GDNSD(8)

NAME
gdnsd - An authoritative DNS daemon

SYNOPSIS
  Usage: gdnsd [-s] [-S] [-d <rootdir> ] <action>
    -s - Force 'zones_strict_startup = true' for this invocation
    -S - Force 'zones_strict_data = true' for this invocation
    -d - [see "THE ROOTDIR ARGUMENT" below]
  Actions:
    checkconf - Checks validity of configuration and zonefiles
    startfg - Start gdnsd in foreground mode with logging to stderr
    start - Start gdnsd as a regular daemon
    stop - Stops a running daemon previously started by 'start'
    reload - Send SIGHUP to running daemon for zone data reload
    restart - Equivalent to checkconf && stop && start, but faster
    force-reload - Aliases 'restart'
    condrestart - Does 'restart' action only if already running
    try-restart - Aliases 'condrestart'
    status - Checks the status of the running daemon

DESCRIPTION
gdnsd is very fast, light, and pluggable authoritative DNS daemon.

Other than the "action" argument, the only other argument is "-d" for setting a chroot directory, which is discussed in detail below. The commandline parsing is sensitive to ordering: "-d" must come before the action, if used.

THE ROOTDIR ARGUMENT
The "-d <rootdir>" argument specifies whether gdnsd will use a chroot directory (or not) and the path of that directory. The special value "system" indicates to *not* use a chroot directory, and use the normal system paths defined via autoconf. The default can be changed at build time, and you can see what your build's default is by executing e.g. "gdnsd --help". The default default is "system".

If a default or commandline-supplied chroot directory is in use, all files which gdnsd interacts with at runtime live within that chroot directory.

In the chroot case, gdnsd will create the chroot directory and all structure within on startup if necessary, but will not create the parent of the chroot directory for you.

BASIC SECURITY
When started as the "root" user, gdnsd will always attempt to drop privileges to another user, and will fail fatally if that does not succeed. The default username for this is "gdnsd", but this can be overridden in the main config file.

If a chroot directory is in use and gdnsd is started as the "root" user, the daemon will also permanently chroot itself into that directory on startup. If a chroot directory is specified, but the daemon is started as a regular user, the daemon will "chdir" to the root directory and use relative paths to mimick the chroot functionality. This can be useful if, for example, you're using external software to secure the daemon in some jail-like structure, or running tests as a regular user against test data.

BASIC CONFIGURATION
There is a single primary configuration file. Its pathname is fixed at build time for the "system" case, and fixed relative to the chroot directory in the chroot case. In the "system" case it will live at $sysconfdir/gdnsd/config, where $sysconfdir will typically be /etc or /usr/local/etc depending on autoconf configuration.

In the chroot case the path is "/etc/config" within the chroot directory.

Note that the configuration file does not have to exist for successful startup. Without a configuration file, gdnsd will load all of the zones in the zones directory and listen on port 53 of all available interfaces using default settings.

ZONE FILES
The zones directory is the subdirectory named "zones" in the same location as the main config file (see above re: chroot -vs- system).

All files in the zones directory are considered zone files. In general there should be exactly one file per zone, and the filename should match the zone name. Filenames beginning with "." are ignored. All other files must be regular files (as opposed to directories, symlinks, sockets, etc).

The zones directory is handled dynamically. It can be empty at startup, which results in all queries returning "REFUSED". As files are added, modified, and deleted in this directory, zone data will automatically change at runtime.

In order to better support the special case of RFC 2137 -style classless in-addr.arpa delegation zones (which contain forward slashes), any "@" symbol in the filename will be translated to a forward slash ("/") when transforming a filename into its corresponding zone name.

For similar reasons, if your server is intended to serve the root of the DNS, the filename for the root zone should be the special filename ROOT_ZONE, rather than the impossible literal filename ..

The standard DNS zone file escape sequences are recognized within the filenames (e.g. "\." for a dot within a label, or "\NNN" where NNN is a decimal integer in the range 0 - 255), if for some reason you need a strange character in your zone name.

Trailing dots on zonefile names are ignored; e.g. example.com and example.com. are functionally equivalent.

Duplicate zones (e.g. having both of the above representations of "example.com" present in the zones directory, and/or adding a different case-mapping such as EXample.Com) are handled by loading both and giving runtime lookup priority to one of the copies based on a couple of simple rules: the highest "serial" wins, and if more than one file has the highest serial, the highest filesystem "mtime" value wins. If the primary copy is later removed, any remaining copy of the zone will be promoted for runtime lookups according to that same ordering.

Subzones (e.g. having zonefiles for both "example.com" and "subz.example.com") are only marginally supported. The child zone will be loaded into memory, but its data won't be available for lookup, as it is suppressed by the existence of the parent zone. If the parent zone is later removed, the subzone data will become available. Logically, it is not possible for a single server to be authoritative for both a subzone and its parent zone at the same time, as each "role" (parent and child) requires different responses to requests for data within the child zone. gdnsd choses to default to the "parent" role in these conflict cases.

See gdnsd.zonefile(5) for details on the internal syntax of the zonefiles themselves.

ACTIONS
gdnsd acts as its own initscript, internalizing daemon management functions. All valid invocations of the gdnsd command include an action, most of which model normal initscript actions. You may still want a light initscript wrapper to comply with distribution standards for e.g. terminal output on success/failure, but it's not necessary for basic functionality.

checkconf
    Checks the validity of the configuration file and zonefiles, setting the exit status appropriately (0 for success).

    The "start", "startfg", and all "restart"-like actions implicitly do the same checks as "checkconf" as they load the configuration for runtime use.

startfg
    Starts gdnsd in foreground mode, with all of the logging that would normally go to syslog appearing instead on stderr. Useful for debugging and testing.

start
    Starts gdnsd as a regular background daemon.

stop
    Stops the gdnsd daemon previously started by start.

restart
    This is equivalent to the sequence "checkconf && stop && start", but faster. What actually happens behind the scenes is a bit more complicated:

    "restart" is a special case of "start" which first does all of the "checkconf" actions (bringing all the runtime data into memory), then stops the existing daemon, and then finishes starting itself (acquiring sockets, dropping privs, spawning threads, etc).

    The net result is that this minimizes the pause in service availability during the restart (especially if you have a large volume of zone data that takes significant time to load), and also leaves the original daemon instance untouched if the configuration is invalid (you've made an error in your new zone data, etc).

reload
    Sends "SIGHUP" to the running daemon, forcing a manual re-check of the zones directory for updated files.

force-reload
    An alias for "restart".

condrestart
    This is basically "restart only if already running".

    Performs the same actions as "restart", but aborts early (with a successful exit value) if the daemon was not already running.

try-restart
    Alias for "condrestart".

status
    Checks the status of the running daemon, returning 0 if it is running or non-zero if it isn't.

Any other commandline option will be treated as invalid, which will result in displaying a short help text to STDERR and exiting with a non-zero exit status. This includes things like the ubiquitous --help and --version.

ENVIRONMENT VARIABLES

TZ  On most systems tested, gdnsd's current solution for getting syslog timestamps correct while under "chroot()" seems to work fine, as it does "tzset()" before "chroot()", and so no special setting of the "TZ" environment variable is required.

    On some older/stranger systems, the syslog messages will revert to UTC timestamps after "chroot()". The workaround for these systems is to either set the "TZ" environment variable in gdnsd's initscript to a value like "/etc/localtime", which will make glibc cache the timezone correctly, or to copy all of the relevant timezone files into the chroot directory (/etc/localtime and perhaps all of /usr/share/zoneinfo). Or whatever your platform may require. Patches welcome.

SIGNALS
Any signal not explicitly mentioned is not explicitly handled. That is to say, they will have their default actions, which often include aborting execution.

SIGTERM, SIGINT
    Causes the daemon to exit gracefully with accompanying log output.

SIGHUP
    Causes the daemon to attempt to load any new changes to the zone data.

SIGPIPE
    Ignored when daemonized.

EXIT STATUS
An exit status of zero indicates success, anything else indicates failure.

SEE ALSO
gdnsd.config(5), gdnsd.zonefile(5)

The gdnsd manual.

COPYRIGHT AND LICENSE
Copyright (c) 2012 Brandon L Black <blblack@gmail.com>

This file is part of gdnsd.

gdnsd is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

gdnsd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with gdnsd. If not, see <http://www.gnu.org/licenses/>.