Creating Nonstandard NIS Maps

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As discussed in NIS Maps, maps are databases that have a special format. The default, or standard, maps are built out of standard system text files. However, NIS maps are flexible in that you can build into a map any information that has a key and a value.

The following example shows how to create a nonstandard map called udir.nam that lists the home directories of users in this domain. You will use the /etc/passwd file as input file for the udir.nam map. (If you use a different file to create the passwd map, use that file instead of /etc/passwd.) The keys for the map are the user names, and their home directories are the corresponding values. To create this new map, enter the following two commands on the master server:

cd /var/yp
awk '{FS=":" ; OFS="\t" ; print $1,$6}' /etc/passwd | \
    makedbm - domain/udir.nam

where domain specifies this NIS domain, and ` is the single forward quote. The awk command extracts from the /etc/passwd file the first and sixth fields. It passes this information to the makedbm command that builds the udir.nam map. You can now propagate and use this map just like any other map. For example, enter the following command to see a list of all the home directories specified in the /etc/passwd file.

ypcat udir.nam

This example used the awk command to filter out the unwanted fields from the /etc/passwd file. However, you can use any system utility or programming language to create the map input. In fact, you can create the map input manually. For example, to create the udir.nam map, you could have entered the command:

makedbm - domain/udir.nam
john /u/john
mary /u/mary
sam /u/sam
<Ctrl^D>

Whatever method you use to create the map input file, you probably want to update the map periodically. To do so, you can add stanzas to the /var/yp/Makefile file so that your nonstandard map can be updated as any other map (see Changing an NIS Map). For detailed information on customizing the /var/yp/Makefile, see the make Command Overview topic in General Programming Concepts: Writing and Debugging Programs.

Note: When you add a new map after the initial set of maps have been pushed to a worker server, you must make the new maps with the NOPUSH option set to 1. For example, use the following command to make newmap map.

make NOPUSH=1 newmap

If you do not use the NOPUSH option, the make command suspends. (This only applies if the new map does not already exist on the worker server.) Next, use the ypxfr command on each worker server for each new map you created (see Propagating an NIS Map).