runc

runc is a CLI tool for spawning and running containers according to the OCF specification.

State of the project

Currently runc is an implementation of the OCF specification. We are currently sprinting to have a v1 of the spec out within a quick timeframe of a few weeks, ~July 2015, so the runc config format will be constantly changing until the spec is finalized. However, we encourage you to try out the tool and give feedback.

Building:

# create a 'github.com/opencontainers' in your GOPATH
cd github.com/opencontainers
git clone https://github.com/opencontainers/runc
cd runc
make
sudo make install

Using:

To run a container that you received just execute runc with the JSON format as the argument or have a container.json file in the current working directory.

runc 
/ $ ps
PID   USER     COMMAND
1     daemon   sh
5     daemon   sh
/ $ 

OCF Container JSON Format:

Below is a sample container.json configuration file. It assumes that the file-system is found in a directory called rootfs and there is a user named daemon defined within that file-system.

{
    "version": "0.1",
    "os": "linux",
    "arch": "amd64",
    "processes": [
        {
            "tty": true,
            "user": "daemon",
            "args": [
                "sh"
            ],
            "env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "TERM=xterm"
            ],
            "cwd": ""
        }
    ],
    "root": {
        "path": "rootfs",
        "readonly": true
    },
    "cpus": 1.1,
    "memory": 1024,
    "hostname": "shell",
    "namespaces": [
        {
            "type": "process"
        },
        {
            "type": "network"
        },
        {
            "type": "mount"
        },
        {
            "type": "ipc"
        },
        {
            "type": "uts"
        }
    ],
    "capabilities": [
        "AUDIT_WRITE",
        "KILL",
        "NET_BIND_SERVICE"
    ],
    "devices": [
        "null",
        "random",
        "full",
        "tty",
        "zero",
        "urandom"
    ],
    "mounts": [
        {
            "type": "proc",
            "source": "proc",
            "destination": "/proc",
            "options": ""
        },
        {
            "type": "tmpfs",
            "source": "tmpfs",
            "destination": "/dev",
            "options": "nosuid,strictatime,mode=755,size=65536k"
        },
        {
            "type": "devpts",
            "source": "devpts",
            "destination": "/dev/pts",
            "options": "nosuid,noexec,newinstance,ptmxmode=0666,mode=0620,gid=5"
        },
        {
            "type": "tmpfs",
            "source": "shm",
            "destination": "/dev/shm",
            "options": "nosuid,noexec,nodev,mode=1777,size=65536k"
        },
        {
            "type": "mqueue",
            "source": "mqueue",
            "destination": "/dev/mqueue",
            "options": "nosuid,noexec,nodev"
        },
        {
            "type": "sysfs",
            "source": "sysfs",
            "destination": "/sys",
            "options": "nosuid,noexec,nodev"
        }
    ]
}

Examples:

Using a Docker image

To test using Docker's busybox image follow these steps:

• Install docker and download the buysbox image: docker pull busybox
• Create a container from that image and export its contents to a tar file: docker export $(docker create busybox) > busybox.tar
• Untar the contents to create your filesystem directory:

mkdir rootfs
tar -C rootfs -xf busybox.tar

• Create a file called container.json using the example from above. Modify the user property to be root.
• Execute runc and you should be placed into a shell where you can run ps:

$ runc
/ # ps
PID   USER     COMMAND
    1 root     sh
    9 root     ps

Using runc with systemd

[Unit]
Description=Minecraft Build Server
Documentation=http://minecraft.net
After=network.target

[Service]
CPUQuota=200%
MemoryLimit=1536M
ExecStart=/usr/local/bin/runc
Restart=on-failure
WorkingDirectory=/containers/minecraftbuild

[Install]
WantedBy=multi-user.target