imskyer / footloose

Container Machines - Containers that look like Virtual Machines

footloose

footloose is a developer tool creating containers that look like virtual machines. Those containers run systemd as PID 1 and a ssh daemon that can be used to login into the container. Such "machines" behave very much like a VM, it's even possible to run dockerd in them :)

footloose can be used for a variety of tasks, wherever you'd like virtual machines but don't want to wait for them to boot or need many of them. An easy way to think about it is: Vagrant, but with containers.

footloose in action:

Install

footloose binaries can be downloaded from the release page:

# For Linux
curl -Lo footloose https://github.com/weaveworks/footloose/releases/download/0.2.0/footloose-0.2.0-linux-x86_64
chmod +x footloose
sudo mv footloose /usr/local/bin/

# For macOS
curl -Lo footloose https://github.com/weaveworks/footloose/releases/download/0.2.0/footloose-0.2.0-darwin-x86_64
chmod +x footloose
sudo mv footloose /usr/local/bin/

Alternatively, build and install footloose from sources. It requires having go >= 1.11 installed:

GO111MODULE=on go get github.com/weaveworks/footloose

Usage

footloose reads a description of the Cluster of Machines to create from a file, by default named Footloose. The config command helps with creating the initial config file:

# Create a Footloose config file. Instruct we want to create 3 machines instead
# of the default, 1.
footloose config create --replicas 3

Start the cluster of 3 machines:

$ footloose create
INFO[0000] Pulling image: quay.io/footloose/centos7 ...
INFO[0007] Creating machine: cluster-node0 ...
INFO[0008] Creating machine: cluster-node1 ...
INFO[0008] Creating machine: cluster-node2 ...

It only takes a second to create those machines. The first time create runs, it will pull the docker image used by the footloose containers so it will take a tiny bit longer.

SSH into a machine with:

$ footloose ssh root@node1
[root@1665288855f6 ~]# ps fx
  PID TTY      STAT   TIME COMMAND
    1 ?        Ss     0:00 /sbin/init
   23 ?        Ss     0:00 /usr/lib/systemd/systemd-journald
   58 ?        Ss     0:00 /usr/sbin/sshd -D
   59 ?        Ss     0:00  \_ sshd: root@pts/1
   63 pts/1    Ss     0:00      \_ -bash
   82 pts/1    R+     0:00          \_ ps fx
   62 ?        Ss     0:00 /usr/lib/systemd/systemd-logind

Choosing the OS image to run

footloose will default to running a centos 7 container image. The --image argument of config create can be used to configure the OS image. Valid OS images are:

• quay.io/footloose/centos7
• quay.io/footloose/fedora29
• quay.io/footloose/ubuntu18.04
• quay.io/footloose/amazonlinux2

For example:

footloose config create --replicas 3 --image quay.io/footloose/fedora29

footloose.yaml

footloose config create creates a footloose.yaml configuration file that is then used by subsequent commands such as create, delete or ssh. If desired, the configuration file can be named differently and supplied with the -c, --config option.

$ footloose config create --replicas 3
$ cat footloose.yaml
cluster:
  name: cluster
  privateKey: cluster-key
machines:
- count: 3
  spec:
    image: quay.io/footloose/centos7
    name: node%d
    portMappings:
    - containerPort: 22

This configuration can naturally be edited by hand. The full list of available parameters are in the reference documentation.

Examples

Interesting things can be done with footloose!

Customize the OS image

It is possible to create docker images that specialize a footloose base image to suit your needs.

For instance, if we want the created machines to run fedora29 with the htop package already pre-installed:

FROM quay.io/footloose/fedora29

# Pre-seed the htop package
RUN dnf -y install htop && dnf clean all

Build that image:

docker build -t fedora29-htop .

Configure footloose.yaml to use that image by either editing the file or running:

footloose config create --image fedora29-htop

htop will be available on the newly created machines!

$ footloose create
$ footloose ssh root@node0
# htop

Running dockerd in Container Machines

To run dockerd inside a docker container, two things are needed:

• Run the container as privileged (we could probably do better! expose capabilities instead!).
• Mount /var/lib/docker as volume, here an anonymous volume. This is because of a limitations of what you can do with the overlay systems docker is setup to use.

cluster:
  name: cluster
  privateKey: cluster-key
machines:
- count: 1
  spec:
    image: quay.io/footloose/centos7
    name: node%d
    portMappings:
    - containerPort: 22
    privileged: true
    volumes:
    - type: volume
      destination: /var/lib/docker

You can then install and run docker on the machine:

$ footloose create
$ footloose ssh root@node0
# yum install -y docker iptables
[...]
# systemctl start docker
# docker run busybox echo 'Hello, World!'
Hello, World!

Under the hood

Under the hood, Container Machines are just containers. They can be inspected with docker:

$ docker ps
CONTAINER ID    IMAGE                        COMMAND         NAMES
04c27967f76e    quay.io/footloose/centos7    "/sbin/init"    cluster-node2
1665288855f6    quay.io/footloose/centos7    "/sbin/init"    cluster-node1
5134f80b733e    quay.io/footloose/centos7    "/sbin/init"    cluster-node0

The container names are derived from cluster.name and cluster.machines[].name.

They run systemd as PID 1, it's even possible to inspect the boot messages:

$ docker logs cluster-node1
systemd 219 running in system mode.
Detected virtualization docker.
Detected architecture x86-64.

Welcome to CentOS Linux 7 (Core)!

Set hostname to <1665288855f6>.
Initializing machine ID from random generator.
Failed to install release agent, ignoring: File exists
[  OK  ] Created slice Root Slice.
[  OK  ] Created slice System Slice.
[  OK  ] Reached target Slices.
[  OK  ] Listening on Journal Socket.
[  OK  ] Reached target Local File Systems.
         Starting Create Volatile Files and Directories...
[  OK  ] Listening on Delayed Shutdown Socket.
[  OK  ] Reached target Swap.
[  OK  ] Reached target Paths.
         Starting Journal Service...
[  OK  ] Started Create Volatile Files and Directories.
[  OK  ] Started Journal Service.
[  OK  ] Reached target System Initialization.
[  OK  ] Started Daily Cleanup of Temporary Directories.
[  OK  ] Reached target Timers.
[  OK  ] Listening on D-Bus System Message Bus Socket.
[  OK  ] Reached target Sockets.
[  OK  ] Reached target Basic System.
         Starting OpenSSH Server Key Generation...
         Starting Cleanup of Temporary Directories...
[  OK  ] Started Cleanup of Temporary Directories.
[  OK  ] Started OpenSSH Server Key Generation.
         Starting OpenSSH server daemon...
[  OK  ] Started OpenSSH server daemon.
[  OK  ] Reached target Multi-User System.