I am new to Ruby on Rails. My questions is:
Is it possible to setup Redmine and install the plugins on my local machine (macOS Sierra), test the Redmine application on localhost, once everything has been done successfully, then only deploy it on a Linux server?
If it is possible, which part of the code should I modify in order to deploy it on Linux server successfully? (Both of my local machine and Linux server are running MySQL database)
Yes it is possible and you don't need to change any part of the Redmine code to do so. Deployment of Rails apps is often done with a tool called Capistrano (http://capistranorb.com/), which executes through ssh on your server, checks out the code and does any additional installation steps necessary. This approach requires you to have your app (Redmine and plugins in your case) in a git repository (or subversion etc). In the simplest case, fork redmine on github and add any plugins as git submodules.
As you're unfamiliar with the platform I'd suggest to start with a simple rails app that you create locally. once you have worked out deployment of that to a remote server, tackle Redmine.
Sounds like a lot of upfront effort but it's worth it since it enables you to work on your local machine, make changes and then deploy the changed code with a single command.
If the Redmine installation on your local host has the same installation path as on the production server, then you can just copy the installation files to the production server. You will also have to copy the database to the production server.
If the installation path is different on your local host and production server, then you will have to install the Redmine and plugin on your production server
