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Overview

ROS2 provides a rich command-line interface for interacting with the robot system. This page covers common ROS2 commands used in the TurtleBot3 development environment.

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Basic commands

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Check ROS2 installation

ros2 --version
Displays the installed ROS2 version (should show jazzy).

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Get help

ros2 --help
ros2 <command> --help
Show available commands or help for a specific command.

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Node commands

Nodes are executable programs that perform computation.

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List running nodes

ros2 node list
Example output: 
/gazebo
/robot_state_publisher
/turtlebot3_diff_drive

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Node information

ros2 node info /node_name
Example: 
ros2 node info /turtlebot3_diff_drive
Shows:
  • Subscribers
  • Publishers
  • Services
  • Actions

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Run a node

ros2 run <package_name> <executable_name>
Example: 
ros2 run turtlebot3_teleop teleop_keyboard

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Topic commands

Topics are named buses over which nodes exchange messages.

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List active topics

ros2 topic list
Common TurtleBot3 topics:
  • /cmd_vel - Velocity commands
  • /odom - Odometry data
  • /scan - Laser scan data
  • /imu - IMU data
  • /joint_states - Joint states

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List topics with types

ros2 topic list -t
Example output: 
/cmd_vel [geometry_msgs/msg/Twist]
/odom [nav_msgs/msg/Odometry]
/scan [sensor_msgs/msg/LaserScan]

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Topic information

ros2 topic info /topic_name
Example: 
ros2 topic info /cmd_vel
Shows:
  • Message type
  • Publisher count
  • Subscription count

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Echo topic messages

ros2 topic echo /topic_name
Example: 
ros2 topic echo /scan
Displays messages in real-time.

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Show message rate

ros2 topic hz /topic_name
Example: 
ros2 topic hz /scan
Output: average rate: 5.000

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Publish to topic

ros2 topic pub /topic_name <msg_type> "<message>"
Example (move robot forward): 
ros2 topic pub --once /cmd_vel geometry_msgs/msg/Twist \
  "{linear: {x: 0.2, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.0}}"
Example (continuous publishing): 
ros2 topic pub /cmd_vel geometry_msgs/msg/Twist \
  "{linear: {x: 0.1}, angular: {z: 0.5}}" -r 10

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Service commands

Services provide request/reply interactions.

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List services

ros2 service list

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List services with types

ros2 service list -t

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Service information

ros2 service type /service_name
Example: 
ros2 service type /gazebo/spawn_entity

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Find services by type

ros2 service find <service_type>
Example: 
ros2 service find std_srvs/srv/Empty

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Call a service

ros2 service call /service_name <service_type> "<request>"
Example (reset Gazebo simulation): 
ros2 service call /reset_simulation std_srvs/srv/Empty

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Parameter commands

Parameters are node configuration values.

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List parameters

ros2 param list
Lists all parameters for all nodes.

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Get parameter value

ros2 param get /node_name parameter_name
Example: 
ros2 param get /turtlebot3_diff_drive wheel_separation

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Set parameter value

ros2 param set /node_name parameter_name value
Example: 
ros2 param set /turtlebot3_diff_drive max_velocity 0.5

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Dump parameters to file

ros2 param dump /node_name
Saves node parameters to YAML file.

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Load parameters from file

ros2 param load /node_name params.yaml

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Action commands

Actions are for long-running tasks with feedback.

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List actions

ros2 action list
Common Navigation2 actions:
  • /navigate_to_pose
  • /follow_path
  • /compute_path_to_pose

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Action information

ros2 action info /action_name
Example: 
ros2 action info /navigate_to_pose

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Send action goal

ros2 action send_goal /action_name <action_type> "<goal>"
Example (navigate to position): 
ros2 action send_goal /navigate_to_pose nav2_msgs/action/NavigateToPose \
  "{pose: {header: {frame_id: 'map'}, pose: {position: {x: 1.0, y: 0.5}}}}"

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Package commands

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List installed packages

ros2 pkg list

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List TurtleBot3 packages

ros2 pkg list | grep turtlebot3

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Find package executables

ros2 pkg executables <package_name>
Example: 
ros2 pkg executables turtlebot3_teleop

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Show package prefix (install location)

ros2 pkg prefix <package_name>

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Launch commands

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Run a launch file

ros2 launch <package_name> <launch_file>
Example: 
ros2 launch turtlebot3_gazebo empty_world.launch.py

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Pass arguments to launch file

ros2 launch <package_name> <launch_file> arg:=value
Example: 
ros2 launch turtlebot3_gazebo turtlebot3_world.launch.py x_pose:=1.0 y_pose:=2.0

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Interface commands

Interface commands show message/service/action definitions.

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List message types

ros2 interface list
ros2 interface list msg

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Show message definition

ros2 interface show <msg_type>
Example: 
ros2 interface show geometry_msgs/msg/Twist
Output: 
Vector3 linear
  float64 x
  float64 y
  float64 z
Vector3 angular
  float64 x
  float64 y
  float64 z

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Show package interfaces

ros2 interface package <package_name>
Example: 
ros2 interface package turtlebot3_msgs

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Bag commands

Bag files record and replay ROS2 data.

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Record topics

ros2 bag record /topic1 /topic2
Example (record all sensor data): 
ros2 bag record /scan /odom /imu

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Record all topics

ros2 bag record -a

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Play bag file

ros2 bag play <bag_file>

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Bag information

ros2 bag info <bag_file>

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Doctor command

Diagnose ROS2 setup issues. 
ros2 doctor
Checks:
  • Network configuration
  • System setup
  • ROS2 environment

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Full report

ros2 doctor --report

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Daemon commands

Manage the ROS2 daemon.

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Stop daemon

ros2 daemon stop

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Start daemon

ros2 daemon start

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Restart daemon

ros2 daemon stop && ros2 daemon start
When to use: If ros2 commands are slow or hanging.

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Common workflows

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Inspect running system

# See what nodes are running
ros2 node list

# See what topics are active
ros2 topic list

# See messages on a topic
ros2 topic echo /scan

# Check message rate
ros2 topic hz /cmd_vel

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Debug robot not moving

# Check if velocity commands are being published
ros2 topic hz /cmd_vel

# Check the actual values
ros2 topic echo /cmd_vel

# Manually send a command
ros2 topic pub --once /cmd_vel geometry_msgs/msg/Twist \
  "{linear: {x: 0.2}}"

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Monitor sensor data

# Check laser scan rate
ros2 topic hz /scan

# View laser data
ros2 topic echo /scan --no-arr

# Check odometry
ros2 topic echo /odom

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Record and replay

# Record a test run
ros2 bag record -a -o test_run

# Play it back later
ros2 bag play test_run

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Environment variables

Key ROS2 environment variables:
VariableValuePurpose
ROS_DISTROjazzyROS2 distribution
ROS_DOMAIN_ID30Network isolation
RMW_IMPLEMENTATIONrmw_cyclonedds_cppDDS implementation
ROS_LOCALHOST_ONLY0 or 1Restrict to localhost

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Check environment

printenv | grep ROS

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Tips and tricks

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Auto-completion

Press Tab to auto-complete commands: 
ros2 topic <Tab><Tab>
ros2 topic echo /cmd<Tab>

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Command history

Search previous commands with Ctrl+R: 
(reverse-i-search)`topic': ros2 topic echo /scan

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Compact output

# Suppress array output for cleaner display
ros2 topic echo /scan --no-arr

# Show only specific fields
ros2 topic echo /odom --field pose.pose.position

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Multiple domains

Run multiple robot systems by changing ROS_DOMAIN_ID: 
export ROS_DOMAIN_ID=31
ros2 run turtlebot3_teleop teleop_keyboard

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