Known Hosts File

Before an agent can connect to a VOLTTRON platform that agent must know the platform’s VIP address and public key (known as the server key). It can be tedious to manually keep track of server keys and match them with their corresponding addresses.

The purpose of the known-hosts file is to save a mapping of platform addresses to server keys. This way the user only has to specify a server key one time.

Saving a Server Key

Suppose a user wants to connect to a platform at, and the platform’s public key is uhjbCUm3kT5QWj5Py9w0XZ7c1p6EP8pdo4Hq4dNEIiQ. To save this address-to-server-key association, the user can run:

volttron-ctl auth add-known-host --host --serverkey uhjbCUm3kT5QWj5Py9w0XZ7c1p6EP8pdo4Hq4dNEIiQ

Now agents on this system will automatically use the correct server key when connecting to the platform at

Server Key for Local Platforms

When a platform starts it automatically adds its public key to the known-hosts file. Thus agents connecting to the local VOLTTRON platform (on the same system and using the same $VOLTTRON_HOME) will automatically be able to retrieve the platform’s public key.

Know-Host-File Details


The following details regarding the known-hosts file are subject to change. These notes are primarily for developers, but the may be helpful if troubleshooting an issue. The known-hosts file should not be edited directly.

File Location

The known-hosts-file is stored at $VOLTTRON_HOME/known_hosts.

File Contents

Here are the contents of an example known-hosts file:

    "@": "FSG7LHhy3v8tdNz3gK35G6-oxUcyln54pYRKu5fBJzU",
    "": "FSG7LHhy3v8tdNz3gK35G6-oxUcyln54pYRKu5fBJzU",
    "": "FSG7LHhy3v8tdNz3gK35G6-oxUcyln54pYRKu5fBJzU",
    "": "FSG7LHhy3v8tdNz3gK35G6-oxUcyln54pYRKu5fBJzU",
    "": "uhjbCUm3kT5QWj5Py9w0XZ7c1p6EP8pdo4Hq4dNEIiQ"

The first four entries are for the local platform. (They were automatically added when the platform started.) The first entry with the @ key is for IPC connections, and the entries with the 127.0.0.* keys are for local TCP connections. Note that a single VOLTTRON platform can bind to multiple TCP addresses, and each address will be automatically added to the known-hosts file. The last entry is for a remote VOLTTRON platform. (It was added in the Saving a Server Key section.)