Overview

This is a Juju layer intended to ease the development of charms that need to execute commands over SSH, such as proxy charms.

What is a proxy charm?

A proxy charm is a limited type of charm that does not interact with software running on the same host, such as controlling and configuring a remote device (a static VM image, a router/switch, etc.). It cannot take advantage of some of Juju's key features, such as scaling, relations, and leadership.

Proxy charms are primarily a stop-gap, intended to prototype quickly, with the end goal being to develop it into a full-featured charm, which installs and executes code on the same machine as the charm is running.

Integration

After you've created your charm, open interfaces.yaml and add layer:sshproxy to the includes stanza, as shown below:

includes: ['layer:basic', 'layer:sshproxy']

Reactive states

This layer will set the following states:

• sshproxy.configured This state is set when SSH credentials have been supplied to the charm.

Example

In reactive/mycharm.py, you can add logic to execute commands over SSH. This example is run via a start action, and starts a service running on a remote host.

...
import charms.sshproxy


@when('sshproxy.configured')
@when('actions.start')
def start():
    """ Execute's the command, via the start action` using the
    configured SSH credentials
    """
    sshproxy.ssh("service myservice start")

Actions

This layer includes a built-in run action useful for debugging or running arbitrary commands:

$ juju run-action mycharm/0 run command=hostname
Action queued with id: 014b72f3-bc02-4ecb-8d38-72bce03bbb63

$ juju show-action-output 014b72f3-bc02-4ecb-8d38-72bce03bbb63
results:
  output: juju-66a5f3-11
status: completed
timing:
  completed: 2016-10-27 19:53:49 +0000 UTC
  enqueued: 2016-10-27 19:53:44 +0000 UTC
  started: 2016-10-27 19:53:48 +0000 UTC

Known Limitations and Issues

Security issues

• Password and key-based authentications are supported, with the caveat that both (password and private key) are stored plaintext within the Juju controller.

Configuration and Usage

This layer adds the following configuration options:

• ssh-hostname
• ssh-username
• ssh-password
• ssh-private-key

Once configure those values at any time. Once they are set, the sshproxy.configured state flag will be toggled:

juju deploy mycharm ssh-hostname=10.10.10.10 ssh-username=ubuntu ssh-password=yourpassword

or

juju deploy mycharm ssh-hostname=10.10.10.10 ssh-username=ubuntu ssh-private-key="`cat ~/.ssh/id_rsa`"

Contact Information

Homepage: https://github.com/AdamIsrael/layer-sshproxy