NAME¶
named - Internet domain name server
SYNOPSIS¶
named [[-4] | [-6]]
[-c config-file]
[-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]
DESCRIPTION¶
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.
OPTIONS¶
-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.
-L logfile
Log to the file logfile by default instead of the
system log.
-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,
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
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 lock-file
Acquire 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
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.
SIGNALS¶
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.
CONFIGURATION¶
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.
FILES¶
/etc/named.conf
The default configuration file.
/var/run/named/named.pid
The default process-id file.
NOTES¶
Red Hat SELinux BIND Security Profile¶
By default, Red Hat ships BIND with the most secure SELinux policy
that will not prevent normal BIND operation and will prevent exploitation of
all known BIND security vulnerabilities . See the selinux(8) man page for
information about SElinux.
It is not necessary to run named in a chroot environment if the
Red Hat SELinux policy for named is enabled. When enabled, this policy is
far more secure than a chroot environment. Users are recommended to enable
SELinux and remove the bind-chroot package.
With this extra security comes some restrictions:
By default, the SELinux policy allows named to write any master
zone database files. Only the root user may create files in the
$ROOTDIR/var/named zone database file directory (the options {
"directory" } option), where $ROOTDIR is set in
/etc/sysconfig/named.
The "named" group must be granted read privelege to
these files in order for named to be enabled to read them.
Any file created in the zone database file directory is
automatically assigned the SELinux file context named_zone_t .
By default, SELinux prevents any role from modifying named_zone_t
files; this means that files in the zone database directory cannot be
modified by dynamic DNS (DDNS) updates or zone transfers.
The Red Hat BIND distribution and SELinux policy creates three
directories where named is allowed to create and modify files:
/var/named/slaves, /var/named/dynamic /var/named/data. By placing files you
want named to modify, such as slave or DDNS updateable zone files and
database / statistics dump files in these directories, named will work
normally and no further operator action is required. Files in these
directories are automatically assigned the 'named_cache_t' file context,
which SELinux allows named to write.
Red Hat BIND SDB support¶
Red Hat ships named with compiled in Simplified Database Backend
modules that ISC provides in the "contrib/sdb" directory. Install
bind-sdb package if you want use them.
The SDB modules for LDAP, PostGreSQL, DirDB and SQLite are
compiled into named-sdb.
See the documentation for the various SDB modules in
/usr/share/doc/bind-sdb-*/ .
AUTHOR¶
Internet Systems Consortium, Inc.
COPYRIGHT¶
Copyright © 2000, 2001, 2003-2009, 2011, 2013-2021 Internet
Systems Consortium, Inc. ("ISC")