In Sudan’s 2008 census, the population of Northern, Western and Eastern Sudan was recorded to be over 30 million. This puts present estimates of the population of Sudan after the secession of South Sudan at a little over 30 million people. This is a significant increase over the past two decades as the 1983 census put the total population of Sudan, including present-day South Sudan, at 21.6 million. The population of metropolitan Khartoum (includingKhartoum, Omdurman, and Khartoum North) is growing rapidly and was recorded to be 5.2 million.
Despite being a refugee-generating country, Sudan also hosts a refugee population. According to the World Refugee Survey 2008, published by the U.S. Committee for Refugees and Immigrants, 310,500 refugees and asylum seekers lived in Sudan in 2007. The majority of this population came from Eritrea(240,400 persons), Chad (45,000), Ethiopia (49,300) and the Central African Republic (2,500). The Sudanese government UN High Commissioner for Refugees in 2007 forcibly deported at least 1,500 refugees and asylum seekers during the year. Sudan is a party to the 1951 Convention Relating to the Status of Refugees.
Ethnic groups 
The Arab presence is estimated at 70% of the Sudanese population. Others include the Arabized ethnic groups of Nubians, Copts, and Beja.Sudan has 597 tribes that speak over 400 different languages and dialects. Sudanese Arabs are by far the largest ethnic group in Sudan, they are almost entirely Muslims; while the majority speak Sudanese Arabic; some other Arab tribes speak different Arabic dialects like Awadia and Fadnia and Bani Araktribes who speak Najdi Arabic; Rufa’a, Bani Hassan, Al-Ashraf, Kinanah and Rashaida who speak Hejazi Arabic. In addition, the Western province comprise various ethnic groups, while few Arab Bedouin of the northern Rizeigat and others who speak Sudanese Arabic and share the same culture and backgrounds of the Sudanese Arabs, The majority of Arabized and indigenous tribes like the Fur, Zaghawa, Masalit and some Baggara ethnic groups, who speak Chadian Arabic, show less cultural integration, not often included in Sudanese Arabs definition, because of cultural, linguistic and genealogical variations with other Arab and Arabized tribes. Sudanese Arabs of Northern and Eastern parts descend primarily from migrants from the Arabian peninsula and some of the pre-existing indigenous populations of Sudan, most predominately the Nubian people who also share a common history with Egypt and Beja. Additionally, a few pre-Islamic Arabian tribes existed in Sudan from earlier migrations into the region from Western Arabia, although most Arabs in Sudan are dated from migrations after the 12th century. The vast majority of Arab tribes in Sudan migrated into the Sudan in the 12th century, intermarried with the indigenous Nubian and African populations and introduced Islam.
In common with much of the rest of the Arab world, the gradual process of Arabization in Sudan following these Arabian migrations after the 12th century led to the predominance of the Arabic language and aspects of Arab culture, leading to the shift among a majority of Sudanese today to an Arab ethnic identity. This process was furthered both by the spread of Islam and an emigration to Sudan of genealogical Arabs from the Arabian Peninsula, and their intermarriage with the Arabized indigenous peoples of the country.
97 percent of the population adheres to Islam. Almost all Muslims are Sunni, although there are significant distinctions between followers of different Sunni traditions. Two popular divisions, the Ansar and the Khatmia, are associated with the opposition Umma and Democratic Unionist Parties, respectively. There are significant but long-established groups of Coptic Orthodox and Greek Orthodox Christians in Khartoum and other northern cities.
There are also Ethiopian and Eritrean Orthodox communities in Khartoum and eastern Sudan, largely made up of refugees and migrants from the past few decades. Other Christian groups with smaller followings in the country include the Africa Inland Church, the Armenian Apostolic Church, the Sudan Church of Christ, the Sudan Interior Church, Jehovah’s Witnesses, the Sudan Pentecostal Church, the Sudan Evangelical Presbyterian Church (in the North) Religious identity plays a role in the country’s political divisions. Northern and western Muslims have dominated the country’s political and economic system since independence. The NCP draws much of its support from Islamists, Salafis/Wahhabis and other conservative Arab Muslims in the north. The Umma Party has traditionally attracted Arab followers of the Ansar sect of Sufism as well as non-Arab Muslims from Darfur and Kordofan. The Democratic Unionist Party (DUP) includes both Arab and non-Arab Muslims in the north and east, especially those in the Khatmia Sufi sect.
Tribes of Sudan 
Info from https://en.wikipedia.org/wiki/Sudan