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rewording of must of the weaveDNS intro

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Matthias Radestock committed 2015-01-07 12:16:16 +00:00
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# Weave DNS server
The Weave DNS server answers name queries in a Weave network. This provides a
simple way for containers to find each other: just give them hostnames and
tell other containers to connect to those names. Unlike Docker `--link`, this
requires no code changes and works across hosts.
The Weave DNS server answers name queries in a Weave network. This
provides a simple way for containers to find each other: just give
them hostnames and tell other containers to connect to those names.
Unlike Docker 'links', this requires no code changes and works across
hosts.
## Using weaveDNS
The weave script command `launch-dns` starts the DNS container, and
then you use the `--with-dns` option on containers you wish to use it.
Subsquently, giving any container a hostname in the domain
`.weave.local` will register it in DNS. For example:
WeaveDNS is deployed as a set of containers that communicate with each
other over the weave network. One such container needs to be started
on every weave host, by invoking the weave script command
`launch-dns`. Application containers are then instructed to use
WeaveDNS as their nameserver by supplying the `--with-dns` option when
starting them. Giving any container a hostname in the `.weave.local`
domain registers it in weaveDNS. For example:
```bash
$ weave launch
@@ -23,26 +27,30 @@ $ docker attach $shell1
...
```
Launch weaveDNS on every host, picking a different IP address from the same
subnet each time. It's best if this subnet is different from the one you use for
application containers. In our example the weaveDNS address is in subnet
10.1.254.0/24 and the ubuntu containers are in subnet 10.1.1.0/24.
Each weaveDNS container started with `launch-dns` needs to be given
its own, unique, IP address, in a subnet that is a) common to all
weaveDNS containers, b) disjoint from the application subnets, and c)
not in use on any of the hosts. In our example the weaveDNS address is
in subnet 10.1.254.0/24 and the application containers are in
subnet 10.1.1.0/24.
As usual, these subnets must not be in use for other purposes on your hosts.
The DNS container can be stopped with `stop-dns`.
WeaveDNS containers can be stopped with `stop-dns`.
## How it works
WeaveDNS runs on every host, and acts as the nameserver for containers on that
host. It is told about hostnames for local containers by the `weave run`
command.
The weaveDNS container running on every host acts as the nameserver
for containers on that host. It is told about hostnames for local
containers by the `weave run` command. If a hostname is in the
`.weave.local` domain then weaveDNS records the association of that
name with the container's weave IP address(es).
WeaveDNS only stores names in the `.weave.local` domain. If it is asked for
a name in `.weave.local` it doesn't know about, it will ask the other weaveDNS
servers.
If asked for a name in another domain it will fall back to using the host's
configured nameserver.
When weaveDNS is queried for a name in the `.weave.local` domain, it
first checks its own records. If the name is not found there, it asks
the weaveDNS servers on the other hosts in the weave network.
When weaveDNS is queried for a name in a domain other than
`.weave.local`, it queries the host's configured nameserver,
which is the standard behaviour for Docker containers.
## Domain search paths