EPICS environment¶

EPNix provides the environment.epics module, enabled by default, which configures standard EPICS configuration parameters.

It configures EPICS environment variables, such as EPICS_CA_ADDR_LIST and EPICS_CA_AUTO_ADDR_LIST. Those variables are set in any user session.

It also configures every EPNix service that supports those parameters, such as ChannelFinder, and Phoebus services.

Default behavior¶

By default, the Channel Access address list is empty, and the “auto address list” parameter is set to yes. From the Channel Access Reference Manual:

For each interface found that is attached to a broadcast capable IP subnet, the broadcast address of that subnet is added to the list

If you don’t want broadcast addresses to be discovered for Channel Access, set environment.epics.ca_auto_addr_list to false.

Setting the address list¶

Use environment.epics.ca_addr_list to set the Channel Access address list.

Setting a manual CA address list¶

{
  environment.epics = {
    ca_addr_list = [
      "localhost"
      "192.168.1.42"
      "192.168.1.42:5066"
      "192.168.1.42:5067"
    ];
    # Don't use discovered broadcast addresses
    ca_auto_addr_list = false;
  };
}

Extending the address list for a service¶

When you specify both environment.epics.ca_addr_list and a service-specific configuration parameter, Nix merges both address lists.

For example, if you set:

Manually extending the CA address list¶

{
  environment.epics = {
    ca_addr_list = [
      "localhost"
      "192.168.1.42"
    ];
    ca_auto_addr_list = false;
  };

  # This list is merged with 'environment.epics.ca_addr_list'.
  services.phoebus-alarm-server.settings."org.phoebus.pv.ca/addr_list" = [
    "192.168.1.5"
    "192.168.1.6"
  ];
}

The Phoebus Alarm Server’s CA address list, in its .properties file, would contain:

192.168.1.5
192.168.1.6
localhost
192.168.1.42

Overriding the address list for a service¶

If you have a service, for which you want a specific CA address list, and bypass the use of the environment.epics module, use lib.mkForce:

Overriding the CA address list¶

{lib, ...}:
{
  environment.epics = {
    ca_addr_list = [
      "localhost"
      "192.168.1.42"
    ];
    ca_auto_addr_list = false;
  };

  # This list will *not* be merged with 'environment.epics.ca_addr_list'.
  services.phoebus-alarm-server.settings."org.phoebus.pv.ca/addr_list" =
    lib.mkForce [
      "192.168.1.5"
      "192.168.1.6"
    ];
}

Note

The service still inherits other values specified under environment.epics.