LPIC-1 102-500 Deep Dive: Shell Scripting, User Management, Networking, and Security

The LPIC-1 102-500 exam is the second of two exams required for the LPIC-1 certification. It covers shell scripting and data management, user interfaces and desktops, administrative tasks, essential networking, and system security.

This guide provides an objective-by-objective breakdown with commands, configuration examples, and exam-relevant details.

Topic 105: Shells, Scripting, and Data Management (weight 15)

105.1 Customize and Use the Shell Environment

Shell configuration files:

File	Scope	When Read
/etc/profile	System-wide	Login shell
~/.profile	User	Login shell
~/.bash_profile	User (bash)	Login shell
~/.bashrc	User (bash)	Interactive non-login
/etc/bash.bashrc	System-wide	Interactive non-login
~/.bash_logout	User	Logout

Login vs non-login shells:

• Login shell: su -, ssh, terminal login. Reads /etc/profile then ~/.profile or ~/.bash_profile.
• Non-login shell: bash, xterm. Reads ~/.bashrc only.

Interactive vs non-interactive shells:

• Interactive: Reads rc files, shows prompt, has job control
• Non-interactive: Script execution, no prompt, no aliases by default

# Check shell type
echo $0                     # Shows bash or -bash (login)
shopt login_shell           # Shows "login_shell" on/off

# Export variables
export PATH=$PATH:/opt/bin
export EDITOR=vim
export PS1='\u@\h:\w\$ '   # Prompt format
export PS2='> '             # Continuation prompt

# Key environment variables
echo $HOME
echo $USER
echo $SHELL
echo $PWD
echo $OLDPWD
echo $TERM

# Set alias
alias ll='ls -l'
alias la='ls -la'
alias rm='rm -i'

# Functions
myfunc() { echo "Hello $1"; }
export -f myfunc            # Export function to subshells

Prompt customization (PS1):

Placeholder	Meaning
\u	Username
\h	Hostname (short)
\H	Full hostname
\w	Current directory (full)
\W	Current directory (basename)
\d	Date (Day Mon Date)
\t	Time (HH:MM:SS)
\@	Time (12h AM/PM)
\$	# for root, $ for user
\!	History number
\#	Command number

105.2 Customize or Write Simple Scripts

#!/bin/bash
# Shebang — determines interpreter

# Variables
NAME="World"
echo "Hello $NAME"
echo "Hello ${NAME}!"
read -p "Enter name: " input_name

# Positional parameters
echo "Script: $0"
echo "Arg 1: $1"
echo "Arg 2: $2"
echo "Arg count: $#"
echo "All args: $@"
echo "All args: $*"
shift                   # Shift positional params left

# Exit status
ls /nonexistent
echo $?                 # Previous command exit code (0=success)
exit 0                  # Exit script with status
exit 1                  # Exit with error

# Conditionals
if [ -f "$file" ]; then
    echo "File exists"
elif [ -d "$dir" ]; then
    echo "Directory exists"
else
    echo "Neither"
fi

# Test operators
# -f file     File exists and is regular
# -d dir      Directory exists
# -e file     File exists (any type)
# -r file     Readable
# -w file     Writable
# -x file     Executable
# -s file     Non-empty
# -z string   String is empty
# -n string   String is non-empty
# file1 -nt file2   Newer than
# file1 -ot file2   Older than

# String comparison
[ "$a" = "$b" ]     # Equal (POSIX)
[ "$a" == "$b" ]    # Equal (bash)
[ "$a" != "$b" ]    # Not equal
[[ "$a" < "$b" ]]    # Less than (lexicographic, bash)

# Integer comparison
[ "$a" -eq "$b" ]   # Equal
[ "$a" -ne "$b" ]   # Not equal
[ "$a" -gt "$b" ]   # Greater than
[ "$a" -ge "$b" ]   # Greater or equal
[ "$a" -lt "$b" ]   # Less than
[ "$a" -le "$b" ]   # Less or equal

# Arithmetic
$(( a + b ))
$(( a * b ))
let "a = a + 1"
(( a++ ))

# Loops
for i in {1..5}; do
    echo $i
done

for file in /etc/*.conf; do
    echo $file
done

while [ "$count" -lt 10 ]; do
    echo $count
    (( count++ ))
done

until [ "$count" -eq 0 ]; do
    echo $count
    (( count-- ))
done

# Case statement
case "$1" in
    start) echo "Starting...";;
    stop)  echo "Stopping...";;
    restart) echo "Restarting...";;
    *)     echo "Usage: $0 {start|stop|restart}"; exit 1;;
esac

# Functions
function myfunction {
    local local_var="I'm local"
    echo "$1 is first arg to function"
}
myfunction "argument"

# Sourcing vs executing
. script.sh      # Source (same shell)
source script.sh # Source (bash)
./script.sh      # Execute (subshell)
bash script.sh   # Execute (subshell)

105.3 SQL Data Management

# Open SQLite
sqlite3 database.db

# SQLite commands
sqlite> .tables           # List tables
sqlite> .schema table     # Show CREATE statement
sqlite> .headers on       # Show column headers
sqlite> .mode column      # Columnar output
sqlite> .quit             # Exit

# Basic SQL
CREATE TABLE users (
    id INTEGER PRIMARY KEY,
    name TEXT NOT NULL,
    email TEXT UNIQUE,
    created DATE DEFAULT CURRENT_DATE
);

INSERT INTO users (name, email) VALUES ('Alice', 'alice@example.com');
SELECT * FROM users;
SELECT name FROM users WHERE email LIKE '%example.com';
UPDATE users SET name='Bob' WHERE id=1;
DELETE FROM users WHERE id=1;
DROP TABLE users;

# Import CSV
.mode csv
.import data.csv table_name

# Export
.output out.csv
SELECT * FROM users;
.output stdout

# Backup
.dump > backup.sql
.restore backup.sql

# From command line
sqlite3 db.db "SELECT * FROM users;"
sqlite3 db.db ".dump" > backup.sql

Topic 106: User Interfaces and Desktops (weight 4)

106.1 Install and Configure X11

# X11 configuration file
cat /etc/X11/xorg.conf
# Modern systems auto-detect; manual config rarely needed

# X server display numbers
# :0 — first local display
# :1 — second local display

# Display manager (DM) — graphical login
# GDM (GNOME), LightDM, SDDM (KDE), XDM

# Window managers
# Stacking: Openbox, Fluxbox, twm
# Tiling: i3, dwm, Awesome, bspwm

# Desktop environments
# GNOME (gtk-based), KDE Plasma (qt-based), Xfce (lightweight)

# Start X manually
startx
xinit /usr/bin/startxfce4

# Remote X forwarding (SSH)
ssh -X user@host       # Trusted forwarding
ssh -Y user@host       # Untrusted forwarding

# DISPLAY variable
export DISPLAY=:0
export DISPLAY=192.168.1.10:0  # Remote display

# Wayland (X11 successor)
# Most modern Linux distributions default to Wayland
echo $XDG_SESSION_TYPE  # x11 or wayland

106.2 Graphical Desktops

# Desktop environments use display managers
# GNOME Keyring — stores credentials
# KDE Wallet — similar functionality

# Accessibility features
# Orca — screen reader
# Compiz — compositing window manager (legacy)
# Mutter — GNOME compositor
# KWin — KDE compositor

106.3 Accessibility

# Accessibility technologies
# Screen readers: Orca, Speakup
# Screen magnifiers: KMagnifier, GNOME Magnifier
# On-screen keyboard: onboard, florence
# Sticky keys, slow keys, bounce keys — assistive technology

# Accessibility settings
gsettings set org.gnome.desktop.a11y.applications screen-reader-enabled true

Topic 107: Administrative Tasks (weight 15)

107.1 Manage User and Group Accounts

# User management
useradd -m -s /bin/bash -G sudo alice
useradd -u 1500 -g users -G wheel -c "Alice Smith" -d /home/alice -s /bin/bash alice
usermod -aG docker alice      # Append to group
usermod -L alice               # Lock account
usermod -U alice               # Unlock
userdel alice                  # Remove user
userdel -r alice               # Remove user and home

# Password management
passwd alice
passwd -l alice                # Lock password
passwd -u alice                # Unlock
passwd -S alice                # Status
passwd -d alice                # Delete password (no login)

# Group management
groupadd developers
groupdel developers
groupmod -n devs developers    # Rename group
gpasswd -a alice developers    # Add user to group
gpasswd -d alice developers    # Remove user from group

# User info commands
id alice
id -u alice
id -g alice
id -G alice                    # All group IDs
whoami
groups alice
finger alice
chfn alice                     # Change full name/office/phone
chsh -s /bin/zsh alice         # Change shell

Key account files:

File	Purpose
/etc/passwd	User accounts (7 colon-delimited fields: user:pass:UID:GID:comment:home:shell)
/etc/shadow	Encrypted passwords and expiry info
/etc/group	Group definitions
/etc/gshadow	Group passwords (rarely used)
/etc/default/useradd	Default values for useradd
/etc/login.defs	System-wide login policy (UID ranges, password aging defaults)
/etc/skel/	Skeleton directory for new users

Password aging:

chage -l alice                 # List aging info
chage -M 90 alice              # Max days (90)
chage -m 7 alice               # Min days between changes
chage -W 14 alice              # Warning days
chage -E 2027-01-01 alice      # Expiration date
chage -d 0 alice               # Force password change on next login

107.2 Automate System Administration Tasks

Cron:

# Format: minute hour day month weekday command
# Example: 30 2 * * * /usr/bin/backup.sh (daily 2:30 AM)

# Special time strings
@reboot     # Run at boot
@daily      # Run once a day (0 0 * * *)
@weekly     # Run once a week (0 0 * * 0)
@monthly    # Run once a month (0 0 1 * *)
@yearly     # Run once a year (0 0 1 1 *)

# Manage crontabs
crontab -e                    # Edit crontab for current user
crontab -l                    # List crontab
crontab -r                    # Remove crontab
crontab -u alice -e           # Edit another user's crontab (root)

# System-wide cron
ls /etc/cron.hourly/
ls /etc/cron.daily/
ls /etc/cron.weekly/
ls /etc/cron.monthly/
cat /etc/crontab              # System crontab (includes user field)
ls /etc/cron.d/               # Package-specific cron jobs

# Cron allow/deny
cat /etc/cron.allow           # Users allowed to use cron
cat /etc/cron.deny            # Users denied from using cron

Systemd timers (cron alternative):

# Create timer unit
cat /etc/systemd/system/backup.timer
# [Unit]
# Description=Daily backup
# [Timer]
# OnCalendar=daily
# Persistent=true
# [Install]
# WantedBy=timers.target

# Create service unit
cat /etc/systemd/system/backup.service
# [Unit]
# Description=Run backup
# [Service]
# ExecStart=/usr/bin/backup.sh

# Manage timers
systemctl enable --now backup.timer
systemctl list-timers

At (one-time scheduled tasks):

at now + 5 minutes
at> /usr/bin/backup.sh
at> Ctrl+D

at now + 2 hours
at 14:00 today
at 3:00 AM tomorrow
at 3:00 PM July 15

atq                       # List pending jobs
atrm 5                    # Remove job 5

batch                     # Run when system load permits

# at allow/deny
cat /etc/at.allow
cat /etc/at.deny

107.3 Localization and Internationalization

# Locale settings
locale                    # Show current locale
locale -a                 # List all available locales
localectl                 # System locale configuration
localectl list-locales

# Set locale
export LANG=en_US.UTF-8
export LC_ALL=en_US.UTF-8
export LC_MESSAGES=de_DE.UTF-8  # Message language

# Environment variables
# LANG, LC_ALL, LC_MESSAGES, LC_TIME, LC_NUMERIC, LC_COLLATE, LC_MONETARY, LC_CTYPE

# Timezone
timedatectl                # Show and set timezone
timedatectl list-timezones
timedatectl set-timezone Europe/Berlin

# Time-related files
cat /etc/timezone
ls -l /etc/localtime       # Symlink to /usr/share/zoneinfo/...

# Character encoding
iconv -f UTF-8 -t ISO-8859-1 input.txt > output.txt
file -i file.txt           # Show character encoding

# Keyboard layout
localectl list-keymaps
localectl set-keymap us
loadkeys de                # Load German layout immediately

Topic 108: Essential System Services (weight 12)

108.1 Maintain System Time

# Hardware clock (RTC)
hwclock                    # Show hardware clock
hwclock --show
hwclock --set --date="2026-07-13 12:00:00"
hwclock --systohc          # Write system time to hardware clock
hwclock --hctosys          # Read hardware clock to system

# NTP with chrony (modern standard)
systemctl status chronyd
chronyc sources            # Show NTP sources
chronyc tracking           # Show system clock offset
chronyc -n sources         # Numeric output
chronyc activity           # Active sources

# NTP with ntpd (traditional)
ntpq -p                    # Show NTP peers
ntpdate pool.ntp.org       # One-time sync (deprecated)

# systemd-timesyncd
timedatectl set-ntp true
cat /etc/systemd/timesyncd.conf

108.2 System Logging

# rsyslog (traditional)
cat /etc/rsyslog.conf
cat /etc/rsyslog.d/*.conf

# Log format: facility.priority  action
# auth.info  /var/log/auth.log
# *.info;mail.none;authpriv.none  /var/log/messages

# Key log files
/var/log/syslog        # Generic system log
/var/log/messages      # System messages (RHEL)
/var/log/auth.log      # Authentication (Debian)
/var/log/secure        # Authentication (RHEL)
/var/log/kern.log      # Kernel
/var/log/dmesg         # Kernel ring buffer
/var/log/boot.log      # Boot messages
/var/log/mail.log      # Mail server
/var/log/apache2/      # Apache web server

# Log rotation (logrotate)
cat /etc/logrotate.conf
cat /etc/logrotate.d/*

# systemd journal
journalctl
journalctl -xe                 # Recent with explanation
journalctl -u nginx.service    # Specific unit
journalctl -p err              # Error priority and above
journalctl -f                  # Follow (like tail -f)
journalctl --since "1 hour ago"
journalctl --until "2026-07-13 12:00"
journalctl -k                  # Kernel messages
journalctl --list-boots        # List boot sessions
journalctl --disk-usage        # Journal size

# Preserve journal across reboots
mkdir -p /var/log/journal
systemd-tmpfiles --create --prefix /var/log/journal

108.3 Mail Transfer Agent (MTA) Basics

# Common MTAs: Postfix, Sendmail, Exim

# Send mail from command line
mail -s "Subject" user@example.com
mail -s "Subject" alice < /tmp/report.txt
echo "Body text" | mail -s "Subject" alice

# Check mail queue
mailq
postqueue -p             # Postfix mail queue

# /etc/aliases - local aliases
# root: alice
# postmaster: root
# Run newaliases after editing
newaliases

# Mail spool
ls /var/mail/
ls /var/spool/mail/

108.4 Manage Printers and Printing

# CUPS (Common Unix Printing System)
systemctl status cups
lpinfo -v                # Available printers/drivers
lpinfo -m                # Available models/drivers

# Add printer
lpadmin -p printername -E -v usb://device -m everywhere

# Print files
lp -d printername file.pdf
lp -n 2 file.pdf         # 2 copies
lp -o media=A4 file.pdf
lp -o sides=two-sided-long-edge file.pdf
lpr -P printername file.pdf

# Check queues
lpq -P printername
lpstat -t
lpstat -p printername
lpstat -d                # Default printer

# Remove jobs
lprm jobid
lprm -P printername -    # Remove all jobs

# Set default printer
lpoptions -d printername
lpadmin -d printername

# CUPS configuration
cat /etc/cups/cupsd.conf

Topic 109: Networking Fundamentals (weight 16)

109.1 Fundamentals of Internet Protocols

# IPv4 addresses
# Classes: A (1-126), B (128-191), C (192-223), D (multicast), E (reserved)
# Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
# Loopback: 127.0.0.0/8

# IPv6
# Format: 2001:db8::1
# Loopback: ::1
# Link-local: fe80::/10

# Subnet masks
# /24 = 255.255.255.0 = 254 hosts
# /16 = 255.255.0.0 = 65534 hosts
# /8 = 255.0.0.0 = 16777214 hosts

# Key protocols
# TCP — connection-oriented, reliable
# UDP — connectionless, fast
# ICMP — error reporting (ping)
# FTP — file transfer (ports 20, 21)
# SSH — secure shell (port 22)
# Telnet — unencrypted remote (port 23)
# SMTP — email sending (port 25)
# DNS — name resolution (port 53)
# HTTP — web (port 80)
# HTTPS — secure web (port 443)
# POP3 — email receiving (port 110)
# IMAP — email receiving (port 143)

109.2 Configure Network Settings

# Network configuration files (Debian/Ubuntu)
cat /etc/network/interfaces
# auto eth0
# iface eth0 inet static
#     address 192.168.1.100
#     netmask 255.255.255.0
#     gateway 192.168.1.1
#     dns-nameservers 8.8.8.8

# Network configuration (RHEL/Fedora)
cat /etc/sysconfig/network-scripts/ifcfg-eth0
# DEVICE=eth0
# BOOTPROTO=static
# IPADDR=192.168.1.100
# NETMASK=255.255.255.0
# GATEWAY=192.168.1.1
# DNS1=8.8.8.8
# ONBOOT=yes

# Netplan (Ubuntu modern)
cat /etc/netplan/*.yaml

# NetworkManager
nmcli dev status
nmcli connection show
nmcli connection up eth0
nmtui                       # Text UI

# ip commands (modern)
ip addr show                # Show interfaces
ip route show               # Show routing table
ip link set eth0 up
ip link set eth0 down
ip addr add 192.168.1.100/24 dev eth0
ip route add default via 192.168.1.1

# ifconfig commands (legacy)
ifconfig
ifconfig eth0 up
ifconfig eth0 192.168.1.100 netmask 255.255.255.0

# DNS
cat /etc/resolv.conf        # Name servers
cat /etc/hosts              # Static host → IP mappings
cat /etc/nsswitch.conf      # Name resolution order

# Hostname
hostname
hostname -f                 # Fully qualified domain name
hostnamectl set-hostname server.example.com

109.3 Basic Network Troubleshooting

# Connectivity
ping 8.8.8.8
ping -c 4 192.168.1.1      # Stop after 4 packets
ping -6 ipv6.google.com

# Path
traceroute 8.8.8.8
traceroute -n 8.8.8.8      # Numeric (no DNS)
mtr 8.8.8.8                 # Combined ping + traceroute

# DNS resolution
host example.com
nslookup example.com
dig example.com
dig -x 8.8.8.8              # Reverse lookup
getent hosts example.com    # Using system name resolution

# Network connections
ss -tulpn                   # Listening ports (modern)
netstat -tulpn              # Listening ports (legacy)
ss -ta                      # All TCP connections
ss -ua                      # All UDP connections

# Bandwidth
iperf3 -c server.example.com
speedtest-cli               # Internet speed test

# ARP
arp -a                      # ARP table
ip neighbor show            # Modern ARP view

# Packet capture
tcpdump -i eth0
tcpdump -i eth0 port 80
tcpdump -i eth0 host 192.168.1.1
tcpdump -w capture.pcap     # Write to file
tcpdump -r capture.pcap     # Read from file

109.4 Configure Client-Side DNS

# /etc/hosts
# 127.0.0.1   localhost
# 192.168.1.100  server.example.com server

# /etc/nsswitch.conf
# hosts: files dns myhostname
# Order: check /etc/hosts first, then DNS

# /etc/resolv.conf
# nameserver 8.8.8.8
# nameserver 8.8.4.4
# search example.com          # Append domain for unqualified names
# options timeout:2 attempts:3 rotate

# systemd-resolved
resolvectl status
resolvectl query example.com
cat /etc/systemd/resolved.conf

109.5 Perform Basic Network Configuration

Already covered in 109.2. Additional tools:

# Wireless
iwconfig
iwlist wlan0 scan
nmcli dev wifi list
nmcli dev wifi connect SSID password PASSWORD

# Bluetooth
bluetoothctl
hciconfig

Topic 110: Security (weight 14)

110.1 Perform Security Administration Tasks

# User authentication files
cat /etc/passwd      # User accounts
cat /etc/shadow      # Encrypted passwords
cat /etc/group       # Groups

# ! in /etc/shadow password field = account locked
# * = no login possible
# $y$ = yescrypt hash, $6$ = SHA-512, $5$ = SHA-256

# Check for empty passwords
awk -F: '($2 == "")' /etc/shadow

# Limits configuration
cat /etc/security/limits.conf
# alice   hard   nproc   100
# @users  soft   nofile  1024

cat /etc/security/limits.d/*.conf

# su and sudo
su alice                  # Switch user (needs password)
su - alice                # Login shell
sudo -l                   # List allowed commands
sudo -u alice command     # Run as user
visudo                    # Edit /etc/sudoers safely

# /etc/sudoers format
# alice    ALL=(ALL:ALL) ALL
# %wheel   ALL=(ALL:ALL) ALL
# alice    ALL=(root) /usr/bin/systemctl

# Kernel parameters
sysctl -a
sysctl net.ipv4.ip_forward
sysctl -w net.ipv4.ip_forward=1
cat /etc/sysctl.conf
cat /etc/sysctl.d/*.conf

110.2 Host Security

# Shadow password suite
pwck                    # Verify /etc/passwd integrity
grpck                   # Verify /etc/group integrity

# File ownership and permissions
find / -nouser -o -nogroup  # Files with no owner/group
find / -perm -4000      # SUID files
find / -perm -2000      # SGID files
find / -perm -1000      # Sticky bit

# SSH security
cat /etc/ssh/sshd_config
# PermitRootLogin no
# PasswordAuthentication no
# PubkeyAuthentication yes
# Port 2222

# Firewall (iptables/nftables)
iptables -L -n -v       # List rules
iptables -A INPUT -p tcp --dport 22 -j ACCEPT
iptables -A INPUT -j DROP  # Default deny

# Firewall (firewalld)
firewall-cmd --list-all
firewall-cmd --add-service=http --permanent
firewall-cmd --reload

# UFW (Uncomplicated Firewall)
ufw enable
ufw allow ssh
ufw allow 80/tcp
ufw status

110.3 Secure Data with Encryption

# GPG
gpg --gen-key                   # Generate key pair
gpg --list-keys
gpg -e -r alice file.txt        # Encrypt for alice
gpg -d file.txt.gpg             # Decrypt
gpg --sign file.txt             # Sign
gpg --verify file.txt.asc       # Verify signature
gpg --export -a alice > alice.asc  # Export public key
gpg --import alice.asc          # Import public key

# SSH key-based auth
ssh-keygen -t ed25519 -C "alice@example.com"
ssh-keygen -t rsa -b 4096
ssh-copy-id alice@server
cat ~/.ssh/id_ed25519.pub       # Public key
cat ~/.ssh/id_ed25519           # Private key (keep secret!)

# SSH agent
eval $(ssh-agent)
ssh-add ~/.ssh/id_ed25519
ssh-add -l                      # List loaded keys
ssh-add -L                      # List public keys

# /dev/null and shred
shred -f file.txt               # Overwrite 3 times
shred -n 10 file.txt            # Overwrite 10 times
shred -z file.txt               # Add final zero overwrite

Exam Tips

1. Practice shell scripting — write at least 10 scripts covering loops, conditionals, and functions
2. Know your network commands — ip, ss, and dig are heavily tested
3. Understand the boot process and systemd — multiple questions on targets and service management
4. Permissions and ownership — expect scenario-based questions about SUID, SGID, sticky bit
5. Manage cron and systemd timers — scheduling tasks is a frequent exam topic
6. Read man pages — man -k keyword is the fastest way to find the right command during the exam (if allowed)

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