ROS 2 Cheat Sheets // SALAMEH

ROS 2 Environment Configuration Cheat Sheet

Commands and Explanations

1. Source the Setup Files

bash

source /opt/ros/<distro>/setup.bash

Activates ROS 2 in the current shell session by setting necessary environment variables.
Replace <distro> with the name of your installed ROS 2 distribution (e.g., humble, galactic, jazzy).

2. Add Sourcing to Shell Startup Script

bash

echo "source /opt/ros/<distro>/setup.bash" >> ~/.bashrc

Automatically sources ROS 2 every time you open a new shell.
Modify ~/.bashrc to include the source command.

Undo this step:

Edit the ~/.bashrc file manually to remove the line added.

3. Check Environment Variables

bash

printenv | grep -i ROS

Verifies if ROS environment variables are correctly set (e.g., ROS_DISTRO, ROS_VERSION).

4. Set the ROS_DOMAIN_ID Variable

bash

export ROS_DOMAIN_ID=<your_domain_id>

Sets a unique domain ID for communication between ROS 2 nodes.
Add to ~/.bashrc for persistence:

bash

echo "export ROS_DOMAIN_ID=<your_domain_id>" >> ~/.bashrc

5. Set the ROS_AUTOMATIC_DISCOVERY_RANGE Variable

bash

export ROS_AUTOMATIC_DISCOVERY_RANGE=<range_value>

Limits ROS 2 discovery range, useful in environments with multiple robots.
Add to ~/.bashrc for persistence:

bash

echo "export ROS_AUTOMATIC_DISCOVERY_RANGE=<range_value>" >> ~/.bashrc

Turtlesim and ROS2 Cheat Sheet

1. Install Turtlesim

Install Turtlesim:

bash

sudo apt update
sudo apt install ros-<ros2-distro>-turtlesim

Check installed executables:

bash

ros2 pkg executables turtlesim

2. Start Turtlesim

Launch the turtlesim node:

bash

ros2 run turtlesim turtlesim_node

3. Control the Turtle

Launch the teleop node to control the turtle:

bash

ros2 run turtlesim turtle_teleop_key

Additional ROS2 commands:

List active nodes:

bash

ros2 node list

List available topics:

bash

ros2 topic list

List available services:

bash

ros2 service list

List available actions:

bash

ros2 action list

4. Install and Use RQT

Install RQT and plugins:

bash

sudo apt update
sudo apt install '~nros-<ros2-distro>-rqt*'

Launch RQT:

bash

rqt

5. Use RQT Service Caller

Select the Service Caller plugin:
- Navigate to: Plugins > Services > Service Caller
Refresh services:
- Click on the Refresh button.

6. Spawn a New Turtle (Service Call)

Call the /spawn service (in RQT Service Caller):
- Name: turtle2
- Coordinates: x = 1.0, y = 1.0
- Click Call to spawn a new turtle.

7. Change Pen Settings (Service Call)

Call the /set_pen service (in RQT Service Caller):
- r = 255 (red)
- width = 5
- Click Call.

8. Remap Topics for Multiple Turtles

Remap the cmd_vel topic for turtle2:

bash

ros2 run turtlesim turtle_teleop_key --ros-args --remap turtle1/cmd_vel:=turtle2/cmd_vel

9. Stop Turtlesim

Stop the turtlesim node:
- Press Ctrl + C in the turtlesim_node terminal.
Stop the teleop node:
- Press q in the turtle_teleop_key terminal.

Understanding Nodes in ROS 2 Cheat Sheet

The ROS 2 Graph

The ROS 2 graph represents the network of ROS 2 elements (nodes, topics, services, etc.) interacting in real-time. A robot system can be visualized as multiple nodes processing data together. Each node in ROS 2 serves a specific modular function (e.g., controlling motors or publishing sensor data).

Nodes in ROS 2

What is a Node?
A node is an executable responsible for a specific task (e.g., controlling motors, publishing sensor data) and communicates with other nodes via topics, services, actions, or parameters.
Single or Multiple Nodes per Executable:
A single ROS 2 executable (written in C++ or Python) can contain multiple nodes.

1. ros2 run

The ros2 run command is used to run an executable from a specific package.

bash

ros2 run <package_name> <executable_name>

Example to run the turtlesim:

bash

ros2 run turtlesim turtlesim_node

This will open a window with a turtle in it.

2. ros2 node list

To list all active nodes in the ROS 2 system:

bash

ros2 node list

3. ros2 node info

The ros2 node info <node_name> command provides detailed information about a node’s publishers, subscribers, services, and actions.

Example to get info about the /turtlesim node:

bash

ros2 node info /turtlesim

3.1 Remapping Node Names and Topics

Remap the node name using --ros-args --remap:

bash

ros2 run turtlesim turtlesim_node --ros-args --remap __node:=my_turtle

This will rename /turtlesim to /my_turtle. If you run ros2 node list, you will see:

bash

/my_turtle
/teleop_turtle

ROS 2 Topic Commands Cheat Sheet

Topics in ROS2

What is a topic
A topic in ROS 2 is a communication channel through which nodes can publish and subscribe to messages, enabling data exchange between them.

1. rqt_graph (Graphical Tool):

Run rqt_graph to visualize the nodes and topics:

bash

rqt_graph

Open via GUI: rqt > Plugins > Introspection > Node Graph.

2. ros2 topic list:

List all active topics:

bash

ros2 topic list

List topics with types:

bash

ros2 topic list -t

3. ros2 topic echo:

Display the data being published on a topic:

bash

ros2 topic echo <topic_name>

Example: To see /turtle1/cmd_vel data:

bash

ros2 topic echo /turtle1/cmd_vel

4. ros2 topic info:

Get info about a specific topic:

bash

ros2 topic info <topic_name>

Example: Info about /turtle1/cmd_vel:

bash

ros2 topic info /turtle1/cmd_vel

5. ros2 interface show:

Show the structure of a message type:

bash

ros2 interface show <msg_type>

Example: For geometry_msgs/msg/Twist:

bash

ros2 interface show geometry_msgs/msg/Twist

6. ros2 topic pub:

Publish data to a topic:

bash

ros2 topic pub <topic_name> <msg_type> "<args>"

Example: To continuously move the turtle:

bash

ros2 topic pub /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 1.8}}"

Publish once:

bash

 ros2 topic pub --once <topic_name> <msg_type> "<args>"

7. ros2 topic hz:

View the rate of data publishing:

bash

ros2 topic hz <topic_name>

Example: Check the rate for /turtle1/pose:

bash

ros2 topic hz /turtle1/pose

8. ros2 topic bw:

Check bandwidth usage for a topic:

bash

ros2 topic bw <topic_name>

Example: Check bandwidth for /turtle1/pose:

bash

ros2 topic bw /turtle1/pose

9. ros2 topic find:

Find topics by message type:

bash

ros2 topic find <msg_type>

Example: Find topics with geometry_msgs/msg/Twist type:

bash

ros2 topic find geometry_msgs/msg/Twist

ROS 2 Services Cheat Sheet

Services in ROS2:

Services in ROS 2 follow a call-and-response model, where nodes request data from a service and receive a response. Unlike topics, services only provide data when specifically called by a client.

1. List Active Services:

View all active services in ROS 2:

bash

ros2 service list

2. Service Type:

Check the type of a service (e.g., /clear):

bash

ros2 service type /clear

3. Service Info:

Get info about a service (e.g., /clear):

bash

ros2 service info /clear

4. Find Services by Type:

Find services of a specific type:

bash

ros2 service find std_srvs/srv/Empty

5. Show Service Interface:

View the request/response structure of a service:

bash

ros2 interface show turtlesim/srv/Spawn

6. Call a Service:

Call a service with or without arguments:

bash

ros2 service call /clear std_srvs/srv/Empty
ros2 service call /spawn turtlesim/srv/Spawn "{x: 2, y: 2, theta: 0.2, name: ''}"

7. Echo Service Data:

View service communication (request/response):

bash

ros2 service echo /add_two_ints

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ROS 2 Parameters Cheat Sheet

Parameters in ROS2:

Parameters in ROS 2 are configuration values for nodes, like settings that can be integers, floats, booleans, strings, and lists. Each node can maintain its own parameters.

1. ros2 param list

List all parameters for all nodes:

bash

ros2 param list

Example output:

CODE

/teleop_turtle:
	scale_angular
	scale_linear
	use_sim_time
/turtlesim:
	background_b
	background_g
    background_r
    use_sim_time

2. ros2 param get

Get the value and type of a parameter:

bash

ros2 param get <node_name> <parameter_name>

Example to get the value of /turtlesim background_g:

bash

ros2 param get /turtlesim background_g

Output:

CODE

Integer value is: 86

3. ros2 param set

Change a parameter’s value:

bash

ros2 param set <node_name> <parameter_name> <value>

Example to change /turtlesim background_r:

bash

ros2 param set /turtlesim background_r 150

Output:

CODE

Set parameter successful

4. ros2 param dump

View and save a node's parameters to a file:

bash

ros2 param dump <node_name> > <file_name>.yaml

Example for /turtlesim:

bash

ros2 param dump /turtlesim > turtlesim.yaml

5. ros2 param load

Load parameters from a file into a node:

bash

ros2 param load <node_name> <parameter_file>

Example:

bash

ros2 param load /turtlesim turtlesim.yaml

Output:

CODE

Set parameter background_b successful
Set parameter background_g successful
Set parameter background_r successful

6. Load Parameter File on Node Startup

Start a node with saved parameters:

bash

ros2 run <package_name> <executable_name> --ros-args --params-file <file_name>

Example:

bash

ros2 run turtlesim turtlesim_node --ros-args --params-file turtlesim.yaml

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ROS 2 Actions Cheat Sheet

Overview of Actions

Actions in ROS 2 are for long-running tasks that can be canceled and provide feedback.
Actions are a combination of Goal, Feedback, and Result.
They use a client-server model similar to topics but allow steady feedback and cancellation.
Action Client sends goals to the Action Server, which processes the goal and sends feedback/results.

1. ros2 node info

View a node's information, including its actions:

bash

ros2 node info <node_name>

Example for /turtlesim:

bash

ros2 node info /turtlesim

This shows the Action Servers and Action Clients for the node.

2. ros2 action list

List all actions in the ROS graph:

bash

ros2 action list

This will return available actions such as /turtle1/rotate_absolute.

3. ros2 action type

Check the action type for a specific action:

bash

ros2 action type /turtle1/rotate_absolute

Output example:

CODE

turtlesim/action/RotateAbsolute

4. ros2 action info

View detailed information about an action:

bash

ros2 action info /turtle1/rotate_absolute

Example output:

CODE

Action: /turtle1/rotate_absolute
Action clients: 1
    /teleop_turtle
Action servers: 1
    /turtlesim

5. ros2 interface show

Inspect the structure of the action type:

bash

ros2 interface show turtlesim/action/RotateAbsolute

This will show the structure of the goal, result, and feedback:

CODE

The desired heading in radians
float32 theta
---
The angular displacement in radians to the starting position
float32 delta
---
The remaining rotation in radians
float32 remaining

6. ros2 action send_goal

Send a goal to an action server:

bash

ros2 action send_goal <action_name> <action_type> <values>

Example:

bash

ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: 1.57}"

Add --feedback to receive feedback during goal execution:

bash

ros2 action send_goal /turtle1/rotate_absolute turtlesim/action/RotateAbsolute "{theta: -1.57}" --feedback

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Using `rqt_console` to view logs

1. Setup

Start rqt_console in a new terminal with the following command:

bash

ros2 run rqt_console rqt_console

Now, start turtlesim in a new terminal with the following command:

bash

ros2 run turtlesim turtlesim_node

2. Messages on rqt_console

To produce log messages for rqt_console to display, let’s have the turtle run into the wall. In a new terminal, enter the ros2 topic pub command below:

bash

ros2 topic pub -r 1 /turtle1/cmd_vel geometry_msgs/msg/Twist "{linear: {x: 2.0, y: 0.0, z: 0.0}, angular: {x: 0.0,y: 0.0,z: 0.0}}"

Press Ctrl+C in the terminal where you ran the ros2 topic pub command to stop your turtle from running into the wall.

3. Set the Default Logger Level

You can set the default logger level when you first run the /turtlesim node using remapping. Enter the following command in your terminal:

bash

ros2 run turtlesim turtlesim_node --ros-args --log-level WARN

Here is a cheat sheet for recording and playing back data using ros2 bag, excluding the previously mentioned commands:

Recording and Playing Back Data in ROS 2

Managing Topic Data

1. Setup

Start the /turtlesim and /teleop_turtle nodes.
Create a directory for saving recordings.

2. Choose a Topic

To list available topics in your system, run:

bash

ros2 topic list

To inspect the data of a topic, run:

bash

ros2 topic echo <topic_name>

3. Record Topics

Single Topic:
Record a single topic:

bash

ros2 bag record <topic_name>

Multiple Topics:
Record multiple topics and specify a custom bag file name:

bash

ros2 bag record -o <file_name> <topic1> <topic2> ...

Record All Topics:

bash

ros2 bag record -a

4. Inspect Topic Data

To see details about a recorded bag file:

bash

ros2 bag info <bag_file_name>

5. Play Topic Data

To replay a bag file:

bash

ros2 bag play <bag_file_name>

Managing Service Data

1. Setup

Start the introspection_service and introspection_client nodes with Service Introspection enabled.

2. Check Service Availability

List all available services:

bash

ros2 service list

To check if Service Introspection is enabled on a specific service:

bash

ros2 service echo --flow-style <service_name>

3. Record Services

Record a Specific Service:

bash

ros2 bag record --service <service_name>

Record All Services:

CODE

ros2 bag record --all-services

4. Inspect Service Data

To inspect a recorded service data bag file:

bash

ros2 bag info <bag_file_name>

5. Play Service Data

To replay service data from the bag file:

bash

ros2 bag play --publish-service-requests <bag_file_name>

ROS 2 Environment Configuration Cheat Sheet

Commands and Explanations

1. Source the Setup Files

2. Add Sourcing to Shell Startup Script

3. Check Environment Variables

4. Set the ROS_DOMAIN_ID Variable

5. Set the ROS_AUTOMATIC_DISCOVERY_RANGE Variable

Turtlesim and ROS2 Cheat Sheet

1. Install Turtlesim

2. Start Turtlesim

3. Control the Turtle

4. Install and Use RQT

5. Use RQT Service Caller

6. Spawn a New Turtle (Service Call)

7. Change Pen Settings (Service Call)

8. Remap Topics for Multiple Turtles

9. Stop Turtlesim

Understanding Nodes in ROS 2 Cheat Sheet

The ROS 2 Graph

Nodes in ROS 2

1. ros2 run

2. ros2 node list

3. ros2 node info

3.1 Remapping Node Names and Topics

ROS 2 Topic Commands Cheat Sheet

Topics in ROS2

1. rqt_graph (Graphical Tool):

2. ros2 topic list:

3. ros2 topic echo:

4. ros2 topic info:

5. ros2 interface show:

6. ros2 topic pub:

7. ros2 topic hz:

8. ros2 topic bw:

9. ros2 topic find:

ROS 2 Services Cheat Sheet

Services in ROS2:

1. List Active Services:

2. Service Type:

3. Service Info:

4. Find Services by Type:

5. Show Service Interface:

6. Call a Service:

7. Echo Service Data:

ROS 2 Parameters Cheat Sheet

Parameters in ROS2:

1. ros2 param list

2. ros2 param get

3. ros2 param set

4. ros2 param dump

5. ros2 param load

6. Load Parameter File on Node Startup

ROS 2 Actions Cheat Sheet

Overview of Actions

1. ros2 node info

2. ros2 action list

3. ros2 action type

4. ros2 action info

5. ros2 interface show

6. ros2 action send_goal

Using rqt_console to view logs

1. Setup

2. Messages on rqt_console

3. Set the Default Logger Level

Recording and Playing Back Data in ROS 2

Managing Topic Data

1. Setup

2. Choose a Topic

3. Record Topics

4. Inspect Topic Data

5. Play Topic Data

Managing Service Data

1. Setup

2. Check Service Availability

3. Record Services

4. Inspect Service Data

5. Play Service Data

Using `rqt_console` to view logs