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\\n |||||||||      |       |\\n ||||||||+-- other: r-x (read, execute)\\n |||||+++--- group: r-x (read, execute)\\n ||+++------ owner: rwx (read, write, execute)\\n |+--------- 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\\n    HostName 192.168.1.100\\n    User ubuntu\\n    IdentityFile ~/.ssh/id_ed25519\\n    Port 22

After saving, connect with simply ssh myserver.

Cron Jobs

Crontab commands

Cron syntax

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

Text Processing

Practical text processing one-liners

# Find and replace a string across a file\\nsed -i 's/oldstring/newstring/g' config.txt\\n\\n# Print the third column from a space-delimited file\\nawk '{print $3}' access.log\\n\\n# Show unique IP addresses from an Nginx access log\\nawk '{print $1}' /var/log/nginx/access.log | sort | uniq -c | sort -rn\\n\\n# Remove blank lines from a file\\nsed -i '/^$/d' file.txt\\n\\n# Extract the second field from a colon-delimited file\\ncut -d':' -f2 /etc/passwd\\n\\n# Count how many times each HTTP status code appears in a log\\nawk '{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\\nss -tulpn | grep :80\\n\\n# Find files larger than 1 GB\\nfind / -type f -size +1G 2>/dev/null\\n\\n# Watch a command refresh every 2 seconds\\nwatch -n 2 df -h\\n\\n# Tail multiple log files at once\\ntail -f /var/log/syslog /var/log/auth.log\\n\\n# Count lines in a log file matching a pattern\\ngrep -c "ERROR" /var/log/app.log\\n\\n# Recursively find and delete files by extension\\nfind /path -name "*.tmp" -delete\\n\\n# Show the 10 largest directories\\ndu -h --max-depth=1 / 2>/dev/null | sort -rh | head -10\\n\\n# Check which process is using a specific port\\nlsof -i :8080\\n\\n# Follow systemd logs for the Docker service\\njournalctl -fu docker\\n\\n# Generate a random 32-character password\\nopenssl rand -base64 32\\n\\n# Show failed login attempts\\ngrep "Failed password" /var/log/auth.log | awk '{print $11}' | sort | uniq -c | sort -rn\\n\\n# Display real-time network interface statistics\\nwatch -n 1 cat /proc/net/dev\\n\\n# Find all SUID files (potential privilege escalation vectors)\\nfind / -perm /4000 -type f 2>/dev/null\\n\\n# Quickly test if a remote port is open (no nmap required)\\ntimeout 3 bash -c 'cat < /dev/null > /dev/tcp/192.168.1.1/22' && echo "Open" || echo "Closed"\\n\\n# Show disk I/O per process\\niotop -o\\n\\n# List the 10 most recently modified files in a directory\\nfind /var/log -type f -printf '%T@ %p\\\\n' | sort -rn | head -10 | awk '{print $2}'\\n\\n# Reload shell configuration without logging out\\nsource ~/.bashrc\\n\\n# Show environment variables sorted alphabetically\\nenv | sort

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