Linux VM + generic Makefile for C programming

• Defines a Virtual Machine with Linux (Ubuntu) to be used e.g. for operating system courses at university.
• The directory that contains the Vagrantfile (= root working directory) is available as a shared folder within the VM at /home/vagrant/os.
• Alternatively, a Docker container is available (e.g., to be used with Apple’s M1 chip).
• A generic Makefile and tools for static code analysis (C language) are provided.
• A generic Makefile for kernel modules is provided as well.

Getting Started

• Install Virtualbox
  • Install the software only – no virtual machine.
    • For Apple users: Virtualbox does not work (yet) with the M1 chip. Alternative solutions (not automated with Vagrant) include Parallels Desktop and UTM or the Docker solution below.
  • https://www.virtualbox.org/
• Install Vagrant
  • https://www.vagrantup.com/
• Download/copy this file to your root working directory
  • Vagrantfile
• (Re-) Provision the Vagrant VM (in your root working directory)
  • vagrant up --provision

Linux Virtual Machine with Vagrant

Usage

• On the command line in the Vagrantfile folder

    vagrant up
    vagrant ssh
  

• The folder with the Vagrantfile is shared

    cd ~/os
  

• When you do not need the VM

    vagrant suspend
  

Troubleshooting

If you get the following error message:

==> Mounting NFS shared folders...
...
mount.nfs: requested NFS version or transport protocol is not supported

Try this solution:

• edit /etc/hosts on your host system
• add 127.0.0.1 localhost (in case this line is missing)

Linux “Virtual Machine” with Docker

• This solution is intended for students with an Apple M1 chip who cannot use Virtualbox (yet).
• A Docker container is not a virtual machine, and Kernel module development is not possible.
  • It would be possible in privileged mode, but there are no header files available for the LinuxKit kernel used on MacOS (March 2022).

Installation

• Install Docker Desktop
  • https://docs.docker.com/desktop/mac/apple-silicon/
• Run Docker.app
  • Grant privileges if necessary.
  • Docker Desktop must be running when using the container.
• Open a shell with your root working directory
  • The folder must not contain a file named Dockerfile.
• Run this command in your root working directory

  curl https://raw.githubusercontent.com/josefhammer/linux-vm-c-programming/main/docker/build-osdocker.sh | bash
  

Usage

• Run the newly created launch script in your root working directory

    ./run-osdocker.sh
  

  • This folder will be available within the container at /home/vagrant/os.
  • Can be run multiple times if more than one shell in parallel is needed.
    • The first one to exit will stop the container.
  • The script has been designed to make the container feel like a Vagrant virtual machine – this is not how one would typically use containers.

Generic Makefile with static code analysis

To guarantee that the static analysis is performed on each run, all *.c files will be compiled regardless of whether they were changed or not. I.e., the typical Make optimization to compile only changed files is disabled (the script is intended for student assignments where build performance is not of major importance).

Targets

Target	Description
format	Auto-format all source files
clean	Remove binary program and all temp files
all	Full build
test	Run program with Valgrind

Limitations

Can link a single program per folder only.

Requirements

sudo apt -y install build-essential valgrind clang clang-format clang-tidy cppcheck

Usage

In the directory with your source file(s) within the VM:

make
make test (in case no command-line arguments are required for your program)
make clean

Notes

• one program per folder only
• if you have your own Makefile in the folder, yours will be used
• no need to copy the Makefile (renamed to Makefile!) into your source folder if the make-macro installation script has been run (e.g., in the Vagrant virtual machine)

Auto-format your source files

In the directory with your source file(s) within the VM

make format

Notes

• uses clang-format with a style based on WebKit style
• you may adapt .clang-format according to your preferences
• sections can be excluded using // clang-format off|on
• many editors/IDEs like Atom and Visual Studio Code have integrations/features that allow to auto-format code (i.e., you won’t have to use make format)

Auto-Format with Visual Studio Code

1. Install the C++ Extension by Microsoft

2. Preferences --> Settings --> search for “format”

   • Editor: activate “Format On Save”
   • C/C++: Clang_format_style = file
     • will format only if a .clang-format is present in any parent directory
   • C/C++: Clang_format_fallback = WebKit
     • will also format if no .clang-format is present
     • if None nothing will be done without a .clang-format file present

Generic Makefile for kernel modules

This Makefile copies a single *.c file to a temp folder, compiles it to a kernel module, and copies the resulting kernel object file back to the current folder. This approach keeps the current folder clean of any temp files.

Usage

Copy the file Makefile-kernel-module to your source folder and rename it to Makefile or makefile.

In the directory with your source file(s) within the VM:

make
make clean

Attention

The provided Makefile must be renamed exactly as mentioned above (no extension!); otherwise, the generic Makefile for regular C programs will be used!

Limitations

The folder must contain a single *.c file only.

License

This project is licensed under the MIT License.