DNS (BIND) versus NIS (YP) versus "/etc/hosts" (long)

Greg Jumper jumper at spf.trw.com
Thu Feb 7 08:59:28 AEST 1991


     What is the "best" choice for individual "hostnames" and for the format
     of the "/etc/hosts" database for a network of Suns using the Internet
     and USENET?

     (I.e., how do BIND and NIS interact?)

Our network:

     A mixture of Sun 3 and Sun 4 systems running SunOS 4.0.3, 4.1, and 4.1.1.
     All systems are connected to a class C Ethernet network; one machine is
     also connected to the corporate class B backbone, which connects to the
     Internet.  The gateway machine (between class B and class C) runs the DNS
     (BIND) software and serves as the "mailhost"; all machines use NIS (YP),
     with the master server one of the machines only on the class C network.
     All hosts use "simple" hostnames, which appear as their "true" names in
     the "hosts" NIS map -- fully-qualified names do not appear.  (See the
     "figure" below.)


     1)  "UNIX System Administration" (Nemeth, Snyder, and Seebass) says that,
         if you run DNS, the "true" hostname must be the fully qualified name.
         However, their example "hosts" files have short hostnames and
         fully-qualified aliases; furthermore, with the exception of
         "sendmail.mx" on our mailhost, everything seems to work fine the
         way we have things set up.  Should one really use fully-qualified
         hostnames?  (Their length is obviously a pain.)

     2)  I thought the problem with "sendmail.mx" on our system was due to a
         problem (previously reported on the net) with name truncation in
         Sun's C library.  However, "nslookup", "ping", "host", etc.  all seem
         to use the resolver just fine on our systems.  Why wouldn't
         "sendmail.mx"?  Any ideas?

I greatly appreciate any light people can shed on these configuration issues!

                                       Thanks a lot,

                                       Greg Jumper
                                       TRW Data Systems Center

                                       jumper at spf.trw.com

PS.  The figure:

                   Corporate Class B Backbone (to Internet)
                                    |     |  SunOS 4.0.3
                                    |     |  Runs DNS (BIND)
                                    |     |  mailhost ("main" sendmail.cf)
     Organizational Class C Ethernet   |
     |               |                                                |
     |               |                                                |
   -----           -----                                            -----
  |     |         |     |                                          |     |
  |     |         |     |                  . . .                   |     |
  |     |         |     |                                          |     |
   -----           -----                                            -----
SunOS 4.0.3
YP master server

                       all use "subsidiary" sendmail.cf

    DNS domain name:     "spf.trw.com"
     YP domain name:     "+spf.trw.com"  (so sendmail doesn't strip of "spf")
    Hostname format:     short name only (not fully qualified)
"/etc/hosts" format:     short name only; fully qualified name is NOT included
                               as an alias

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