Linux Administration Study Guide

flowchart TD
    A[Hub] --> B[Key Concepts]
    A --> C[Core Principles]
    A --> D[Practical Applications]
    B --> E[Fundamental definitions]
    C --> F[Design patterns]
    D --> G[Real-world usage]

Why This Guide Exists

Linux powers the majority of the world’s servers, cloud infrastructure, embedded systems, and supercomputers. Whether you are managing a home server, deploying applications to the cloud, or administering enterprise infrastructure, Linux administration is an essential skill for any systems professional.

This hub page maps every resource on this site. The guides cover the core competencies of Linux administration: the command line, file systems, process management, networking, systemd, security, and package management. Each section provides both conceptual understanding and practical, hands-on commands that you can apply immediately. The goal is not to memorise every command, but to understand the system deeply enough that you can solve problems you have never encountered before.

Why Linux
Linux Distributions
CLI Fundamentals
File Systems
Process Management
Networking
systemd
Security
Package Management
LVM and Disk Partitioning
Cross-Site Resources
FAQ

Why Linux

Linux dominates the server market for several reasons:

Open source — free to use, modify, and distribute
Stability — Linux servers routinely run for years without rebooting
Security — strong permissions model, rapid patching, and community vigilance
Performance — efficient resource usage; runs on everything from Raspberry Pi to supercomputers
Ecosystem — vast package repositories, community support, and enterprise distributions
Cloud native — all major cloud providers default to Linux for virtual machines and containers

Who Should Learn Linux?

System administrators managing servers
DevOps engineers building and deploying infrastructure
Software developers deploying to Linux servers
Security professionals conducting assessments
Students pursuing careers in IT or computer science
Anyone who wants to understand how computers actually work

Linux Distributions

Linux distributions package the Linux kernel with system libraries, package managers, and default configurations. The major distributions fall into several families.

Debian-Based

Debian — the foundation; known for stability and reliability
Ubuntu — user-friendly; the most popular desktop and cloud distribution
Linux Mint — Ubuntu-based with a focus on desktop usability

Red Hat-Based

Red Hat Enterprise Linux (RHEL) — enterprise-grade; commercial support
CentOS / AlmaLinux / Rocky Linux — free RHEL-compatible alternatives
Fedora — cutting-edge; upstream for RHEL

Arch-Based

Arch Linux — rolling release; minimal base; user assembles the system
Manjaro — Arch-based with easier installation and configuration

Choosing a Distribution

Use Case	Recommended Distribution
Enterprise servers	RHEL, AlmaLinux, Rocky Linux
Cloud deployments	Ubuntu, Amazon Linux
Desktop use	Ubuntu, Fedora, Linux Mint
Learning Linux	Arch Linux, Gentoo
Home servers	Ubuntu Server, Debian
Security testing	Kali Linux, Parrot OS

CLI Fundamentals

The command line is the primary interface for Linux administration. Mastering the CLI is the single most important skill for a Linux administrator.

pwd                     # Print working directory
ls                      # List directory contents
ls -la                  # List all files with details
cd /path/to/dir         # Change directory
cd ~                    # Go to home directory
cd -                    # Go to previous directory
tree                    # Display directory tree

File Operations

cp source dest          # Copy files
cp -r source dest       # Copy directories recursively
mv source dest          # Move or rename files
rm file                 # Delete a file
rm -rf directory        # Delete a directory recursively
mkdir -p path/to/dir    # Create directories recursively
touch file              # Create an empty file or update timestamp
ln -s target link       # Create a symbolic link

Text Processing

cat file                # Display file contents
less file               # View file with paging
head -n 20 file         # First 20 lines
tail -n 20 file         # Last 20 lines
tail -f file            # Follow file changes in real time
grep "pattern" file     # Search for pattern in file
grep -r "pattern" dir   # Recursive search
sed 's/old/new/g' file  # Stream editor substitution
awk '{print $1}' file   # Process text by columns
wc -l file              # Count lines
sort file               # Sort lines
uniq file               # Remove duplicate lines
cut -d: -f1 /etc/passwd # Extract fields

Permissions

chmod 755 file          # Set permissions (owner=rwx, group=rx, other=rx)
chmod u+x file          # Add execute permission for owner
chmod -R 644 dir        # Recursive permission change
chown user:group file   # Change file ownership
chown -R user:group dir # Recursive ownership change

Permission meanings:

Number	Permission	Symbol
4	Read	r
2	Write	w
1	Execute	x
0	None	---

Piping and Redirection

command1 | command2     # Pipe output of command1 to command2
command > file          # Redirect stdout to file (overwrite)
command >> file         # Redirect stdout to file (append)
command 2> file         # Redirect stderr to file
command &> file         # Redirect both stdout and stderr
command < file          # Redirect file to stdin
command1 && command2    # Run command2 only if command1 succeeds
command1 || command2    # Run command2 only if command1 fails

File Systems

Understanding Linux file systems is essential for managing storage, permissions, and backups.

Directory Structure

/                    — root directory
├── bin/             — essential user binaries
├── boot/            — boot loader files
├── dev/             — device files
├── etc/             — system configuration
├── home/            — user home directories
├── lib/             — shared libraries
├── mnt/             — temporary mount points
├── opt/             — optional software
├── proc/            — process information (virtual)
├── root/            — root user's home directory
├── sbin/            — system binaries
├── srv/             — service data
├── sys/             — system information (virtual)
├── tmp/             — temporary files
├── usr/             — user programs and data
│   ├── bin/         — user binaries
│   ├── lib/         — libraries
│   └── share/       — architecture-independent data
└── var/             — variable data (logs, mail, spool)
    ├── log/         — system logs
    └── tmp/         — persistent temporary files

File System Types

Type	Description	Use Case
ext4	Default Linux file system	General purpose
XFS	High-performance; large files	Databases, media
Btrfs	Copy-on-write; snapshots	Desktops, backup targets
ZFS	Advanced; RAID, compression, snapshots	Storage servers
tmpfs	RAM-based file system	/tmp, /run
proc	Virtual file system	Process and kernel info

Mounting

mount /dev/sdb1 /mnt/data     # Mount a partition
mount -t ext4 /dev/sdb1 /mnt  # Specify file system type
umount /mnt/data               # Unmount
cat /proc/mounts               # View mounted file systems
blkid                          # View block device UUIDs and types
lsblk                          # List block devices

/etc/fstab

The /etc/fstab file defines file systems mounted at boot:

UUID=xxx  /mnt/data  ext4  defaults  0  2

Fields: device, mount point, type, options, dump, fsck order.

Process Management

Linux is a multitasking operating system. Understanding process management is essential for diagnosing performance issues and maintaining system stability.

Viewing Processes

ps aux                  # List all running processes
ps -ef                  # Full-format listing
top                     # Interactive process viewer
htop                    # Improved top (if installed)
pstree                  # Display process tree
pgrep nginx             # Find process by name
pidof nginx             # Get PID by name

Process Control

kill PID                # Send SIGTERM (graceful stop)
kill -9 PID             # Send SIGKILL (force stop)
killall nginx           # Kill all processes named nginx
pkill -f "pattern"      # Kill processes matching pattern
nice -n 10 command      # Run command with lower priority
renice -n 5 -p PID      # Change priority of running process
nohup command &         # Run command immune to hangups
bg                      # Background a stopped process
fg                      # Foreground a background process
jobs                    # List background jobs

Process States

State	Description
R	Running or runnable
S	Sleeping (interruptible)
D	Uninterruptible sleep (usually I/O)
Z	Zombie (terminated but not reaped)
T	Stopped (by signal)

Resource Monitoring

free -h                 # Memory usage
vmstat 1 5              # Virtual memory statistics (1-second intervals, 5 reports)
iostat 1 5              # I/O statistics
sar -u 1 5              # CPU usage over time
dstat                   # Versatile resource statistics
nmon                    # Interactive performance monitor

Networking

Linux networking is powerful and flexible. Most network configuration and troubleshooting happens at the command line.

Network Configuration

ip addr show            # Show IP addresses
ip link show            # Show network interfaces
ip route show           # Show routing table
ip neigh show           # Show ARP table
ifconfig                # Legacy interface configuration (deprecated)
hostname                # Show/set hostname
hostname -I             # Show IP addresses only

Connectivity Testing

ping google.com         # Test connectivity
traceroute google.com   # Trace route to destination
mtr google.com          # Combined ping and traceroute
nslookup domain.com     # DNS lookup
dig domain.com          # Detailed DNS lookup
host domain.com         # Simple DNS lookup
curl -I https://example.com  # HTTP headers
wget https://example.com/file  # Download a file

Network Utilities

ss -tlnp                # Show listening TCP ports
ss -ulnp                # Show listening UDP ports
netstat -tlnp           # Legacy version of ss
lsof -i :80             # Show processes using port 80
tcpdump -i eth0         # Capture network traffic
nmap -sT target         # Port scan
scp file user@host:/path  # Secure copy over SSH
rsync -avz source dest    # Synchronise files

SSH

ssh user@host           # Connect to remote host
ssh -p 2222 user@host   # Connect on non-standard port
ssh-keygen -t ed25519   # Generate SSH key pair
ssh-copy-id user@host   # Copy public key to remote host
ssh -L 8080:localhost:80 user@host  # Local port forwarding
ssh -R 8080:localhost:80 user@host  # Remote port forwarding

Firewall

# iptables (legacy)
iptables -L -n              # List rules
iptables -A INPUT -p tcp --dport 22 -j ACCEPT  # Allow SSH

# nftables (modern)
nft list ruleset             # List all rules

# ufw (Ubuntu)
ufw status                   # Check firewall status
ufw allow ssh                # Allow SSH
ufw enable                   # Enable firewall

# firewalld (RHEL/Fedora)
firewall-cmd --list-all      # List all rules
firewall-cmd --add-service=ssh --permanent  # Allow SSH

systemd

systemd is the init system and service manager for most modern Linux distributions. It manages services, mounts, timers, and system state.

Service Management

systemctl status nginx          # Check service status
systemctl start nginx           # Start a service
systemctl stop nginx            # Stop a service
systemctl restart nginx         # Restart a service
systemctl reload nginx          # Reload configuration
systemctl enable nginx          # Start at boot
systemctl disable nginx         # Do not start at boot
systemctl is-active nginx       # Check if running
systemctl is-enabled nginx      # Check if enabled at boot
systemctl list-units --type=service  # List all services

Journal and Logs

journalctl -u nginx             # Logs for a specific service
journalctl -f                   # Follow all logs
journalctl --since "1 hour ago"  # Logs from the last hour
journalctl -p err               # Error-level messages and above
journalctl --disk-usage         # Check journal size
journalctl --vacuum-size=500M   # Limit journal to 500 MB

Timers (Cron Replacement)

systemd timers replace cron for scheduling tasks:

[Unit]
Description=Daily backup timer

[Timer]
OnCalendar=daily
Persistent=true

[Install]
WantedBy=timers.target

systemctl list-timers           # List all timers
systemctl start backup.timer    # Start a timer
systemctl enable backup.timer   # Enable at boot

System State

systemctl reboot                # Reboot the system
systemctl poweroff              # Shut down the system
systemctl suspend               # Suspend to RAM
systemctl hibernate             # Hibernate to disk
systemctl isolate multi-user.target  # Switch to multi-user mode

Security

Linux security is built on a permissions model, but securing a Linux system requires attention to many areas.

User Management

useradd -m -s /bin/bash username  # Create a user
passwd username                    # Set password
usermod -aG sudo username         # Add to sudo group (Ubuntu)
usermod -aG wheel username        # Add to wheel group (RHEL)
userdel -r username               # Delete user and home directory
id username                        # Show user groups
who                                # Show logged-in users
last                               # Show login history

SSH Hardening

Use key-based authentication; disable password authentication
Change the default SSH port
Restrict SSH access to specific users or groups
Use AllowUsers or AllowGroups in /etc/ssh/sshd_config
Enable fail2ban to block brute-force attempts

File Permissions and Security

chmod 600 sensitive-file     # Owner read/write only
chmod 700 ~/.ssh            # Restrict SSH directory
chattr +i immutable-file    # Make file immutable
lsattr file                 # View file attributes
find / -perm -4000          # Find SUID binaries
find / -writable -type f    # Find world-writable files

AppArmor and SELinux

AppArmor — path-based mandatory access control (Ubuntu, SUSE)
SELinux — label-based mandatory access control (RHEL, Fedora)

Both restrict what processes can do, even as root. Learning to work with them (rather than disabling them) is essential for secure Linux administration.

Auditing and Monitoring

ausearch -m LOGIN           # Search audit logs
aureport                    # Generate audit reports
logwatch                    # Summarise log files
rkhunter                    # Rootkit detection
clamscan                    # Antivirus scanning

Package Management

Package managers handle installing, updating, and removing software. Each distribution family has its own package manager.

APT (Debian/Ubuntu)

apt update                      # Update package lists
apt upgrade                     # Upgrade installed packages
apt install package             # Install a package
apt remove package              # Remove a package
apt purge package               # Remove with configuration
apt search keyword              # Search for packages
apt show package                # Show package details
apt autoremove                  # Remove unused dependencies
dpkg -i package.deb             # Install a .deb file
dpkg -l                         # List installed packages

DNF/YUM (RHEL/Fedora)

dnf update                      # Update packages
dnf install package             # Install a package
dnf remove package              # Remove a package
dnf search keyword              # Search for packages
dnf info package                # Show package details
dnf list installed              # List installed packages
rpm -ivh package.rpm            # Install an .rpm file

Pacman (Arch)

pacman -Syu                     # Full system upgrade
pacman -S package               # Install a package
pacman -R package               # Remove a package
pacman -Rns package             # Remove with config and dependencies
pacman -Ss keyword              # Search for packages
pacman -Qi package              # Show package details
pacman -Qs                      # List installed packages

Snap and Flatpak

Universal package managers that work across distributions:

snap install package            # Install a snap
snap list                       # List installed snaps
flatpak install package         # Install a Flatpak
flatpak list                    # List installed Flatpaks

LVM and Disk Partitioning

LVM (Logical Volume Manager) provides flexible disk management, allowing you to resize volumes, add disks, and create snapshots.

LVM Concepts

Physical Volume (PV) — a disk or partition initialised for LVM
Volume Group (VG) — a pool of storage from one or more physical volumes
Logical Volume (LV) — a virtual partition carved from a volume group

LVM Operations

pvcreate /dev/sdb              # Initialise a disk for LVM
pvdisplay                      # Show physical volumes
vgcreate myvg /dev/sdb         # Create a volume group
vgdisplay                      # Show volume groups
lvcreate -L 10G -n mylv myvg   # Create a 10 GB logical volume
lvcreate -l 100%FREE -n mylv myvg  # Use all free space
lvdisplay                      # Show logical volumes
mkfs.ext4 /dev/myvg/mylv       # Format the logical volume
mount /dev/myvg/mylv /mnt      # Mount the logical volume

LVM Resizing

lvextend -L +5G /dev/myvg/mylv    # Add 5 GB to a logical volume
resize2fs /dev/myvg/mylv           # Resize ext4 file system
xfs_growfs /mnt                    # Resize XFS file system

Disk Partitioning

fdisk /dev/sdb                # Partition with fdisk (MBR)
gdisk /dev/sdb                # Partition with gdisk (GPT)
parted /dev/sdb               # Partition with parted
lsblk                         # View partition layout
partprobe                     # Inform kernel of partition changes

RAID with mdadm

mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1
mdadm --detail /dev/md0       # Check RAID status
cat /proc/mdstat              # View RAID status

Cross-Site Resources

Linux administration connects to many other areas:

TrueNAS Administration — TrueNAS SCALE runs on Linux; ZFS and Linux administration overlap
Networking — network configuration and troubleshooting
Security — security hardening and vulnerability assessment
Performance Tuning — system-level optimisation
Docker and Kubernetes — containerisation on Linux
Developer Tools — development environments on Linux

Frequently Asked Questions

Which Linux distribution should I learn?

For server administration, learn Ubuntu or RHEL/AlmaLinux. Ubuntu is the most popular cloud distribution and has the largest community. RHEL dominates enterprise environments. For learning Linux deeply, Arch Linux forces you to understand every component. For desktop use, Ubuntu or Fedora are excellent choices.

How do I become proficient in the command line?

Practice daily. Replace GUI tasks with command-line equivalents. Work through tutorials. Set up a home server and administer it entirely via SSH. The command line becomes intuitive through repetition — there is no shortcut.

What is the difference between init systems?

SysVinit is the traditional init system. Upstart replaced it in some distributions. systemd is the current standard, used by most major distributions. systemd provides faster boot times, better service management, and integrated logging. Learning systemd is essential for modern Linux administration.

How do I recover from a broken system?

Boot from a live USB or rescue mode. Mount your root filesystem. Use chroot to enter the installed system. Repair configuration files, reinstall bootloaders, or restore from backups. Having a rescue plan and regular backups is essential for any production system.

Do I need to learn Linux for a development career?

If you deploy to cloud servers (AWS, GCP, Azure), almost certainly yes. Most cloud instances run Linux. Even if you develop on macOS or Windows, your deployment target is likely Linux. Basic Linux skills — SSH, file management, process control — are expected of most backend and DevOps engineers.

How do I keep a Linux system secure?

Keep it updated. Minimise installed packages. Use firewall rules. Enable SELinux or AppArmor. Use SSH keys. Monitor logs. Run services with least privilege. Regularly audit for vulnerabilities. Security is not a one-time setup — it requires ongoing attention.

Last updated: 24 July 2026

Written by Wyatt. For questions or feedback, visit wyattau.com.

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