Overview
Docker supports the ability to link containers. This is similar to having the two containers on the same network. One container can access the other by using the container name or alias.
This is helpful when connecting a database container with an app container.
Linking Containers
The --link
flag takes the form:
--link <name or id>:alias
Where name
is the name of the container we’re linking to and alias
is an alias for the link name. That alias is used shortly. The --link
flag also takes the form:
--link <name or id>
In this case the alias matches the name.
How it works?
If we look into the container that is linked to another we will see that the /etc/hosts file has been updated with a hostname pointing to the other container.
For example:
> docker run --link mysql --name="confluence" -d -p 8090:8090 -p 8091:8091
In this example we linked a previous container called mysql with our confluence container. If we connect to the confluence container, we will see that the hosts file has been updated.
> docker exec -it confluence bash bash-4.4# cat /etc/hosts 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters 10.0.3.4 mysql 4157a451ee8c 10.0.3.2 bac14530534d