf
man 3 malloc
man 3 strlen

cat << 'EOF' > ~/man-essential-commands.txt
Essential Commands (Section 1):
man 1 ls, cd, pwd, cp, mv, rm, mkdir, rmdir
man 1 cat, more, less, head, tail
man 1 grep, find, locate
man 1 tar, gzip, bzip2
man 1 chmod, chown, chgrp

Essential Config Files (Section 5):
man 5 passwd, group, shadow
man 5 fstab, hosts, resolv.conf
man 5 crontab, sudoers

Essential Admin Commands (Section 8):
man 8 useradd, userdel, usermod
man 8 groupadd, groupdel
man 8 mount, umount
man 8 fdisk, mkfs
man 8 systemctl, journalctl
EOF

# Commands starting with 'find'
man -k . | grep "^find"

# Commands ending with 'add'
man -k . | grep "add (.*)"

# All 'user' commands (section 8)
man -k user | grep -E "user.* \(8\)"

# Config files with 'conf' in name
man -k . | grep -E "conf.* \(5\)"

# Alternatives to cat
man -k "display.*file"
# Find: cat, more, less, head, tail

# Alternatives to grep
man -k search | grep "(1)"
# Find: grep, egrep, awk, sed

# Alternatives to top
man -k "process.*monitor"
# Find: top, htop, ps, pgrep

# Compare:
man cat
man less
# less has more features than cat

man ls
# SEE ALSO: dir, vdir, chown, chmod

man passwd
# SEE ALSO: chpasswd, passwd(5), shadow(5)

# Follow references:
man chpasswd
man 5 shadow

# Build relationship map
cat << 'EOF'
passwd ecosystem:
- passwd (1): Change password
- passwd (5): Password file format
- shadow (5): Shadow password format
- chpasswd (8): Batch password changes
- pwconv (8): Convert to shadow passwords
EOF

# Task 1: Find fsck
man -k "check filesystem"
man -k fsck
# Find: fsck(8)
man 8 fsck

# Task 2: Disk space
man -k "disk space"
man -k "disk usage"
# Find: df(1), du(1)

# Task 3: Service management
man -k service | grep "(8)"
# Find: systemctl(8), service(8)

# Task 4: Network diagnostics
man -k network | grep -E "(ping|interface|route)"
# Find: ping(8), ip(8), route(8)

start=$(date +%s)

# Task 1: Compressed tar
man -k archive | grep tar
man 1 tar
# Search: /gzip or /compress
# Answer: tar -czf

# Task 2: Add group
man -k "add group" | grep "(8)"
man 8 groupadd

# Task 3: /etc/services format
man -k services | grep "(5)"
man 5 services

# Task 4: System load
man -k "system load"
man -k load | grep "(1)"
# Find: uptime, top, w

# Task 5: Cron job
man -k cron
man 5 crontab  # File format
man 1 crontab  # Command

# Task 6: Change hostname
man -k hostname | grep "(8)"
man 8 hostnamectl
# Or: man 1 hostname

# Task 7: Logged-in users
man -k "logged users"
man -k who
# Find: who, w, last

# Task 8: Synchronize files
man -k sync
man -k rsync
man 1 rsync

end=$(date +%s)
duration=$((end - start))

cat << EOF
=== FINAL CHALLENGE RESULTS ===
Time: $duration seconds
Target: 600 seconds (10 minutes)

ANSWERS:
1. Compressed tar: tar -czf archive.tar.gz files/
2. Add group: groupadd groupname
3. Services file: man 5 services
4. System load: uptime, top, w
5. Cron job: crontab -e (man 1 crontab), format in man 5 crontab
6. Change hostname: hostnamectl or hostname
7. Logged users: who, w, last
8. Sync files: rsync

$(if [ $duration -lt 600 ]; then
    echo "✅ MASTERY ACHIEVED! Under 10 minutes!"
else
    echo "⏱️ Good effort! Practice to improve speed."
fi)
EOF