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<H2>BIND Configuration File Guide -- <CODE>logging</CODE> Statement</H2>

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<A NAME="Syntax"><H3>Syntax</H3></A>

<PRE>
logging {
  [ channel <VAR>channel_name</VAR> {
    ( file <VAR><A HREF="docdef.html">path_name</A></VAR>
       [ versions ( <VAR>number</VAR> | unlimited ) ]
       [ size <VAR><A HREF="docdef.html">size_spec</A></VAR> ]
     | syslog ( kern | user | mail | daemon | auth | syslog | lpr |
                news | uucp | cron | authpriv | ftp |
                local0 | local1 | local2 | local3 |
                local4 | local5 | local6 | local7 )
     | null );

    [ severity ( critical | error | warning | notice |
                 info  | debug [ <VAR>level</VAR> ] | dynamic ); ]
    [ print-category <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
    [ print-severity <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
    [ print-time <VAR><A HREF="docdef.html">yes_or_no</A></VAR>; ]
  }; ]

  [ category <VAR>category_name</VAR> {
    <VAR>channel_name</VAR>; [ <VAR>channel_name</VAR>; ... ]
  }; ]
  ...
};
</PRE>

<A NAME="Usage"><H3>Definition and Usage</H3></A>

<P>The <CODE>logging</CODE> statement configures a wide variety of
logging options for the nameserver.  Its <CODE>channel</CODE> phrase
associates output methods, format options and severity levels with
a name that can then be used with the <CODE>category</CODE> phrase to
select how various classes of messages are logged.</P>

<P>Only one <CODE>logging</CODE> statement is used to define as many
channels and categories as are wanted.  If there are multiple logging
statements in a configuration, the first defined determines the logging,
and warnings are issued for the others.  If there is no logging statement,
the logging configuration will be:</P>

<PRE>
    logging {
        category default { default_syslog; default_debug; };
        category panic { default_syslog; default_stderr; };
        category packet { default_debug; };
        category eventlib { default_debug; };
    };
</PRE>

The logging configuration is established as soon as the
<CODE>logging</CODE> statement is parsed.  If you want to redirect
messages about processing of the entire configuration file, the
<CODE>logging</CODE>statement must appear first.  Even if you do not
redirect configuration file parsing messages, we recommend
always putting the <CODE>logging</CODE> statement first so that this
rule need not be consciously recalled if you ever do need want the
parser's messages relocated.

<H4>The <CODE>channel</CODE> phrase</H4>

<P>All log output goes to one or more "channels"; you can make as many
of them as you want.</P>

<P>Every channel definition must include a clause that says whether
messages selected for the channel go to a file, to a particular syslog
facility, or are discarded.  It can optionally also limit the message
severity level that will be accepted by the channel (default is
"info"), and whether to include a <CODE>named</CODE>-generated time
stamp, the category name and/or severity level (default is not to
include any).</P>

<P>The word <CODE>null</CODE> as the destination option for the
channel will cause all messages sent to it to be discarded; other
options for the channel are meaningless.</P>

<P>The <CODE>file</CODE> clause can include limitations both on how
large the file is allowed to become, and how many versions of the file
will be saved each time the file is opened.  

<P>The <CODE>size</CODE> option for files is simply a hard ceiling on
log growth.  If the file ever exceeds the size, then
<CODE>named</CODE> will just not write anything more to it until the
file is reopened; exceeding the size does not automatically trigger a
reopen.  The default behavior is to not limit the size of the file.</P>

<P>If you use the <CODE>version</CODE> logfile option, then
<CODE>named</CODE> will retain that many backup versions of the file
by renaming them when opening.  For example, if you choose to keep 3
old versions of the file "lamers.log" then just before it is opened
lamers.log.1 is renamed to lames.log.2, lamers.log.0 is renamed to
lamers.log.1, and lamers.log is renamed to lamers.log.0.  No rolled
versions are kept by default; any existing log file is simply
appended.  The <CODE>unlimited</CODE> keyword is synonymous with
<CODE>99</CODE> in current BIND releases.</P>

<P>The argument for the <CODE>syslog</CODE> clause is a syslog
facility as described in the <CODE>syslog</CODE> manual page.  How
<CODE>syslogd</CODE> will handle messages sent to this facility is
described in the <CODE>syslog.conf</CODE> manual page.  If you have a
system which uses a very old version of <CODE>syslog</CODE> that only
uses two arguments to the <CODE>openlog()</CODE> function, then this
clause is silently ignored.</P>

<P>The <CODE>severity</CODE> clause works like <CODE>syslog</CODE>'s
"priorities", except that they can also be used if you are writing
straight to a file rather than using <CODE>syslog</CODE>.  Messages
which are not at least of the severity level given will not be
selected for the channel; messages of higher severity levels will be
accepted.</P>

<P>If you are using <CODE>syslog</CODE>, then the
<CODE>syslog.conf</CODE> priorities will also determine what
eventually passes through.  For example, defining a channel facility
and severity as <CODE>daemon</CODE> and <CODE>debug</CODE> but only
logging <CODE>daemon.warning</CODE> via <CODE>syslog.conf</CODE> will
cause messages of severity <CODE>info</CODE> and <CODE>notice</CODE>
to be dropped.  If the situation were reversed, with
<CODE>named</CODE> writing messages of only <CODE>warning</CODE> or
higher, then <CODE>syslogd</CODE> would print all messages it received
from the channel.</P>

<P>The server can supply extensive debugging information when it is in
debugging mode.  If the server's global debug level is greater than
zero, then debugging mode will be active.  The global debug level is
set either by starting the <CODE>named</CODE> server with the "-d"
flag followed by a positive integer, or by sending the running server the
SIGUSR1 signal (for example, by using "ndc trace").  The global debug
level can be set to zero, and debugging mode turned off, by sending
the server the SIGUSR2 signal ("ndc notrace").  All debugging messages
in the server have a debug level, and higher debug levels give more
more detailed output.
Channels that specify a specific debug severity, e.g.

<PRE>
    channel specific_debug_level {
        file "foo";
        severity debug 3;
    };
</PRE>

<P>will get debugging output of level 3 or less any time the
server is in debugging mode, regardless of the global debugging level.
Channels with <code>dynamic</code> severity use the server's global
level to determine what messages to print.

<P>If <CODE>print-time</CODE> has been turned on, then the date and
time will be logged.  <CODE>print-time</CODE> may be specified for a
syslog channel, but is usually pointless since syslog also prints the
date and time.  If <CODE>print-category</CODE> is requested,
then the category of the message will be logged as well.  Finally, if
<CODE>print-severity</CODE> is on, then the severity level of the
message will be logged.  The <CODE>print-</CODE> options may be used
in any combination, and will always be printed in the following order:
time, category, severity.  Here is an example where all three
<CODE>print-</CODE> options are on:

<PRE>
    28-Apr-1997 15:05:32.863 default: notice: Ready to answer queries.
</PRE>

<P>There are four predefined channels that are used for
<CODE>named</CODE>'s default logging as follows.  How they are used
used is described in the next section, The <CODE>category</CODE> phrase.

<PRE>
    channel default_syslog {
        syslog daemon;        # send to syslog's daemon facility
        severity info;        # only send priority info and higher
    };

    channel default_debug {
        file "named.run";     # write to named.run in the working directory
                              # Note: stderr is used instead of "named.run"
                              # if the server is started with the "-f" option.
        severity dynamic;     # log at the server's current debug level
    };

    channel default_stderr {  # writes to stderr
        file "&lt;stderr&gt;";      # this is illustrative only; there's currently
                              # no way of specifying an internal file
                              # descriptor in the configuration language.
        severity info;        # only send priority info and higher
    };

    channel null {            
        null;                 # toss anything sent to this channel
    };
</PRE>

<P>Once a channel is defined, it cannot be redefined.  Thus you cannot
alter the built-in channels directly, but you can modify the default
logging by pointing categories at channels you have defined.</P>

<H4>The <CODE>category</CODE> phrase</H4>

<P>There are many categories, so you can send the logs you want to see
wherever you want, without seeing logs you don't want.  If you don't specify
a list of channels for a category, then log messages in that category will
be sent to the <CODE>default</CODE> category instead.  If you don't specify
a default category, the following "default default" is used:

<PRE>
    category default { default_syslog; default_debug; };
</PRE>

<P>As an example, let's say you want to log security events to a file,
but you also want keep the default logging behavior.  You'd specify the
following:

<PRE>
    channel my_security_channel {
        file "my_security_file";
        severity info;
    };
    category security { my_security_channel; default_syslog; default_debug; };
</PRE>

<P>To discard all messages in a category, specify the
<CODE>null</CODE> channel:

<PRE>
    category lame-servers { null; };
    category cname { null; };
</PRE>

<P>The following
categories are available:</P>

<DL>
<DT><CODE>default</CODE>
<DD>
The catch-all.  Many things still aren't classified into categories,
and they all end up here.  Also, if you don't specify any channels for
a category, the default category is used instead.  If you do not
define the default category, the following definition is used:
<CODE>category default { default_syslog; default_debug; };</CODE>

<DT><CODE>config</CODE>
<DD>  
High-level configuration file processing.

<DT><CODE>parser</CODE>
<DD>
Low-level configuration file processing.

<DT><CODE>queries</CODE>
<DD>
A short log message is generated for every query the server receives.

<DT><CODE>lame-servers</CODE>
<DD>
Messages like "Lame server on ..."

<DT><CODE>statistics</CODE>
<DD>
Statistics.

<DT><CODE>panic</CODE>
<DD>
If the server has to shut itself down due to an internal problem, it
will log the problem in this category as well as in the problem's native
category.  If you do not define the panic category, the following definition
is used: <CODE>category panic { default_syslog; default_stderr; };</CODE>

<DT><CODE>update</CODE>
<DD>
Dynamic updates.

<DT><CODE>ncache</CODE>
<DD>
Negative caching.

<DT><CODE>xfer-in</CODE>
<DD>
Zone transfers the server is receiving.

<DT><CODE>xfer-out</CODE>
<DD>
Zone transfers the server is sending.

<DT><CODE>db</CODE>
<DD>
All database operations.

<DT><CODE>eventlib</CODE>
<DD>
Debugging info from the event system.  Only one channel may be specified for
this category, and it must be a file channel.  If you do not define the
eventlib category, the following definition is used: <CODE>category eventlib
{ default_debug; };</CODE>

<DT><CODE>packet</CODE>
<DD>
Dumps of packets received and sent.  Only one channel may be specified for
this category, and it must be a file channel.  If you do not define the
packet category, the following definition is used: <CODE>category packet
{ default_debug; };</CODE>

<DT><CODE>notify</CODE>
<DD>
The NOTIFY protocol.

<DT><CODE>cname</CODE>
<DD>
Messages like "... points to a CNAME".

<DT><CODE>security</CODE>
<DD>
Approved/unapproved requests.

<DT><CODE>os</CODE>
<DD>
Operating system problems.

<DT><CODE>insist</CODE>
<DD>
Internal consistency check failures.

<DT><CODE>maintenance</CODE>
<DD>
Periodic maintenance events.

<DT><CODE>load</CODE>
<DD>
Zone loading messages.

<DT><CODE>response-checks</CODE>
<DD>
Messages arising from response checking, such as
"Malformed response ...", "wrong ans. name ...",
"unrelated additional info ...", "invalid RR type ...", and "bad referral ...".

</DL>

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