Mr Ennis (36) was found with an apparent stab wound in the early hours of Tuesday morning at a flat in Claddagh Court in Ballyfermot.
A woman in her late 40s, who had been arrested in connection with his death was later released without charge, a garda spokesperson said.
A notice on RIP.ie states that “the tragic death has occurred of David Thomas Ennis, on November 8 in Dublin.
“Formerly of Ballivor, Co Meath,” it adds. “Predeceased by his father Peter and his sister Shirley. Sadly missed by his mother Geraldine, his brothers Oliver and Lee, partners, nieces, nephews, aunts, uncles, relatives and friends.”
Alongside the notice people have taken to the condolences section to offer their sympathies.
One reads: “So sad to hear the news of David’s passing. Sending Love, thoughts and prayers to Ollie & Lee and David’s family. Rest in Peace David.”
Another adds: “Rip David, still can't believe it. Condolences to brothers Lee an Olliver an mum Geraldine an to extended family.”
One person offers, “my deepest Sympathy to Geraldine & family on David’s sudden passing. Such a likeable gentle young man. A hard time for you all. May his gentle soul Rest in Peace.”
“No words can describe your loss thinking of ye all,” one person has added.
“Rest in Eternal Peace David,” another has said. “You were a great friend and a gentleman. I’ll miss you having a jam on the guitar and your laugh. Deepest Sympathies to Geraldine, Ollie and Lee.”
Local councillor Daithí Doolan, who is chairperson of the Joint Policing Committee, said it was a “sad day for Ballyfermot”.
“This level of violence affects the whole community. My thoughts and sympathies are with the family of the victim.”
He added: "I would encourage anyone with any information, no matter how small or insignificant they believe it is, to please contact the gardaí."