Lionel Messi hit four for Barcelona during another incredible performance, while Paulinho and Denis Suarez were also on the scoresheet as the Catalan giants moved five points clear of second-placed Sevilla at the top of the table.
Nelson Semedo, Javier Mascherano, Lucas Digne, Paulinho, Denis Suarez and Gerard Deulofeu all came into the Barcelona team, with Luis Suarez, Samuel Umtiti and Jordi Alba among those to drop out as head coach Ernesto Valverde took the chance to rotate.
The visitors had a wonderful chance to take the lead in the fourth minute when Sergi Enrich broke into a one-on-one situation with Marc-Andre ter Stegen after a super pass from Junca, but the Barcelona goalkeeper was on hand to make a smart save.
Ter Stegen then had to keep out a low strike from Inui in the 10th minute as Eibar continued to look the team more likely to make the breakthrough in the early stages at Camp Nou.
Barcelona were finding it difficult to create opportunities against a stern Eibar defence, but the Catalan giants were handed a controversial penalty in the 20th minute when Alejandro Galvez was adjudged to have brought Semedo to the ground inside the box.
Messi stepped forward for the home side, and the Argentine found the corner of the net to break the deadlock in the 21st minute.
Barcelona's record goalscorer almost doubled his tally in the 26th minute after curling one towards the top corner, but Eibar goalkeeper Marko Dmitrovic was on hand to make a smart save.
Enrich had another half-chance for Eibar just before the 30-minute mark, but the number nine headed wide at the near post as Barcelona led into the latter stages of the first period.
The scoreline got worse for Eibar in the 38th minute, however, when Paulinho rose highest inside the away side's box to head a Denis Suarez corner past Dmitrovic as the Brazilian scored his second Barcelona goal in the space of three days.
Deulofeu threatened to send the home side 3-0 ahead early in the second period after meeting a through-ball from Andres Iniesta, but Eibar goalkeeper Dmitrovic raced off his line to make the clearance.
Barcelona had their third in the 53rd minute, however, when Denis Suarez smashed the ball past Dmitrovic after the Serbian had palmed a Messi strike straight into the path of the Spain international.
Eibar had a goal of their own in the 57th minute when Enrich turned a Junca cross past Ter Stegen, but Barcelona were again three goals clear two minutes later when Messi simply passed the ball into the corner of the net.
Messi then completed his hat-trick in the 62nd minute when the Argentine collected a through-pass from Paulinho before holding off the challenge of three Eibar defenders and finishing under the onrushing goalkeeper.
Digne almost made it six for the home side 20 minutes from time, but the Frenchman could not find a route past Dmitrovic, who was continually deserted by his defence in the second period.
Ruben Pera came close to scoring a second for Eibar in the 86th minute after breaking into the Barcelona box, but the second-half substitute hit the inside of the post.
The scoring was not finished, however, with Messi netting his fourth in the 87th minute after Aleix Vidal had found the Argentine with a clever pass inside the Eibar box.
Eibar finished with a flurry as Charles hit the crossbar before Inui had one deflected over the crossbar, but the visitors were on the end of a thumping from a Barcelona team that are now seven points clear of champions Real Madrid in Spain's top flight.
Barcelona will attempt to make it six straight wins at the start of the new La Liga season when they travel to Girona on Saturday night. Eibar, meanwhile, are next in action at home to Celta Vigo on Sunday night.