taler-mdb-network-check.sh(1)
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   Name
   ====

   **taler-mdb-network-check.sh** - Taler multi-drop bus vending machine network check tool


Synopsis
========

**taler-mdb-network-check.sh**
[**-c** *FILENAME*]
[**-f** *FAIL_HELPER*]
[**-h**]
**--**
*PROGRAM*

Description
===========

**taler-mdb-network-check.sh** is a command-line tool to call a program when the network goes down.
It depends on **dig**.

Its options are as follows:

**-c** *FILENAME*
   Use the configuration and other resources for the command to operate from *FILENAME*.

**-f** *FAIL_HELPER*
   Overwrites the Taler config's *FAIL_HELPER* value. See taler.conf(5)

**-h**
   Print short help on options.


When the network goes down, it will kill *PROGRAM*, then call *FAIL_HELPER* with one of the following error codes (followed by killing *FAIL_HELPER* and relaunching *PROGRAM* once the network is up again) - note that we check in the order these are listed:

**no-ip**
   Network Down: Could not reach the DNS Server. (DNS Server is first **nameserver** entry in **/etc/resolv.conf**.)

**backend-dns-resolution-failure**
   Name Resolution Failed: Could not resolve the Taler backend hostname. Check DNS. (**dig** picks its own nameservers; we do not force it to use the one we pinged.)

**backend-unreachable**
   Backend Unreachable: Could not reach payment backend.

**backend-no-webserver**
   Backend No Webserver: We cannot find a webserver on a backend. Ensure requests are properly routing to it. (X509 certificate is not verified here.)

**backend-x509-cert-bad**
   Bad Certificate: The Taler backend gave us a bad TLS certificate. Check the X509 setup.

**backend-auth-failure**
   Backend Authentication Failure: The credentials are invalid. Check your configuration.


The aforementioned *FAIL_HELPER* also gets called if the network is not up in the first place.

In short, *FAIL_HELPER* will be running whenever the network is down, and *PROGRAM* will be running whenever its up.

The network is checked every **30 seconds**.

Example
=======

A canonical use of the script to launch taler-mdb would be:

.. code-block:: console

  # /usr/bin/taler-mdb-network-check.sh -c /etc/taler-mdb.conf -- \
    /usr/bin/taler-mdb -c /etc/taler-mdb.conf


See Also
========

taler-mdb(1), taler-mdb-show.sh(1), taler.conf(5).


Bugs
====

Report bugs by using https://bugs.taler.net or by sending electronic
mail to <taler@gnu.org>.