They have fled their homes, schools, and farmland, often more than two years ago, and still cannot return home.

Ever since the armed group Boko Haram started its campaign of violence in 2009 in northeastern Nigeria, more than 2.1 million Nigerians have been on the run. According to the United Nations Office for the Coordination of Humanitarian Affairs (OCHA), there are currently 1.9 million internally displaced people (IDP) in the West African country.

Reports about this humanitarian crisis often come from IDP camps, and the people finding refuge there. This is just a part of the story.

Most displaced Nigerians did not go to camps for shelter; they went to people's homes. According to the UN, more than 80 percent of IDPs found refuge with fellow Nigerians. Al Jazeera travelled around Nigeria's north to learn what compelled some of these hosts to open their doors, and homes, to people fleeing violence.

Kano: 'You give what you have, however little'

Haruna Ya'u was about seven and his mother was cooking tuwo masara, his favourite corn meal dish, when their neighbour arrived to see his father.

His family was hungry, the neighbour explained, and he did not have money to feed them.

"Before I knew it, my father instructed my mother to give the food to the neighbours," Haruna, now 35, recalls. His mother just smiled and took the food next door.

"From my parents, I learned that whenever you see someone who needs help, you give them what you have. However little it is."

When the first people fleeing Boko Haram violence reached Kano, Nigeria's largest northern city, Haruna felt it was only natural to help. It was early 2015 and the number of displaced Nigerians from the northeast was soaring as Boko Haram swept through town after town.

Haruna, who is a bricklayer, built a wall in his compound to divide it into two. He then told people at his mosque that his doors were open to anyone who needed help. He thought that he and his family of three wives and 10 children were well-off enough to afford to make space for more people.

Sani Baga's family had just celebrated the new year and his newborn son's naming ceremony in the town of Baga, which lies on the Nigerian border with Chad.

The very next day, Boko Haram stormed the town in an attack that would come to be known as the massacre of Baga.

Sani and his family managed to escape into the mountains while the fighting was still a distance away; only later would they hear about the atrocities that happened there. The family eventually ended up in Maiduguri, the capital of Borno State which was so full of displaced people that the number of inhabitants had effectively doubled.

He took us in as strangers, but treated us as family. Sani Baga, IDP

Sani decided to travel west, to Kano, with one of his two wives - the other stayed behind to take care of the children - to see if his family could find refuge there.

"I didn't know anybody here and nobody knew me," he recalls of arriving in the town more than 700 kilometres away from Baga.

He had heard on the radio that Kano's religious authority Hisbah was helping IDPs but, when he arrived at their office, they told him they could accommodate him only for a couple of days. Then someone who was waiting at the office told him about Haruna, the man whom most people know as Yaya, which is the Hausa word for "big brother".

"I went to meet him and told him about my family. He simply gave us half of his house to stay [in]," says Sani, who then sent for his other wife and his 17 children who were waiting in Maiduguri.

"He has a good heart," Sani says of his host. The two men say they now live together as full brothers, and when one of them is not around, the other becomes the head of the two families.

In the two and a half years they have stayed in Kano, Sani says he never felt any pressure from his host to leave.

Even though Boko Haram has been driven out of Baga, the businessman says he cannot return home just yet. Outside the town it is dangerous; many who fled the violence haven't returned to Baga. Sani's trade and his shop in the Baga market where he sold maize, millet, rice, and beans, simply would not yield enough income to feed his family.

Sani's 25-year-old daughter Zulai grinds millet in a wooden mortar for that evening's meal. She longs to return home, where she used to make money selling food. But she is sure she'll miss Haruna. To her, their host is another father.

"He took us in as strangers, but treated us as family," she says. "Even when we go back home, we will stay in touch. We are family now."

READ MORE: When schools and students become spoils of war

Maiduguri: 'It is my duty to my people'

Alhaji Ibrahim Abbas had only the clothes on his back when he fled his hometown Gwoza on August 6, 2015, the day Boko Haram attacked this town in northeastern Nigeria.

Now, Alhaji lives in exile in the state capital Maiduguri, a little over 100 kilometres northwest of his place of birth. Life is not easy for him, his two wives, and nine children. Still, the doors of his rented house are always open to anyone from Gwoza who needs refuge: most of the time these guests outnumber his family members.

"At times I don't even know how many are staying in the house. But it is my duty to my people," he says.

As the Chiroma of Gwoza, a district head of his town, he would be turned to for help by the people there.

"They all know me as their traditional leader. People would come to me from villages all around when they had problems. When a husband and wife were quarrelling, I would sometimes host the woman for three months until their problems were solved. It is our tradition. Even a mad person can stay with me if he asks."

The Chiroma is used to having many strangers in his compound; this is how he grew up.

"I saw it at home in my childhood because I inherited the title from my father. I hope my children also grow up learning to be hospitable. My son, who goes to university, is used to it. When he comes home, he just as easily sleeps on a mat in the parlour with everyone else."

His first wife, Bilkisu, knew what she was getting into when she married the Chiroma. "There were always guests in my husband's house," she said.

At the moment, they share their six rooms in Maiduguri with 24 others. In late 2014, during the height of the Boko Haram crisis, there were 66 of them.

It hasn't always been easy feeding so many people, she admits. "When we arrived in Maiduguri, people knew we came with nothing, and many would help us with foodstuffs, but gradually the help went down."

They share what they have, and their guests also contribute. "My children eat together with everyone else. I don't want to make exceptions," she says, as she points at Ibrahim, her six-year-old son playing at her feet, who missed school that day because of a fever.

My children eat together with everyone else. I don't want to make exceptions. Bilkisu, host in Maiduguri

When asked if there are ever problems with so many strangers in the same space, Bilkisu shrugs.

In the beginning, there were many women among their guests, and sometimes she would get irritated when the younger women didn't help her cook. But now, even the men help with household chores. "We all have to contribute," Bilkisu says.

Umar Guwa and his family were among the first to be hosted by the Chiroma. His wife and children are now staying at an IDP camp nearby, because they wanted to lessen the pressure on the Chiroma's household.

But the butcher now sees his traditional leader as a father: "He never knew us from Adam, but took us in like his own. I am overwhelmed by his kindness. I promised myself, when I get back on my feet, I will return the favour to others."

David John is one of the few Christians among the guests of his Muslim host. He says his religion has never been an issue. "From the beginning, the doors were open for Muslims and Christians alike," he says.

The 30-year-old bachelor enrolled in a computer engineering course in the Maiduguri polytechnic after a talk with the Chiroma about his plans for the future. "He has advised me and is helping me with the school fees."

Staying with so many strangers has taught him to pull his own weight, he says.

"If I wake up and see rubbish on the floor, I pick it up. And I am not too good to peel yam or potatoes, fetch water or cook meat. We all have to chip in."

READ MORE: Boko Haram's decline raises hopes of the displaced

Rumdekila: 'Next time, it could be us'

Mohammed Jidda has lived in Rumdekila, a farmers' village of about 150 families not far from Yola, the capital city of Adamawa State, for all 77 years of his life.

Whenever you see a visitor, you don't send them away. You don't ask about his tribe or his religion. You welcome everyone who needs rescue. Mohammed Jidda, resident of Rumdekila

One afternoon in September 2014, someone knocked on his thatched gate. It was his friend from Madagali, a town on the border with Cameroon almost 300 kilometres north of Rumdekila, who used to ride a keke, a threewheeler taxi, around Yola and park in Mohammed's compound at night.

His friend wasn't alone. With him were about 300 people, all seeking refuge after fighting erupted between the Nigerian army and Boko Haram in Madagali.

"Too many for me to take in," Mohammed recalls. So he went to see the village head about the displaced people at his gate, some of whom were Christian, some Muslim, and some from Madagali, while others had fled the border town of Gwoza earlier to find shelter in Madagali, only to find themselves on the run again with their hosts.

That same afternoon, the villagers decided they would shelter all the displaced people and divided the families between the compounds.

"Whenever you see a visitor, you don't send them away. You don't ask about his tribe or his religion. You welcome everyone who needs rescue," Mohammed says.

At that time, the nearby building that now houses an IDP camp still functioned as a school. But even if there had already been such a facility, the villagers still would have offered their help.

It is seen as a disgrace to a community if they send away people in dire need, the farmer explains. This solidarity also came from the realisation that soon they might need such help themselves, Mohammed explains.

In mid-November 2014, Boko Haram was seizing towns and villages across Nigeria's northeast and drew dangerously close to Rumdekila.

"Everyone was affected. We realised that next time, it could be us," Mohammed says.

Mohammed's wife Fatima Yusuf, 48, still can't explain how the village was able to provide for all the extra mouths they had to feed.

"All of a sudden, help came from everywhere," she says. A local NGO built toilets in the village, other organisations provided bags of rice, and individuals donated clothes and blankets. "When you do good, God will open a door for you," Fatima says.

Her husband's hospitality went even further. When the septuagenarian realised that Mairo, one of the women from Gwoza, had been abandoned by her husband, he offered to marry her. He knew that a woman on her own is especially vulnerable, says Mairo, who is now Mohammed's second wife.

"I have six children. When they attack, I cannot run and leave my children behind. I need to take care of them. A marriage would protect me," she says.

Mairo is the only one of the IDPs not planning to go home.

"Rumdekila is my home now," she says. "Even the people in my village were happy about the marriage."

Since they married in November 2014, her new husband has looked after Mairo and her children and she worries a lot less about their future.

"He pays the school fees and my children haven't been hungry for a day," she says.

Fatima, while seated on the mat in her compound's mud-walled reception room next to the gate, smiles when asked how she felt about her husband's second marriage.

"He spoke to me before asking her, and I agreed," she says. "Besides, he didn't forget about me. For the marriage he brought me the same number of wrappers [a cloth skirt] as he gave her."