Obnam configuration files and settings
======================================

This chapter discusses Obnam configuration files: where they are, what
they contain, and how they are used.

Where is my configuration?
--------------------------

Obnam looks for its configuration files in a number of places:

* `/etc/obnam.conf`
* `/etc/obnam/*.conf`
* `~/.obnam.conf`
* `~/.config/obnam/*.conf`

Note that in `/etc/obnam` and `~/.config/obnam`, all files that have a
`.conf` suffix are loaded, in "asciibetical" order, which is like
alphabetical, but based on character codes rather than what humans
understand, but unlike alphabetical isn't dependent on the language
being used.

Any files in the list above may or may not exist. If it exists, it is
read, and then the next file is read. A setting in one file can be
overridden by a later file, if it is set there as well.
For example, `/etc/obnam.conf` might set `log-level` to `INFO`,
but `~/.obnam.conf` may then set it to `DEBUG`, if a user wants more
detailed log files.

The Obnam configuration files in `/etc` apply to everyone who runs
Obnam on that machine. This is important: they are not just for when
`root` runs Obnam.

If you want to have several Obnam configurations, for example for
different backup repositories, you need to name or place the files so
they aren't on the list above. For example:

* `/etc/obnam/system-backup.profile`
* `~/.config/obnam/online.profile`
* `~/.config/obnam/usbdrive.profile`

You would then need to specify that file for Obnam to use it:

    obnam --config ~/.config/obnam/usbdrive.profile`

If you want to not be affected by any configuration files, except
the ones you specify explicitly, you need to also use the
`--no-default-config` option:

    obnam --no-default-config --config ~/.obnam-is-fun.conf

Command line options override values from configuration files.

Configuration file syntax
-------------------------

Obnam configuration files use the [INI file] syntax, specifically
the variant implemented by the Python [ConfigParser] library.
They look like this:

    [config]
    log-level = debug
    log = /var/log/obnam.log
    encrypt-with = CAFEBEEF
    root = /
    one-file-system = yes

[INI file]: https://en.wikipedia.org/wiki/INI_file
[ConfigParser]: http://docs.python.org/2/library/configparser.html

Names of configuration variables are the same as the corresponding
command line options. If `--foo` is the option, then the variable in
the file is `foo`. Any command line option `--foo=bar` can be used in
a configuration file as `foo = bar`. There's are exceptions to this
(`--no-default-config`, `--config`, `--help`, and a few others), but
they're all things you wouldn't put in a configuration file anyway.

Every option, or setting, has a type. Mostly this doesn't matter,
unless you give it a value that isn't suitable. The two important
exceptions to this are:

* Boolean or yes/no or on/off settings. For example,
  `--exclude-caches` is a setting that is either turned on (when the
  option is used) or off (when it's not used). For every Boolean
  setting `--foo`, there is an option `--no-foo`. In a configuration
  files, `foo` is turned on by setting it to `yes` or `true`, and off
  by setting it to `no` or `false`.

* Some settings can be lists of values, such as `--exclude`. You can
  use `--exclude` as many times as you want, each time a new exclusion
  pattern is added, rather than replacing the previous patterns.
  In a configuration file, you would write all the values at once,
  separated by commas and optional spaces: for example,
  `exclude = foo, bar, baz`. In a configuration file, the previous
  list of values is replaced entirely rather than added to.

For a more detailed explanation of Obnam configuration file syntax,
see the **cliapp**(5) manual page on your system, or [cliapp man page]
on the WWW.

[cliapp man page]: http://liw.fi/cliapp/cliapp.5.txt

Checking what my configuration is
---------------------------------

Obnam can read configuration files from a number of places, and it can
be tricky to figure out what the actual configuration is. The
`--dump-config` option helps here.

    obnam --config ~/.obnam.fun --exclude-caches --dump-config

The option will tell Obnam to write out (to the standard output) a
configuration file that captures every setting, and reporting the
value that it would have if `--dump-config` weren't used.

This is a good way to see what the current settings are and also as
a starting point if you want to make a configuration file from
scratch.

Finding out all the configuration settings
------------------------------------------

This manual does not yet have a list of all the settings, and their
explanation. Obnam provides built-in help (run `obnam --help`) and a
manual page automatically generated from the built-in help
(run `man obnam` or see [obnam man page]). Some day, this chapter will
include an automatically generated section that explains each setting.
Until then, you're free to point fingers at Obnam's author and giggle
at his laziness.

[obnam man page]: http://obnam.org/obnam.1.txt
