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| -rw-r--r-- | docs/debugging.rst | 36 |
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diff --git a/docs/debugging.rst b/docs/debugging.rst index a4c73d15..e65e06ab 100644 --- a/docs/debugging.rst +++ b/docs/debugging.rst @@ -76,6 +76,42 @@ will have the same effect as ``touch /tmp/vyos.ifconfig.debug``. ``sudo systemctl stop vyos-configd`` or make this reboot-safe by calling ``sudo systemctl disable vyos-configd``. +Debugging Python Code with PDB +------------------------------ + +Sometimes it might be useful to debug Python code interactively on the live +system rather than a IDE. This can be achieved using pdb. + +Let us assume you want to debug a Python script that is called by an op-mode +command. After you found the script by looking up the op-mode-defitions you +can edit the script in the live system using e.g. vi: +``vi /usr/libexec/vyos/op_mode/show_xyz.py`` + +Insert the following statement right before the section where you want to +investigate a problem (e.g. a statement you see in a backtrace): +``import pdb; pdb.set_trace()`` +Optionally you can surrounded this statement by an ``if`` which only triggers +under the condition you are interested in. + +Once you run ``show xyz`` and your condition is triggered you should be dropped +into the python debugger: + + +.. code-block:: none + + > /usr/libexec/vyos/op_mode/show_nat_translations.py(109)process() + -> rule_type = rule.get('type', '') + (Pdb) + +You can type ``help`` to get an overview of the available commands, and +``help command`` to get more information on each command. + +Useful commands are: + +* examine variables using ``pp(var)`` +* contine execution using ``cont`` +* get a backtrace using ``bt`` + Config Migration Scripts ------------------------ |