Ja'far was likely the son of Dinar ibn Abdallah, an army commander and provincial governor who was active during the caliphate of al-Ma'mun (r. 813–833).
[1] He himself first appears in the last years of al-Ma'mun's reign, when he participated in the caliph's 830 invasion of Byzantine Anatolia and was sent with Ujayf ibn Anbasah to receive the submission of the commander of fortress of Sinan.
[4] In 839 he received the governorship of the Yemen and appointed deputy governors to enforce his rule in that province, but in 840 he incurred the anger of the caliph, who dismissed him from his position and briefly imprisoned him in the custody of Ashinas.
Shortly after this he decided to withdraw to the province altogether and returned to Iraq, leaving his son Muhammad to stay behind as his deputy until Himyar ibn al-Harith was appointed as governor in his stead.
[6] During the caliphate of al-Mutawakkil (r. 847–861), Ja'far oversaw the events of the festival season (mawsim) during the annual pilgrimages of 854 to 858, and was also assigned the supervision of the Mecca Road.