23.2 The K Configuration Command

The K configuration command is used to associate a symbolic name with a database-map type. The symbolic name will later be used in the RHS of rules. The form of the K command looks like this:

Kname type args

The name is the symbolic name, the type is the kind of database map to use, and the args specifies its location and properties. We describe each in turn.

23.2.1 The name

The name portion of the K configuration command immediately follows the K. Whitespace between the K and the name is optional:

K name type args
  
 optional whitespace

The name must begin with a letter or digit and can contain only letters, digits, and the underscore character:

K local_hosts   good
K $andcents     bad

The case of the letters in name does not matter. All names are converted to lowercase before they are stored:

K LOCAL_Hosts
K local_hosts   the same

If you begin a name with a bad character, the following error will be printed and that K line will be ignored:

configfile: line num: readcf: config K line: no map name 

If a bad character appears in the middle of a name, the part preceding the bad character will be taken as the name, and the part following the bad character will be taken as the type. For example, the name me@home will produce this error:

configfile: line num: readcf: map me: class home  not available 

23.2.2 The type

Recall that the type^[2] portion of the K configuration command follows the name:

^[2] The sendmail source calls this class, but we chose type to make it clear that this is different from class macros.

Kname type args

Note that whitespace between the name and the type can be a joined indented line, which allows commenting and improves readability:

Kname             # Why this name
        type      # Why this type
        args      # and so on

The type declares which sort of database map to use. It must be one of the types listed in Table 23-2.

Table 23-2. Possible K command types

Type	§	Version	Description
arith	arith	V8.10 and above	Perform arithmetic computations
btree	btree	V8.1 and above	A db(3) form of database
bestmx	bestmx	V8.7 and above	Look up the best MX record for a host
dbm	dbm	V8.1 and above	Really ndbm supplied with most versions of Unix
dequote	dequote	V8.6 and above	Remove quotation marks
dns	dns	V8.12 and above	Look up information using DNS
hash	hash	V8.1 and above	A db(3) form of database
hesiod	hesiod	V8.7 and above	MIT network user authentication services
host	host	V8.1 and above	Internal table to store and look up hostnames
implicit	implicit	V8.1 and above	Search for an aliases database entry
ldap	ldap (was ldapx)	V8.8 and above	The Lightweight Directory Access Protocol (LDAP)
ldapx	ldap (was ldapx)	V8.9 and earlier	Replaced by ldap
macro	macro	V8.10 and above	Store a value into a macro via a rule
netinfo	netinfo	V8.7 and above	NeXT, Darwin, and Mac OS X network information services
nis	nis	V8.1 and above	Sun's Network Information Services (NIS)
nisplus	nisplus	V8.7 and above	Sun's newer version of NIS (NIS+)
nsd	nsd	V8.10 and above	Irix nsd database maps
null	null	V8.7 and above	Provide a never-found service
ph	ph	V8.10 and above	CCSO Nameserver (ph) lookups
program	program	V8.7 and above	Run an external program to look up the key
regex	regex	V8.9 and above	Use regular expressions
sequence	sequence	V8.7 and above	Search a series of database maps
stab	stab	V8.10 and above	Internally load aliases into the symbol table
switch	switch	V8.7 and above	Build sequences based on service switch
syslog	syslog	V8.10 and above	Log information using syslog(3) via rule sets
text	text	V8.7 and above	Look up in flat text files
userdb	userdb	V8.7 and above	Look up in the User Database
user	user	V8.7 and above	Look up local passwd information

All of these database-map types are described in Section 23.7 at the end of this chapter. If the type is not one of those listed, or if support for the type was not compiled in, the following error is printed and the K command is ignored:

configfile: line num: readcf: map name: class type  not available 

23.2.3 The args

The args of the K configuration command follow the symbolic name and type:

Kname type args

The args specify (among other things) the location of the database file or the name of a network database map. The args is like a miniature command line, and its general form looks like this:

switches file_or_map

The switches are letters prefixed with a - character that modify the use of the database. (We'll discuss them in the next section.) The file_or_map is the location of the database file or the name of a network database map. The file_or_map should exclude the .pag and .dir suffixes for dbm-type files and exclude the .db suffix for hash or btree-type files.

A database map is opened for reading when the configuration file is processed. If the file cannot be opened (and the -o is omitted, -o), an appropriate error is printed. The file_or_map should be an absolute pathname of a file (such as /etc/mail/uuhosts) or a literal network database-map name (such as hosts.byname). An nis database-map specification can include a domain:

map@domain

Relative filenames (names that omit a leading /) are interpreted as relative to the queue directory and should never be used.

The database files must live in a safe directory (one whose every component is writable only by root or the user defined by the TrustedUser option, TrustedUser). If the file itself is unsafe or its directory is unsafe, one of several errors will be printed or logged, depending on how you run sendmail. (See the description of the DontBlameSendmail option (DontBlameSendmail) for more information about this safety check.)