named - Internet domain name server
named [-4] [-6] [-c config-file] [-d debug-level] [-D string] [-E engine-name] [-f] [-g] [-M option] [-m flag] [-n #cpus] [-p port] [-s] [-S #max-socks] [-t directory] [-U #listeners] [-u user] [-v] [-V] [-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 RFCs 1033, 1034, and 1035. When invoked without arguments, named will read the default configuration file /etc/named.conf, read any initial data, and listen for queries.
-4 Use IPv4 only even if the host machine is capable of IPv6. -4 and -6 are mutually exclusive. -6 Use IPv6 only even if the host machine is capable of IPv4. -4 and -6 are mutually exclusive. -c config-file Use config-file as the configuration file instead of the default, /etc/named.conf. To ensure that reloading the configuration file continues to work 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. -d debug-level Set the daemon's debug level to debug-level. Debugging traces from named become more verbose as the debug level increases. -D string 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, specifies the hardware to use for cryptographic operations, such as a secure key store used for signing. When BIND is built with OpenSSL PKCS#11 support, this defaults to the string "pkcs11", which identifies an OpenSSL engine that can drive a cryptographic accelerator or hardware service module. 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 Run the server in the foreground (i.e. do not daemonize). -g Run the server in the foreground and force all logging to stderr. -M option Sets the default memory context options. Currently the only supported option is external, which causes the internal memory manager to be bypassed in favor of system-provided memory allocation functions. -m flag Turn 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 Create #cpus worker threads to take advantage of multiple CPUs. If not specified, named will try to determine the number of CPUs present and create one thread per CPU. If it is unable to determine the number of CPUs, a single worker thread will be created. -p port Listen for queries on port port. If not specified, the default is port 53. -s Write 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 Allow named to use up to #max-socks sockets. The default value is 4096 on systems built with default configuration options, and 21000 on systems built with "configure --with-tuning=large". 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 a little fewer than the specified value because named reserves some file descriptors for its internal use. -t directory 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(2) is defined allows a process with root privileges to escape a chroot jail. -U #listeners Use #listeners worker threads to listen for incoming UDP packets on each address. If not specified, named will calculate a default value based on the number of detected CPUs: 1 for 1 CPU, 2 for 2-4 CPUs, and the number of detected CPUs divided by 2 for values higher than 4. 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. -u user 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(2) 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(2). -v Report the version number and exit. -V Report the version number and build options, and exit. -x cache-file Load data from cache-file into the cache of the default view. Warning: This option must not be used. 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. SIGHUP Force a reload of the server. SIGINT, SIGTERM Shut down the server. 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.
RFC 1033, RFC 1034, RFC 1035, named-checkconf(8), named-checkzone(8), rndc(8), lwresd(8), named.conf(5), BIND 9 Administrator Reference Manual.
Internet Systems Consortium
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