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authorrebortg <github@ghlr.de>2021-09-13 19:45:06 +0200
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contributing: clear structure
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-.. _debugging:
-
-#########
-Debugging
-#########
-
-There are two flags available to aid in debugging configuration scripts.
-Since configuration loading issues will manifest during boot, the flags are
-passed as kernel boot parameters.
-
-ISO image build
-===============
-
-When having trouble compiling your own ISO image or debugging Jenkins issues
-you can follow the steps at :ref:`iso_build_issues`.
-
-System Startup
-==============
-
-The system startup can be debugged (like loading in the configuration
-file from ``/config/config.boot``. This can be achieve by extending the
-Kernel command-line in the bootloader.
-
-Kernel
-------
-
-* ``vyos-debug`` - Adding the parameter to the linux boot line will produce
- timing results for the execution of scripts during commit. If one is seeing
- an unexpected delay during manual or boot commit, this may be useful in
- identifying bottlenecks. The internal flag is ``VYOS_DEBUG``, and is found
- in vyatta-cfg_. Output is directed to ``/var/log/vyatta/cfg-stdout.log``.
-
- In addition this setting creates the runtime debug files for some Live system
- components (see below). Those files are: ``/tmp/vyos-config-status``,
- ``/tmp/vyos.container.debug``, ``/tmp/vyos.frr.debug``,
- ``/tmp/vyos.ifconfig.debug``.
-
-* ``vyos-config-debug`` - During development, coding errors can lead to a
- commit failure on boot, possibly resulting in a failed initialization of the
- CLI. In this circumstance, the kernel boot parameter ``vyos-config-debug``
- will ensure access to the system as user ``vyos``, and will log a Python
- stack trace to the file ``/tmp/boot-config-trace``.
- File ``boot-config-trace`` will generate only if config loaded with a failure
- status.
-
-Live System
-===========
-
-A number of flags can be set up to change the behaviour of VyOS at runtime.
-These flags can be toggled using either environment variables or creating
-files.
-
-For each feature, a file called ``vyos.feature.debug`` can be created to
-toggle the feature on. If a parameter is required it can be placed inside
-the file as its first line.
-
-The file can be placed in ``/tmp`` for one time debugging (as the file
-will be removed on reboot) or placed in '/config' to stay permanently.
-
-For example, ``/tmp/vyos.ifconfig.debug`` can be created to enable
-interface debugging.
-
-It is also possible to set up the debugging using environment variables.
-In that case, the name will be (in uppercase) VYOS_FEATURE_DEBUG.
-
-For example running, ``export VYOS_IFCONFIG_DEBUG=""`` on your vbash,
-will have the same effect as ``touch /tmp/vyos.ifconfig.debug``.
-
-* ``ifconfig`` - Once set, all commands used, and their responses received
- from the OS, will be presented on the screen for inspection.
-
-* ``command`` - Once set, all commands used, and their responses received
- from the OS, will be presented on the screen for inspection.
-
-* ``developer`` - Should a command fail, instead of printing a message to the
- user explaining how to report issues, the python interpreter will start a
- PBD post-mortem session to allow the developer to debug the issue. As the
- debugger will wait from input from the developer, it has the capacity to
- prevent a router to boot and therefore should only be permanently set up
- on production if you are ready to see the OS fail to boot.
-
-* ``log`` - In some rare cases, it may be useful to see what the OS is doing,
- including during boot. This option sends all commands used by VyOS to a
- file. The default file is ``/tmp/full-log`` but it can be changed.
-
-.. note:: In order to retrieve the debug output on the command-line you need to
- disable ``vyos-configd`` in addition. This can be run either one-time by
- calling ``sudo systemctl stop vyos-configd`` or make this reboot-safe by
- calling ``sudo systemctl disable vyos-configd``.
-
-FRR
----
-
-Recent versions use the ``vyos.frr`` framework. The Python class is located
-inside our ``vyos-1x:python/vyos/frr.py``. It comes with an embedded debugging/
-(print style) debugger as vyos.ifconfig does.
-
-To enable debugging just run: ``$ touch /tmp/vyos.frr.debug``
-
-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
-------------------------
-
-When writing a new configuration migrator it may happen that you see an error
-when you try to invoke it manually on a development system. This error will
-look like:
-
-.. code-block:: none
-
- vyos@vyos:~$ /opt/vyatta/etc/config-migrate/migrate/ssh/0-to-1 /tmp/config.boot
- Traceback (most recent call last):
- File "/opt/vyatta/etc/config-migrate/migrate/ssh/0-to-1", line 31, in <module>
- config = ConfigTree(config_file)
- File "/usr/lib/python3/dist-packages/vyos/configtree.py", line 134, in __init__
- raise ValueError("Failed to parse config: {0}".format(msg))
- ValueError: Failed to parse config: Syntax error on line 240, character 1: Invalid syntax.
-
-The reason is that the configuration migration backend is rewritten and uses
-a new form of "magic string" which is applied on demand when real config
-migration is run on boot. When runnint individual migrators for testing,
-you need to convert the "magic string" on your own by:
-
-.. code-block:: none
-
- vyos@vyos:~$ /usr/libexec/vyos/run-config-migration.py --virtual --set-vintage vyos /tmp/config.boot
-
-Configuration Error on System Boot
-----------------------------------
-
-Beeing brave and running the latest rolling releases will sometimes trigger
-bugs due to corner cases we missed in our design. Those bugs should be filed
-via Phabricator_ but you can help us to narrow doen the issue. Login to your
-VyOS system and change into configuration mode by typing ``configure``. Now
-re-load your boot configuration by simply typing ``load`` followed by return.
-
-You shoudl now see a Python backtrace which will help us to handle the issue,
-please attach it to the Phabricator_ task.
-
-Boot Timing
------------
-
-During the migration and extensive rewrite of functionality from Perl into
-Python a significant increase in the overall system boottime was noticed. The
-system boot time can be analysed and a graph can be generated in the end which
-shows in detail who called whom during the system startup phase.
-
-This is done by utilizing the ``systemd-bootchart`` package which is now
-installed by default on the VyOS 1.3 (equuleus) branch. The configuration is
-also versioned so we get comparable results. ``systemd-bootchart`` is configured
-using this file: bootchart.conf_
-
-To enable boot time graphing change the Kernel commandline and add the folowing
-string: ``init=/usr/lib/systemd/systemd-bootchart``
-
-This can also be done permanently by changing ``/boot/grub/grub.cfg``.
-
-Priorities
-==========
-
-VyOS CLI is all about priorities. Every CLI node has a corresponding
-``node.def`` file and possibly an attached script that is executed when the
-node is present. Nodes can have a priority, and on system bootup - or any
-other ``commit`` to the config all scripts are executed from lowest to higest
-priority. This is good as this gives a deterministic behavior.
-
-To debug issues in priorities or to see what's going on in the background
-you can use the ``/opt/vyatta/sbin/priority.pl`` script which lists to you
-the execution order of the scripts.
-
-.. stop_vyoslinter
-
-.. _vyatta-cfg: https://github.com/vyos/vyatta-cfg
-.. _bootchart.conf: https://github.com/vyos/vyos-build/blob/current/data/live-build-config/includes.chroot/etc/systemd/bootchart.conf
-.. include:: /_include/common-references.txt
-
-.. start_vyoslinter