INADYN(8) System Manager's Manual (smm) INADYN(8)

inadyn — Internet Automated Dynamic DNS Client

inadyn [-1, --once] [--force] [--cache-dir PATH] [-c, --cmd /path/to/cmd] [-C, --continue-on-error] [-e, --exec /path/to/cmd] [--exec-mode MODE] [-f, --config FILE] [-h, --help] [-i, --iface IFNAME] [-I, --ident NAME] [-j, --json] [-l, --loglevel LEVEL] [-L, --list-providers] [-n, --foreground] [--no-pidfile] [-P, --pidfile FILE] [-p, --drop-privs USER[:GROUP]] [-s, --syslog] [-S, --show-provider -NAME] [-t, --startup-delay SEC] [-v, --version]

inadyn, or In-a-Dyn, periodically checks your actual Internet accessible IP for changes. When it changes inadyn updates your name server record(s) automatically.

Common DDNS service providers supported by inadyn are listed below. Some of these services are free of charge for non-commercial use, others take a small fee, but also provide more domain names to choose from.

inadyn defaults to HTTPS for all providers, some may however not support this so try disabling SSL for your provider in case of problems. Providers known to support SSL updates are listed below with . The list is ordered by the plugin that support the service:

DDNS providers not listed here, e.g. ⟨https://www.namecheap.com⟩, can often be configured using the custom DDNS provider plugin. See inadyn.conf(5) for examples.

Earlier versions of inadyn supported more command line options, from v2.0 inadyn has been greatly simplified. See inadyn.conf(5) for details of the /etc/inadyn.conf configuration file format.

--once
Run only once and quit, updates only if too old or unknown. Use --force to for an update before exiting.
Force one update. Only works with -1, --once flag, ignored for all other use-cases.
PATH
Set directory for persistent cache files, defaults to /var/cache/inadyn

The cache files are used to keep track of which addresses have been successfully sent to their respective DDNS provider and when. The latter 'when' is important to prevent inadyn from banning you for excessive updates.

When restarting inadyn or rebooting your server, or embedded device, inadyn reads the cache files to seed its internal data structures with the last sent IP address and when the update was performed. It is therefore very important to both have a cache file and for it to have the correct time stamp. The absence of a cache file will currently cause a forced update.

On an embedded device with no RTC, or no battery backed RTC, it is strongly recommended to pair this setting with the --startup-delay SEC command line option.

--cmd /path/to/cmd [optional args]
Full path to command, or script, to run to check for IP address change. This is the same as the configuration file option checkip-command but will apply to providers. This command line option is only provided for convenience, it is recommended to instead use the configuration file. For more details, see the inadyn.conf(5) man page. You will need to quote the complete command if any arguments, or pipe, is given.
Ignore errors from DDNS provider and try again later. This command line option tells inadyn to not exit on errors from a DDNS provider and instead try again later. Please do not use this, it usually indicates that we are sending a malformed request, e.g. wrong username, password or DNS alias for the given account. Continuing could possibly lock you out of your account!
--exec=/path/to/cmd [optional args]
Full path to command, or script, to run. The following environment variables are set: INADYN_IP, INADYN_HOSTNAME. The first environment variable contains the new IP address, the second the host name alias. The cmd is called for each listed host name. If inadyn is started with the -i IFNAME command line option, the INADYN_IFACE environment variable is also set. You will need to quote the complete command if any arguments, or pipe, is given.
MODE
Use MODE to set the exec script run mode: compat, event: - compat: run exec handler on successful DDNS update only, default - event: run exec handler on any update status The following environment variables are set: INADYN_EVENT, INADYN_ERROR, INADYN_ERROR_MESSAGE. INADYN_EVENT contains the event, one of: nochg, update, error. The event nochg indicates that no update had to be sent, the event update indicates that an update was sent successully, the event error indicates that the update was sent and an error occurred. INADYN_ERROR contains the error code, INADYN_ERROR_MESSAGE contains the error message for the error code.
--config FILE
Use FILE for configuration. By default /etc/inadyn.conf, is used. See inadyn.conf(5) for examples.
--help
Show summary of command line options and exit
--iface IFNAME
Check IP of IFNAME instead of querying an external server. With this command line option the external IP check is disabled and inadyn will report the IP address of IFNAME to all DDNS providers listed in the configuration file. This can be useful to register LAN IP addresses, or, when connected directly to a public IP address, to speed up the IP check if the DDNS provider's check-ip servers are slow to respond.

This option can also be given as a configuration option in inadyn.conf(5), both serve a purpose, use whichever one works for you.

--ident NAME
Specify program identity (name) to be used for PID file and syslog messages. Useful with multiple instances of inadyn, or to simply replace the inadyn name with something more generic, e.g. "DDNS", without renaming the binary. Note, this option only changes the base name of the PID file, not the location, which is system specific. Usually /var/run/inadyn.pid or /run/inadyn.pid.
--json
Output provider listing in JSON format, see also -L.
--loglevel LEVEL
Set log level: none, err, info, notice, debug. The default is notice, but you might want to set this to -l warning.
--list-providers
List available DDNS providers.
--foreground
Run in foreground, default is to daemonize and continue in the background. This option is usually required when running under process supervisors like systemd and Finit, but is also useful when running from the terminal, when debugging a config or at initial set up. Remember to also give the -s option if you still want to redirect log messages to the syslog.
--drop-privs USER[:GROUP]
Drop root privileges after initial setup to the given user and group.
When running as a daemon, even when running in the foreground with -n, inadyn creates a PID file so users can easily find the PID of the process to send signals to. See SIGNALS for more information on this. This option tells inadyn to create a PID file. Some users prefer this when running under systemd.
--pidfile FILE
Set PID file name and location, defaults to /run/inadyn.pid, derived from --ident NAME, which is strongly recommended to change over this option. However, some users want to keep application runtime files in separate directories, usually in combination with --drop-privs, for such cases this is the option to use.
--syslog
Use syslog(3) for log messages, warnings and error conditions. This is the default when running in the background. When running in the foreground, see -n, log messages are printed to stdout.
--show-provider NAME
Show information about DDNS provider NAME, substring search supported.
--startup-delay SEC
Initial startup delay. Default is 0 seconds. Any signal can be used to abort the startup delay early, but SIGUSR2 is the recommended to use. See SIGNALS below for full details of how inadyn responds to signals.

Intended to allow time for embedded devices without a battery backed real time clock to set their clock via NTP at bootup. This is so that the time since the last update can be calculated correctly from the inadyn cache file and the forced-update SEC setting honored across reboots, avoiding unnecessary IP address updates.

--version
Show program version and exit.

inadyn prints a message when the IP is updated. If no update is needed then by default it prints a single “.” character, unless --loglevel is set to none. Therefore, unless --loglevel is set to none, the log will contain lots of dots. When the connection goes down inadyn may print some harmless error messages which should be followed by “OK” messages after the Internet connection is restored.

inadyn responds to the following signals:

HUP
Reload the .conf file, standard UNIX behavior
TERM
Tell inadyn to exit gracefully
INT
Same as TERM
USR1
Force update now, even if the IP address has not changed
USR2
Check IP address change now. Useful when a new DHCP/PPPoE lease or new gateway is received. Please note that inadyn does not track such events by itself. You need an external monitor for that

For convenience in sending signals, inadyn writes its process ID to /var/run/inadyn.pid, unless the --ident NAME option is used.

/etc/inadyn.conf
 
/run/inadyn.pid
 
/var/cache/inadyn/dyndns.org.cache
 
/var/cache/inadyn/freedns.afraid.org.cache
 
... one .cache file per DDNS provider
 

inadyn.conf(5)

The inadyn home page is at GitHub: ⟨https://github.com/troglobit/inadyn⟩

inadyn was originally written by Narcis Ilisei ⟨mailto:inarcis2002@hotpop.com⟩ and Steve Horbachuk. Current patch monkey is Joachim Wiberg ⟨mailto:troglobit@gmail.com⟩ with a lot of help from Andrey Tikhomirov and Mike Fleetwood.

This manual page was originally written for the project by Shaul Karl ⟨mailto:shaul@debian.org⟩, and is currently maintained by Joachim Wiberg.

February 20, 2020 Linux 6.16.7-arch1-1