docker_modify_container

Modify the Container Environment

We will now make some changes to the container from the interactive Bash session we just initiated.

• This initial image is very barebones. It does not have a text editor yet, so we will install one now:

apt update && apt install -y nano

• Optionally, replace nano with your text editor of choice.
• Use the text editor to edit ros_entrypoint.sh.
  • E.g. nano /ros_entrypoint.sh.
  • This is a script that will be run immediately after your container is launched.
• Modify the contents to read:

#!/bin/bash
set -e

# setup ros environment
source "/opt/ros/$ROS_DISTRO/setup.bash"

/run_my_system.bash

• Now the entrypoint will call the run_my_system.bash script. This script does not exist yet, so let's create it. Run:

nano /run_my_system.bash

• Copy the following text into the file

#!/bin/bash

# Create ros master if not already started
rostopic list > /dev/null 2>&1
retVal=$?
if [ $retVal -ne 0 ]; then
    roscore &
    echo "Wait for 5s to allow rosmaster to start"
    sleep 5s
else
    echo "rosmaster already setup"
fi

# Send forward command
RATE=1
CMD=2
echo "Sending forward command"
rostopic pub /cora/thrusters/left_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD} &
rostopic pub /cora/thrusters/right_thrust_cmd std_msgs/Float32 -r ${RATE} -- ${CMD}

• Save and exit.
• Run chmod +x /run_my_system.bash to make it executable.
• To test this script, run

source /opt/ros/melodic/setup.bash
/run_my_system.bash &
sleep 5s;rostopic echo /cora/thrusters/left_thrust_cmd

• You should receive /cora/thrusters/left_thrust_cmd data.
• Type CTRL-C to exit.

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