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goinit

Introduction

goinit is a task-specific Linux init implementation aimed at mimicking the unikernel strategy within a traditional Linux kernel environment. It is designed to execute "flashing" actions, such as fetching and writing the root filesystem, boot items like device tree, U-Boot environment variables, or kernel image. The project's goal is to simplify and standardize these tasks within a Linux environment. goinit is integrated into the Linux kernel and replaces the typical initramfs. It can be embedded into the kernel image, allowing U-Boot to fetch and execute the kernel. U-Boot controls goinit using kernel arguments in the format pr.<command>=value.

Build

To build the goinit project, follow these steps:

Download the Repository: Clone the goinit repository from the source repository:

git clone https://github.com/alessandrocarminati/goinit

Replace https://github.com/alessandrocarminati/goinit with the URL of the repository.

Build the Project: Navigate to the root directory of the cloned repository and run the following command to build the project:

make

This command compiles the source code and generates the necessary binaries. Retrieve the Root Filesystem rootfs.cpio: After the build process completes, you can find the root filesystem rootfs.cpio in the bin directory of the project. The rootfs.cpio file contains the root filesystem required for goinit operation.

With these steps completed, you have successfully built the goinit project and obtained the root filesystem required for further usage.

Kernel Integration

For goinit to be functional, it must be integrated with a working kernel for the board. The Linux kernel provides a configuration option that facilitates this integration. Ensure that your kernel configuration includes the following items:

CONFIG_INITRAMFS_SOURCE="<path to the cpio>"
CONFIG_INITRAMFS_ROOT_UID=0
CONFIG_INITRAMFS_ROOT_GID=0

• CONFIG_INITRAMFS_SOURCE: This option specifies the path to the root filesystem rootfs.cpio generated by goinit during the build process.
• CONFIG_INITRAMFS_ROOT_UID: Sets the UID (user identifier) of the root user in the initramfs to 0 (root).
• CONFIG_INITRAMFS_ROOT_GID: Sets the GID (group identifier) of the root user in the initramfs to 0 (root).

By configuring the kernel with these options, the resulting kernel image will include goinit embedded within it. This kernel image will be recognized as a "U-Boot executable," allowing U-Boot to fetch and execute it accordingly. Ensure that you build the kernel with these configurations to produce a kernel image that incorporates goinit seamlessly.

Usage

Supported Kernel Arguments

• pr.ifname: Specifies the interface to bring up (supports DHCP only).
• pr.syslogIP: Specifies the syslog server to send message logs.
• pr.action: Specifies the action to execute (e.g., flashRootfs, writeKernel, writeDTB, writeUbootEnv, Reboot, etc.).
• pr.actionArgx: Represents arguments passed to the action specified by pr.action.
• pr.debuglevel: Adjusts the debug level of goinit.
• pr.reboot: Instructs goinit to reboot the system after completing its tasks. [Insert additional usage instructions or examples here]

goinit is developed as part of the automation process for the provisioner tool, serving as the provisioner agent on the board.