Network Manipulation
Facilitates communication between containers running on the same host or different hosts, allowing them to interact with each other.
Create a User-defined bridge
Two containers are completely isolated from each other and are oblivious to each other's existence. So how do you connect the two? Won't that be a challenge?
You connect them by putting them under a user-defined bridge network.
A user-defined bridge has some extra features over the default one.
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User-defined bridges provide automatic DNS resolution between containers: Containers attached to the same network can communicate with each others using the container name.
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User-defined bridges provide better isolation: All containers are attached to the default bridge network by default which can cause conflicts among them. Attaching containers to a user-defined bridge can ensure better isolation.
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Containers can be attached and detached from user-defined networks on the fly: During a container’s lifetime, you can connect or disconnect it from user-defined networks on the fly. To remove a container from the default bridge network, you need to stop the container and recreate it with different network options.
A network can be created using the network create command:
docker network create <network name>
We can try these following commands:
docker network create skynet
# 7bd5f351aa892ac6ec15fed8619fc3bbb95a7dcdd58980c28304627c8f7eb070
docker network ls
# NETWORK ID NAME DRIVER SCOPE
# be0cab667c4b bridge bridge local
# 124dccee067f host host local
# 506e3822bf1f none null local
# 7bd5f351aa89 skynet bridge local
Attach a Container to a Network
We can use the network connect command to attach a container to a network.
docker network connect <network identifier> <container identifier>
To connect the hello-dock container to the skynet network, execute:
docker network connect skynet hello-dock
docker network inspect --format='{{range .Containers}} {{.Name}} {{end}}' skynet
# hello-dock
docker network inspect --format='{{range .Containers}} {{.Name}} {{end}}' bridge
# hello-dock
Another way to attach a container to a network is by using the --network option for the container run or container create commands.
--network <network identifier>
We can execute the following command:
docker container run --network skynet --rm --name alpine-box -it alpine sh
# lands you into alpine linux shell
/ # ping hello-dock
# PING hello-dock (172.18.0.2): 56 data bytes
# 64 bytes from 172.18.0.2: seq=0 ttl=64 time=0.191 ms
# 64 bytes from 172.18.0.2: seq=1 ttl=64 time=0.103 ms
# 64 bytes from 172.18.0.2: seq=2 ttl=64 time=0.139 ms
# 64 bytes from 172.18.0.2: seq=3 ttl=64 time=0.142 ms
# 64 bytes from 172.18.0.2: seq=4 ttl=64 time=0.146 ms
# 64 bytes from 172.18.0.2: seq=5 ttl=64 time=0.095 ms
# 64 bytes from 172.18.0.2: seq=6 ttl=64 time=0.181 ms
# 64 bytes from 172.18.0.2: seq=7 ttl=64 time=0.138 ms
# 64 bytes from 172.18.0.2: seq=8 ttl=64 time=0.158 ms
# 64 bytes from 172.18.0.2: seq=9 ttl=64 time=0.137 ms
# 64 bytes from 172.18.0.2: seq=10 ttl=64 time=0.145 ms
# 64 bytes from 172.18.0.2: seq=11 ttl=64 time=0.138 ms
# 64 bytes from 172.18.0.2: seq=12 ttl=64 time=0.085 ms
--- hello-dock ping statistics ---
13 packets transmitted, 13 packets received, 0% packet loss
round-trip min/avg/max = 0.085/0.138/0.191 ms
In order for the automatic DNS resolution to work you must assign custom names to the containers. Using the randomly generated name will not work.
Detach a Container from a Network
We can use the network disconnect command for this.
docker network disconnect <network identifier> <container identifier>
For example, we can execute the following command:
docker network disconnect skynet hello-dock
Remove Networks
Networks can be removed using the network rm command.
docker network rm <network identifier>
For example, we can execute the following command:
docker network rm skynet
You can also use the network prune command to remove any unused networks from your system.
The command also has the -f or --force and -a or --all options.