Linux Commands Cheat Sheet: Home Lab and Server Reference

This reference covers Ubuntu and Debian-based distributions and is aimed at server administrators and home lab builders running systems such as Ubuntu Server, Proxmox, Docker hosts, and NAS platforms. Commands are intended for use in a standard bash terminal. Where a command requires elevated privileges, sudo is noted or implied.

Navigation and File Operations

Viewing and Editing Files

Permissions and Ownership

Understanding ls -la output

-rwxr-xr-x  1  ubuntu  www-data  4096  May 10 09:00  script.sh
 |||||||||      |       |
 ||||||||+-- other: r-x (read, execute)
 |||||+++--- group: r-x (read, execute)
 ||+++------ owner: rwx (read, write, execute)
 |+--------- file type: - file, d directory, l symlink

Numeric permission reference

Permission and ownership commands

User and Group Management

Process Management

Disk and Storage

Network Commands

System Information

Package Management (apt — Ubuntu/Debian)

systemd Service Management

SSH and Remote Access

SSH config shortcut

Create or edit ~/.ssh/config to define aliases for frequently accessed hosts:

Host myserver
    HostName 192.168.1.100
    User ubuntu
    IdentityFile ~/.ssh/id_ed25519
    Port 22

After saving, connect with simply ssh myserver.

Cron Jobs

Crontab commands

Cron syntax

# ┌───────────── minute (0–59)
# │ ┌─────────── hour (0–23)
# │ │ ┌───────── day of month (1–31)
# │ │ │ ┌─────── month (1–12)
# │ │ │ │ ┌───── day of week (0–7, Sunday = 0 or 7)
# │ │ │ │ │
# * * * * *  command to execute

Text Processing

Practical text processing one-liners

# Find and replace a string across a file
sed -i 's/oldstring/newstring/g' config.txt

# Print the third column from a space-delimited file
awk '{print $3}' access.log

# Show unique IP addresses from an Nginx access log
awk '{print $1}' /var/log/nginx/access.log | sort | uniq -c | sort -rn

# Remove blank lines from a file
sed -i '/^$/d' file.txt

# Extract the second field from a colon-delimited file
cut -d':' -f2 /etc/passwd

# Count how many times each HTTP status code appears in a log
awk '{print $9}' /var/log/nginx/access.log | sort | uniq -c | sort -rn

Archives and Compression

Useful One-Liners

# Check what's listening on a specific port
ss -tulpn | grep :80

# Find files larger than 1 GB
find / -type f -size +1G 2>/dev/null

# Watch a command refresh every 2 seconds
watch -n 2 df -h

# Tail multiple log files at once
tail -f /var/log/syslog /var/log/auth.log

# Count lines in a log file matching a pattern
grep -c "ERROR" /var/log/app.log

# Recursively find and delete files by extension
find /path -name "*.tmp" -delete

# Show the 10 largest directories
du -h --max-depth=1 / 2>/dev/null | sort -rh | head -10

# Check which process is using a specific port
lsof -i :8080

# Follow systemd logs for the Docker service
journalctl -fu docker

# Generate a random 32-character password
openssl rand -base64 32

# Show failed login attempts
grep "Failed password" /var/log/auth.log | awk '{print $11}' | sort | uniq -c | sort -rn

# Display real-time network interface statistics
watch -n 1 cat /proc/net/dev

# Find all SUID files (potential privilege escalation vectors)
find / -perm /4000 -type f 2>/dev/null

# Quickly test if a remote port is open (no nmap required)
timeout 3 bash -c 'cat < /dev/null > /dev/tcp/192.168.1.1/22' && echo "Open" || echo "Closed"

# Show disk I/O per process
iotop -o

# List the 10 most recently modified files in a directory
find /var/log -type f -printf '%T@ %p\n' | sort -rn | head -10 | awk '{print $2}'

# Reload shell configuration without logging out
source ~/.bashrc

# Show environment variables sorted alphabetically
env | sort

Related articles: n8n Expressions Cheat Sheet: Variables, Functions and Syntax, Proxmox Cheat Sheet: CLI Commands for VMs, LXC and Storage, Git Cheat Sheet: Every Command You Need, How to Revive an Old PC with Linux