Pakistan likely to play with the same squad.
Sohail (31) fell to a stunning low catch from Porterfield that gave Thompson his first Test wicket and left Pakistan 71 for 3.
Pace bowlers Tim Murtagh, Boyd Rankin and Stuart Thompson all took two wickets apiece. The 19-year-old was the primary aggressor as the two batsman started to form a burgeoning partnership.
Ireland went on to bag back-to-back wickets to make it 13-2 in what was a memorable start to their inaugural Test match.
The hosts finally made their long-awaited entrance into the Test arena after an opening day washout at Malahide Cricket Club near Dublin. Naturally, a few players could be seen getting emotional during the ceremony.
An expectant crowd of nearly 6,000 filled the temporary stands in anticipation of witnessing a piece of sporting history, with Tim Murtagh, the Middlesex seamer, delivering the historic first ball - and it wasn't without drama.
Non-striker Imam, in scrambling to complete the run, found himself sandwiched between wicket-keeper Niall O'Brien and Tyrone Kane in a heavy collision.
It is a historic match for both teams and especially for Ireland. O'Reilly, who also works with Dublin's senior footballers, would not have expected to be dealing with an impact injury after the first ball.
Boyd Rankin, who had previously taken one scalp in a lone Test appearance for England before switching allegiance to his native country, was the man to provide the breakthrough, becoming Ireland's first wicket-taker in the five-day format, producing an edge to second slip to reduce Pakistan to 13/1.
Barring Boyd Rankin, who had represented England in the 2013-14 Ashes, all the other 10 players in the Ireland side bagged their maiden Test caps.
They didn't have to wait long for a second as Murtagh struck next ball, trapping Imam leg-before for seven on his Test debut with a ball that would have hit middle stump.
At tea, Tim Murtagh and fellow pacemen Rankin and Stuart Thompson had taken two wickets each.
Murtagh got his second wicket after continuing his excellent line of attack, beating the bat on numerous occasions.
Rankin had an uncertain Azhar (four) edging to Porterfield at second slip.
Rankin and Thompson removed Asad Shafiq and Sarfraz Ahmed respectively before Ashraf and Khan steered Pakistan to the close.
Stirling's attempt to replicate John Mooney's famous Gaelic football solo from the 2007 World Cup win over Pakistan was miscued as it shanked off his right foot, but at 159 for six, there was giddiness on the pitch as well as off.