Hosts

The HOSTATTRS list

This is a plist of lists, such that for each keyword symbol identifying a type of static informational attribute (“hostattr”), there is a list of entries. Property :HOSTATTRS subroutines may only push new entries to the front of each such sublist, using the function PUSH-HOSTATTR. Use GET-HOSTATTRS and GET-HOSTATTRS-CAR to access the lists.

The relationship between older and newer entries in the sublist for each type of static informational attribute is attribute-dependent. For example, for the :DATA attribute, the order of entries does not matter and each item is equally a piece of prerequisite data required by the host’s properties. For other kinds of attribute, it might be that later entries supercede earlier ones, or that the entries should be combined in some way. Property :APPLY subroutines decide how to interpret each type of static informational attribute.

Reserved names for static informational attributes

For attributes that will only be used among a co-ordinating group of properties, use a non-keyword symbol, whose package is one in which some or all of those properties are defined. This minimises the risk of any clashes. Many attributes, however, will be shared across properties, and should use keyword symbols. The semantics of these attributes are documented here:

  • :HOSTNAME: the host’s hostname – if the host has a domain name, then the FQDN, not just the part before the first dot

  • :ALIASES: see NETWORK:ALIASES

  • :IPV4: the host’s public IPv4 addresses

  • :IPV6: the host’s public IPv6 addresses

  • :DATA: items of prerequisite data required by the host

  • :OS: the operating system of the host

  • :APT.MIRRORS: for hosts running Debian or a Debian derivative, the host’s preferred apt mirrors

Host designators

A string designates a host with that hostname and no properties. Using strings to designate hosts is not valid in all contexts – some macros and properties where it might be useful to pass a string instead of a HOST object call ENSURE-HOST to convert, but this is not done everywhere.