Udasi group was started by Baba Sri Chand. Since he was more interested in asceticism, Guru Sahib did not choose him as His successor. This caused him great pain so he did not follow Guru Sahib’s successors and started his own following. He built Dera Baba Nanak Gurdwara and his brother Baba Lakhmi Das toured the areas Guru Sahib had visited to collect sakhis and compiled a short Janamsakhi which grew later on. Udasi at first was a rival group. They composed their own bani such as Ratan Mala. Over time, Baba Sri Chand’s bitterness went away and he came to accept Gurmat as the true path upon meeting Guru Raamdas Ji and seeing His humbleness. He admitted the fact that his father had chosen the right successor. When he grew old and saw his end drawing near, he went to meet Guru Hargobind Ji and handed over control of his group to Guru Ji. This was because he had realized that while his father had had five successors he could not find a single person worthy enough to carry out his mission. He realized futility of asceticism and wished to hand it over to Guru Sahib so he could channel it towards spreading Gurmat. Guru Sahib appointed his son Baba Gurditta Ji as its successor and organized the group into five sections with each section having its own head. All of the heads were Gurmat practicing Sikhs. Their role was to establish Dharamsaals everywhere to do parchaar. Udasis quickly spread far and wide and established Dharamsaals. They also took the task to make copies of Gurbani Pothis and later on Gurbani Birs. They also established their dera at Hindu holy places to attract large following to Gurmat. Slowly, over time they drifted away from Gurmat and became more of Hinduized udasis rather than Gurmat udasis. When British arrived, they were made to believe that Gurdwaras were their personal property. Everybody knows the history of Gurdwara Reform Movement.
See The Turban and the Sword of the Sikhs for more information on Udasis and other groups. Guru Rakha
ਸਤਿਗੁਰਬਚਨਕਮਾਵਣੇਸਚਾਏਹੁਵੀਚਾਰੁ॥