Merge pull request #19765 from dvdksn/engine-managed-ifaces

engine: add troubleshooting for managed ifaces

.github/vale/config/vocabularies/Docker/accept.txt

@@ -1,6 +1,7 @@
 A?GPL(v3)?
 APIs?
 ARM
+Netplan
 AWS
 Admin Console
 Amazon

content/config/daemon/troubleshoot.md

@@ -368,6 +368,152 @@ To turn off `dnsmasq` on RHEL, CentOS, or Fedora:
 {{< /tab >}}
 {{< /tabs >}}
 
+### Docker networks disappearing
+
+If a Docker network, such as the `docker0` bridge or a custom network, randomly
+disappears or otherwise appears to be working incorrectly, it could be because
+another service is interfering with or modifying Docker interfaces. Tools that
+manage networking interfaces on the host are known to sometimes also
+inappropriately modify Docker interfaces.
+
+Refer to the following sections for instructions on how to configure your
+network manager to set Docker interfaces as un-managed, depending on the
+network management tools that exist on the host:
+
+- If `netscript` is installed, consider [uninstalling it](#uninstall-netscript)
+- Configure the network manager to [treat Docker interfaces as un-managed](#un-manage-docker-interfaces)
+- If you're using Netplan, you may need to [apply a custom Netplan configuration](#prevent-netplan-from-overriding-network-configuration)
+
+#### Uninstall `netscript`
+
+If `netscript` is installed on your system, you can likely fix this issue by
+uninstalling it. For example, on a Debian-based system:
+
+```console
+$ sudo apt-get remove netscript-2.4
+```
+
+#### Un-manage Docker interfaces
+
+In some cases, the network manager will attempt to manage Docker interfaces by
+default. You can try to explicitly flag Docker networks as un-managed by
+editing your system's network configuration settings.
+
+{{< tabs >}}
+{{< tab name="NetworkManager" >}}
+
+If you're using `NetworkManager`, edit your system network configuration under
+`/etc/network/interfaces`
+
+1. Create a file at `/etc/network/interfaces.d/20-docker0` with the following
+   contents:
+
+   ```text
+   iface docker0 inet manual
+   ```
+
+   Note that this example configuration only "un-manages" the default `docker0`
+   bridge, not custom networks.
+
+2. Restart `NetworkManager` for the configuration change to take effect.
+
+   ```console
+   $ systemctl restart NetworkManager
+   ```
+
+3. Verify that the `docker0` interface has the `unmanaged` state.
+
+   ```console
+   $ nmcli device
+   ```
+
+{{< /tab >}}
+{{< tab name="systemd-networkd" >}}
+
+If you're running Docker on a system using `systemd-networkd` as a networking
+daemon, configure the Docker interfaces as un-managed by creating configuration
+files under `/etc/systemd/network`:
+
+1. Create `/etc/systemd/network/docker.network` with the following contents:
+
+   ```ini
+   # Ensure that the Docker interfaces are un-managed
+
+   [Match]
+   Name=docker0 br-* veth*
+
+   [Link]
+   Unmanaged=yes
+
+   ```
+
+2. Reload the configuration.
+
+   ```console
+   $ sudo systemctl restart systemd-networkd
+   ```
+
+3. Restart the Docker daemon.
+
+   ```console
+   $ sudo systemctl restart docker
+   ```
+
+4. Verify that the Docker interfaces have the `unmanaged` state.
+
+   ```console
+   $ networkctl
+   ```
+
+{{< /tab >}}
+{{< /tabs >}}
+
+### Prevent Netplan from overriding network configuration
+
+On systems that use [Netplan](https://netplan.io/) through
+[`cloud-init`](https://cloudinit.readthedocs.io/en/latest/index.html), you may
+need to apply a custom configuration to prevent `netplan` from overriding the
+network manager configuration:
+
+1. Follow the steps in [Un-manage Docker interfaces](#un-manage-docker-interfaces)
+   for creating the network manager configuration.
+2. Create a `netplan` configuration file under `/etc/netplan/50-cloud-init.yml`.
+
+   The following example configuration file is a starting point.
+   Adjust it to match the interfaces you want to un-manage.
+   Incorrect configuration can lead to network connectivity issues.
+
+   ```yaml {title="/etc/netplan/50-cloud-init.yml"}
+   network:
+     ethernets:
+       all:
+         dhcp4: true
+         dhcp6: true
+         match:
+           # edit this filter to match whatever makes sense for your system
+           name: en*
+     renderer: networkd
+     version: 2
+   ```
+
+3. Apply the new Netplan configuration.
+
+   ```console
+   $ sudo netplan apply
+   ```
+
+4. Restart the Docker daemon:
+
+   ```console
+   $ sudo systemctl restart docker
+   ```
+
+5. Verify that the Docker interfaces have the `unmanaged` state.
+
+   ```console
+   $ networkctl
+   ```
+
 ## Volumes
 
 ### Unable to remove filesystem

hugo_stats.json

@@ -76,6 +76,7 @@
       "Mac-with-Apple-silicon",
       "Mac-with-Intel-chip",
       "Manually-create-assets",
+      "NetworkManager",
       "Node",
       "Non-compliant",
       "Okta",
@@ -429,6 +430,7 @@
       "svg-container",
       "svg-icon",
       "syntax-light",
+      "systemd-networkd",
       "text-2xl",
       "text-base",
       "text-black",