So a really good first step would be to add strictures to your code before you port it and clean up any issues raised on the old system. If possible it would also be smart to add some regression tests so you can have some confidence behavior hasn't changed in important places during the migration. Also run through checking that system calls are checked for errors and handled correctly - if you are moving to a new system filed and directories may have moved around in surprising ways and file operations may begin failing as a result.