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This was discussed and agreed in #246. It will probably break a few outstanding PRs as well as a few external links but it's for the better good long term.
133 lines
2.6 KiB
Markdown
133 lines
2.6 KiB
Markdown
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class: title
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# Naming and inspecting containers
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---
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## Objectives
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In this lesson, we will learn about an important
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Docker concept: container *naming*.
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Naming allows us to:
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* Reference easily a container.
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* Ensure unicity of a specific container.
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We will also see the `inspect` command, which gives a lot of details about a container.
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---
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## Naming our containers
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So far, we have referenced containers with their ID.
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We have copy-pasted the ID, or used a shortened prefix.
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But each container can also be referenced by its name.
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If a container is named `thumbnail-worker`, I can do:
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```bash
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$ docker logs thumbnail-worker
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$ docker stop thumbnail-worker
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etc.
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```
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---
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## Default names
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When we create a container, if we don't give a specific
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name, Docker will pick one for us.
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It will be the concatenation of:
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* A mood (furious, goofy, suspicious, boring...)
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* The name of a famous inventor (tesla, darwin, wozniak...)
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Examples: `happy_curie`, `clever_hopper`, `jovial_lovelace` ...
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---
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## Specifying a name
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You can set the name of the container when you create it.
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```bash
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$ docker run --name ticktock jpetazzo/clock
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```
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If you specify a name that already exists, Docker will refuse
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to create the container.
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This lets us enforce unicity of a given resource.
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---
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## Renaming containers
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* You can rename containers with `docker rename`.
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* This allows you to "free up" a name without destroying the associated container.
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---
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## Inspecting a container
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The `docker inspect` command will output a very detailed JSON map.
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```bash
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$ docker inspect <containerID>
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[{
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...
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(many pages of JSON here)
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...
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```
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There are multiple ways to consume that information.
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---
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## Parsing JSON with the Shell
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* You *could* grep and cut or awk the output of `docker inspect`.
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* Please, don't.
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* It's painful.
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* If you really must parse JSON from the Shell, use JQ! (It's great.)
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```bash
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$ docker inspect <containerID> | jq .
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```
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* We will see a better solution which doesn't require extra tools.
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---
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## Using `--format`
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You can specify a format string, which will be parsed by
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Go's text/template package.
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```bash
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$ docker inspect --format '{{ json .Created }}' <containerID>
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"2015-02-24T07:21:11.712240394Z"
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```
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* The generic syntax is to wrap the expression with double curly braces.
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* The expression starts with a dot representing the JSON object.
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* Then each field or member can be accessed in dotted notation syntax.
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* The optional `json` keyword asks for valid JSON output.
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<br/>(e.g. here it adds the surrounding double-quotes.)
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