Any aspirant desiring to don the rank of a Sub Divisional Magistrate can follow these two pathways.
1. UPSC Exam or Union Public Service Commission
2.State Public Service Commission or the State PCS

1)Through UPSC
a) The first and foremost step is to fulfil the Education, which is being a graduate from any stream.
b) Appear and Qualify the UPSC Civil Services Exam.
c) Get into the Indian Administrative Services.
The IAS Officer after completing the probation period is posted as the first posting at the Sub-divisional level of a district.

2.Through State PCS
The steps are almost similar with minor differences. Just like the pathway of an IAS Officer, the State PCS needs to be a
1) Graduate from any stream
2) Qualify the PCS of your State
3) However, in order to secure the rank of an SDM, he needs to secure a top rank in the PCS Exam.