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README_PODMAN.md

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Using the dnsname plugin with Podman

The dnsname plugin allows containers to resolve each other by name. The plugin adds each container's name to an instance of a dnsmasq server. The plugin is enabled through adding it to a network's CNI configuration. The containers will only be able to resolve each other if they are on the same CNI network.

Note: This plugin does not work with rootless containers.

This tutorial assumes you already have Podman, containernetwork-plugins, and a golang development environment installed.

Install dnsmasq

Using your package manager, install the dnsmasq package. For Fedora, this would be: sudo dnf install dnsmasq

Build and install

  1. using git, clone the github.com/containers/dnsname repository.
  2. make install PREFIX=/usr -- this will install the dnsname plugin into /usr/libexec/cni where your CNI plugins should already exist.

Configure a CNI network for Podman

  1. Create a new network using podman network create. For example, podman network create foobar will suffice.
  2. Using your favorite editor, edit /etc/cni/net.d/foobar.conflist and add the following with the plugins stanza:
      {
     "type": "dnsname",
         "domainName": "podman.io"
      }

The following example configuration file shows a usable example for Podman.

Example: container name resolution

  1. sudo podman run -dt --name web --network foobar quay.io/libpod/alpine_nginx:latest 5139d65d22135e9ecab511559d863754550894a32285befd94dab231017048c2

    Note: we use the --network foobar here. Also, in this test image, the nginx server will respond with podman rulez on an http request.

  2. sudo podman run -it --name client --network cni-podman1 quay.io/libpod/alpine_nginx:latest curl http://web/ podman rulez

Enabling name resolution on the default Podman network

After making sure the dnsplugin is functioning properly, you can add name resolution to your default Podman network. This can be done two different ways:

  1. Add the dnsname plugin as described in above to your default Podman network. This default network is usually /etc/cni/net.d/87-podman-bridge.conflist.

  2. Add a new network as described above and then edit /etc/containers/libpod.conf and change the cni_default_network key to your network name.