Both nohup and & serve to run processes in the background, but they solve different problems in Linux/Unix environments.

# Using ampersand alone
python long_running_script.py &

# Using nohup
nohup python critical_process.py &

The ampersand (&) simply detaches the process from your current terminal session:

• For short-lived background tasks you want to monitor
• When you don't need output preservation
• For processes that can safely terminate with your session

# Good for temporary background tasks
rsync -avz /source user@remote:/destination &

nohup (no hangup) makes processes immune to SIGHUP signals and is essential for:

# Long-running processes that must survive logout
nohup ./start_server.sh > server.log 2>&1 &

# Critical batch jobs
nohup python data_pipeline.py > pipeline.log 2>&1 &

For enterprise applications, combine both with proper output redirection:

nohup java -jar app.jar > /var/log/app.log 2>&1 &

# Verify running process
ps aux | grep app.jar

• Forgetting output redirection with nohup (fills up disk)
• Using & for long-running processes that need to survive reboots
• Not monitoring nohup processes (consider using screen/tmux for critical jobs)

For production systems, consider:

# Systemd service units
sudo systemctl enable myapp.service

# Using tmux/screen
tmux new -s mysession
./long_running_process
# Detach with Ctrl+B D

When working with Linux command-line operations, two common techniques for process management are the nohup command and the & operator. While both allow processes to run in the background, they serve different purposes in different scenarios.

Using & at the end of a command makes it run in the background immediately:

python3 long_running_script.py &

Key characteristics:

• Returns control to the shell immediately
• Process becomes a child of the current shell
• Process will terminate if the parent shell exits
• Output still goes to the terminal by default

nohup makes commands immune to hangup signals and detaches them from the terminal:

nohup python3 critical_process.py > output.log 2>&1 &

Essential features:

• Ignores SIGHUP signals (sent when terminal closes)
• Redirects output to nohup.out by default
• Process survives terminal/session termination
• Often combined with & for background execution

When to use &:

# Quick background task while maintaining session
tar -czf backup.tar.gz /important_data &

When to use nohup:

# Long-running server process that must survive logout
nohup java -jar production_server.jar > server.log 2>&1 &

For maximum control:

# Redirect output, ignore hangups, and run in background
nohup ./data_processor.sh > processing.log 2>&1 &

# Check running background jobs
jobs -l

# Disown a process to fully detach it from shell
python3 background_task.py &
disown %1

# Check if process survived terminal exit
ps aux | grep python

# Verify nohup output location
ls -lh nohup.out

# Alternative modern approach using screen/tmux
tmux new -s mysession
python3 persistent_script.py
# Detach with Ctrl+B then D