Chief Minister (India)

In the Republic of India, a Chief Minister is the elected head of government of each of twenty-nine states and two union territories (Delhi and Puducherry). According to the Constitution of India, the Governor is a state's de jure head, but de facto executive authority rests with the Chief Minister. Following elections to the state legislative assembly, the Governor usually invites the party (or coalition) with a majority of seats to form the government. The Governor appoints and swears in the Chief Minister, whose council of ministers are collectively responsible to the assembly. Based on the Westminster system, given that he retains the confidence of the assembly, the Chief Minister's term can last for the length of the assembly's life—a maximum of five years. There are no limits to the number of terms that the Chief Minister can serve.

The Constitution of India sets the principle qualifications one must meet to be eligible to the office of the Chief Minister. A Chief Minister must be:

The chief minister is elected through a majority in the state legislative assembly. This is procedurally established by the vote of confidence in the legislative assembly, as suggested by the governor of the state who is the appointing authority.

Since, according to the constitution, the chief minister is appointed by the governor, the swearing in is done before the governor of the state.

The oath of office.

I, <Name of Minister>, do swear in the name of God/solemnly affirm that I will bear true faith and allegiance to the Constitution of India as by law established, that I will uphold the sovereignty and integrity of India, that I will faithfully and conscientiously discharge my duties as a Minister for the State of <Name of the State> and that I will do right to all manner of people in accordance with the Constitution and the law without fear or favour, affection or ill-will.

...
Wikipedia