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diff --git a/Documentation/user/variables.rst b/Documentation/user/variables.rst index a13de1b22c..974ab88221 100644 --- a/Documentation/user/variables.rst +++ b/Documentation/user/variables.rst @@ -25,6 +25,47 @@ other variable. You can also directly assign a value during creation:: to assigning a value with ``global.myvar1=foobar``, but the latter fails when a variable has not been created before. +.. _config_device: + +Non volatile variables +---------------------- + +Additionally to global variables barebox also has non volatile (nv) variables. +Unlike the global variables the config variables are persistent over reboots. + +Each nv variable is linked with the global variable of the same name. +Whenever the nv variable changes its value the corresponding global +variable also changes its value. The other way round though is not true: +Changing a global variable does not change the corresponding nv variable. +This means that changing a global variable changes the behaviour for the +currently running barebox, while changing a nv variable changes the +behaviour persistently over reboots. + +nv variables can be created or removed with the :ref:`command_nv` +command. The nv variables are made persistent using the environment +facilities of barebox, so a :ref:`saveenv` must be issued to store the actual +values. + +examples: + +.. code-block:: sh + + barebox@Phytec phyCARD-i.MX27:/ devinfo nv + barebox@Phytec phyCARD-i.MX27:/ nv model=myboard + barebox@myboard:/ devinfo nv + Parameters: + model: myboard + barebox@myboard:/ devinfo global + Parameters: + [...] + model: myboard + [...] + barebox@myboard:/ global.model=yourboard + barebox@yourboard:/ devinfo nv + Parameters: + model: myboard + barebox@yourboard:/ + .. _magicvars: Magic variables |