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netbox-dnsmasq

This tool can be used to improve your machine provisioning system by mirroring the IP address assignments from netbox to dnsmasq. This enables you to directly boot a machine to its correct address rather than booting to a temporary environment with an ephemeral address and having to re-assign the address later.

The following configuration variables are supported which may be set in the environment:

  • VERBOSE - Enable logging on standard error.
  • NETBOX_SITE - Filter to only the given site, rather than all global data.
  • NETBOX_TOKEN - Token with suitable permissions to read netbox data.
  • NETBOX_TAG - Only service hosts that have a specific tag.
  • NETBOX_URL - URL to the netbox server.
  • DNSMASQ_TEMPLATE - A go template expression for the dhcp-hosts file. Defaults to a suitable configuration for IPv4. The default template is {{JoinStrings .HWAddr ","}},{{.Addr}}.
  • DNSMASQ_HOSTSFILE - A file to write out the dhcp hosts configuration to. This must match wherever you configure your dnsmasq config file to search for dhcp hosts.
  • SHOELACES_MAPFILE - A file to write out shoelaces mappings too. Must be named mappings.yaml and at the path expected by shoelaces. Only relevant in images that contain shoelaces.
  • SHOELACES_TAG_PREFIX - A prefix that if found on a tag will be used to form the mapping for shoelaces to supply the correct boot files to the machine without human interaction.

The search through netbox by default pulls hosts that have the $NETBOX_TAG tag set. Hosts are then filtered to ensure they have a primary IPv4 address and at least one interface that has a MAC address set. Hosts that have the correct tag but do not have at least one MAC address associated with a non-management-only interface and a primary address are skipped. You can see which hosts are skipped by enabling verbose logging.

The primary address is made available to all MAC addresses that are not associated with a management-only interface due to the way netbox models the network. Typically the network is modeled from the perspective of a booted and initialized machine, which may make use of bonds, interface teaming, or other advanced interface topologies. At install time, it is more likely that only one interface will be brought up, but it is still prefered that the machine get its final address.

Configuring dnsmasq

You will need to supply a suitable dnsmasq config file that points to the auto-generated dhcp-hosts file. Here is an example config that is known to work:

keep-in-foreground
log-facility=-
enable-tftp
port=0
listen-address=10.0.0.10
tftp-root=/var/lib/tftp
dhcp-option=option:T1,300
dhcp-option=option:T2,525
dhcp-option=option:router,10.0.0.1
dhcp-option=option:dns-server,10.0.0.1
dhcp-option=option:netmask,255.255.0.0
dhcp-option=option:domain-name,resinstack.io
dhcp-userclass=set:ipxe,iPXE
dhcp-boot=tag:!ipxe,ipxe.efi
dhcp-boot=tag:ipxe,http://10.0.0.10:8081/poll/1/${netX/mac:hexhyp}
dhcp-range=10.0.0.10,static
dhcp-hostsfile=/run/dhcp-hosts
domain=resinstack.io

In this example the server hosting the PXE services is located at 10.0.0.10 and the network has a default route and DNS available from 10.0.0.1. The ,static token in the dhcp-range block instructs dnsmasq not to provide services to hosts that do not have a pre-existing reservation, which can be useful if your network does not use DHCP except for machine installation.

Using with Shoelaces

Shoelaces is a powerful ipxe mapping tool that can mux different boot images to different machines by hand or by address. Each build of the containers from this repo comes in a non-shoelaces flavor and a shoelaces flavor. Using shoelaces will provide a web interface on port 8081 that allows you to manually select ipxe scripts. Shoelaces expects to find your template scripts in /var/lib/shoelaces/ipxe and can serve static assets for you from /var/lib/shoelaces/static.

Shoelaces is also capable of directly mapping a machine to its boot scripts based on tags in netbox. To use this behavior configure the value of SHOELACES_TAG_PREFIX to the prefix used by the tags you have set in Netbox. For example, if you wanted machines that posess the tags pxe-zerotouch-deb11 to boot with the ipxe script deb11.ipxe, you would configure the tag to be pxe-zerotouch-. Only the first tag found will be mapped, so its a good idea to carefully plan the tag structure in use for these tags to be unique.