Low Level Container Runtime

How to run

1. Build the program using gcc (this requires libnl and libcap, so make sure you have these libraries):

$> make

2. Download a minimal/base ubuntu root filesystem from https://cdimage.ubuntu.com/ubuntu-base/releases/22.04.4/release/.

3. Extract the rootfs

# the rootfs will be here
$ mkdir rootfs
$ tar xzvf <tar file> -C rootfs

3. Run the program as root :

$ sudo ./container --rootfs <root_fs_path> --memory <memory_limit> -- <command> [command_args]

# Example (from the previous step of ubuntu image):
$ sudo ./container --rootfs ./rootfs --memory 1G -- /bin/bash

Remember, the rootfs cannot be on the current mounted root, pivot_root will give out error.

Status

• UID and GID mapping
• clone setup
• filesystem Setup
• cgroup limits setup
• network setup (to be done after I study more about kernel networking and netlink, or as part of CNI implementation in near future)

Playground

• playground/ has small standalone programs that I used for practising.

To build the program run gcc container.c -o container -lcap
To run the program you need CAP_SYS_ADMIN, so you can use sudo: sudo ./container /bin/bash

Notes

My in-depth notes on cgroups, namespaces and other container topics are available at : https://www.sheharyaar.in/notes/linux-containers/