CCP §415.50: (a) A summons may be served by publication if upon affidavit it appears to the satisfaction of the court in which the action is pending that the party to be served cannot with reasonable diligence be

(a) A summons may be served by publication if upon affidavit it appears to the satisfaction of the court in which the action is pending that the party to be served cannot with reasonable diligence be served in another manner specified in this article and that either: (1) A cause of action exists against the party upon whom service is to be made or he or she is a necessary or proper party to the action. (2) The party to be served has or claims an interest in real or personal property in this state that is subject to the jurisdiction of the court or the relief demanded in the action consists wholly or in part in excluding the party from any interest in the property. (b) The court shall order the summons to be published in a named newspaper, published in this state, that is most likely to give actual notice to the party to be served. If the party to be served resides or is located out of this state, the court may also order the summons to be published in a named newspaper outside this state that is most likely to give actual notice to that party. The order shall direct that a copy of the summons, the complaint, and the order for publication be forthwith mailed to the party if his or her address is ascertained before expiration of the time prescribed for publication of the summons. Except as otherwise provided by statute, the publication shall be made as provided by Section 6064 of the Government Code unless the court, in its discretion, orders publication for a longer period. (c) Service of a summons in this manner is deemed complete as provided in Section 6064 of the Government Code. (d) Notwithstanding an order for publication of the summons, a summons may be served in another manner authorized by this chapter, in which event the service shall supersede any published summons. (e) As a condition of establishing that the party to be served cannot with reasonable diligence be served in another manner specified in this article, the court may not require that a search be conducted of public databases where access by a registered process server to residential addresses is prohibited by law or by published policy of the agency providing the database, including, but not limited to, voter registration rolls and records of the Department of Motor Vehicles.