How to create a custom NIS map

nis

I'd like to create a custom NIS map in order to be able to look up my own information using ypmatch and map between local and centralised usernames. How can this be achieved?

Best Answer

First off, edit /var/yp/Makefile to add in the new map. You’ve probably got something like this:

PASSWD = $(YPPWDDIR)/passwd

We need to add a new line for the new map. This is going to be the new username map, so call it usermap.

USERMAP = $(YPSRCDIR)/usermap

YPSRCDIR is /etc in my case, but obviously choose the path that suits you the best.

Now find a line that starts all:. This is the list of maps to update. Add your new map to the end, so it’ll be something like

all: auto.home auto.master group hosts netgrp passwd usermap

Further down where there is a group of lines like this:

passwd:         passwd.byname passwd.byuid

you should add in your own map:

usermap : usermap.byname

The byname part is an indicator for what the map key is and isn’t that important for us.

You now need to add a section to tell the makefile how to update your map:

usermap.byname: $(USERMAP) $(YPDIR)/Makefile
        @echo "Updating $@..."
        @$(AWK) -F: '!/^[-+#]/ { if ($$1 != "" && $$2 != "" ) \
                print $$1"\t"$$2 }' $(USERMAP) \
                | $(DBLOAD) -i $(USERMAP) -o $(YPMAPDIR)/$@ - $@
        -@$(NOPUSH) || $(YPPUSH) -d $(DOMAIN) $@

This processes the file /etc/usermap and generates the map file. Essentially you just need to print key\tvalue into $(DBLOAD) …. This example extracts data from the file assuming it is in the format key:value.

Now edit /var/yp/nicknames to add your new map:

usermap    usermap.byname

then run make in /var/yp as normal.

If you have a slave server you’ll probably have a timeout with the new map at this point. To get round this, you need to run ypxfr on the slave to get the map first:

/usr/lib/yp/ypxfr -d <yp domain> -h <yp master host> usermap.byname
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