New module

Hello,

I'm French, I'm sorry for my bad English.

I would like to develop a module to update the status of a website (in maintenance, production, etc.). Is this possible ? How can I retrieve the list of installed on the server and then display sites ? In the Shell module is that you can get the code and adapt it to execute commands with parameters ?

I would like to add categories on the left. I went into the admin panel to add, but they are not displayed.

Thank you for your answers. Good Day.

Cordially.