user15675: I'm using Ubuntu 14.04 with arduino Galileo and the newest arduino IDE from arduino.cc and every time I compile I got this warnings with any library in place of EEPROM, SD, Wire, Wifi and a lot of others.
When I check the boards manager I got the following:
Invalid library found in /home/User/.arduino15/packages/Intel/hardware/i586/1.6.2+1.0/libraries/Wire: /home/User/.arduino15/packages/Intel/hardware/i586/1.6.2+1.0/libraries/Wire 
Anyone knows how to solve this?

user27894: From: https://www.bountysource.com/issues/29336127-one-wire-library-still-in-v2-3-0-causes-useless-warning

The Arduino library manager still defaults to v2.3.0, which causes the
  IDE to raise the following warning on compile :
WARNING: Category '' in library OneWire is not valid. Setting to
  'Uncategorized'

Solution (In 1.6.12):

Sketch -> Include Library -> Manage Libraries
In the upper-right "Filter Your Search" box enter (without the quotes): "OneWire"
Click the "OneWire by Jim Studt, Tom P..." 
Select version 2.3.1 (or newer)
Click "Install"


user28268: As sated above you need to "Edit or add library.properties to that folder so that you specify a valid category."
This link has some good info on the structure of the file: https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification
From that link:
library.properties file format
The library.properties file is a key=value properties list. Every field in this file is UTF-8 encoded. The available fields are:
**name** - the name of the library
version - version of the library. Version should be semver compliant. 1.2.0 is correct; 1.2 is accepted; r5, 003, 1.1c are invalid
**author** - name/nickname of the authors and their email addresses (not mandatory) separated by comma ","
**maintainer** - name and email of the maintainer
**sentence** - a sentence explaining the purpose of the library
**paragraph** - a longer description of the library. The value of sentence always will be prepended, so you should start by writing the second sentence here
**category** - if present, one of these: "Display", "Communication", "Signal Input/Output", "Sensors", "Device Control", "Timing", "Data Storage", "Data Processing", "Other"
**url** - the URL of the library project, for a person to visit. Can be a github or similar page as well
architectures - a comma separated list of architectures supported by the library. If the library doesn’t contain architecture specific code use “*” to match all architectures
**dot_a_linkage** - (available from IDE 1.6.0 / arduino-builder 1.0.0-beta13) when set to true, the library will be compiled using a .a (archive) file. First, all source files are compiled into .o files as normal. Then instead of including all .o files in the linker command directly, all .o files are saved into a .a file, which is then included in the linker command.
**includes** - (available from IDE 1.6.10) a comma separated list of files to be added to the sketch as #include <...> lines. This property is used with the "Include library" command in the IDE. If the property is undefined all the headers files (.h) on the root source folder are included.


user11529: Edit or add library.properties to that folder so that you specify a valid category. 
Example of library.properties:
name=WebServer
version=1.0
author=Cristian Maglie <c.maglie@example.com>, Pippo Pluto <pippo@example.com>
maintainer=Cristian Maglie <c.maglie@example.com>
sentence=A library that makes coding a Webserver a breeze.
paragraph=Supports HTTP1.1 and you can do GET and POST.
category=Communication
url=http://example.com/
architectures=avr


15675: <p>I'm using Ubuntu 14.04 with arduino Galileo and the newest arduino IDE from arduino.cc and every time I compile I got this warnings with <em>any library</em> in place of EEPROM, SD, Wire, Wifi and a lot of others.</p>

<p>When I check the boards manager I got the following:</p>

<p>Invalid library found in /home/User/.arduino15/packages/Intel/hardware/i586/1.6.2+1.0/libraries/Wire: /home/User/.arduino15/packages/Intel/hardware/i586/1.6.2+1.0/libraries/Wire </p>

<p>Anyone knows how to solve this?</p>
 27894: <p>From: <a href="https://www.bountysource.com/issues/29336127-one-wire-library-still-in-v2-3-0-causes-useless-warning" rel="nofollow noreferrer">https://www.bountysource.com/issues/29336127-one-wire-library-still-in-v2-3-0-causes-useless-warning</a></p>

<blockquote>
  <p>The Arduino library manager still defaults to v2.3.0, which causes the
  IDE to raise the following warning on compile :</p>
  
  <p>WARNING: Category '' in library OneWire is not valid. Setting to
  'Uncategorized'</p>
</blockquote>

<p>Solution (In 1.6.12):</p>

<ol>
<li>Sketch -> Include Library -> Manage Libraries</li>
<li>In the upper-right "Filter Your Search" box enter (without the quotes): "OneWire"</li>
<li>Click the "OneWire by Jim Studt, Tom P..." </li>
<li>Select version 2.3.1 (or newer)</li>
<li>Click "Install"</li>
</ol>
 28268: <p>As sated above you need to "Edit or add library.properties to that folder so that you specify a valid category."</p>

<p>This link has some good info on the structure of the file: <a href="https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification" rel="nofollow noreferrer">https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification</a></p>

<p>From that link:</p>

<p>library.properties file format</p>

<p>The library.properties file is a key=value properties list. Every field in this file is UTF-8 encoded. The available fields are:</p>

<pre><code>**name** - the name of the library
version - version of the library. Version should be semver compliant. 1.2.0 is correct; 1.2 is accepted; r5, 003, 1.1c are invalid
**author** - name/nickname of the authors and their email addresses (not mandatory) separated by comma ","
**maintainer** - name and email of the maintainer
**sentence** - a sentence explaining the purpose of the library
**paragraph** - a longer description of the library. The value of sentence always will be prepended, so you should start by writing the second sentence here
**category** - if present, one of these: "Display", "Communication", "Signal Input/Output", "Sensors", "Device Control", "Timing", "Data Storage", "Data Processing", "Other"
**url** - the URL of the library project, for a person to visit. Can be a github or similar page as well
architectures - a comma separated list of architectures supported by the library. If the library doesn’t contain architecture specific code use “*” to match all architectures
**dot_a_linkage** - (available from IDE 1.6.0 / arduino-builder 1.0.0-beta13) when set to true, the library will be compiled using a .a (archive) file. First, all source files are compiled into .o files as normal. Then instead of including all .o files in the linker command directly, all .o files are saved into a .a file, which is then included in the linker command.
**includes** - (available from IDE 1.6.10) a comma separated list of files to be added to the sketch as #include &lt;...&gt; lines. This property is used with the "Include library" command in the IDE. If the property is undefined all the headers files (.h) on the root source folder are included.
</code></pre>
 11529: <p>Edit or add library.properties to that folder so that you specify a valid category. </p>

<p>Example of library.properties:</p>

<pre><code>name=WebServer
version=1.0
author=Cristian Maglie &lt;c.maglie@example.com&gt;, Pippo Pluto &lt;pippo@example.com&gt;
maintainer=Cristian Maglie &lt;c.maglie@example.com&gt;
sentence=A library that makes coding a Webserver a breeze.
paragraph=Supports HTTP1.1 and you can do GET and POST.
category=Communication
url=http://example.com/
architectures=avr
</code></pre>
