Docker — system/info

When to Use

Operations dashboard: Populate a host capacity dashboard with live container counts, CPU, and memory figures sourced directly from the Docker daemon.
Pre-deploy capacity check: Verify that the target host has sufficient free resources (CPU cores, memory) before creating resource-intensive containers.
Host inventory: Enumerate all Docker hosts with their system profiles (OS, kernel, Docker version, architecture) for asset management.
Configuration drift detection: Compare DockerRootDir and daemon configuration fields against the expected baseline to detect unauthorized changes.
Incident debugging: Retrieve full host context (OS, kernel version, storage driver, daemon version) to include in incident reports when diagnosing deployment failures.

Configuration

Connection

Field	Type	Default	Description
`dockerHost`	string	`unix:///var/run/docker.sock`	Docker daemon socket path or TCP endpoint.
`connectionType`	string	`unixsocket`	One of: `unixsocket`, `tcp`, `tcptls`.
`tlsCertPath`	string	—	TLS certificate directory. Required for `tcptls`. optional
`timeoutSeconds`	int	30	Operation timeout. optional

Operation Fields

This operation requires no additional input fields. Set resource to system and operation to info.

Sample Configuration

{
  "resource": "system",
  "operation": "info",
  "connection": {
    "dockerHost": "unix:///var/run/docker.sock",
    "connectionType": "unixsocket"
  }
}

Validation Errors

Error Code	Condition	Resolution
`CONFIG_ERROR`	Connection settings missing or malformed.	Check `dockerHost` and `connectionType`.
`AUTH_FAILED`	TLS handshake failed.	Verify `tlsCertPath` certificates.
`DOCKER_API_ERROR`	Daemon returned an unexpected error or is unreachable.	Check daemon status on the host. Use `system/ping` for a lightweight connectivity check first.

Output

Success Port

Field	Type	Description
`status`	string	`"ok"` on success.
`resource`	string	`"system"`
`operation`	string	`"info"`
`dockerInfo.Containers`	int	Total container count (all states).
`dockerInfo.ContainersRunning`	int	Number of running containers.
`dockerInfo.ContainersPaused`	int	Number of paused containers.
`dockerInfo.ContainersStopped`	int	Number of stopped containers.
`dockerInfo.Images`	int	Total number of images on the host.
`dockerInfo.MemTotal`	int	Total host memory in bytes.
`dockerInfo.NCPU`	int	Number of logical CPUs available to the daemon.
`dockerInfo.DockerRootDir`	string	Docker data root directory path.
`dockerInfo.ServerVersion`	string	Docker daemon version string.
`dockerInfo.OperatingSystem`	string	Host operating system name.
`dockerInfo.KernelVersion`	string	Host kernel version string.

Error Port

Fires when the operation fails. Output contains status: "error", errorCode, and errorMessage.

Sample Output

{
  "status": "ok",
  "resource": "system",
  "operation": "info",
  "dockerInfo": {
    "Containers": 12,
    "ContainersRunning": 8,
    "ContainersPaused": 0,
    "ContainersStopped": 4,
    "Images": 23,
    "MemTotal": 17179869184,
    "NCPU": 8,
    "DockerRootDir": "/var/lib/docker",
    "ServerVersion": "26.1.3",
    "OperatingSystem": "Ubuntu 24.04.1 LTS",
    "KernelVersion": "6.8.0-40-generic"
  }
}

Expression Reference

Expression	Returns
`{{ $output.dockerInfo.ContainersRunning }}`	Count of running containers — use in dashboard.
`{{ $output.dockerInfo.MemTotal }}`	Total host memory in bytes.
`{{ ($output.dockerInfo.MemTotal / 1073741824).toFixed(1) }}`	Total memory in GB.
`{{ $output.dockerInfo.NCPU }}`	Logical CPU count — use for capacity planning assertions.
`{{ $output.dockerInfo.ServerVersion }}`	Docker daemon version — use in compliance audit records.

Node Policies & GuardRails

Policy	Enforcement
Never expose Docker daemon TCP without TLS	Use `tcptls` for remote connections. Plain `tcp` is blocked in production GuardRail profiles.
Store TLS certificates in Credentials Manager	Reference `tlsCertPath` via `{{ $credentials.dockerTlsCertPath }}`.
Use system/ping before system/info in health-check workflows	`system/ping` is a lightweight connectivity test. Reserve `system/info` for when full daemon metadata is needed.
Never interpolate user input into connection fields	The `dockerHost` value must come from credentials or fixed configuration.
Always handle the error port	A daemon-down scenario will route to the error port — wire it to an alerting or failover node.
Restrict container/exec to approved commands	Arbitrary exec access is root-equivalent. GuardRail exec policies restrict allowed command prefixes.

Examples

Example 1 — Pre-Deploy Capacity Gate

Before deploying a resource-intensive container (e.g., ML inference server requiring 8 GB RAM), check that the host has sufficient total memory and available container headroom.

// After system/info:
// Condition: enough memory?
{{ $output.dockerInfo.MemTotal >= 8589934592 }} // 8 GB in bytes

// Condition: not overloaded?
{{ $output.dockerInfo.ContainersRunning < 50 }}

Example 2 — Host Inventory Report

Call system/info on each Docker host in a scheduled workflow and write results to an asset database.

{
  "hostEndpoint": "{{ $loopItem.endpoint }}",
  "os": "{{ $output.dockerInfo.OperatingSystem }}",
  "kernel": "{{ $output.dockerInfo.KernelVersion }}",
  "dockerVersion": "{{ $output.dockerInfo.ServerVersion }}",
  "cpus": "{{ $output.dockerInfo.NCPU }}",
  "memoryGB": "{{ ($output.dockerInfo.MemTotal / 1073741824).toFixed(1) }}"
}

Example 3 — Configuration Drift Detection

Compare the host's DockerRootDir and ServerVersion against the expected values stored in a configuration baseline. Alert if they differ.

// Drift condition:
{{ $output.dockerInfo.DockerRootDir !== '/var/lib/docker' ||
   $output.dockerInfo.ServerVersion !== $vars.expectedDockerVersion }}
// If true → send drift alert to ops channel