When containers may not know the network to which they will be attached, Weave Net enables you to dynamically attach and detach containers to and from a given network, even when a container is already running.
To illustrate…
host1$ C=$(docker run -e WEAVE_CIDR=none -dti weaveworks/ubuntu)
host1$ weave attach $C
10.2.1.3
where,
-
C=$(docker run -e WEAVE_CIDR=none -dti weaveworks/ubuntu)
starts a container and assigns its ID to a variable -
weave attach
– the Weave Net command to attach to the specified container -
10.2.1.3
- the allocated IP address output byweave attach
, in this case in the default subnet
Note If you are using the Weave Docker API proxy, it will have modified
DOCKER_HOST
to point to the proxy and therefore you will have to pass-e WEAVE_CIDR=none
to start a container that doesn’t get automatically attached to the weave network for the purposes of this example.
If weave attach
sees the container has a hostname with a
domain-name, it will add those into WeaveDNS (unless you turn this off
with the --without-dns
argument).
host1$ docker run -dti --name=c1 --hostname=c1.weave.local weaveworks/ubuntu
host1$ weave attach c1
10.32.0.1
host1$ weave dns-lookup c1
10.32.0.1
If you would like /etc/hosts
to contain the Weave Net address (the
same way the proxy does),
specify --rewrite-hosts
when running weave attach
:
host1$ weave attach --rewrite-hosts c1
Dynamically Detaching Containers
A container can be detached from a subnet, by using the weave detach
command:
host1$ weave detach $C
10.2.1.3
You can also detach a container from one network and then attach it to a different one:
host1$ weave detach net:default $C
10.2.1.3
host1$ weave attach net:10.2.2.0/24 $C
10.2.2.3
or, attach a container to multiple application networks, effectively sharing the same container between applications:
host1$ weave attach net:default
10.2.1.3
host1$ weave attach net:10.2.2.0/24
10.2.2.3
Finally, multiple addresses can be attached or detached using a single command:
host1$ weave attach net:default net:10.2.2.0/24 net:10.2.3.0/24 $C
10.2.1.3 10.2.2.3 10.2.3.1
host1$ weave detach net:default net:10.2.2.0/24 net:10.2.3.0/24 $C
10.2.1.3 10.2.2.3 10.2.3.1
Important! Any addresses that were dynamically attached will not be re-attached if the container restarts.
See Also