named - Internet domain name server
named [ [-4] | [-6] ] [-c config-file]
[-C] [-d debug-level] [-D string] [-E
engine-name] [-f] [-g] [-L logfile] [-M option]
[-m flag] [-n #cpus] [-p port] [-s] [-S
#max-socks] [-t directory] [-U #listeners] [-u user]
[-v] [-V] [-X lock-file] [-x cache-file]
named is a Domain Name System (DNS) server, part of the
BIND 9 distribution from ISC. For more information on the DNS, see RFC
1033, RFC 1034, and RFC 1035.
When invoked without arguments, named reads the default
configuration file /etc/named.conf, reads any initial data, and
listens for queries.
- -4
- This option tells named to use only IPv4, even if the host machine
is capable of IPv6. -4 and -6 are mutually exclusive.
- -6
- This option tells named to use only IPv6, even if the host machine
is capable of IPv4. -4 and -6 are mutually exclusive.
- -c
config-file
- This option tells named to use config-file as its
configuration file instead of the default, /etc/named.conf. To
ensure that the configuration file can be reloaded after the server has
changed its working directory due to to a possible directory option
in the configuration file, config-file should be an absolute
pathname.
-C
This option prints out the default built-in configuration
and exits.
NOTE: This is for debugging purposes only and is not an accurate
representation of the actual configuration used by named at
runtime.
- -d
debug-level
- This option sets the daemon's debug level to debug-level. Debugging
traces from named become more verbose as the debug level
increases.
- -D string
- This option specifies a string that is used to identify a instance of
named in a process listing. The contents of string are not
examined.
- -E
engine-name
- When applicable, this option specifies the hardware to use for
cryptographic operations, such as a secure key store used for signing.
When BIND 9 is built with OpenSSL, this needs to be set to the
OpenSSL engine identifier that drives the cryptographic accelerator or
hardware service module (usually pkcs11). When BIND is built with
native PKCS#11 cryptography (--enable-native-pkcs11), it defaults
to the path of the PKCS#11 provider library specified via
--with-pkcs11.
- -f
- This option runs the server in the foreground (i.e., do not
daemonize).
- -g
- This option runs the server in the foreground and forces all logging to
stderr.
- -L logfile
- This option sets the log to the file logfile by default, instead of
the system log.
-M option
This option sets the default (comma-separated) memory
context options. The possible flags are:
- external: use system-provided memory allocation functions; this is
the implicit default.
- internal: use the internal memory manager.
- fill: fill blocks of memory with tag values when they are allocated
or freed, to assist debugging of memory problems; this is the implicit
default if named has been compiled with
--enable-developer.
- nofill: disable the behavior enabled by fill; this is the
implicit default unless named has been compiled with
--enable-developer.
- -m flag
- This option turns on memory usage debugging flags. Possible flags are
usage, trace, record, size, and mctx.
These correspond to the ISC_MEM_DEBUGXXXX flags described in
<isc/mem.h>.
- -n #cpus
- This option controls the number of CPUs that named assumes the
presence of. If not specified, named tries to determine the number
of CPUs present automatically; if it fails, a single CPU is assumed to be
present.
named creates two threads per each CPU present (one
thread for receiving and sending client traffic and another thread for
sending and receiving resolver traffic) and then on top of that a single
thread for handling time-based events.
- -p port
- This option listens for queries on port. If not specified, the
default is port 53.
- -s
- This option writes memory usage statistics to stdout on exit.
NOTE:
This option is mainly of interest to BIND 9 developers
and may be removed or changed in a future release.
- -S #max-socks
- This option allows named to use up to #max-socks sockets.
The default value is 21000 on systems built with default configuration
options, and 4096 on systems built with configure
--with-tuning=small.
WARNING:
This option should be unnecessary for the vast majority
of users. The use of this option could even be harmful, because the specified
value may exceed the limitation of the underlying system API. It is therefore
set only when the default configuration causes exhaustion of file descriptors
and the operational environment is known to support the specified number of
sockets. Note also that the actual maximum number is normally slightly fewer
than the specified value, because named reserves some file descriptors
for its internal use.
- -t directory
- This option tells named to chroot to directory after
processing the command-line arguments, but before reading the
configuration file.
WARNING:
This option should be used in conjunction with the
-u option, as chrooting a process running as root doesn't enhance
security on most systems; the way chroot is defined allows a process
with root privileges to escape a chroot jail.
- -U #listeners
- This option tells named the number of #listeners worker
threads to listen on, for incoming UDP packets on each address. If not
specified, named calculates a default value based on the number of
detected CPUs: 1 for 1 CPU, and the number of detected CPUs minus one for
machines with more than 1 CPU. This cannot be increased to a value higher
than the number of CPUs. If -n has been set to a higher value than
the number of detected CPUs, then -U may be increased as high as
that value, but no higher. On Windows, the number of UDP listeners is
hardwired to 1 and this option has no effect.
- -u user
- This option sets the setuid to user after completing privileged
operations, such as creating sockets that listen on privileged ports.
NOTE:
On Linux, named uses the kernel's capability
mechanism to drop all root privileges except the ability to bind to a
privileged port and set process resource limits. Unfortunately, this means
that the -u option only works when named is run on kernel 2.2.18
or later, or kernel 2.3.99-pre3 or later, since previous kernels did not allow
privileges to be retained after setuid.
- -v
- This option reports the version number and exits.
- -V
- This option reports the version number, build options, supported
cryptographics algorithms, and exits.
- -X lock-file
- This option acquires a lock on the specified file at runtime; this helps
to prevent duplicate named instances from running simultaneously.
Use of this option overrides the lock-file option in
named.conf. If set to none, the lock file check is
disabled.
- -x cache-file
- This option loads data from cache-file into the cache of the
default view.
WARNING:
This option must not be used in normal operations. It is
only of interest to BIND 9 developers and may be removed or changed in a
future release.
In routine operation, signals should not be used to control the
nameserver; rndc should be used instead.
The result of sending any other signals to the server is
undefined.
The named configuration file is too complex to describe in
detail here. A complete description is provided in the BIND 9 Administrator
Reference Manual.
named inherits the umask (file creation mode mask)
from the parent process. If files created by named, such as journal
files, need to have custom permissions, the umask should be set
explicitly in the script used to start the named process.
- /etc/named.conf
- The default configuration file.
- /var/run/named/named.pid
- The default process-id file.
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