Troubleshooting

This chapter discusses how to debug problems with Obnam. It covers things such as log files, various levels of logging and tracing, and common problems with Obnam use. It also explains what things go where in an Obnam backup repository.

Turning on full logging

Obnam can write a log file. There are several options controlling that. Knowing these can help get out the most information when there's a problem that needs to be investigated.

• --log=obnam.log tells Obnam where to log. The log is a simple text file.
• --log-level=debug tells Obnam to log at the most detailed level. The default level is info, which excludes most debug information.
• --trace=obnamlib --trace=larch tells Obnam to log additional debug information. The two arguments match all filenames in Obnam and the Larch library Obnam uses. This additional information is mostly useful to someone who can read and understand the program source code.

Note that these settings can make log files be quite large, in the order of tens of megabytes. The size depends on how many files and how much data your live data has.

Reporting problems ("bugs")

If you have a problem with Obnam, and you want to report it (please do!), including the following information is helpful and makes it easier to figure out what the problem is.

• You should report problems to the obnam-support@obnam.org mailing list. This is a publicly archived mailing list where various people help others use Obnam.

If you respond to messages on obnam-support, always keep the list in the cc list. This means others will see the response, and there's a chance that they can help you better than the particular person you're responding to. Also, the archived discussion may be helpful to later readers, perhaps years afterwards.

• What is the problem? What did you try to achieve? What actually happened?

• The version of Obnam and Larch you're using, and how you installed it.

  • On Debian, run dpkg -l obnam python-larch on the command line and include the output.

• The exact command line you used. Copy-paste it instead of typing it again into the mail. Sometimes the problem can be hidden if you don't copy the command line exactly. Also, copying by typing is boring, and we should avoid boring things in life.

• If there's an error message, copy-paste that into the mail.

• The output of obnam --dump-config, which includes the full configuration. Include it as an attachment to your mail to obnam-support. If you have some secret information, such as filenames or hostnames, you can replace those with XXXX.

• If you can reproduce the problem while running with --log-level=debug, --log=obnam.log and --trace=obnamlib --trace=larch options, include a suitable amount from the end of the log file. The suitable amount may depend on the situation, but if you give the last two hundred lines, and it's not enough, we'll ask for more. Again, feel free to replace any sensitive filenames, etc, with XXXX.

• The output of the env command, in the same terminal window in which you ran Obnam. (Again, as an attachment.)

• If your bug is about performance, please run Obnam under profiling, and attach the profiling file. To run Obnam under profiling, install the Python profile (python-profiler package in Debian/Ubuntu), and set the OBNAM_PROFILE environment variable to the name of the file with the profiling output (that's the file you should send by mail). For example: OBNAM_PROFILE=obnam.prof obnam backup would run the backup under the profiler, and write the result to obnam.prof.

Thank you for your help in making Obnam better.