Users and authentication

This section deals with topics related to user authentication and general user security.

Users and passwords

There are two ways users are introduced into Juju: the initial administrator of a controller via the controller creation step and a non-administrator via the user registration step. The latter sets up the user's Juju password but the former is left without an actual password. This is why if such a user tries to log out (juju logout) before creating a password the command will fail and a warning will be displayed. An administrator should, therefore, create a password once the controller is created. They must do so if multiple Juju users will be using the same system user account:

juju bootstrap aws mycontroller
juju change-user-password

See Creating a controller for details on controller creation.

Credentials

Credentials managed in Juju are related to the accessing of the chosen cloud-backed resource. They are not related to Juju users themselves in any way. Credentials added to Juju remain local to the system user (on Ubuntu: ~/.local/share/juju/credentials.yaml).

See Cloud credentials for more on this topic.

SSH access

SSH access is managed on a per-model basis. That is, if a public key is added to a model then that key is placed on all machines (present and future) in that model.

Each Juju machine provides a user account named 'ubuntu' and it is to this account that public keys are added when using the Juju SSH commands ( juju add-ssh-key and juju import-ssh-key). Because this user is effectively the 'root' user (passwordless sudo privileges), the granting of SSH access must be done with due consideration.

It is possible to connect to a Juju machine in one of two ways:

• Via Juju, using the juju ssh command
• Direct access, using a standard SSH client (e.g PuTTY on Windows or ssh [OpenSSH] on Linux)

Connecting via Juju involves a second degree of security, as explained below.

Regardless of the method used to connect, a public SSH key must be added to the model. In the case of direct access, it remains possible for a key to be added to an individual machine using standard methods (manually copying a key to the authorized_keys file or by way of a command such as ssh-import-id for Debian-based Linux distributions such as Ubuntu).

Juju ssh

When using the juju ssh command, Juju's own user rights system imposes an extra degree of security by permitting access solely from a Juju user, and only one with sufficient permissions. How this works depends on whether the user is an admin or a non-admin. See Juju users for a breakdown of the different user types.

For example, to connect to a machine with an id of '0':

juju ssh 0

An interactive pseudo-terminal (pty) is enabled by default. For the OpenSSH client, this corresponds to the -t option ("force pseudo-terminal allocation").

Admin user

When a controller is created (see Creating a controller) a passphraseless SSH keypair will be generated and placed under ~/.local/share/juju/ssh. The public key (juju_id_rsa.pub) will be installed in the 'ubuntu' account on every machine created within every model belonging to this controller. During creation, if there is an existing public key named ~/.ssh/id_rsa.pub then it will also be placed on every machine.

As long as the controller administrator has access to either of the above keys he/she can connect to any machine with the juju ssh command.

Regular user

In order for a regular Juju user to connect with juju ssh the user must:

• be created (juju add-user)
• be registered (juju register)
• be logged in (juju login)
• have 'admin' rights to the model (juju grant)
• have their public key added to the model by an admin (juju add-ssh-key or juju import-ssh-key)
• be in possession of the corresponding private key

See Users and models for information on managing user permissions.

In terms of the private key, the easiest way to ensure it is used is to have it stored as ~/.ssh/id_rsa. Otherwise, you can do one of two things:

1. Use ssh-agent
2. Specify the key manually

The second option above, applied to the previous example, will look like this:

juju ssh 0 -i ~/.ssh/my-private-key

Direct SSH access

When using a standard SSH client if one's public key has been installed into a model, then, as expected, a connection to the 'ubuntu' user account can be made. All that is needed is the corresponding keypair and adequate network connectivity.

For example, to connect to a machine with an IP address of 10.149.29.143 with the OpenSSH client:

ssh ubuntu@10.149.29.143