Introduction
In this lab, you will learn how to use the docker info command to display comprehensive information about your Docker system. You will begin by executing the basic docker info command to view details about the Docker daemon, including container and image counts, storage driver, and other system-level information.
Following the basic display, you will explore how to format the output of the docker info command in different ways. Specifically, you will learn how to format the output as JSON for easier parsing and how to use a custom template to display only the specific information you need. This lab will equip you with the skills to effectively retrieve and interpret Docker system information.
Display basic Docker system information
In this step, you will learn how to display basic information about your Docker system using the docker info command. This command provides details about the Docker daemon, including the number of containers and images, storage driver, and other system-level information.
Open the terminal in the LabEx environment. You can execute the docker info command directly.
docker info
You should see output similar to this (the exact details will vary depending on your environment):
Client:
Context: default
Debug Mode: false
Plugins:
buildx: Docker Buildx (Docker Inc.)
Version: v0.10.4
Build: 8842a472b58241d32996951f172f32259cd758e5
compose: Docker Compose (Docker Inc.)
Version: v2.17.2
Build: 6833407
scan: Docker Scan (Docker Inc.)
Version: v0.23.0
Build: 2c50987
Server:
Containers: 0
Running: 0
Paused: 0
Stopped: 0
Images: 0
Server Version: 20.10.21
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Native Overlay Diff: true
userxattr: false
Logging Driver: json-file
Cgroup Driver: systemd
Cgroup Version: 2
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local logentries splunk syslog
Swarm: inactive
Runtimes: io.containerd.runc.v2 io.containerd.runtime.v1.linux runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 9ba4b2555a59f71c4c1c1897e93a540b0c52b883
runc version: v1.1.4-0-g5fd4c4d
init version: de40ad0
Security Options:
apparmor
seccomp
Profile: default
cgroupns
Kernel Version: 5.15.0-76-generic
Operating System: Ubuntu 22.04.2 LTS
OSType: linux
Architecture: x86_64
CPUs: 2
Total Memory: 3.84GiB
Name: labex-vm
ID: 6111111111111111111111111111111111111111111111111111111111111111
Docker Root Dir: /var/lib/docker
Debug Mode: false
Experimental: false
Insecure Registries:
127.0.0.0/8
Live Restore Enabled: false
WARNING: No blkio weight, cpus, or mem limits set, Docker may behave unexpectedly without them.
The output provides a comprehensive overview of your Docker installation and its current state. You can see information like the Docker version, the number of running containers and images, the storage driver being used, and details about the underlying operating system and hardware.
Format docker info output as JSON
In the previous step, you saw the default output of the docker info command. This output is human-readable but can be difficult to parse programmatically. Docker provides the --format flag to customize the output format. In this step, you will learn how to format the docker info output as JSON.
The --format flag uses Go's text/template package. To output the information as JSON, you can use the . | json template.
Execute the following command in your terminal:
docker info --format '{{json .}}'
You should see the same information as before, but now formatted as a single JSON object:
{
"Client": {
"Context": "default",
"DebugMode": false,
"Plugins": {
"buildx": {
"Version": "v0.10.4",
"Build": "8842a472b58241d32996951f172f32259cd758e5"
},
"compose": {
"Version": "v2.17.2",
"Build": "6833407"
},
"scan": {
"Version": "v0.23.0",
"Build": "2c50987"
}
}
},
"Server": {
"Containers": 0,
"ContainersRunning": 0,
"ContainersPaused": 0,
"ContainersStopped": 0,
"Images": 0,
"ServerVersion": "20.10.21",
"StorageDriver": "overlay2",
"LoggingDriver": "json-file",
"CgroupDriver": "systemd",
"CgroupVersion": "2",
"Plugins": {
"Volume": ["local"],
"Network": ["bridge", "host", "ipvlan", "macvlan", "null", "overlay"],
"Log": [
"awslogs",
"fluentd",
"gcplogs",
"gelf",
"journald",
"json-file",
"local",
"logentries",
"splunk",
"syslog"
]
},
"Swarm": {
"NodeID": "",
"LocalNodeState": "inactive",
"ControlAvailable": false,
"Error": null,
"RemoteManagers": null
},
"Runtimes": {
"io.containerd.runc.v2": {
"path": "io.containerd.runc.v2"
},
"io.containerd.runtime.v1.linux": {
"path": "io.containerd.runtime.v1.linux"
},
"runc": {
"path": "runc"
}
},
"DefaultRuntime": "runc",
"InitBinary": "docker-init",
"ContainerdVersion": "9ba4b2555a59f71c4c1c1897e93a540b0c52b883",
"RuncVersion": "v1.1.4-0-g5fd4c4d",
"InitVersion": "de40ad0",
"SecurityOptions": ["apparmor", "seccomp", "cgroupns"],
"KernelVersion": "5.15.0-76-generic",
"OperatingSystem": "Ubuntu 22.04.2 LTS",
"OSType": "linux",
"Architecture": "x86_64",
"NCPU": 2,
"MemTotal": 4123631616,
"Name": "labex-vm",
"ID": "6111111111111111111111111111111111111111111111111111111111111111",
"DockerRootDir": "/var/lib/docker",
"DebugMode": false,
"ExperimentalBuild": false,
"InsecureRegistries": ["127.0.0.0/8"],
"LiveRestoreEnabled": false,
"Warnings": [
"No blkio weight, cpus, or mem limits set, Docker may behave unexpectedly without them."
]
}
}
Formatting the output as JSON is useful when you want to process the information with other tools or scripts.
Format docker info output using a custom template
In addition to formatting the output as JSON, you can use the --format flag with a custom Go template to display specific information from the docker info output. This allows you to extract only the data you are interested in.
The docker info command provides a data structure that you can access within the template. For example, to display the Docker Server Version and the total number of CPUs, you can use the template 'Server Version: {{.ServerVersion}}, CPUs: {{.NCPU}}'.
Execute the following command in your terminal:
docker info --format 'Server Version: {{.ServerVersion}}, CPUs: {{.NCPU}}'
You should see output similar to this:
Server Version: 20.10.21, CPUs: 2
In this template:
{{.ServerVersion}}accesses theServerVersionfield from thedocker infodata structure.{{.NCPU}}accesses theNCPUfield, which represents the number of CPUs.
You can explore the JSON output from the previous step to identify other fields you might want to include in your custom template. For instance, to display the Operating System and the Docker Root Directory, you could use the template 'OS: {{.OperatingSystem}}, Docker Root Dir: {{.DockerRootDir}}'.
Try executing this command:
docker info --format 'OS: {{.OperatingSystem}}, Docker Root Dir: {{.DockerRootDir}}'
You should see output similar to this:
OS: Ubuntu 22.04.2 LTS, Docker Root Dir: /var/lib/docker
Using custom templates gives you fine-grained control over the output of the docker info command, making it easier to integrate Docker information into scripts or reports.
Summary
In this lab, you learned how to use the docker info command to display comprehensive information about your Docker system. You started by executing the basic docker info command to view details about the Docker daemon, including container and image counts, storage driver, and other system-level information.
Furthermore, you explored how to format the output of the docker info command. You learned to output the information in JSON format for easier parsing and integration with other tools, and also how to use a custom Go template to display specific information in a tailored format. These formatting options provide flexibility in how you access and utilize Docker system details.
