That is not very helpful for linux users on where to place personal libraries, sketches or new hardware packages.
Also the default default locations the IDE uses are kind of goofy on linux as they don't go in a "Arduino" directory,
the simply go right in the users home directory. ~/sketchbook
My suggestion is bring up the IDE,
click on [File]->Preferences
Change the Sketchbook location to be something like
{home directory}/Arduino
rather than {home directory}/sketchbook
Then go to that directory and create 3 more subdirectories:
sketches
libraries
hardware
You now should have
~/Arduino
~/Arduino/sketches
~/Arduino/libraries
~/Arduino/hardware
Copy any of your old sketches over to ~/Arduino/sketches
You can now place all the libraries you write or collect under the ~/Arduino/libraries directory
And any new hardware packages like say the ATTINY package under ~/Arduino/hardware.
It keeps everything nice and clean and all under a single Arduino directory that is easy to locate
rather than having
~/sketchbook for sketches
and ~/sketchbook/libraries for libraries
and ~/sketchbook/hardware for hardware packages
Its what I've done since I prefer having everything under a directory called "Arduino"
vs "sketchbook".
That is not very helpful for linux users on where to place personal libraries, sketches or new hardware packages.
Also the default default locations the IDE uses are kind of goofy on linux as they don't go in a "Arduino" directory,
the simply go right in the users home directory. ~/sketchbook
Its what I've done since I prefer having everything under a directory called "Arduino"
vs "sketchbook".