Simple Linux Character Device Driver (with Docker Environment)

This repository provides a minimal Linux character device driver, along with a Docker-based build and test environment that works safely on any Linux host.

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Content

.
├── Dockerfile                  # Docker image for kernel module development
├── .gitignore                  # Ignore build artifacts
└── dev/
    └── simple_char_driver/
        ├── Makefile           # Kernel module build rules
        └── simple_char_driver.c  # The char device driver source

Build Docker image

docker build -t char_dev_env .

# If you get permission denied, use
sudo docker build -t char_dev_env .

Run the Docker container

docker run --rm -it \
  --privileged \
  --name char_dev \
  -v /lib/modules:/lib/modules \
  -v /usr/src:/usr/src \
  -v $(pwd)/dev:/home/dev/dev \
  char_dev_env

Build the driver

cd ~/dev/simple_char_driver
make

Insert and test the driver

sudo insmod simple_char_driver.ko
dmesg | tail

You’ll see something like: Simple char driver loaded: major=509

Now create the device node (replace 509 with your actual major):

sudo mknod /dev/simple_char c 509 0
sudo chmod 666 /dev/simple_char

Testing

echo "Hello Driver" > /dev/simple_char
cat /dev/simple_char

Expected output: Hello Driver

cleanup

sudo rmmod simple_char_driver