Double-clicking on .md or .mkd or .markdown files doesn't open them in ReText but in the default text editor

Solution 1:

You can probably try with mimeopen, which is a tool used to pair a specific mimetype with a particular application.

Use a file with .mkd extension as a parameter of mimeopen.

As an example:

$ mimeopen file.mkd 
Please choose a default application for files of type text/x-retext-markdown

    1) ReText  (retext)
    2) GNU Emacs 23  (emacs23)
    3) gedit  (gedit)
    4) LibreOffice Writer  (libreoffice-writer)
    5) Other...

use application #

Now, enter the number of the application (in this case, 1) and all .mkd files should now open in Retext.

Solution 2:

You should be able too (I can after a quick LXDE install) right click on a file and choose "Properties".

There should (according to what I find) be a tab called "Open With".

Select "ReText" and then "Set as Default". That worked for me.