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Edited content in the Hello World section

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Signed-off-by: Lynda O'Leary <lyndaoleary29@gmail.com>
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Lynda O'Leary 2016-03-04 18:50:48 +00:00
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142
docs/userguide/containers/dockerizing.md
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@ -24,147 +24,131 @@ Running an application inside a container takes a single command: `docker run`.
## Run a Hello world
Let's try it now.
Let's run a hello world container.
$ docker run ubuntu /bin/echo 'Hello world'
Hello world
And you just launched your first container!
You just launched your first container!
So what just happened? Let's step through what the `docker run` command
did.
In this example:
First we specified the `docker` binary and the command we wanted to
execute, `run`. The `docker run` combination *runs* containers.
Next we specified an image: `ubuntu`. This is the source of the container
we ran. Docker calls this an image. In this case we used the Ubuntu
operating system image.
* `docker run` runs a container.
* `ubuntu` is the image you run, for example the Ubuntu operating system image.
When you specify an image, Docker looks first for the image on your
Docker host. If it can't find it then it downloads the image from the public
image registry: [Docker Hub](https://hub.docker.com).
Docker host. If the image does not exist locally, then the image is pulled from the public
image registry [Docker Hub](https://hub.docker.com).
Next we told Docker what command to run inside our new container:
* `/bin/echo` is the command to run inside the new container.
/bin/echo 'Hello world'
When our container was launched Docker created a new Ubuntu
environment and then executed the `/bin/echo` command inside it. We saw
the result on the command line:
The container launches. Docker creates a new Ubuntu
environment and executes the `/bin/echo` command inside it and then prints out:
Hello world
So what happened to our container after that? Well Docker containers
only run as long as the command you specify is active. Here, as soon as
`Hello world` was echoed, the container stopped.
So what happened to the container after that? Well, Docker containers
only run as long as the command you specify is active. Therefore, in the above example,
the container stops once the command is executed.
## An interactive container
## Run an interactive container
Let's try the `docker run` command again, this time specifying a new
command to run in our container.
Let's specify a new command to run in the container.
$ docker run -t -i ubuntu /bin/bash
root@af8bae53bdd3:/#
Here we've again specified the `docker run` command and launched an
`ubuntu` image. But we've also passed in two flags: `-t` and `-i`.
The `-t` flag assigns a pseudo-tty or terminal inside our new container
and the `-i` flag allows us to make an interactive connection by
In this example:
* `docker run` runs a container.
* `ubuntu` is the image you would like to run.
* `-t` flag assigns a pseudo-tty or terminal inside the new container.
* `-i` flag allows you to make an interactive connection by
grabbing the standard in (`STDIN`) of the container.
* `/bin/bash` launches a Bash shell inside our container.
We've also specified a new command for our container to run:
`/bin/bash`. This will launch a Bash shell inside our container.
So now when our container is launched we can see that we've got a
The container launches. We can see there is a
command prompt inside it:
root@af8bae53bdd3:/#
Let's try running some commands inside our container:
Let's try running some commands inside the container:
root@af8bae53bdd3:/# pwd
/
root@af8bae53bdd3:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
You can see we've run the `pwd` to show our current directory and can
see we're in the `/` root directory. We've also done a directory listing
of the root directory which shows us what looks like a typical Linux
file system.
In this example:
You can play around inside this container and when you're done you can
use the `exit` command or enter Ctrl-D to finish.
* `pwd` displays the current directory, the `/` root directory.
* `ls` displays the directory listing of the root directory of a typical Linux file system.
Now, you can play around inside this container. When completed, run the `exit` command or enter Ctrl-D
to exit the interactive shell.
root@af8bae53bdd3:/# exit
As with our previous container, once the Bash shell process has
finished, the container is stopped.
>**Note:** As with our previous container, once the Bash shell process has
finished, the container stops.
## A daemonized Hello world
## Start a daemonized Hello world
Now a container that runs a command and then exits has some uses but
it's not overly helpful. Let's create a container that runs as a daemon,
like most of the applications we're probably going to run with Docker.
Again we can do this with the `docker run` command:
Let's create a container that runs as a daemon.
$ docker run -d ubuntu /bin/sh -c "while true; do echo hello world; sleep 1; done"
1e5535038e285177d5214659a068137486f96ee5c2e85a4ac52dc83f2ebe4147
Wait, what? Where's our "hello world" output? Let's look at what we've run here.
It should look pretty familiar. We ran `docker run` but this time we
specified a flag: `-d`. The `-d` flag tells Docker to run the container
and put it in the background, to daemonize it.
In this example:
We also specified the same image: `ubuntu`.
* `docker run` runs the container.
* `-d` flag runs the container in the background (to daemonize it).
* `ubuntu` is the image you would like to run.
Finally, we specified a command to run:
Finally, we specify a command to run:
/bin/sh -c "while true; do echo hello world; sleep 1; done"
This is the (hello) world's silliest daemon: a shell script that echoes
`hello world` forever.
So why aren't we seeing any `hello world`'s? Instead Docker has returned
a really long string:
In the output, we do not see `hello world` but a long string:
1e5535038e285177d5214659a068137486f96ee5c2e85a4ac52dc83f2ebe4147
This really long string is called a *container ID*. It uniquely
This long string is called a *container ID*. It uniquely
identifies a container so we can work with it.
> **Note:**
> The container ID is a bit long and unwieldy. A bit later,
> we'll see a shorter ID and ways to name our containers to make
> The container ID is a bit long and unwieldy. Later, we will cover the short
> ID and ways to name our containers to make
> working with them easier.
We can use this container ID to see what's happening with our `hello world` daemon.
Firstly let's make sure our container is running. We can
do that with the `docker ps` command. The `docker ps` command queries
the Docker daemon for information about all the containers it knows
First, let's make sure our container is running. Run the `docker ps` command.
The `docker ps` command queries the Docker daemon for information about all the containers it knows
about.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1e5535038e28 ubuntu /bin/sh -c 'while tr 2 minutes ago Up 1 minute insane_babbage
Here we can see our daemonized container. The `docker ps` has returned some useful
information about it, starting with a shorter variant of its container ID:
`1e5535038e28`.
In this example, we can see our daemonized container. The `docker ps` returns some useful
information:
* `1e5535038e28` is the shorter variant of the container ID.
* `ubuntu` is the used image.
* the command, status, and assigned name `insane_babbage`.
We can also see the image we used to build it, `ubuntu`, the command it
is running, its status and an automatically assigned name,
`insane_babbage`.
> **Note:**
> Docker automatically generates names for any containers started.
> We'll see how to specify your own names a bit later.
Okay, so we now know it's running. But is it doing what we asked it to do? To
Now, we know the container is running. But is it doing what we asked it to do? To
see this we're going to look inside the container using the `docker logs`
command. Let's use the container name Docker assigned.
command.
Let's use the container name `insane_babbage`.
$ docker logs insane_babbage
hello world
@ -172,29 +156,27 @@ command. Let's use the container name Docker assigned.
hello world
. . .
The `docker logs` command looks inside the container and returns its standard
output: in this case the output of our command `hello world`.
In this example:
Awesome! Our daemon is working and we've just created our first
* `docker logs` looks inside the container and returns `hello world`.
Awesome! The daemon is working and you have just created your first
Dockerized application!
Now we've established we can create our own containers let's tidy up
after ourselves and stop our detached container. To do this we use the
`docker stop` command.
Next, run the `docker stop` command to stop our detached container.
$ docker stop insane_babbage
insane_babbage
The `docker stop` command tells Docker to politely stop the running
container. If it succeeds it will return the name of the container it
has just stopped.
container and returns the name of the container it stopped.
Let's check it worked with the `docker ps` command.
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
Excellent. Our container has been stopped.
Excellent. Our container is stopped.
# Next steps

5
docs/userguide/intro.md
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@ -8,7 +8,7 @@ parent="engine_guide"
+++
<![end-metadata]-->
# Introduction to Engine user guide
# Engine user guide
This guide takes you through the fundamentals of using Docker Engine and
integrating it into your environment. You'll learn how to use Engine to:
@ -38,7 +38,7 @@ Go to [Dockerizing Applications](containers/dockerizing.md).
Once you get a grip on running your applications in Docker containers, you'll learn how to manage those containers. To find out
about how to inspect, monitor and manage containers:
Go to [Working With Containers](containers/usingdocker.md).
Go to [Working with Containers](containers/usingdocker.md).
## Working with Docker images
@ -116,4 +116,3 @@ Go to [Docker Swarm user guide](https://docs.docker.com/swarm/).
* [Docker on Twitter](https://twitter.com/docker)
* Get [Docker help](https://stackoverflow.com/search?q=docker) on
StackOverflow
* [Docker.com](https://www.docker.com/)