No, not all Federal jobs require a security clearance. Only jobs that require a candidate to access classified information and secure facilities require a clearance.
However, all federal positions require something called a suitability determination. This is a background investigation that helps the government decide if you are suitable for federal employment. This process includes a review of your personal and professional conduct, helping ensure the integrity, efficiency and effectiveness of the federal workforce.
You can find out if a job requires a security clearance in the Background and security clearance section of the job announcement.