Difficulty Level: 🟢 Beginner
Risk Level: 🟢 Safe - These are read-only or basic commands
Essential Linux commands you'll need for daily server management. No prior Linux experience required!
Understanding where you are and how to move around is the foundation of Linux.
/ # Root directory (top of everything)
├── home/ # User home directories
│ └── USERNAME/ # Your home directory
│ └── docker/ # Your Docker setup
│ ├── maintenance/# Maintenance scripts
│ ├── storage/ # Docker's mounting point
│ └── backups/ # Backups
├── etc/ # System configuration files
├── var/ # Variable data (logs, databases)
│ └── log/ # Log files
└── opt/ # Optional software packages
pwd - Print Working Directory (where am I?)
pwd
# Output:
/home/USERNAME/docker
ls - List files and directories
# Simple list
ls
# Detailed list with permissions, size, date
ls -l
# Include hidden files (start with .)
ls -a
# Human-readable sizes
ls -lh
# Sort by modification time (newest first)
ls -lt
# Combine options
ls -lah
Example ls -lh output:
-rw-r--r-- 1 username username 2.1K Jan 15 10:25 docker-compose.yml
-rw------- 1 username username 512 Jan 15 09:15 .env
drwxr-xr-x 2 username username 4.0K Jan 15 10:30 storage
drwxr-xr-x 3 username username 4.0K Jan 14 15:20 maintenance
drwxr-xr-x 3 username username 4.0K Jan 14 08:14 backup
Understanding the output:
drwxr-xr-x - Permissions (d=directory, -=file)username username - Owner and group4.0K - File/folder sizeJan 15 10:30 - Last modified date/timedocker - Namecd - Change Directory
# Go to your home directory
cd
cd ~
# Go to docker folder
cd ~/docker
cd /home/USERNAME/docker
# Go up one level
cd ..
# Go up two levels
cd ../..
# Go to previous directory
cd -
# Go to root directory
cd /
# Navigate to specific path
cd /var/log
Pro tips:
# See where you'll end up before changing
ls /path/to/directory
cd /path/to/directory
# Use tab completion (press Tab key)
cd ~/doc[TAB] # Autocompletes to ~/docker/
Absolute path - Starts from root (/)
cd /home/USERNAME/docker
Relative path - Relative to current location
# If you're in /home/USERNAME
cd docker
# If you're in /home
cd USERNAME/docker
Special shortcuts:
~ - Your home directory (/home/USERNAME). - Current directory.. - Parent directory (one level up)- - Previous directory# Display entire file
cat docker-compose.yml
# Display with line numbers
cat -n docker-compose.yml
# Display multiple files
cat file1.txt file2.txt
⚠️ NOTE:
catshows the entire file at once. For large files, uselessinstead.
# View file with pagination
less docker-compose.yml
Navigation inside less:
Space or Page Down - Next pageb or Page Up - Previous pageG - Go to end of fileg - Go to beginning of file/searchterm - Search forward?searchterm - Search backwardn - Next search resultq - Quit# First 10 lines (default)
head docker-compose.yml
# First 20 lines
head -n 20 docker-compose.yml
# First 5 lines
head -5 docker-compose.yml
# Last 10 lines (default)
tail docker-compose.yml
# Last 20 lines
tail -n 20 docker-compose.yml
# Follow file in real-time (great for logs!)
tail -f /var/log/auth.log
# Follow with line numbers
tail -fn 50 /var/log/auth.log
# Stop following: Ctrl + C
💡 TIP:
tail -fis perfect for watching log files live!
# Search for text in a file
grep "n8n" docker-compose.yml
# Case-insensitive search
grep -i "N8N" docker-compose.yml
# Show line numbers
grep -n "n8n" docker-compose.yml
# Search recursively in directory
grep -r "error" /var/log/
# Search with context (3 lines before/after)
grep -C 3 "error" logfile.txt
# Count matches
grep -c "n8n" docker-compose.yml
# Invert match (lines that DON'T contain text)
grep -v "comment" docker-compose.yml
# Multiple patterns
grep -E "n8n|mysql|traefik" docker-compose.yml
Real-world examples:
# Find your IP in logs
grep "YOUR_IP" /var/log/auth.log
# Find errors in last 100 lines
tail -n 100 /var/log/syslog | grep -i error
# Find failed login attempts
sudo grep "Failed password" /var/log/auth.log
# Find Docker containers in compose file
grep "container_name:" docker-compose.yml
# Create or edit a file
nano filename.txt
# Edit with sudo (for system files)
sudo nano /etc/hosts
nano keyboard shortcuts: (do not change CTRL for ⌘ on MACOS)
Ctrl + O - Save (Write Out)Ctrl + X - ExitCtrl + K - Cut lineCtrl + U - Paste lineCtrl + W - SearchCtrl + \ - Search and replaceCtrl + G - Show helpAlt + U - UndoAlt + E - RedoPro tips:
# Open file at specific line number
nano +25 docker-compose.yml
# Create backup when saving
nano -B filename.txt
# Create new empty file
touch newfile.txt
# Create multiple files
touch file1.txt file2.txt file3.txt
# Update timestamp of existing file
touch existing-file.txt
# Create single directory
mkdir new-folder
# Create nested directories
mkdir -p parent/child/grandchild
# Create with specific permissions
mkdir -m 755 new-folder
# Create multiple directories
mkdir folder1 folder2 folder3
# Create file with content
echo "Hello World" > file.txt
# Append to existing file
echo "New line" >> file.txt
# Create multi-line file
cat > file.txt << 'EOF'
Line 1
Line 2
Line 3
EOF
⚠️ WARNING:
>overwrites the file,>>appends to it.
# Copy file
cp source.txt destination.txt
# Copy file to directory
cp file.txt /home/USERNAME/docker/
# Copy directory recursively
cp -r source-folder/ destination-folder/
# Copy with verbose output
cp -v file.txt backup/
# Copy preserving attributes (permissions, timestamps)
cp -p file.txt backup/
# Interactive (ask before overwrite)
cp -i file.txt destination.txt
# Create backup of existing file
cp -b file.txt destination/
Real-world examples:
# Backup docker-compose file
cp docker-compose.yml docker-compose.yml.backup
# Copy .env file before editing
cp .env .env.backup.$(date +%Y%m%d)
# Copy entire docker folder
cp -r ~/docker ~/docker-backup
# Rename file
mv oldname.txt newname.txt
# Move file to directory
mv file.txt /home/USERNAME/docker/
# Move multiple files
mv file1.txt file2.txt /destination/
# Move with verbose output
mv -v file.txt /destination/
# Interactive (ask before overwrite)
mv -i file.txt /destination/
# Move directory
mv old-folder/ new-folder/
Real-world examples:
# Rename backup file with date
mv .env.backup .env.backup.$(date +%Y%m%d)
# Move log files to archive
mv *.log /var/log/archive/
# Rename docker folder
mv docker docker-old
# Remove single file
rm file.txt
# Remove multiple files
rm file1.txt file2.txt file3.txt
# Interactive (ask for confirmation)
rm -i file.txt
# Remove directory and contents
rm -r folder/
# Force remove (no confirmation)
rm -f file.txt
# Remove directory forcefully
rm -rf folder/
# Verbose output
rm -v file.txt
# Remove with wildcard
rm *.log
⚠️ DANGER:
rm -rfis EXTREMELY DANGEROUS! It deletes without confirmation and can't be undone!
Safe removal practices:
# ALWAYS use -i for interactive mode when starting
alias rm='rm -i'
# Better: Move to trash instead
mkdir -p ~/.trash
mv file.txt ~/.trash/
# Preview what will be deleted
ls *.log # See what matches
rm *.log # Then delete
# Never run these without thinking:
rm -rf / # DESTROYS YOUR ENTIRE SYSTEM
rm -rf /* # DESTROYS YOUR ENTIRE SYSTEM
rm -rf ~ # DELETES YOUR HOME DIRECTORY
💡 TIP: There's no "undo" or "recycle bin" in Linux by default. Deleted = gone forever!
-rwxrw-r--
│││││││││└─ Other: read
││││││││└── Other: write (no)
│││││││└─── Other: execute (no)
││││││└──── Group: read
│││││└───── Group: write
││││└────── Group: execute (no)
│││└─────── Owner: read
││└──────── Owner: write
│└───────── Owner: execute
└────────── File type (- = file, d = directory, l = link)
Permission numbers:
r (read) = 4w (write) = 2x (execute) = 1Common permission combinations:
755 = rwxr-xr-x - Owner: full, Others: read+execute644 = rw-r--r-- - Owner: read+write, Others: read only600 = rw------- - Owner: read+write, Others: nothing777 = rwxrwxrwx - Everyone: full access (DANGEROUS!)# Numeric mode
chmod 755 script.sh
chmod 644 file.txt
chmod 600 .env
# Symbolic mode
chmod u+x script.sh # Add execute for owner
chmod g-w file.txt # Remove write for group
chmod o-r file.txt # Remove read for others
chmod a+r file.txt # Add read for all
# Recursive
chmod -R 755 folder/
# Common fixes
chmod 600 ~/.ssh/id_ed25519 # SSH private key
chmod 644 ~/.ssh/id_ed25519.pub # SSH public key
chmod 700 ~/.ssh # SSH directory
chmod 600 ~/.ssh/authorized_keys # Authorized keys
Real-world examples:
# Fix .env file permissions
chmod 600 ~/docker/.env
# Make script executable
chmod +x backup.sh
# Fix SSH permissions after copying
chmod 700 ~/.ssh
chmod 600 ~/.ssh/*
chmod 644 ~/.ssh/*.pub
# Change owner
sudo chown username file.txt
# Change owner and group
sudo chown username:groupname file.txt
# Recursive
sudo chown -R username:groupname folder/
# Change only group
sudo chown :groupname file.txt
⚠️ NOTE: You need
sudoto change ownership (except for your own files).
# Find by name
find /path/to/search -name "filename.txt"
# Case-insensitive name search
find . -iname "*.log"
# Find directories only
find . -type d
# Find files only
find . -type f
# Find by size
find . -size +100M # Larger than 100MB
find . -size -1M # Smaller than 1MB
# Find by modification time
find . -mtime -7 # Modified in last 7 days
find . -mtime +30 # Modified more than 30 days ago
# Find and delete
find . -name "*.tmp" -delete
# Find and execute command
find . -name "*.log" -exec gzip {} \;
Real-world examples:
# Find large log files
find /var/log -type f -size +100M
# Find docker-compose files
find ~ -name "docker-compose.yml"
# Find files modified today
find ~/docker -type f -mtime -1
# Find and list .env files with details
find ~ -name ".env" -exec ls -lh {} \;
# Find empty directories
find . -type d -empty
# Search file database (faster than find)
locate docker-compose.yml
# Case-insensitive
locate -i dockerfile
# Update database first (run with sudo)
sudo updatedb
locate docker-compose.yml
💡 TIP:
locateis faster thanfindbut requires updating its database withupdatedb.
# Find where a command is located
which docker
which nano
which python3
# Find all matches
which -a python
# Kernel name
uname
# All information
uname -a
# Kernel version
uname -r
# Machine hardware
uname -m
# Operating system
uname -o
# Show hostname
hostname
# Show IP address
hostname -I
# Show all addresses
hostname -A
# Show how long system has been running
uptime
# Pretty format
uptime -p
Example output:
15:24:32 up 42 days, 3:15, 2 users, load average: 0.15, 0.20, 0.18
# Show memory in MB
free -m
# Show memory in GB
free -g
# Human-readable format
free -h
# Show total line
free -ht
Example output:
total used free shared buff/cache available
Mem: 7.8G 2.1G 3.2G 156M 2.5G 5.3G
Swap: 2.0G 0B 2.0G
# Show disk usage
df
# Human-readable format
df -h
# Show specific filesystem
df -h /
# Show inodes
df -i
Example output:
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 50G 15G 33G 31% /
# Current user's processes
ps
# All processes
ps aux
# All processes in tree format
ps auxf
# Process by name
ps aux | grep docker
# Detailed process info
ps -ef
# Sort by memory usage
ps aux --sort=-%mem | head
# Sort by CPU usage
ps aux --sort=-%cpu | head
# Launch top
top
# Sort by memory (press M)
# Sort by CPU (press P)
# Kill process (press k, then enter PID)
# Quit (press q)
Better alternative: htop
# Install htop (more user-friendly)
sudo apt install htop
# Run htop
htop
# Replace PID by the PID number given by the ps command seen above.
# Graceful stop (SIGTERM)
kill PID
# Force kill (SIGKILL)
kill -9 PID
# Kill by name
pkill process-name
# Kill all processes matching pattern
killall process-name
# Interactive kill
kill -15 PID # Ask nicely
sleep 5
kill -9 PID # Force if still running
Find PID of a process:
# Method 1: Using ps
ps aux | grep docker
# Method 2: Using pgrep
pgrep docker
# Method 3: Using pidof
pidof dockerd
# Check service status
sudo systemctl status docker
# Start service
sudo systemctl start docker
# Stop service
sudo systemctl stop docker
# Restart service
sudo systemctl restart docker
# Enable service (start on boot)
sudo systemctl enable docker
# Disable service (don't start on boot)
sudo systemctl disable docker
# Reload service configuration
sudo systemctl reload docker
# View service logs
sudo journalctl -u docker
# Follow service logs in real-time
sudo journalctl -fu docker
Common services:
docker - Docker daemonsshd - SSH serverfail2ban - Fail2ban serviceufw - Firewall# Size of current directory
du -sh .
# Size of specific directory
du -sh ~/docker
# Size of all subdirectories
du -h
# Show only totals
du -sh */
# Sort by size
du -h | sort -h
# Top 10 largest directories
du -h | sort -hr | head -10
# Include hidden files
du -sh .[^.]* *
Real-world examples:
# Check docker folder size
du -sh ~/docker
# Find largest folders in home directory
du -h ~ | sort -hr | head -20
# Check log folder size
sudo du -sh /var/log
# Check Docker volumes size
sudo du -sh /var/lib/docker/volumes/*
# Install ncdu
sudo apt install ncdu
# Analyze current directory
ncdu
# Analyze specific path
ncdu /var/log
# Inside ncdu:
# Arrow keys to navigate
# Enter to explore directory
# d to delete
# q to quit
💡 TIP:
ncduis much more user-friendly thandufor finding large files!
# Show current username
whoami
# Show current user ID
id
# Show all user info
id -a
# List logged in users
users
# Detailed list
who
# Who with more details
w
# Run single command as root
sudo command
# Switch to root user
sudo -i
sudo su
# Run command as another user
sudo -u USERNAME command
# Check sudo access
sudo -v
# List sudo privileges
sudo -l
⚠️ WARNING: Doing your maintenance as a SUDO user is very convenient but is considered as a very bad practice.
# Update package list
sudo apt update
# Upgrade all packages
sudo apt upgrade
# Upgrade with automatic "yes"
sudo apt upgrade -y
# Install package
sudo apt install package-name
# Remove package
sudo apt remove package-name
# Remove package and config files
sudo apt purge package-name
# Remove unused packages
sudo apt autoremove
# Search for package
apt search package-name
# Show package info
apt show package-name
# List installed packages
apt list --installed
# List upgradable packages
apt list --upgradable
Real-world examples:
# Update system
sudo apt update && sudo apt upgrade -y
# Install useful tools
sudo apt install htop ncdu
# Remove old packages
sudo apt autoremove
# Check what can be updated
apt list --upgradable
# Ping a host
ping google.com
# Ping 4 times only
ping -c 4 google.com
# Ping with timestamp
ping -D google.com
# Stop pinging: Ctrl + C
Very useful in a n8n environment as you can use it to simulate and try API calls.
# Download file
curl -O https://example.com/file.txt
# Save to specific name
curl -o myfile.txt https://example.com/file.txt
# Show only headers
curl -I https://example.com
# Follow redirects
curl -L https://example.com
# POST request
curl -X POST -d "data=value" https://api.example.com
# With authentication
curl -u USERNAME:password https://example.com
# JSON POST
curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' https://api.example.com
# Download file
wget https://example.com/file.txt
# Save to specific name
wget -O myfile.txt https://example.com/file.txt
# Continue interrupted download
wget -c https://example.com/largefile.zip
# Download in background
wget -b https://example.com/file.txt
# Download multiple files
wget -i urls.txt
# Show all interfaces
ip addr
# Show specific interface
ip addr show eth0
# Show routing table
ip route
# Show network statistics
ip -s link
# Show all connections
ss -a
# Show listening ports
ss -l
# Show TCP connections
ss -t
# Show listening TCP ports
ss -tl
# Show UDP connections
ss -u
# Show process using ports
ss -tulpn
# Show specific port
ss -tunlp | grep :80
# Show all connections
netstat -a
# Show listening ports
netstat -l
# Show TCP connections
netstat -t
# Show with process info
netstat -tulpn
# Show specific port
netstat -tunlp | grep :80
# Show command history
history
# Show last 20 commands
history 20
# Search history
history | grep docker
# Re-run command by number
!123
# Re-run last command
!!
# Re-run last command with sudo
sudo !!
# Search history interactively
Ctrl + R # Then type to search
# Clear history
history -c
Navigation:
Ctrl + A - Beginning of lineCtrl + E - End of lineCtrl + Left/Right - Move word by wordAlt + B - Back one wordAlt + F - Forward one wordEditing:
Ctrl + K - Cut from cursor to endCtrl + U - Cut from cursor to beginningCtrl + W - Cut word before cursorCtrl + Y - Paste cut textCtrl + L - Clear screen (same as clear)Process control:
Ctrl + C - Stop current commandCtrl + Z - Suspend current commandCtrl + D - Exit shell or EOFPipe (|) - Send output to another command:
# Count lines
cat file.txt | wc -l
# Search in output
docker ps | grep n8n
# Sort and show unique
cat file.txt | sort | uniq
# Chain multiple commands
ps aux | grep docker | grep -v grep | awk '{print $2}'
Redirect (>) - Save output to file:
# Overwrite file
ls > file-list.txt
# Append to file
ls >> file-list.txt
# Redirect errors
command 2> error.log
# Redirect both output and errors
command > output.log 2>&1
# Discard output
command > /dev/null
# Discard errors
command 2> /dev/null
# Discard everything
command > /dev/null 2>&1
# Run second command only if first succeeds (&&)
sudo apt update && sudo apt upgrade
# Run second command only if first fails (||)
command1 || command2
# Run both regardless (;)
command1 ; command2
# Run in background (&)
long-running-command &
Create shortcuts for common commands:
# Temporary alias (this session only)
alias ll='ls -lah'
alias update='sudo apt update && sudo apt upgrade'
# Permanent alias (add to ~/.bashrc)
echo "alias ll='ls -lah'" >> ~/.bashrc
source ~/.bashrc
# View all aliases
alias
# Remove alias
unalias ll
Useful aliases:
alias ll='ls -lah'
alias la='ls -A'
alias l='ls -CF'
alias ..='cd ..'
alias ...='cd ../..'
alias grep='grep --color=auto'
alias update='sudo apt update && sudo apt upgrade -y'
alias dps='docker ps'
alias dlog='docker compose logs -f'
# To add at the end of your .bashrc
# the command lsc will then list the content of a folder with all the directories first, then the hidden files, then the normal files
lsc() {
(ls -lAhd */ 2>/dev/null; ls -lAh | grep "^-" | grep "^\-.*\s\.\|^-.*\s\."; ls -lAh | grep "^-" | grep -v "^\-.*\s\.") | awk 'NR==1 || !/^total/'
}
Make your life easier:
# Type partial command/path and press Tab
cd ~/doc[TAB] # Completes to ~/docker/
# Press Tab twice to see all options
cd ~/d[TAB][TAB] # Shows all directories starting with 'd'
# Complete command options
docker [TAB][TAB] # Shows all docker commands
# * matches any characters
ls *.txt # All .txt files
rm backup* # All files starting with 'backup'
# ? matches single character
ls file?.txt # file1.txt, file2.txt, etc.
# [] matches character set
ls file[12].txt # file1.txt and file2.txt
ls file[a-z].txt # filea.txt through filez.txt
# {} matches patterns
cp file.{txt,log} backup/ # Copies file.txt and file.log
# Use output of command as argument
echo "Today is $(date)"
# Older syntax (backticks)
echo "Current directory: `pwd`"
# Examples
cp file.txt file.txt.backup.$(date +%Y%m%d)
tar -czf backup-$(date +%Y%m%d).tar.gz ~/docker/
# Show environment variable
echo $HOME
echo $USER
echo $PATH
# Show all environment variables
env
printenv
# Set temporary variable (this session)
export MY_VAR="value"
# Set permanent variable (add to ~/.bashrc)
echo 'export MY_VAR="value"' >> ~/.bashrc
source ~/.bashrc
# Common variables
$HOME # Your home directory
$USER # Your USERNAME
$PATH # Command search paths
$PWD # Current directory
$SHELL # Your shell
# Navigation
pwd # Where am I?
ls -lah # List files
cd ~/docker # Change directory
# File operations
cat file.txt # View file
nano file.txt # Edit file
cp source dest # Copy
mv old new # Move/rename
rm file.txt # Delete (CAREFUL!)
# Searching
find . -name "*.txt" # Find files
grep "text" file # Search in file
# System info
df -h # Disk space
free -h # Memory
ps aux # Processes
top # Live processes
# Permissions
chmod 644 file # Change permissions
chown user:group file # Change owner
# Package management
sudo apt update # Update package list
sudo apt upgrade # Upgrade packages
sudo apt install pkg # Install package
# Network
ping google.com # Test connectivity
curl example.com # HTTP request
ss -tulpn # Show ports
Try these to build confidence:
Navigate your system:
cd ~
pwd
ls -lah
cd docker
pwd
cd ..
View and search files:
cat docker-compose.yml
grep "n8n" docker-compose.yml
tail -f /var/log/syslog
Check system resources:
df -h
free -h
ps aux | grep docker
Create and manage files:
touch test.txt
nano test.txt # Add some text
cat test.txt
cp test.txt test-backup.txt
rm test.txt
Next Guide: 05 - Docker Management Cheatsheet
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