Lab Configuration¶

A lab is a set of hosts described in one or more hosts.json files. Each file lists every host in a given location; each host entry declares which lab names it belongs to, so a single file can serve multiple labs and a host can belong to more than one lab at once. This page is the full per-host schema reference. For repo-level settings (paths, libs, init modules) see Repository Setup.

Lab files¶

Each directory listed under the labs key in .otto/settings.toml may contain a hosts.json file. The file is a JSON array of host objects:

[
    {
        "ip": "10.10.200.11",
        "ne": "carrot",
        "board": "seed",
        "creds": { "vagrant": "vagrant" },
        "labs": ["veggies"]
    },
    {
        "ip": "192.0.2.1",
        "ne": "sprout",
        "board": "seed",
        "osType": "zephyr",
        "labs": ["embedded"]
    }
]

Each entry carries a labs field listing the lab names it belongs to. Pass --lab veggies (or set OTTO_LAB=veggies) and otto loads every host whose labs field includes "veggies".

The host id used by get_host(), --list-hosts, and the rest of the CLI is derived from the ne, board, and neId fields. carrot with board seed becomes carrot_seed; carrot with board seed and neId 2 becomes carrot_seed_2.

Per-host fields¶

Required¶

Common optional¶

Host type / OS¶

Embedded-only fields¶

These fields apply only to hosts with an embedded base type (e.g. osType: "zephyr" or osType: "embedded"). See Embedded Hosts for full details.

File transfer for embedded hosts uses "console" or "tftp" — see Embedded Hosts.

SNMP monitoring¶

The optional snmp block configures SNMP polling for a host’s metrics. See the SNMP section of otto monitor.

Per-protocol option tables¶

Each of the following keys accepts an object that overrides individual protocol fields. They merge per-key with repo-level [host_defaults]; the host’s own values win. See otto host for the full connection-options reference.

Coverage toolchain¶

The toolchain object points to the cross-toolchain binaries used by the coverage pipeline. See Coverage Collection.

Example¶

Two real entries from the test fixture — one Unix host and one Zephyr host:

[
    {
        "ip": "10.10.200.11",
        "ne": "carrot",
        "osType": "unix",
        "board": "seed",
        "term": "ssh",
        "transfer": "scp",
        "is_virtual": true,
        "creds": {
            "vagrant": "vagrant",
            "test": "Password1"
        },
        "resources": [
            "carrot"
        ],
        "labs": [
            "veggies"
        ]
    },
    {
        "ip": "192.0.2.1",
        "ne": "sprout",
        "osType": "zephyr",
        "osVersion": "3.7",
        "transfer": "console",
        "filesystem": "fat-ram",
        "max_filename_len": 32,
        "is_virtual": true,
        "hop": "basil_seed",
        "snmp": {
            "address": "10.10.200.14",
            "port": 16101,
            "community": "public",
            "oids": [
                "1.3.6.1.2.1.1.3.0",
                "1.3.6.1.4.1.63245.1.1.0",
                "1.3.6.1.4.1.63245.1.2.0",
                "1.3.6.1.4.1.63245.1.3.0",
                "1.3.6.1.4.1.63245.1.4.0"
            ]
        },
        "resources": [
            "sprout"
        ],
        "labs": [
            "embedded"
        ]
    }
]

Repo-level host defaults¶

Most labs share a common set of connection conventions — a non-standard SSH port, a longer connect timeout, an alternate nc binary, etc. Restating those values on every host entry is repetitive and error-prone. Move the shared values into [host_defaults] in .otto/settings.toml and let the per-host *_options tables override only the values that genuinely differ.

# .otto/settings.toml

[host_defaults.ssh_options]
port = 2222
connect_timeout = 5.0
keepalive_interval = 30

[host_defaults.telnet_options]
cols = 200
echo_negotiation_timeout = 1.0

[host_defaults.nc_options]
exec_name = "ncat"
port_strategy = "proc"

Valid sub-table names are exactly the per-host option keys: ssh_options, telnet_options, sftp_options, scp_options, ftp_options, nc_options. Unknown keys raise at startup so typos fail loudly instead of silently no-opping.

Precedence (lowest to highest):

1. The hardcoded dataclass defaults in otto.host.options.

2. [host_defaults] from each repo, applied in OTTO_SUT_DIRS order. When the same field appears in two repos, the later repo wins.

3. The host’s own *_options table in hosts.json.

Merging happens per key at every layer. Setting only port on a host still inherits connect_timeout from the repo default; setting only connect_timeout in the repo default still inherits port from the dataclass default.

The merge is performed at host construction time, so the resulting host carries the fully-resolved *_options instances — nothing has to be re-resolved at use time.

Merging labs¶

Pass multiple lab names to combine them:

otto --lab lab_a,lab_b test TestDevice

Hosts from all labs are merged into a single lab. If two labs define the same host ID, the later lab’s definition wins.

Exploring labs¶

otto --lab my_lab --list-labs      # list all available lab names
otto --lab my_lab --list-hosts     # list host IDs in the loaded lab
otto --lab my_lab --show-lab       # full lab details (use -v for expanded output)