A Hukamnama refers to a hymn from the Guru Granth Sahib which is given as an order to Sikhs or a historical order given by one of the Guru’s of Sikhism.
The Hukamnama also refers to a hymn randomly selected from the Guru Granth Sahib on a daily basis. This is seen as the order of God fohat particular day. The Hukamnama is distributed and then read aloud in Gurudwaras throughout the world.
Hukamnama, is a compound of two words hukam, meaning command or order, and namah, meaning statement. Hukamanama, order or thought of the day is taken as of great importance in the life of a Sikh.
In Harmandir Sahib as soon as Sri Guru Granth Sahib arrives for installation every morning, the priest (Granthi) will unfold the rumalas wrapped around the holy book among reciting of swaiyias (the couplets of bani) of Bhatts. As soon as Guru Granth Sahib is opened, the first hymn on the very left side is read out loudly. This hymn is called order or thought of the day or Hukamnama.
It has such a great importance that the very first hymn that was read in 1604 on installation of Guru Granth Sahib in Harmandir Sahib has become a part of the Sikh history.
Again in the evening, after Rehras (the evening prayer and ardas) the priest will read the very last hymn on the right side loudly. The hymn that comes in the morning is displayed on a board specially set for the purpose near two Nishan Sahib (Saffron flags) outside Darshani Deori.
Source: Wikipedia, Internet