Ardour stores configuration files in two places. The system configuration directory and the user configuration directory. The system configuration directory is used for stock configuration files and is used by all users on any one system. The user configuration directory is used by Ardour to store configuration changes made in the GUI as well as being a place the user can add control surface device files, scripts etc.
Ardour tries to use standard places for these directories for the platform it is running on.
Linux is the most variable of the platforms mainly due to Ardour obtained from a distro package. If Ardour is obtained from ardour.org as a ready to install and run bundle, the system configuration directory will always be in /opt/Ardour-major.minor.sub/share/ That is it will match the name of the file you downloaded. If Ardour is self built and installed with the default install path (yes you can change this) then system configuration will be in /usr/local/share/ardour*/ where * is the major number such as /usr/local/share/ardour5/ for Ardour 5.6. If you have installed Ardour as a package from your distro, then distro policy will dictate where it is installed. /usr/share/ardour*/ is quite common and a good place to start looking. However, the Ardour development team does not support these distro builds nor keep track of where they may put things.
The user configuration directory will be somewhere inside the user's home directory. A normal place to find this is ~/.config/ardour*/ where * is the major version. However this can be set by the system with the $XDG_CONFIG_HOME environment variable to something else. If you can not find ~/.config/ on your system try echo ${XDG_CONFIG_HOME} to see if your distro is using something else.
maybe someone who has a MAC can complete this section.
This section also needs someone with real knowledge to complete it.
Plugins will be installed in various places, some by standard and some by developer whim. Some are installed incorrectly by distro policy.
In linux there are 3 kinds of plugins Ardour can use. LADSPA, LV2 (LADSPA version 2) or lxvst (VSTs compiles as native linux binaries). While it is possible with some strange magic to run Windows VSTs on linux, their whereabouts would follow the Windows info below.
LADSPA plugins should be found in /usr/lib/ladspa/, /usr/local/lib/ladspa/ or in a directory mentioned in your LADSPA_PATH environment variable. The most common mistake made by distro packagers, is to use a path like /usr/lib/$ARCH/ladspa/ and find that Ardour will not find that by default. The user can either add a link from this actual directory to the standard directory or add this path to LADSPA_PATH.
LADSPA plugins should be found in /usr/lib/lv2/, /usr/local/lib/lv2/ or in a directory mentioned in your LV2_PATH environment variable. The most common mistake made by distro packagers, is to use a path like /usr/lib/$ARCH/lv2/ and find that Ardour will not find that by default. The user can either add a link from this actual directory to the standard directory or add this path to LV2_PATH.
They are typically installed in /usr/lib/lxvst, /usr/local/lib/lxvst or a directory mentioned in your LXVST_PATH environment variable. However, this is not a standard and the VST plugin developer may install the plugin just about anywhere. Therefore Ardour allows the user to set extra VST paths in the preferences GUI under Plugins>VST.
On the Mac, plugins are expected to be installed correctly Ardour uses the system tool to scan for AU style plugins and LV2s should be in the right place. LV2 should be in $HOME/Library/Audio/Plug-Ins/LV2 /Library/Audio/Plug-Ins/LV2 /usr/local/lib/lv2 /usr/lib/lv2 If an AU or LV2 plugin does not show up on a Mac it is probably a development fault with the plugin and the plugin will not work with anything. Ardour in Ardour 5.6 has support for native VST plugins. That is VST plugins built for OSX. I am not sure if these have a standard place to be, but as with other VSTs the search path can be edited at Plugins>VST.
The most common plugins on Windows are VSTs. However, LADSPA and LV2 plugins are available for windows as well. In fact Ardours built in plugins are LV2s. The biggest advanatage of LV2 plugins is that they are the most likely to be cross platform and therefore allow the same Ardour project to be worked on in Windows, OSX and Linux.
As with other platforms, VSTs on Windows do not have a standard place to reside. Ardour Preferences>Plugins>VST allows setting the VST path from the GUI.
The LV2 standard for Windows is %APPDATA%/LV2 or %COMMONPROGRAMFILES%/LV2
While there are LADSPA plugins for Windows, I have been unable to find the standard path for them... perhaps someone knows?
Ardour places a project directory where the user tells it to. This directory is chosen when creating a project. In most cases the user does not need to know about the files inside of the project directory. However there are a few subdirectories worth noting.
This is the subdirectory where exported files end up.