> ## Documentation Index
> Fetch the complete documentation index at: https://dragonwingdocs.qualcomm.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Troubleshooting

## `/dev/ttyACM0` Permission Denied

You have not yet logged out since being added to `dialout`. Use this wrapper until you do:

```bash theme={null}
sg dialout -c '. /opt/ros/jazzy/setup.sh; . ~/turtlebot3_ws/install/setup.sh; \
  export TURTLEBOT3_MODEL=burger OPENCR_PORT=/dev/ttyACM0 LDS_MODEL=LDS-02; \
  ros2 launch turtlebot3_bringup robot.launch.py'
```

After one logout/login this wrapper is no longer needed.

## LiDAR Scan Empty / Cartographer Stuck

`Queue waiting for data: (0, scan)` usually means the wrong LDS model is set.

```bash theme={null}
echo $LDS_MODEL    # must be LDS-02
ls /dev/ttyUSB0    # must exist
```

If `LDS_MODEL=LDS-01`, fix it:

```bash theme={null}
sed -i 's/export LDS_MODEL=LDS-01/export LDS_MODEL=LDS-02/' ~/.bashrc
source ~/.bashrc
```

## `package 'ld08_driver' not found`

```bash theme={null}
sudo apt install -y ros-jazzy-ld08-driver
```

## `cmd_vel` Commands Do Nothing

ROS 2 Jazzy changed the `cmd_vel` topic type from `geometry_msgs/Twist` to `geometry_msgs/TwistStamped`. If you are publishing `Twist` directly (e.g. from a custom node or an older tutorial), add a `header` field:

```python theme={null}
from geometry_msgs.msg import TwistStamped
from builtin_interfaces.msg import Time

msg = TwistStamped()
msg.header.stamp = self.get_clock().now().to_msg()
msg.twist.linear.x = 0.2
msg.twist.angular.z = 0.0
publisher.publish(msg)
```

The built-in `turtlebot3_teleop teleop_keyboard` node already handles this correctly — this only affects custom publishers.

## Map Saver Fails Silently

Always include `-t /map` explicitly:

```bash theme={null}
ros2 run nav2_map_server map_saver_cli -t /map -f ~/my_map
```

## `apt` Locked by Background Process

```bash theme={null}
sudo systemctl stop apt-daily.service apt-daily-upgrade.service packagekit.service
sudo pkill -f aptd || true
sudo apt update
```