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DNS Dynamic Updates (RFC 2136) DNS Change Notification (RFC 1996) Completely new configuration syntax Flexible, categorized logging system IP-address-based access control for queries, zone
transfers, and updates that may be specified on a zone-by-zone basis More efficient zone transfers Improved performance for servers with thousands
of zones The server no longer forks for outbound zone transfers
BIND 8 is much more configurable than the previous release
of BIND. There are entirely new areas of configuration, such as
access control lists and categorized logging. Many options that
previously applied to all zones can now be used selectively. These
features, plus a consideration of future configuration needs led
to the creation of a new configuration file format. BIND Configuration File Guide — Logging Statement | |
Syntaxlogging { [ channel channel_name { ( file path_name [ versions ( number | unlimited ) ] [ size size_spec ] | 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 [ level ] | dynamic ); ] [ print-category yes_or_no; ] [ print-severity yes_or_no; ] [ print-time yes_or_no; ] }; ] |
[ category category_name { channel_name; [ channel_name; ... ] }; ] ... }; |
The logging statement configures a wide variety of logging
options for the nameserver. Its channel phrase associates output
methods, format options and severity levels with a name that can
then be used with the category phrase to select how various classes
of messages are logged. Only one logging 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: logging { category default { default_syslog; default_debug; }; category panic { default_syslog; default_stderr; }; category packet { default_debug; }; category eventlib { default_debug; }; }; |
All log output goes to one or more "channels";
make as many of them as you want. 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
named generated time stamp, the
category name and/or severity level (default is not to include any). The word null as the destination option for the channel will
cause all messages sent to it to be discarded; other options for
the channel are meaningless. The file 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. The size option for files is simply a hard ceiling on log
growth. If the file ever exceeds the size, then named
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. If you use the version logfile option, then named
will retain 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. The unlimited keyword is
synonymous with 99 in current BIND releases. The argument for the syslog clause is a syslog facility described
earlier in this manual. How syslog will handle messages sent to
this facility is described under syslog.conf
earlier in this manual. If you have a system which uses a very old
version of syslog and that only uses two arguments to the openlog()
function, then this clause is silently ignored. The severity clause works like syslog's "priorities",
except that they can also be used if you are writing straight to
a file rather than using syslog. 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. If you are using syslog, then the syslog.conf
priorities will also determine what eventually passes through. For
example, defining a channel facility and severity as daemon and
debug but only logging daemon.warning
via syslog.conf will cause messages
of severity information and notice to be dropped. If the situation
were reversed, with named writing
messages of only warning or higher, then syslog would print all
messages it received from the channel. 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 server with the "-d"
flag followed by a positive integer, or by sending the 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 detailed output. Channels that specify a
specific debug severity, for example, channel specific_debug_level { file "foo"; severity debug 3; }; |
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 dynamic severity use the server's
global level to determine what messages to print. If print-time has been turned
on, then the date and time will be logged. print-time
may be specified for a syslog channel, but is usually pointless
since syslog also prints the date and time. If print-category
is requested, then the category of the message will be logged as
well. Finally, if print-severity
is on, then the severity level of the message will be logged. The
print options may be used in any combination, and will always be
printed in the following order: time, category, and severity. Here
is an example where all three print options are on: 28-Apr-1997 15:05:32.863 default: notice: Ready to answer queries. |
There are four predefined channels that are used for named's
default logging as follows. How they are used is described in the
next section, The category phrase. 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 "<stderr>"; # 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 }; |
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. 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 default category
instead. If you don't specify a default category, the following
"default" is used: category default { default_syslog; default_debug; }; |
As an example, you want to log security events to a file,
but you also want keep the default logging behavior. You'd
specify the following: channel my_security_channel { file "my_security_file"; severity info }; category security { my_security_channel; default_syslog; default_debug; }; |
To discard all messages in a category, specify the null channel: category lame-servers { null; }; category cname { null; }; |
The following categories are available: - default
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: category default { default_syslog; default_debug; };
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- config
High-level configuration file processing. - parser
Low-level configuration file processing. - queries
A short log message is generated for every query
the server receives. - lame-servers
Messages like "Lame server on ..." - statistics
Statistics. - panic
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: category panic { default_syslog; default_stderr; }; - update
Dynamic updates. - ncache
Negative caching. - xfer-in
Zone transfers the server is receiving. - xfer-out
Zone transfers the server is sending. - db
All database operations. - eventlib
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: category eventlib { default_debug; }; - packet
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: category packet { default_debug; }; - notify
The NOTIFY protocol. - cname
Messages like "... points to a CNAME". - security
Approved/unapproved requests. - os
Operating system problems. - insist
Internal consistency check failures. - maintenance
Periodic maintenance events. - load
Zone loading messages. - response-checks
Messages arising from response checking, such as
"Malformed response ...", "wrong ans.
name ...", "unrelated additional info ...",
"invalid RR type ...", and "bad referral
...".
BIND Configuration File Guide—Zone Statement | |
Syntaxzone domain_name [ ( in | hs | hesiod | chaos ) ] { type master; file path_name; [ check-names ( warn | fail | ignore ); ] [ allow-update { address_match_list }; ] [ allow-query { address_match_list }; ] [ allow-transfer { address_match_list }; ] [ notify yes_or_no; ] [ also-notify { ip_addr; [ ip_addr; ... ] }; }; |
zone domain_name [ ( in | hs | hesiod | chaos ) ] { type ( slave | stub ); [ file path_name; ] masters { ip_addr; [ ip_addr; ... ] }; [ check-names ( warn | fail | ignore ); ] [ allow-update { address_match_list }; ] [ allow-query { address_match_list }; ] [ allow-transfer { address_match_list }; ] [ max-transfer-time-in number; ] [ notify yes_or_no; ] [ also-notify { ip_addr; [ ip_addr; ... ] }; }; |
zone "." [ ( in | hs | hesiod | chaos ) ] { type hint; file path_name; [ check-names ( warn | fail | ignore ); ] }; |
The zone's name may optionally be followed by a class.
If a class is not specified, class in is used. - check-names
See Name Checking. - allow-query
See the description of allow-query in the Access
Control section. - allow-update
Specifies which hosts are allowed to submit Dynamic
DNS updates to the server. The default is to deny updates from all
hosts. - allow- transfer
See the description of allow-transfer in the Access
Control section. - max-transfer-time-in
See the description of max-transfer-time-in
in the Zone Transfers section. - notify
See the description of notify in the Boolean Options
section. - also-notify
also-notify is
only meaningful if notify is active for this zone. The set of machines that will receive a DNS NOTIFY message
for this zone is made up of all the listed nameservers for the zone
(other than the primary master) plus any IP addresses specified
with also-notify. also-notify
is not meaningful for stub zones. The default is the empty list.
BIND Configuration File Guide — Options Statement | |
Syntaxoptions { [ directory path_name; ] [ named-xfer path_name; ] [ dump-file path_name; ] [ memstatistics-file path_name; ] [ pid-file path_name; ] [ statistics-file path_name; ] [ auth-nxdomain yes_or_no; ] [ deallocate-on-exit yes_or_no; ] [ fake-iquery yes_or_no; ] [ fetch-glue yes_or_no; ] [ host-statistics yes_or_no; ] [ multiple-cnames yes_or_no; ] [ notify yes_or_no; ] [ recursion yes_or_no; ] [ forward ( only | first ); ] [ forwarders { [ in_addr ; [ in_addr ; ... ] ] }; ] [ check-names ( master | slave | response ) ( warn | fail | ignore); ] [ allow-query { address_match_list }; ] [ allow-transfer { address_match_list }; ] [ listen-on [ port ip_port ] { address_match_list }; ] [ query-source [ address ( ip_addr | * ) ] [ port ( ip_port | * ) ] ; ] [ max-transfer-time-in number; ] [ transfer-format ( one-answer | many-answers ); ] [ transfers-in number; ] [ transfers-out number; ] [ transfers-per-ns number; ] [ coresize size_spec ; ] [ datasize size_spec ; ] [ files size_spec ; ] [ stacksize size_spec ; ] [ cleaning-interval number; ] [ interface-interval number; ] [ statistics-interval number; ] [ topology { address_match_list }; ] }; |
The options statement sets up global options to be used by
BIND. This statement may appear at only once in a configuration
file; if more than one occurrence is found, the first occurrence
determines the actual options used, and a warning will be generated.
If there is no options statement, an options block with each option
set to its default will be used. Pathnames- directory
The working directory of the server. Any non-absolute
pathnames in the configuration file will be taken as relative to
this directory. The default location for most server output files,
for example, "named.run"
is this directory. If a directory is not specified, the working
directory defaults to ".", the directory from
which the server was started. The directory specified should be
an absolute path. - named-xfer
The pathname to the named-xfer
program that the server uses for inbound zone transfers. If not
specified, the default is system dependent for example, "/usr/sbin/named-xfer". - dump-file
The pathname of the file the server dumps the database
to when it receives SIGINT signal
(ndc dumpdb). If not specified, the default is "named_dump.db". - memstatistics- file
The pathname of the file the server writes memory
usage statistics to on exit, if deallocate-on-exit
is yes. If not specified, the default is "named.memstats". - pid-file
The pathname of the file the server writes its process
ID in. If not specified, the default is operating system dependent,
but is usually "/var/run/named.pid"
or "/etc/named.pid".
The pid-file is used by programs like "ndc" that
want to send signals to the running nameserver. - statistics- file
The pathname of the file the server appends statistics
to when it receives SIGILL signal
(ndc stats). If not specified, the default is "named.stats".
Boolean Options- auth-nxdomain
If yes, then the AA
bit is always set on NXDOMAIN responses,
even if the server is not actually authoritative. The default is
yes. Do not turn off auth-nxdomain
unless you are sure you know what you are doing, as some older software
won't like it. - deallocate-on- exit
If yes, then when the server exits it will painstakingly
deallocate every object it allocated, and then write a memory usage
report to the memstatistics-file.
The default is no, because it is faster to let the operating system
clean up. deallocate-on-exit is
handy for detecting memory leaks. - fake-iquery
If yes, the server will simulate the obsolete DNS
query type IQUERY. The default
is no. - fetch-glue
If yes (the default), the server will fetch "glue"
resource records it doesn't have when constructing the
additional data section of a response. fetch-glue no
can be used in conjunction with recursion no
to prevent the server's cache from growing or becoming
corrupted (at the cost of requiring more work from the client). - host- statistics
If yes, then statistics are kept for every host
that the nameserver interacts with. The default is no.
| | | | | NOTE: Turning on host-statistics can consume huge amounts
of memory. | | | | |
- multiple- cnames
If yes, then multiple CNAME
resource records will be allowed for a domain name. The default
is no. Allowing multiple CNAME
records is against standards and is not recommended. Multiple CNAME
support is available because previous versions of BIND allowed multiple
CNAME records, and these records
have been used for load balancing by a number of sites. - notify
If yes (the default), DNS NOTIFY
messages are sent when a zone the server is authoritative for changes.
The use of NOTIFY speeds convergence
between the master and its slaves. Slave servers that receive a
NOTIFY message and understand it,
will contact the master server for the zone and see if they need
to do a zone transfer, and if they do, they will initiate it immediately.
The notify option may also be specified in the zone statement, in
which case it overrides the options notify statement. - recursion
If yes, and a DNS query requests recursion, then
the server will attempt to do all the work required to answer the
query. If recursion is not on, the server will return a referral
to the client if it doesn't know the answer. The default
is yes. See also fetch-glue.
ForwardingThe forwarding facility can be used to create a large sitewide
cache on a few servers, reducing traffic over links to external
nameservers. It can also be used to allow queries by servers that
do not have direct access to the Internet, but wish to look up exterior
names anyway. Forwarding occurs only on those queries for which
the server is not authoritative and does not have the answer in
its cache. - forward
This option is only meaningful if the forwarders
list is not empty. A value of first, the default, causes the server
to query the forwarders first, and if that doesn't answer
the question the server will then look for the answer itself. If
only is specified, the server will only query the forwarders. - forwarders
Specifies the IP addresses to be used for forwarding.
The default is the empty list (no forwarding).
Future versions of BIND 8 will provide a more powerful forwarding
system. The syntax described above will continue to be supported. Name CheckingThe server can check domain names based upon their expected
client contexts. For example, a domain name used as a hostname can
be checked for compliance with the RFCs defining valid hostnames. Three checking methods are available: - ignore
No checking is done. - warn
Names are checked against their expected client
contexts. Invalid names are logged, but processing continues normally. - fail
Names are checked against their expected client
contexts. Invalid names are logged, and the offending data is rejected.
The server can check names in three areas; master zone files,
slave zone files, and in responses to queries the server has initiated.
If check-names response fail
has been specified, and answering the client's question
would require sending an invalid name to the client, the server
will send a REFUSED response code
to the client. The defaults are: check-names master fail; check-names slave warn; check-names response ignore;
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check-names may also be specified
in the zone statement, in which case it overrides the options check-names
statement. When used in a zone statement, the area is not specified
(because it can be deduced from the zone type). Access ControlAccess to the server can be restricted based on the IP address
of the requesting system. See address_match_list
for details on how to specify IP address lists. - allow-query
Specifies which hosts are allowed to ask ordinary
questions. allow-query may also
be specified in the zone statement, in which case it overrides the
options allow-query statement.
If not specified, the default is to allow queries from all hosts. - allow- transfer
Specifies which hosts are allowed to receive zone
transfers from the server. allow-transfer
may also be specified in the zone statement, in which case it overrides
the options allow-transfer statement.
If not specified, the default is to allow transfers from all hosts.
InterfacesThe interfaces and ports that the server will answer queries
from may be specified using the listen-on
option. listen-on takes an optional
port, and an address_match_list.
The server will listen on all interfaces allowed by the address
match list. If a port is not specified, port 53 will be used. Multiple listen-on statements
are allowed. For example: listen-on { 5.6.7.8; }; listen-on port 1234 { !1.2.3.4; 1.2/16; };
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If no listen-on is specified,
the server will listen on port 53 on all interfaces. Query AddressIf the server doesn't know the answer to a question,
it will query other nameservers. query-source
specifies the address and port used for such queries. If address
is * or is omitted, a wildcard IP address (INADDR_ANY)
will be used. If port is * or is omitted, a random unprivileged
port will be used. The default is query-source address * port *;
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| | | | | NOTE: Query-source currently applies only to UDP queries;
TCP queries always use a wildcard IP address and a random unprivileged
port. | | | | |
Zone Transfers- max-transfer- time-in
Inbound zone transfers (named-xfer
processes) running longer than this many minutes will be terminated.
The default is 120 minutes (2 hours). - transfer- format
The server supports two zone transfer methods. one-answer
uses one DNS message per resource record transferred. many-answers
packs as many resource records as possible into a message. many-answers
is more efficient, but is only known to be understood by BIND 8.1
and patched versions of BIND 4.9.5. The default is one-answer.
transfer-format may be overridden
on a per-server basis by using
the server statement. - transfers-in
The maximum number of inbound zone transfers that
can be running concurrently. The default value is 10. Increasing
transfers-in may speed up the convergence
of slave zones, but it also may increase the load on the local system. - transfers-out
This option will be used in the future to limit
the number of concurrent outbound zone transfers. It is checked
for syntax, but is otherwise ignored. - transfers-per-ns
The maximum number of inbound zone transfers (named-xfer
processes) that can be concurrently transferring from a given remote
nameserver. The default value is 2. Increasing transfers-per-ns
may speed up the convergence of slave zones, but it also may increase
the load on the remote nameserver. transfers-per-ns
may be overridden on a per-server
basis by using the transfers phrase of the server statement.
Resource LimitsThe server's usage of many system resources can be
limited. Some operating systems don't support some of the
limits. On such systems, a warning will be issued if the unsupported
limit is used. Some operating systems don't support limiting
resources, and on these systems a cannot set resource limits on
this system message will be logged. Scaled values are allowed when specifying resource limits.
For example, 1G can be used instead
of 1073741824 to specify a limit
of one gigabyte. unlimited requests unlimited use, or the maximum
available amount. default uses the limit that was in force when
the server was started. See size_spec
for more details. Periodic Task Intervals- cleaning- interval
The server will remove expired resource records
from the cache every cleaning-interval
minutes. The default is 60 minutes. If set to 0, no periodic cleaning
will occur. - interface- interval
The server will scan the network interface list
every interface-interval minutes.
The default is 60 minutes. If set to 0, interface scanning
will only occur when the configuration file is loaded. After the
scan, listeners will be started on any new interfaces (provided
they are allowed by the listen-on
configuration). Listeners on interfaces that have gone away will
be cleaned up. - statistics- interval
Nameserver statistics will be logged every statistics-interval
minutes. The default is 60. If set to 0, no statistics will be logged.
TopologyAll other things being equal, when the server chooses a nameserver
to query from a list of nameservers, it prefers the one that is
topologically closest to itself. The topology statement takes an
address_match_list and interprets
it in a special way. Each top-level list element is assigned a distance.
Non-negated elements get a distance based on their position in the
list, where the closer the match is to the start of the list, the
shorter the distance is between it and the server. A negated match
will be assigned the maximum distance from the server. If there
is no match, the address will get a distance which is further than
any non-negated list element, and closer than any negated element.
For example, topology { 10/8; !1.2.3/24; { 1.2/16; 3/8; }; };
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will prefer servers on network 10 the most, followed by hosts
on network 1.2.0.0 (netmask 255.255.0.0)
and network 3, with the exception
of hosts on network 1.2.3 (netmask 255.255.255.0),
which is preferred least of all. The default topology is topology { localhost; localnets; };
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Converting From BIND 4.9.x | |
BIND 4.9.x configuration files can be converted to the new
format by using src/bin/named/named-bootconf.pl,
a perl script that is part of the BIND 8.1 source kit.
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