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       nslint - perform consistency checks on dns files


       nslint [ -d ] [ -c named.conf ] [ -C nslint.conf ]
       nslint [ -d ] [ -b named.boot ] [ -B nslint.boot ]


       Nslint  reads  the nameserver configuration files and performs a number
       of  consistency  checks  on  the  dns  records.  If  any  problems  are
       discovered,  error  messages  are  displayed on stderr and nslint exits
       with a non-zero status.

       Here is a partial list of errors nslint detects:

              Records that are malformed.

              Names that contain dots but are missing a trailing dot.

              PTR records with names that are missing a trailing dot.

              Names that contain illegal characters (rfc1034).

              A records without matching PTR records

              PTR records without matching A records

              Names with more than one address on the same subnet.

              Addresses in use by more than one name.

              Names with CNAME and other records (rfc1033).

              Unknown service and/or protocol keywords in WKS records.

              Missing semicolons and quotes.


       -b     Specify  an  alternate   named.boot   file.   The   default   is

       -c     Specify  an  alternate  named.conf  file.  The default is

       -B     Specify an alternate nslint.boot  file.  The  default  is
              nslint.boot  in  the  last  directory  line  processed in
              named.boot (or the current working directory).  This file
              is  processed  like a second named.boot.  The most common
              use is to tell nslint about  A  records  that  match  PTR
              records   that   point  outside  the  domains  listed  in

       -C     Specify an alternate nslint.conf  file.  The  default  is
              nslint.conf  in  the  last  directory  line  processed in
              named.conf (or the current working directory).  This file
              is processed like a second named.conf.

       -d     Raise  the  debugging  level.  Debugging  information  is
              displayed on stdout.

       Nslint knows how to read BIND 8 and 9's named.conf configuration
       file and also older BIND's named.boot file. If both files exist,
       nslint will prefer named.conf (on the theory that you forgot  to
       delete named.boot when you upgraded BIND).


       There  are  some cases where it is necessary to use the advanced
       configuration features of  nslint.   Advanced  configuration  is
       done  with  the  nslint.conf file. (You can also use nslint.boot
       which has a syntax similar to named.boot but  is  not  described

       The  most  common is when a site has a demilitarized zone (DMZ).
       The problem here is that the DMZ network will have  PTR  records
       for  hosts  outside  its  domain.  For  example lets say we have
       128.0.rev with:

              1.1     604800  in      ptr
              2.1     604800  in      ptr

       Obviously  we  will  define  an  A  record  for
       pointing to but we will get errors because there is no
       A record defined for  The solution is to  create
       a  nslint.conf  file  (in  the  same  directory as the other dns
       files) with:

              zone "" {
                     type master;
                     file "";

       And then create the file with:

              gateway 1       in      a

       Another problem occurs when there is a CNAME that  points  to  a
       host  outside  the local domains. Let's say we have
       pointing to

              info    604800  in      cname

       In this case we would need:

              zone "" {
                     type master;
                     file "";

       in nslint.boot and:

              larry   1       in      txt     "place holder"

       One last problem when a pseudo host is setup to allow  two  more
       more actual hosts provide a service. For, let's say that

              server  604800  in      a
              server  604800  in      a
              tom     604800  in      a
              tom     604800  in      mx 0
              jerry   604800  in      a
              jerry   604800  in      mx 0

       In this case nslint would complain about missing PTR records and
       ip  addresses  in  use by more than one host.  To suppress these
       warnings, add you would the lines:

              zone "" {
                     type master;
                     file "";

              zone "" {
                     type master;
                     file "nslint.128.0.rev";

       to nslint.conf and create with:

              server  1       in      allowdupa
              server  1       in      allowdupa

       and create nslint.128.0.rev with:

              6.6     604800  in      ptr
              94.6    604800  in      ptr

       In this example, the allowdupa keyword tells nslint that it's ok
       for  and  to be shared by,, and

       Another nslint feature helps detect hosts that  have  mistakenly
       had  two  ip  addresses  assigned  on  the same subnet. This can
       happen when two different people request an ip address  for  the
       same  hostname  or  when  someone  forgets  an  address has been
       assigned and requests a new number.

       To  detect  such  A  records,  add  a  nslint  section  to  your
       nslint.conf containing something similar to:

              nslint {
                     network "128.0.6/22";


              nslint {
                     network "128.0.6";

       These  two  examples  are are equivalent ways of saying the same
       thing; that subnet 128.0.6 has a 22 bit wide subnet mask.

       Using information from the above network statement, nslint would
       would flag the following A records as being in error:

              server  1       in      a
              server  1       in      a

       Note  that  if you specify any network lines in your nslint.conf
       file, nslint requires you to include  lines  for  all  networks;
       otherwise  you  might  forget  to  add  network  lines  for  new

       Sometimes you have a zone that nslint just can't  deal  with.  A
       good  example is a dynamic dns zone. To handle this, you can add
       the following to

              nslint {
                     ignorezone "";

       This will  suppress  "name  referenced  without  other  records"


       /etc/named.conf - default named configuration file
       /etc/named.boot - old style named configuration file
       nslint.conf - default nslint configuration file
       nslint.boot - old style nslint configuration file


       named(8), rfc1033, rfc1034


       Craig  Leres  of  the  Lawrence  Berkeley  National  Laboratory,
       University of California, Berkeley, CA.

       The current version is available via anonymous ftp:



       Please send bug reports to

       Not everyone is guaranteed to agree with all the checks done.

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