## Running GIO applications

GIO inspects a few environment variables in addition to the ones used by GLib.

`XDG_DATA_HOME`, `XDG_DATA_DIRS`. GIO uses these environment variables to locate MIME information. For more information, see the Shared MIME-info Database and the Base Directory Specification.

`GVFS_DISABLE_FUSE`. This variable can be set to keep Gvfs from starting the fuse backend, which may be unwanted or unnecessary in certain situations.

`GIO_USE_VFS`. This environment variable can be set to the name of a GVfs implementation to override the default for debugging purposes. The GVfs implementation for local files that is included in GIO has the name "local", the implementation in the gvfs module has the name "gvfs". Most commonly, system software will set this to "local" to avoid having `GFile` APIs perform unnecessary DBus calls.

The following environment variables are only useful for debugging GIO itself or modules that it loads. They should not be set in a production environment.

`GIO_USE_FILE_MONITOR`. This variable can be set to the name of a GFileMonitor implementation to override the default for debugging purposes. The GFileMonitor implementation for local files that is included in GIO on Linux has the name "inotify", others that are built are built as modules (depending on the platform) are called "fam" and "fen".

`GIO_USE_VOLUME_MONITOR`. This variable can be set to the name of a GVolumeMonitor implementation to override the default for debugging purposes. The GVolumeMonitor implementation for local files that is included in GIO has the name "unix", the udisks2-based implementation in the gvfs module has the name "udisks2".

`GIO_USE_TLS`. This variable can be set to the name of a GTlsBackend implementation to override the default for debugging purposes. GIO does not include a GTlsBackend implementation, the gnutls-based implementation in the glib-networking module has the name "gnutls".

`GIO_MODULE_DIR`. When this environment variable is set to a path, GIO will load modules from this alternate directory instead of the directory built into GIO. This is useful when running tests, for example.

`GIO_EXTRA_MODULES`. When this environment variable is set to a path, or a set of paths separated by a colon, GIO will attempt to load additional modules from within the path.

`GSETTINGS_BACKEND`. This variable can be set to the name of a GSettingsBackend implementation to override the default for debugging purposes. The memory-based implementation that is included in GIO has the name "memory", the one in dconf has the name "dconf-settings".

`GSETTINGS_SCHEMA_DIR`. This variable can be set to the name of a directory that is considered in addition to the `glib-2.0/schemas` subdirectories of the XDG system data dirs when looking for compiled schemas for GSettings.

`DBUS_SYSTEM_BUS_ADDRESS`. This variable is consulted to find the address of the D-Bus system bus. For the format of D-Bus addresses, see the D-Bus specification. Setting this variable overrides platform-specific ways of determining the system bus address.

`DBUS_SESSION_BUS_ADDRESS`. This variable is consulted to find the address of the D-Bus session bus. Setting this variable overrides platform-specific ways of determining the session bus address.

`DBUS_STARTER_BUS_TYPE`. This variable is consulted to find out the 'starter' bus for an application that has been started via D-Bus activation. The possible values are 'system' or 'session'.

`G_DBUS_DEBUG`. This variable can be set to a list of debug options, which cause GLib to print out different types of debugging information when using the D-Bus routines.

transport | Show IO activity (e.g. reads and writes)
message | Show all sent and received D-Bus messages
payload | Show payload for all sent and received D-Bus messages (implies message)
call | Trace `g_dbus_connection_call()` and `g_dbus_connection_call_sync()` API usage
signal | Show when a D-Bus signal is received
incoming | Show when an incoming D-Bus method call is received
return | Show when a reply is returned via the GDBusMethodInvocation API
emission | Trace `g_dbus_connection_emit_signal()` API usage
authentication | Show information about connection authentication
address | Show information about D-Bus address lookups and autolaunching

The special value `all` can be used to turn on all debug options. The special value `help` can be used to print a list of supported options to standard output.

`G_DBUS_COOKIE_SHA1_KEYRING_DIR`. Can be used to override the directory used to store the keyring used in the `DBUS_COOKIE_SHA1` authentication mechanism. Normally the directory used is `.dbus-keyrings` in the user's home directory.

`G_DBUS_COOKIE_SHA1_KEYRING_DIR_IGNORE_PERMISSION`. If set, the permissions of the directory used to store the keyring used in the `DBUS_COOKIE_SHA1` authentication mechanism won't be checked. Normally the directory must be readable only by the user.