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.TH nslint 8 "2 May 2002"
.UC 4
.SH NAME
nslint - perform consistency checks on dns files
.SH SYNOPSIS
.B nslint
[
.B -d
] [
.B -c
.I named.conf
] [
.B -C
.I nslint.conf
]
.br
.B nslint
[
.B -d
] [
.B -b
.I named.boot
] [
.B -B
.I nslint.boot
]
.SH DESCRIPTION
.B 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
.I stderr
and
.B nslint
exits with a non-zero status.
.LP
Here is a partial list of errors
.B nslint
detects:
.IP
Records that are malformed.
.IP
Names that contain dots but are missing a trailing dot.
.IP
.B PTR
records with names that are missing a trailing dot.
.IP
Names that contain illegal characters (rfc1034).
.IP
.B A
records
without matching
.B PTR
records
.IP
.B PTR
records
without matching
.B A
records
.IP
Names with more than one address on the same subnet.
.IP
Addresses in use by more than one name.
.IP
Names with
.B CNAME
and other records (rfc1033).
.IP
Unknown service and/or protocol keywords in
.B WKS
records.
.IP
Missing semicolons and quotes.
.LP
.SH OPTIONS
.TP
.B -b
Specify an alternate
.I named.boot
file. The default is
.IR /etc/named.boot .
.TP
.TP
.B -c
Specify an alternate
.I named.conf
file. The default is
.IR /etc/named.conf .
.TP
.B -B
Specify an alternate
.I nslint.boot
file. The default is
.I nslint.boot
in the last
.B directory
line processed in
.I named.boot
(or the current working directory).
This file is processed like a second
.IR named.boot .
The most common use is to tell
.B nslint
about
.B A
records that match
.B PTR
records that point outside the domains listed in
.IR named.boot .
.TP
.B -C
Specify an alternate
.I nslint.conf
file. The default is
.I nslint.conf
in the last
.B directory
line processed in
.I named.conf
(or the current working directory).
This file is processed like a second
.IR named.conf .
.TP
.B -d
Raise the debugging level. Debugging information is
displayed on
.IR stdout .
.LP
.B Nslint
knows how to read
BIND 8 and 9's
.I named.conf
configuration file and also
older BIND's
.I named.boot
file. If both files exist,
.B nslint
will prefer
.I named.conf
(on the theory that you forgot to delete
.I named.boot
when you upgraded BIND).
.LP
.SH "ADVANCED CONFIGURATION"
There are some cases where it is necessary to use the
advanced configuration features of
.BR nslint .
Advanced configuration is done with the
.I nslint.conf
file. (You can also use
.I nslint.boot
which has a syntax similar to
.I named.boot
but is not described here.)
.LP
The most common is when a site has a demilitarized zone (DMZ).
The problem here is that the DMZ network will have
.B PTR
records for hosts outside its domain. For example lets say
we have
.I 128.0.rev
with:
.LP
.RS
.nf
.sp .5
1.1     604800  in      ptr     gateway.lbl.gov.
2.1     604800  in      ptr     gateway.es.net.
.sp .5
.fi
.RE
.LP
Obviously we will define an
.B A
record for
.I gateway.lbl.gov
pointing to
.I 128.0.1.1
but we will get errors because there is no
.B A
record defined for
.IR gateway.es.net .
The solution is to create a
.I nslint.conf
file (in the same directory as the other dns files)
with:
.LP
.RS
.nf
.sp .5
zone "es.net" {
.RS
type master;
file "nslint.es.net";
.RE
};
.sp .5
.fi
.RE
.LP
And then create the file
.I nslint.es.net
with:
.LP
.RS
.nf
.sp .5
gateway 1       in      a       128.0.1.2
.sp .5
.fi
.RE
.LP
Another problem occurs when there is a
.B CNAME
that points to a host outside the local domains. Let's say we have
.I info.lbl.gov
pointing to
.IR larry.es.net :
.LP
.RS
.nf
.sp .5
info    604800  in      cname   larry.es.net.
.sp .5
.fi
.RE
.LP
In this case we would need:
.LP
.RS
.nf
.sp .5
zone "es.net" {
.RS
type master;
file "nslint.es.net";
.RE
};
.sp .5
.fi
.RE
.LP
in
.I nslint.boot
and:
.LP
.RS
.nf
.sp .5
larry   1       in      txt     "place holder"
.sp .5
.fi
.RE
.LP
.IR nslint.es.net .
.LP
One last problem
when a pseudo host is setup to allow two more
more actual hosts provide a service. For, let's say that
.I lbl.gov
contains:
.LP
.RS
.nf
.sp .5
server  604800  in      a       128.0.6.6
server  604800  in      a       128.0.6.94
;
tom     604800  in      a       128.0.6.6
tom     604800  in      mx 0    lbl.gov.
;
jerry   604800  in      a       128.0.6.94
jerry   604800  in      mx 0    lbl.gov.
.sp .5
.fi
.RE
.LP
In this case
.B nslint
would complain about missing
.B PTR
records and ip addresses in use by more than one host.
To suppress these warnings, add you would the lines:
.LP
.RS
.nf
.sp .5
zone "lbl.gov" {
.RS
type master;
file "nslint.lbl.gov";
.RE
};
.LP
zone "0.128.in-addr.arpa" {
.RS
type master;
file "nslint.128.0.rev";
.RE
};
.sp .5
.fi
.RE
.LP
to
.I nslint.conf
and create
.I nslint.lbl.gov
with:
.LP
.RS
.nf
.sp .5
server  1       in      allowdupa       128.0.6.6
server  1       in      allowdupa       128.0.6.94
.sp .5
.fi
.RE
.LP
and create
.I nslint.128.0.rev
with:
.LP
.RS
.nf
.sp .5
6.6     604800  in      ptr     server.lbl.gov.
94.6    604800  in      ptr     server.lbl.gov.
.sp .5
.fi
.RE
.LP
In this example, the
.B allowdupa
keyword tells
.B nslint
that it's ok for
.I 128.0.6.6
and
.I 128.0.6.94
to be shared by
.IR server.lbl.gov ,
.IR tom.lbl.gov ,
and
.IR jerry.lbl.gov .
.LP
Another
.B 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.
.LP
To detect such
.B A
records, add a
.B nslint
section to your
.I nslint.conf
containing something similar to:
.LP
.RS
.nf
.sp .5
nslint {
.RS
network "128.0.6/22";
.RE
};
.sp .5
.fi
.RE
.LP
or:
.LP
.RS
.nf
.sp .5
nslint {
.RS
network "128.0.6 255.255.252.0";
.RE
};
.sp .5
.fi
.RE
.LP
These two examples are are equivalent ways of saying the same thing;
that subnet
.I 128.0.6
has a 22 bit wide subnet mask.
.LP
Using information from the above
.B network
statement,
.B nslint
would would flag the following
.B A
records as being in error:
.LP
.RS
.nf
.sp .5
server  1       in      a       128.0.6.48
server  1       in      a       128.0.7.16
.sp .5
.fi
.RE
.LP
Note that if you specify any
.B network
lines in your
.I nslint.conf
file,
.B nslint
requires you to include lines for all networks;
otherwise you might forget to add
.B network
lines for new networks.
.LP
Sometimes you have a zone that
.B nslint
just can't deal with. A good example is
a dynamic dns zone. To handle this, you can
add the following to
.IB nslint.com :
.LP
.RS
.nf
.sp .5
nslint {
.RS
ignorezone "dhcp.lbl.gov";
.RE
};
.sp .5
.fi
.RE
.LP
This will suppress "name referenced without other records" warnings.
.LP
.SH FILES
.na
.nh
.nf
/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
.ad
.hy
.fi
.LP
.SH "SEE ALSO"
.na
.nh
.IR named (8),
rfc1033,
rfc1034
.ad
.hy
.SH AUTHOR
Craig Leres of the
Lawrence Berkeley National Laboratory, University of California, Berkeley, CA.
.LP
The current version is available via anonymous ftp:
.LP
.RS
.I ftp://ftp.ee.lbl.gov/nslint.tar.gz
.RE
.SH BUGS
Please send bug reports to nslint@ee.lbl.gov.
.LP
Not everyone is guaranteed to agree with all the checks done.