Add headers to usage.rst to make config headings linkable

- Config options described in usage.rst are now linkable.

Change-Id: Ibe918b28d45d0b08b36af4af89f146d0f9930131
Partial-Bug: #1673530

doc/source/usage.rst

@@ -13,12 +13,14 @@ local.conf settings
 -------------------
 
 COLLECTD_BRANCH
+~~~~~~~~~~~~~~~
     (<git branch>) Indicates which branch of collectd to checkout before
     compiling.
 
     Default: collectd-5.7
 
 COLLECTD_CONF_DIR
+~~~~~~~~~~~~~~~~~
     (directory) Specify a directory where collectd conf files reside.
     This is required if you use a distro other than Ubuntu or Fedora, or if
     the config file is in a non default location. This config directory will
@@ -26,11 +28,13 @@ COLLECTD_CONF_DIR
     Default: /etc/collectd/collectd.conf.d (Ubuntu) /etc/collectd.d (Fedora)
 
 COLLECTD_DIR
+~~~~~~~~~~~~
     (directory) Destination of the cloned collectd source code.
     Default: $DEST/collectd-$COLLECTD_BRANCH/
 
 
 COLLECTD_INSTALL
+~~~~~~~~~~~~~~~~
     (True|False) Indicates whether to install collectd.
     Set this to False if you are running a pre-built version of collectd or do
     not want to upgrade installed version.
@@ -39,26 +43,32 @@ COLLECTD_INSTALL
 
 
 COLLECTD_BATCH_SIZE
+~~~~~~~~~~~~~~~~~~~
     Set the amount of samples to be buffered before sending.
     Default: 1 i.e. no batching/buffering.
 
 
 CEILOMETER_TIMEOUT
+~~~~~~~~~~~~~~~~~~
     Sets the ceilometer's request timeout. The value is passed in milliseconds.
     Default: 1000 i.e. 1 sec.
 
+
 COLLECTD_LOG_FILE
+~~~~~~~~~~~~~~~~~
     (file) The path of the collectd log file.
     Default: /opt/stack/logs/collectd.log
 
 
 COLLECTD_LOG_LEVEL
+~~~~~~~~~~~~~~~~~~
     (debug|info|notice|warning|err) All log messages with lower log level than
     this are going to be filtered out from the log file.
     Default: info
 
 
 COLLECTD_CEILOMETER_CUSTOM_UNITS
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     (meter=unit) a comma seperated list of pairs, defining meters and their units.
     Allows existing units to be changed and new units to be set for new meters.
     The "meter" is generally in the form of "plugin.type", where plugin and
@@ -68,6 +78,7 @@ COLLECTD_CEILOMETER_CUSTOM_UNITS
 
 
 COLLECTD_GNOCCHI_CUSTOM_UNITS
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     (meter=unit) a comma seperated list of pairs, defining meters and their units.
     Allows existing units to be changed and new units to be set for new meters.
     The "meter" is generally in the form of "plugin.type", where plugin and
@@ -77,21 +88,25 @@ COLLECTD_GNOCCHI_CUSTOM_UNITS
 
 
 COLLECTD_CEILOMETER_ENABLED
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
     (True|False) Toggle whether collectd-ceilometer-plugin is enabled.
 
     Default: False
 
 COLLECTD_GNOCCHI_ENABLED
+~~~~~~~~~~~~~~~~~~~~~~~~
     (True|False) Toggles whether collectd-gnocchi-plugin is enabled.
 
     Default: True
 
 COLLECTD_AODH_ENABLED
+~~~~~~~~~~~~~~~~~~~~~
     (True|False) Toggles whether collectd-aodh-plugin is enabled.
 
     Default: False
 
 COLLECTD_CEILOMETER_VERBOSE
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
     (True|False) Set this to True to make collectd-ceilometer debugging messages
     visible as info messages. This is useful when running the plugin inside a
     collectd compiled without debug message support.
@@ -99,6 +114,7 @@ COLLECTD_CEILOMETER_VERBOSE
     Default: False
 
 COLLECTD_GNOCCHI_VERBOSE
+~~~~~~~~~~~~~~~~~~~~~~~~
     (True|False) Set this to True to make collectd-gnocchi debugging messages
     visible as info messages. This is useful when running the plugin inside a
     collectd compiled without debug message support.
@@ -106,6 +122,7 @@ COLLECTD_GNOCCHI_VERBOSE
     Default: $COLLECTD_CEILOMETER_VERBOSE
 
 COLLECTD_AODH_VERBOSE
+~~~~~~~~~~~~~~~~~~~~~
     (True|False) Set this to True to make collectd-aodh debugging messages
     visible as info messages. This is useful when running the plugin inside
     a collectd compiled without debug message support.
@@ -113,6 +130,7 @@ COLLECTD_AODH_VERBOSE
     Default: $COLLECTD_CEILOMETER_VERBOSE
 
 COLLECTD_INSTALL_TYPE
+~~~~~~~~~~~~~~~~~~~~~
     (source|binary) Specify whether the collectd installation should use the
     package manager or install from source.
 
@@ -120,12 +138,14 @@ COLLECTD_INSTALL_TYPE
 
 
 COLLECTD_REPO
+~~~~~~~~~~~~~
     (url) Location of git repo to clone collectd from.
 
     Default: https://github.com/collectd/collectd.git
 
 
 COLLECTD_PREFIX
+~~~~~~~~~~~~~~~
     (directory) The directory to install collectd under.
 
     Default: /usr/
@@ -138,18 +158,22 @@ following environment variables are used in this plugin for authentication
 to Keystone API v3
 
 OS_IDENTITY_API_VERSION
+~~~~~~~~~~~~~~~~~~~~~~~
     specifies version of keystone API used, should be set to 3 as 2.0 is
     deprecated.
     Default: 3
 
 OS_AUTH_URL
+~~~~~~~~~~~
     url where keystone is listening
     Default: based on $KEYSTONE_AUTH_URI/v$IDENTITY_API_VERSION
 
 OS_PASSWORD
+~~~~~~~~~~~
     password for service tenant used for keystone authentication
     Default: based on $SERVICE_PASSWORD
 
 OS_TENANT_NAME
+~~~~~~~~~~~~~~
     name of service tenant used for keystone authentication
     Default: based on $SERVICE_TENANT_NAME