The ndbm(3) form of database uses two files (.pag and .dir) for each database. Databases cannot be shared by different architectures across a network. If you intend to support aliasing in an efficient manner, you should at least define this NDBM (or NEWDB, described next) in your Build m4 file:

APPENDDEF(`confMAPDEF', `-DNDBM')

The ndbm(3) routines are used primarily to look up aliases. They can also be used to declare dbm-type maps (Section 23.2.2) with the K configuration command.

Library routines to support ndbm(3) are available with most modern commercial versions of Unix. You might have to specify library support with a -lndbm in the confLIBS line of your Build m4 file. If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1) to determine if NDBM support is included (if it appears in the list, support is included).

If, when you build sendmail, you get an error something like this:

"map.c", line 23: syntax error at or near variable name "README"

you are using a defectively installed db library. Versions of the db package from 2.0 through 2.3.1 can interfere with ndbm, unless precautionary steps are taken. Read the file sendmail/README for a description of how to correct this problem.