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Update 'usingdocker' tutorial to name the container #1165

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257 changes: 145 additions & 112 deletions engine/tutorials/usingdocker.md
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,6 @@ redirect_from:
- /engine/userguide/containers/usingdocker/
description: Learn how to manage and operate Docker containers.
keywords: docker, the docker guide, documentation, docker.io, monitoring containers, docker top, docker inspect, docker port, ports, docker logs, log, logs
menu:
main:
parent: engine_learn_menu
weight: -5
title: Run a simple application
---

Expand All @@ -21,59 +17,68 @@ background. In the process you learned about several Docker commands:

## Learn about the Docker client

The `docker` program is called the Docker client. Each action you can take with
the client is a command and each command can take a series of flags and arguments.

# Usage: [sudo] docker [subcommand] [flags] [arguments] ..
# Example:
$ docker run -i -t ubuntu /bin/bash

You can see this in action by using the `docker version` command to return
version information on the currently installed Docker client and daemon.

$ docker version

This command will not only provide you the version of Docker client and
daemon you are using, but also the version of Go (the programming
language powering Docker).

Client:
Version: 1.12.5
API version: 1.24
Go version: go1.6.4
Git commit: 7392c3b
Built: Fri Dec 16 02:42:17 2016
OS/Arch: windows/amd64

Server:
Version: 1.12.5
API version: 1.24
Go version: go1.6.4
Git commit: 7392c3b
Built: Fri Dec 16 02:42:17 2016
OS/Arch: linux/amd64
The `docker` program is called the Docker client. To control Docker using the
client, you use commands, flags, and arguments. Have a look at the following
example, which uses the `run` command, the `-i` and `-t` flags, and the `ubuntu`
and `/bin/bash` arguments.

```bash
$ docker run -i -t ubuntu /bin/bash
```

The `docker version` command shows information about the version of Docker the
client is using, as well as other version-specific information.

```bash
$ docker version

Client:
Version: 1.12.5
API version: 1.24
Go version: go1.6.4
Git commit: 7392c3b
Built: Fri Dec 16 02:42:17 2016
OS/Arch: windows/amd64

Server:
Version: 1.12.5
API version: 1.24
Go version: go1.6.4
Git commit: 7392c3b
Built: Fri Dec 16 02:42:17 2016
OS/Arch: linux/amd64
```

## Get Docker command help

You can display the help for specific Docker commands. The help details the
options and their usage. To see a list of all the possible commands, use the
following:
Each Docker command has associated usage information, which you can see when you
use the `--help` flag. You can use `--help` for the `docker` command itself, or
for its sub-commands.

To see usage information for the entire `docker` command, including a list of
all the possible commands, use `docker --help`.

$ docker --help
```bash
$ docker --help
```

To see usage for a specific command, specify the command with the `--help` flag:
To see usage for a specific command, add the `--help` flag after that specific
command. For instance, the following command shows the help text for the
`docker attach` command.

$ docker attach --help
```bash
$ docker attach --help

Usage: docker attach [OPTIONS] CONTAINER
Usage: docker attach [OPTIONS] CONTAINER

Attach to a running container
Attach to a running container

Options:
--detach-keys string Override the key sequence for detaching a container
--help Print usage
--no-stdin Do not attach STDIN
--sig-proxy Proxy all received signals to the process (default true)
Options:
--detach-keys string Override the key sequence for detaching a container
--help Print usage
--no-stdin Do not attach STDIN
--sig-proxy Proxy all received signals to the process (default true)
```

> **Note:**
> For further details and examples of each command, see the
Expand All @@ -82,18 +87,20 @@ To see usage for a specific command, specify the command with the `--help` flag:
## Run a web application in Docker

Now that you've learned a bit more about the Docker client, you can move onto
the important stuff: running more containers. So far none of the
containers you've run did anything particularly useful, so you can
change that by running an example web application in Docker.
the important stuff: running more containers. First, run an example Python Flask
web application as a Docker container.

For the web application you're going to run a Python Flask application.
Start with a `docker run` command.

$ docker run -d -P training/webapp python app.py
```bash
$ docker run -d -P --name my_webapp training/webapp python app.py
```

This command consists of the following parts:

* The `-d` flag runs the container in the background (as a so-called daemon).
* The `--name my_webapp` flag names the container `my_webapp`. If you do not
specify a name, Docker creates a random (and sometimes amusing) name for the

@sanscontext sanscontext Jan 18, 2017

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+1 on sometimes amusing, thank you :D

container. This name is guaranteed to be unique among all the containers
running on a given Docker host.
* The `-P` flag maps any required network ports inside the container to your
host. This lets you view the web application.
* The `training/webapp` image is a pre-built image that contains a simple Python
Expand All @@ -108,43 +115,46 @@ This command consists of the following parts:

## View the web application container

Now you can see your running container using the `docker ps` command.
To see information about your running container, use the `docker ps` command.

$ docker ps -l
```bash
$ docker ps -l

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
bc533791f3f5 training/webapp:latest python app.py 5 seconds ago Up 2 seconds 0.0.0.0:49155->5000/tcp nostalgic_morse
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
bc533791f3f5 training/webapp:latest python app.py 5 seconds ago Up 2 seconds 0.0.0.0:49155->5000/tcp my_webapp
```

The `-l` flag shows only the details of the *last* container started.

> **Note:**
> By default, the `docker ps` command only shows information about running
> containers. If you want to see stopped containers too, use the `-a` flag.

You can see the same details you saw [when you first dockerized a
container](dockerizing.md), with one important addition in the `PORTS`
column.
In particular, have a look at the `PORTS` column.

PORTS
0.0.0.0:49155->5000/tcp
```none
PORTS
0.0.0.0:49155->5000/tcp
```

When you passed the `-P` flag to the `docker run` command,
Docker mapped any ports exposed in the container to your host.
When you passed the `-P` flag to the `docker run` command, Docker mapped any

@sanscontext sanscontext Jan 18, 2017

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Hm, I felt this was kinda useful actually. What's your thinking in removing it?

@mdlinville mdlinville Jan 18, 2017

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I left it in, just moved it up a bit.

ports exposed in the container to ports on your host machine. In this case,
port 5000 (the default port for Python Flask) is mapped to port 49155 on the
Docker host.

> **Note:**
> You'll learn more about how to expose ports in Docker images when
> [you learn how to build images](dockerimages.md).

In this case Docker has exposed port 5000 (the default Python Flask
port) on port 49155.

Network port bindings are very configurable in Docker. In the last example the
`-P` flag is a shortcut for `-p 5000` that maps port 5000 inside the container
to a high port (from *ephemeral port range* which typically ranges from 32768
to 61000) on the local Docker host. You can also bind Docker containers to
specific ports using the `-p` flag, for example:

$ docker run -d -p 80:5000 training/webapp python app.py
```bash
$ docker run -d --name my_other_webapp -p 80:5000 training/webapp python app.py
```

This would map port 5000 inside your container to port 80 on your local
host. You might be asking about now: why wouldn't we just want to always
Expand Down Expand Up @@ -179,9 +189,11 @@ so Docker has a useful shortcut you can use: `docker port`.
To use `docker port`, specify the ID or name of your container and then
the port for which you need the corresponding public-facing port.

$ docker port nostalgic_morse 5000
```bash
$ docker port my_webapp 5000

0.0.0.0:49155
0.0.0.0:49155
```

In this case you've looked up what port is mapped externally to port 5000 inside
the container.
Expand All @@ -191,11 +203,13 @@ the container.
You can also find out a bit more about what's happening with your
application and use another of the commands you've learned, `docker logs`.

$ docker logs -f nostalgic_morse
```basg
$ docker logs -f my_webapp

* Running on http://0.0.0.0:5000/
10.0.2.2 - - [06/Nov/2016 20:16:31] "GET / HTTP/1.1" 200 -
10.0.2.2 - - [06/Nov/2016 20:16:31] "GET /favicon.ico HTTP/1.1" 404 -
* Running on http://0.0.0.0:5000/
10.0.2.2 - - [06/Nov/2016 20:16:31] "GET / HTTP/1.1" 200 -
10.0.2.2 - - [06/Nov/2016 20:16:31] "GET /favicon.ico HTTP/1.1" 404 -
```

The `-f` flag causes the `docker logs` command to act like the `tail -f` command
and watch the container's standard output. You can see here the logs from Flask
Expand All @@ -206,10 +220,12 @@ showing the application running on port 5000 and the access log entries for it.
In addition to the container's logs you can also examine the processes
running inside it using the `docker top` command.

$ docker top nostalgic_morse
```bash
$ docker top my_webapp

PID USER COMMAND
854 root python app.py
PID USER COMMAND
854 root python app.py
```

Here you can see that the `python app.py` command is the only process
running inside the container.
Expand All @@ -220,45 +236,56 @@ Lastly, you can take a low-level dive into the Docker container using the
`docker inspect` command. It returns a JSON document containing useful
configuration and status information for the specified container.

$ docker inspect nostalgic_morse
```bash
$ docker inspect my_webapp
```

You can see a sample of that JSON output.

[{
"ID": "bc533791f3f500b280a9626688bc79e342e3ea0d528efe3a86a51ecb28ea20",
"Created": "2014-05-26T05:52:40.808952951Z",
"Path": "python",
"Args": [
"app.py"
],
"Config": {
"Hostname": "bc533791f3f5",
"Domainname": "",
"User": "",
. . .
```none
[{
"ID": "bc533791f3f500b280a9626688bc79e342e3ea0d528efe3a86a51ecb28ea20",
"Created": "2014-05-26T05:52:40.808952951Z",
"Path": "python",
"Args": [
"app.py"
],
"Config": {
"Hostname": "bc533791f3f5",
"Domainname": "",
"User": "",
...
}]
```

You can also narrow down the information you want to return by requesting a
specific element, for example to return the container's IP address, you would:

{% raw %}
$ docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' nostalgic_morse
{% endraw %}
```bash
{% raw %}
$ docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' my_webapp

172.17.0.5
172.17.0.5
{% endraw %}
```

## Stop the web application container

The web application is still running inside the container. You can stop it using
the `docker stop` command and the name of the container: `nostalgic_morse`.
the `docker stop` command and the name of the container: `my_webapp`.

$ docker stop nostalgic_morse
```bash
$ docker stop my_webapp

nostalgic_morse
my_webapp
```

You can now use the `docker ps` command to check if the container has
been stopped.

$ docker ps -l
```bash
$ docker ps -l
```

## Restart the web application container

Expand All @@ -267,41 +294,47 @@ developer needs the container back. From here you have two choices: you
can create a new container or restart the old one. Look at
starting your previous container back up.

$ docker start nostalgic_morse
```bash
$ docker start my_webapp

nostalgic_morse
my_webapp
```

Now quickly run `docker ps -l` again to see the running container is
back up or browse to the container's URL to see if the application
responds.

> **Note:**
> Also available is the `docker restart` command that runs a stop and
> then start on the container.
> The `docker restart` command is also available. It is the equivalent of
> running `docker stop` followed by `docker start`.

## Remove the web application container

Your colleague has let you know that they've now finished with the container
and won't need it again. Now, you can remove it using the `docker rm` command.

$ docker rm nostalgic_morse
```bash
$ docker rm my_webapp

Error: Impossible to remove a running container, please stop it first or use -f
2014/05/24 08:12:56 Error: failed to remove one or more containers
Error: Impossible to remove a running container, please stop it first or use -f
2014/05/24 08:12:56 Error: failed to remove one or more containers
```

What happened? You can't actually remove a running container. This protects
you from accidentally removing a running container you might need. You can try
this again by stopping the container first.

$ docker stop nostalgic_morse
```bash
$ docker stop my_webapp

nostalgic_morse
my_webapp

$ docker rm nostalgic_morse
$ docker rm my_webapp

nostalgic_morse
my_webapp
```

And now the container is stopped and deleted.
Now the container is stopped and deleted.

> **Note:**
> Always remember that removing a container is final!
Expand Down