Container interconnect-linking System in Docker

Source: Internet
Author: User
Tags docker ps

Container interconnect-linking System in Docker
Docker has a linking system that can connect multiple containers. It creates a pair of parent-child relationships that can see the selected
The information for the child container.
1) naming System for containers
The linking system executes according to the name of the container. When we create a container, the system randomly assigns a name. Of course we
You can also name the container yourself, which has 2 benefits:
• It's good to remember when we specify a name, like a web app we can call it a Web
• When we want to connect to other containers, we can serve as a useful reference point, such as connecting a Web container to a DB container
Use the--name tag to name the container
$ sudo docker run-d-P--name web Training/webapp python app.py
Use Docker-ps to verify the naming we set
$ sudo docker ps-l
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS
NAMES
Aed84ee21bde training/webapp:latest python app.py hours ago up 2 seconds 0.0.0.0:49154-
>5000/TCP Web
You can also use Docker inspect to view the container's name
$ sudo docker inspect-f "{{. Name}} "Aed84ee21bde
/web
Note: The name of the container is unique. If you name a container called Web, when you want to use the name of the web again
You need to use Docker RM to delete the container you created earlier, or you can add the-RM tag to stop when you execute Docker run
The old container and delete, RM and-D parameters are incompatible.
2) Container interconnect
Links allows for secure interaction between containers, using--link tags. The following first creates a new database container,
$ sudo docker run-d--name db training/postgres
Delete a previously created web container
$ Docker Rm-f Web
Create a new Web container and link it to the DB container
$ sudo docker run-d-P--name web--link db:db training/webapp python app.py
--link tagged Format:--link name:alias,name is the name of the container we want to link to, alias is the alias of this link.
Use Docker PS to view the container's links
$ docker PS
CONTAINER ID IMAGE COMMAND CREATED STATUS
PORTS NAMES
349169744e49 training/postgres:latest su postgres-c ' usr about a minute ago up about a minute
5432/TCP DB, web/db
Aed84ee21bde training/webapp:latest python app.py hours ago up 2 minutes
0.0.0.0:49154->5000/TCP Web
We can see the container we named, the DB and the names column of the WEB,DB container have DB also web/db. This means that the web capacity
Link to the DB container, they are a parent-child relationship. In this link, there are a couple of parent-child relationships in 2 containers. Docker in 2
A secure connection is created between the containers without mapping their ports to the host host. When you start the DB container, you do not
Marked with-p and-P. After using link, we can not expose the database port to the network.
Docker exposes connection information to the container for parent-child relationships in 2 ways:
• Environment variables
• Update/etc/hosts files
Use the ENV command to view the container's environment variables
$ sudo docker run--rm--name web2--link db:db Training/webapp env
. . .
db_name=/web2/db
db_port=tcp://172.17.0.5:5432
db_port_5000_tcp=tcp://172.17.0.5:5432
Db_port_5000_tcp_proto=tcp
db_port_5000_tcp_port=5432
db_port_5000_tcp_addr=172.17.0.5
. . .
In addition to environment variables, Docker also adds host information to the parent container's/etc/hosts file. The following is the hosts file for the parent container web
$ sudo docker run-t-i--rm--link db:db training/webapp/bin/bash
[Email protected]:/opt/webapp# cat/etc/hosts

172.17.0.7 Aed84ee21bde
. . .
172.17.0.5 DB
There are 2 hosts, the first of which is the Web container, the Web container uses the ID as his hostname, the second is the IP and host of the DB container
Name
[Email protected]:/opt/webapp# apt-get install-yqq inetutils-ping
[Email protected]:/opt/webapp# Ping db
PING db (172.17.0.5): bytes Data
Bytes from 172.17.0.5:icmp_seq=0 ttl=64 time=0.267 ms
Bytes from 172.17.0.5:icmp_seq=1 ttl=64 time=0.250 ms
Bytes from 172.17.0.5:icmp_seq=2 ttl=64 time=0.256 ms
Ping the DB container with Ping, it will parse into 172.17.0.5
Note: The official Ubuntu image does not have ping installed by default

Note: You can link multiple child containers to the parent container, for example we can link multiple web to DB containers.

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Container interconnect-linking System in Docker

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