[Feature Request] Support EROFS for image Rootfs and Guest OS images

[novahe]

Motivation

CubeSandbox currently relies on ext4 for Rootfs and Guest OS images. However, ext4 is not the most efficient choice for read-only, high-density AI sandbox environments. It leads to larger image sizes and suboptimal IO performance during massive concurrent cold starts.

Proposed Solution

Support EROFS (Enhanced Read-Only File System) as a modern alternative to ext4 to achieve:

• Reduced Image Size: Leverage transparent compression (LZ4) to significantly cut down distribution bandwidth and storage overhead.
• Performance Optimization: Faster metadata lookups and lower IO latency during high-concurrency cold starts.
• Native Integrity: A natively immutable filesystem that provides better security for read-only Rootfs.

Proposed Implementation

• CubeMaster: Integrate mkfs.erofs into the image building pipeline and update metadata to support EROFS media type.
• Cubelet: Remove the hardcoded block for EROFS and support dynamic FsType for pmem devices.
• CubeShim: Allow rootfstype=erofs in the VM boot configuration.

Additional Context

This alignment follows industry best practices for container runtimes, similar to the work being done in Kata Containers: kata-containers/pull/13019.

The NVIDIA images go down from 1.2GB to less than 500MB.

[kinwin-ustc]

I agree with your proposal, can you help submit a PR?