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dna exec

Execute commands in a running DNA container.

Synopsis

dna exec [OPTIONS] [SERVICE] [--] COMMAND [ARGS...]

Description

The dna exec command executes commands and arguments in a running DNA container. This is useful for running specific commands, scripts, or tools within the containerized environment without needing to attach to the container interactively.

Services

Service Description
develop Execute in development service (default)
deploy Execute in deployment service

Options

Option Description
-e, --env stringArray Set container environment variables
-w, --workdir string Override path to working directory
-T, --no-TTY Disable pseudo-TTY allocation
--detach Execute COMMAND in the background
--dry-run Dry run mode (requires --detach flag)
--help, -h Show help message and exit

Positional Arguments

Argument Description
COMMAND [ARGS...] Command and arguments to execute inside the container (default: bash)

Examples

Basic Command Execution

# Execute a simple command
dna exec ls -la

# Execute with specific service
dna exec develop python3 --version
dna exec deploy ./deploy_script.sh

Working Directory Override

# Execute command in specific directory
dna exec --workdir "/" -- bash -c 'tree -L 1 -a $(pwd)'

# Run tests from test directory
dna exec --workdir "/ros2_ws" -- colcon test

Environment Variables

# Set environment variables
dna exec -e "DEBUG=true" -e "LOG_LEVEL=info" -- python3 debug_script.py

# Multiple environment variables
dna exec --env "ROS_DOMAIN_ID=42" --env "VERBOSE=1" -- ros2 node list

Background Execution

# Run command in background
dna exec --detach -- ros2 launch my_package my_launch.py

# Background with dry run
dna exec --dry-run --detach -- long_running_process.sh

Advanced Examples

# Complex command with shell interpretation
dna exec -- bash -c 'echo "Hello from container: $(hostname)"'

# Execute without TTY (useful for scripts)
dna exec -T -- python3 automated_script.py

# Chain multiple commands
dna exec -- bash -c 'cd /ros2_ws && source install/setup.bash && ros2 run my_package my_node'

Use Cases

Development Tasks

# Build ROS workspace
dna exec --workdir "/ros2_ws" -- colcon build

# Run tests
dna exec -- pytest tests/

# Install Python packages
dna exec -- pip3 install numpy matplotlib

System Administration

# View logs
dna exec -- journalctl -u my_service --since "1 hour ago"

# Update packages
dna exec -- apt-get update && apt-get upgrade -y

Debugging and Inspection

# Check environment variables
dna exec -- env | grep ROS

# Inspect file system
dna exec -- find /ros2_ws -name "*.py" | head -10

# Check running processes
dna exec -- ps aux

Execution vs. Attachment

When to use dna exec

  • Single commands: For executing specific commands
  • Automation: For scripted operations
  • Background tasks: For non-interactive operations
  • CI/CD pipelines: For automated testing and deployment

When to use dna attach instead

  • Interactive development: When you need a full shell session
  • Long-running sessions: For extended development work
  • Container exploration: When you want to explore the container environment

Command Behavior

Default Behavior

  • Working directory: Uses container's default working directory
  • Environment: Inherits container's environment variables
  • User context: Runs as the configured container user
  • TTY allocation: Automatically allocated for interactive commands

Service Discovery

The exec command automatically discovers the appropriate service:

  1. Explicit service: If you specify develop or deploy
  2. Offline deployment: Automatically detects offline deployment services
  3. Default fallback: Uses develop service if no other option

Background Execution

Detached Mode

# Start long-running process in background
dna exec --detach -- python3 long_running_script.py

# Check if process is still running
docker exec DN_CONTAINER_NAME ps aux | grep python3

Process Management

# Start background service
dna exec --detach -- ros2 launch my_package service.launch.py

# Monitor logs
docker logs -f DN_CONTAINER_NAME

# Stop background process (if needed)
dna exec -- pkill -f "ros2 launch"

Troubleshooting

Command Not Found

Problem: "command not found" error.

Solutions:

  1. Check PATH: Verify command is in container's PATH

    dna exec -- which python3
dna exec -- echo $PATH

  2. Use full path: Specify complete path to executable

    dna exec -- /usr/local/bin/python3 script.py

  3. Install missing packages: Install required software

    dna exec -- apt-get update && apt-get install -y package-name

Permission Denied

Problem: Permission errors when executing commands.

Solutions:

  1. Check file permissions:

    dna exec -- ls -la /path/to/file

  2. Use appropriate user: Run as root if necessary

    dna exec --user root -- command

  3. Fix ownership: Correct file ownership

    dna exec -- sudo chown user:group /path/to/file

Environment Issues

Problem: Environment variables not set correctly.

Solutions:

  1. Set explicitly: Use -e flag

    dna exec -e "VAR=value" -- command

  2. Source environment: Load environment files

    dna exec -- bash -c 'source /opt/ros/humble/setup.bash && command'

Container Not Running

Problem: Cannot execute command because container is not running.

Solutions:

  1. Start container: Ensure container is running

    dna up --no-attach

  2. Check container status:

    docker ps

Integration with CI/CD

Automated Testing

# Run unit tests
dna exec --no-TTY -- pytest tests/ --junit-xml=results.xml

# Run integration tests
dna exec --detach deploy -- ./integration_tests.sh

Build Automation

# Build project
dna exec --workdir "/ros2_ws" -- colcon build --cmake-args -DCMAKE_BUILD_TYPE=Release

# Package application
dna exec -- ./package_script.sh

Performance Considerations

  • Command overhead: Each exec call has minimal overhead
  • Resource sharing: Commands share container resources
  • Network access: Commands have same network access as container
  • File system: Commands operate on container's file system

See Also

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