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inspect

Return low-level information on Docker objects

Options

Name	Type	Description
`-f`, `--format`	`string`	Format output using a custom template: 'json': Print in JSON format 'TEMPLATE': Print output using the given Go template. Refer to https://docs.docker.com/go/formatting/ for more information about formatting output with templates
`-s`, `--size`		Display total file sizes if the type is container
`--type`	`string`	Return JSON for specified type

Description

Docker inspect provides detailed information on constructs controlled by Docker.

By default, docker inspect will render results in a JSON array.

Format the output (--format)

If a format is specified, the given template will be executed for each result.

Go's text/template package describes all the details of the format.

Specify target type (--type)

The docker inspect command matches any type of object by either ID or name. In some cases multiple type of objects (for example, a container and a volume) exist with the same name, making the result ambiguous.

To restrict docker inspect to a specific type of object, use the --type option.

The following example inspects a volume named "myvolume"

$ docker inspect --type=volume myvolume

Inspect the size of a container (-s, --size)

The --size, or short-form -s, option adds two additional fields to the docker inspect output. This option only works for containers. The container doesn't have to be running, it also works for stopped containers.

$ docker inspect --size mycontainer

The output includes the full output of a regular docker inspect command, with the following additional fields:

SizeRootFs: the total size of all the files in the container, in bytes.
SizeRw: the size of the files that have been created or changed in the container, compared to it's image, in bytes.

$ docker run --name database -d redis
3b2cbf074c99db4a0cad35966a9e24d7bc277f5565c17233386589029b7db273
$ docker inspect --size database -f '{{ .SizeRootFs }}'
123125760
$ docker inspect --size database -f '{{ .SizeRw }}'
8192
$ docker exec database fallocate -l 1000 /newfile
$ docker inspect --size database -f '{{ .SizeRw }}'
12288

Examples

Get an instance's IP address

For the most part, you can pick out any field from the JSON in a fairly straightforward manner.

$ docker inspect --format='{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $INSTANCE_ID

Get an instance's MAC address

$ docker inspect --format='{{range .NetworkSettings.Networks}}{{.MacAddress}}{{end}}' $INSTANCE_ID

Get an instance's log path

$ docker inspect --format='{{.LogPath}}' $INSTANCE_ID

Get an instance's image name

$ docker inspect --format='{{.Config.Image}}' $INSTANCE_ID

List all port bindings

You can loop over arrays and maps in the results to produce simple text output:

$ docker inspect --format='{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{(index $conf 0).HostPort}} {{end}}' $INSTANCE_ID

Find a specific port mapping

The .Field syntax doesn't work when the field name begins with a number, but the template language's index function does. The .NetworkSettings.Ports section contains a map of the internal port mappings to a list of external address/port objects. To grab just the numeric public port, you use index to find the specific port map, and then index 0 contains the first object inside of that. Then we ask for the HostPort field to get the public address.

$ docker inspect --format='{{(index (index .NetworkSettings.Ports "8787/tcp") 0).HostPort}}' $INSTANCE_ID

Get a subsection in JSON format

If you request a field which is itself a structure containing other fields, by default you get a Go-style dump of the inner values. Docker adds a template function, json, which can be applied to get results in JSON format.

$ docker inspect --format='{{json .Config}}' $INSTANCE_ID

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