nsinit

nsinit

nsinit is a cli application which demonstrates the use of libcontainer.
It is able to spawn new containers or join existing containers.

How to build?

First add the libcontainer/vendor into your GOPATH. It's because libcontainer vendors all its dependencies, so it can be built predictably.

export GOPATH=$GOPATH:/your/path/to/libcontainer/vendor

Then get into the nsinit folder and get the imported file. Use make command to make the nsinit binary.

cd libcontainer/nsinit
go get
make

We have finished compiling the nsinit package, but a root filesystem must be provided for use along with a container configuration file.

Choose a proper place to run your container. For example we use /busybox.

mkdir /busybox 
curl -sSL 'https://github.com/jpetazzo/docker-busybox/raw/buildroot-2014.11/rootfs.tar' | tar -xC /busybox

Then you may need to write a configuration file named container.json in the /busybox folder. Environment, networking, and different capabilities for the container are specified in this file. The configuration is used for each process executed inside the container.

See the sample_configs folder for examples of what the container configuration should look like.

cp libcontainer/sample_configs/minimal.json /busybox/container.json
cd /busybox

You can customize container.json per your needs. After that, nsinit is ready to work.

To execute /bin/bash in the current directory as a container just run the following as root:

nsinit exec --tty --config container.json /bin/bash

If you wish to spawn another process inside the container while your current bash session is running, run the same command again to get another bash shell (or change the command). If the original process (PID 1) dies, all other processes spawned inside the container will be killed and the namespace will be removed.

You can identify if a process is running in a container by looking to see if state.json is in the root of the directory.

You may also specify an alternate root directory from where the container.json file is read and where the state.json file will be saved.