2.12. Docker container connection

Earlier, we implemented access to services running in the docker container through network ports.

Some network applications can be run in the container, and to make them accessible externally, you can specify the port mapping with the-P or-p parameter.

Let’s implement a port connection to a docker container.

2.12.1. Network port mapping ¶

We created a container for python applications.

runoob@runoob:~$ docker run -d -P training/webapp python app.py fce072cc88cee71b1cdceb57c2821d054a4a59f67da6b416fceb5593f059fc6d 

In addition, we can specify the network address of the container binding, such as binding 127.0.0.1.

We use -P Bind port number, using docker ps You can see that container port 5000 is bound to host port 32768.

runoob@runoob:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper 

We can also use it. -p Identity to specify that the container port is bound to the host port.

The difference between the two ways is:

-P : Is the internal port of the container 随机 The port mapped to the host.
-p : Is the container internal port bound to the 指定 The host port of.

runoob@runoob:~$ docker run -d -p 5000:5000 training/webapp python app.py 33e4523d30aaf0258915c368e66e03b49535de0ef20317d3f639d40222ba6bc0 

runoob@runoob:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper 

In addition, we can specify the network address of the container binding, such as binding 127.0.0.1.

runoob@runoob:~$ docker run -d -p 127.0.0.1:5001:5000 training/webapp python app.py 95c6ceef88ca3e71eaf303c2833fd6701d8d1b2572b5613b5a932dfdfe8a857c runoob@runoob:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 95c6ceef88ca training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5001->5000/tcp adoring_stonebraker 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper 

In this way, we can access port 5000 of the container by accessing 127.0.0.1 virtual 5001.

In the above example, the default is to bind the tcp port. If you want to bind the UDP port, you can add the /udp .

runoob@runoob:~$ docker run -d -p 127.0.0.1:5000:5000/udp training/webapp python app.py 6779686f06f6204579c1d655dd8b2b31e8e809b245a97b2d3a8e35abe9dcd22a runoob@runoob:~$ docker ps CONTAINER ID IMAGE COMMAND ... PORTS NAMES 6779686f06f6 training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5000->5000/udp drunk_visvesvaraya 95c6ceef88ca training/webapp "python app.py" ... 5000/tcp, 127.0.0.1:5001->5000/tcp adoring_stonebraker 33e4523d30aa training/webapp "python app.py" ... 0.0.0.0:5000->5000/tcp berserk_bartik fce072cc88ce training/webapp "python app.py" ... 0.0.0.0:32768->5000/tcp grave_hopper 

docker port The command allows us to quickly view the binding of the port.

runoob@runoob:~$ docker port adoring_stonebraker 5000 127.0.0.1:5001

2.12.2. Interconnection of Docker containers ¶

Port mapping is not the only way to connect docker to another container.

Docker has a connection system that allows multiple containers to be connected together to share connection information.

The docker connection creates a parent-child relationship where the parent container can see the information of the child container.

2.12.3. Container naming ¶

When we create a container, docker automatically names it. In addition, we can also use –name Identity to name the container, for example:

runoob@runoob:~$ docker run -d -P --name runoob training/webapp python app.py 43780a6eabaaf14e590b6e849235c75f3012995403f97749775e38436db9a441 

We can use it. docker ps Command to view the container name.

runoob@runoob:~$ docker ps -l CONTAINER ID IMAGE COMMAND ... PORTS NAMES 43780a6eabaa training/webapp "python app.py" ... 0.0.0.0:32769->5000/tcp runoob 

Create a new network ¶

Let’s start by creating a new Docker network.

$ docker network create -d bridge test-net

Parameter description:

-d : parameter specifies the Docker network type, including bridge and overlay.

The overlay network type is used for Swarm mode, which you can ignore in this section.

Connect the container ¶

Run a container and connect to the new test-net network:

$ docker run -itd --name test1 --network test-net ubuntu /bin/bash

Open a new terminal, run a container, and join the test-net network:

$ docker run -itd --name test2 --network test-net ubuntu /bin/bash

Click on the picture to see the larger picture:

` <../wp-content/uploads/2016/05/docker-net2.png>` _ _ below use ping to prove that the test1 container and the test2 container have established an interconnection.

If there is no ping command in the test1 or test2 containers, execute the following command to install ping in the container (that is, you can install it in a container, submit the container to the image, and rerun the above two containers with a new image).

apt-get update apt install iputils-ping 

Enter the following command in the test1 container:

Click on the picture to see the larger picture:

` <../wp-content/uploads/2016/05/docker-net3.png>` _ _ similarly, the test2 container will also successfully connect to:

Click on the picture to see the larger picture:

` <../wp-content/uploads/2016/05/docker-net4.png>` In this way, an interconnection is established between the test1 container and the test2 container.

If you have multiple containers that need to be connected to each other, it is recommended to use Docker Compose, which will be described later.

2.12.4. Configure DNS ¶

We can set the DNS of all containers by adding the following to the / etc/docker/daemon.json file of the host:

{ "dns" : [ "114.114.114.114", "8.8.8.8" ] } 

Once set, the DNS of the startup container is automatically configured to 114.114.114.114 and 8.8.8.8.

After configuration, you need to restart docker to take effect.

To see if the container’s DNS is valid, you can use the following command, which outputs the container’s DNS information:

$ docker run -it --rm ubuntu cat etc/resolv.conf

Click on the picture to see the larger picture:

` <../wp-content/uploads/2016/05/docker-net5.png>` __ 手动指定容器的配置

If you only want to set DNS in the specified container, you can use the following command:

$ docker run -it --rm -h host_ubuntu --dns=114.114.114.114 --dns-search=test.com ubuntu 

Parameter description:

–rm Automatically clean up the file system inside the container when the container exits

-h HOSTNAME 或者 –hostname=HOSTNAME Set the hostname of the container, which will be written to / etc/hostname and / etc/hosts in the container.

–dns=IP_ADDRESS Add a DNS server to the container’s / etc/resolv.conf and let the container use this server to resolve all hostnames that are not in / etc/hosts.

–dns-search=DOMAIN : set the container’s search domain, when setting the search field to .example.com, when searching for a host named host, DNS searches not only host, but also host.example.com.

Click on the picture to see the larger picture:

` <../wp-content/uploads/2016/05/docker-net6.png>` _ _ if not specified when the container is started –dns And –dns-search Docker defaults to / etc/resolv.conf on the host host to configure the DNS of the container.