The passive can be used in reports when ‘who’ is not important, or when ‘who’ is something we don’t want to discuss:
‘The winning goal was scored in the 89th minute.’
‘Because profits were badly affected during the crisis, it was decided that twenty-five percent of jobs should be cut. Cutting jobs is seen as the only way to save the company.’
To say who did something, use ‘by’. Linux was originally developed by Linus Torvalds.
The passive is created using ‘to be’ + the past participle. Changes in the tense are made by changing ‘to be’.