Bars and restaurants around the country are enjoying the first night of indoor hospitality.
Today saw the resumption of indoor hospitality for the first time since last December.
Some of the so-called wet pubs, which do not serve food, also opened their doors for the first time in nearly 500 days.
Restaurant representatives said around 25% of their members will not be reopening for a number of reasons, such as lack of staff.
People who are fully vaccinated or who have recovered from Covid-19 in the past six months can avail of indoor hospitality, along with accompanied minors.
Contact tracing is now only required for the lead person at a table and for solo customers under new updated guidelines, which were agreed last night.
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Restaurants Association of Ireland Chief Executive Adrian Cummins said another change is that designated tables have been removed.
"This means businesses don't have to keep a record of what table a party sat at - we only heard about these updated guidelines through an email at ten past midnight this morning."
Businesses that have reopened will also be able to avail of the three-week double payment of the Covid Restrictions Support Scheme.
The Taoiseach appealed to the public to continue to heed public health advice as indoor hospitality resumes.
Speaking in Cork, Micheál Martin confirmed that he would be happy to have a meal inside a restaurant with his family, but said he would be "careful" when doing so.
"We have made good progress over the past six months in reopening sectors of society," he said.
"We want to protect that progress so, even though we are opening indoor dining and hospitality today, with the vaccinated having access, we still have to be very, very careful."
Taoiseach Micheal Martin has called on the public to exercise caution as indoor hospitality resumes. Speaking in Kinsale in Co. Cork, he said the Delta variant of Covid-19 remains a threat. | Read more: https://t.co/rnF6NJHlKk pic.twitter.com/t8fNKvJw3W— RTÉ News (@rtenews) July 26, 2021
Fáilte Ireland said the guidelines on indoor hospitality are challenging, but aim to strike a balance between having a robust system in place and ensuring there is a reasonable process for businesses to operate.
Director of Sector Development Jenny De Saulles said they are delighted the recommendation to record only the contact details for the lead person in a group was taken on board.
Health officials have urged people to embrace the reopening safely with Health Service Executive CEO Paul Reid asking people to "make it work".
'Nice to see people pop in for some breakfast'
The Managing Director of Bewley's on Dublin's Grafton Street said there had not been a "tsunami of people" this morning, but it had been nice to see people spontaneously pop in for some breakfast.
Speaking on RTÉ's Today with Claire Byrne, Cól Campbell said people are being offered indoor or outdoor seating, and those who chose to dine indoors are asked to provide proof of their Covid certification.
He said there were some issues getting an Italian cert to scan, but that people from the US have been in, as have a number of Irish customers.
One of the owners of Roly's restaurant in Ballsbridge said he decided not to reopen indoor dining until Thursday, because advance booking has been so slow.
In addition, John O'Sullivan said he cannot get enough staff as many previous employees have returned home to their own countries.
David Lavell, the co-owner of eco pizzeria in Gorey, said they have decided not to reopen indoor dining because the many staff members are young and unvaccinated.
He said this decision was made on 2 July, adding that "the game is moving all the time", but said he does not
see the restaurant opening fully before September.
He said it will be tricky for businesses to take QR codes and contact details, but that everyone will adjust to it.
Mr Lavelle also said it would be "no bad thing" for restaurants to take a deposit to ensure that customers keep their bookings.
Ireland in a 'very different space' - McConalogue
Earlier, Minister for Agriculture, Food and the Marine Charlie McConalogue said the success of the vaccination programme has put the country in a very different space, but the Government will be guided by public health advice at all times.
Speaking on RTÉ's Morning Ireland, he said every step that is being taken is with the objective of keeping services open and the country will continue to go forward with a cautious, but certain approach.
The minister paid tribute to the tremendous engagement of the hospitality sector with the Government.
He also said he understands that certificates given to people who have been vaccinated in Northern Ireland, will be compatible with the app being used by pubs and restaurants in the Republic.
Vintners' Federation of Ireland CEO Padraig Cribben welcomed the changes that were made to the contact tracing element of the guidelines.
Speaking on the same programme, he said it had been almost 500 days since some businesses were able to open and while there is a lot of relief in the industry, there was also a lot of anxiety.
He urged people to work with publicans and stick to the public health guidelines, and said he did not accept that the spread of Covid-19 over Christmas was as a result of indoor dining and alcohol.
Mr Cribben added that he is still waiting to see the regulation in respect of vaccination certificates for people from the US, UK and Northern Ireland, and there is "quite an amount of work still to be done".
VFI President Paul Moynihan, who runs his family pub in Donard, Co Wicklow, said: "The reopening of indoor hospitality marks the end of an extremely challenging 16-month period that began on 15 March 2020 when all pubs were instructed to close in the face of the advancing pandemic.
"It's only fair that pubs with no outdoor space are allowed reopen. While outdoor trading has been a success for some publicans, reopening indoors gives businesses a chance to make ends meet."
The owner of Conway's Corner House in Drumshanbo, Co Leitrim, which has been closed since March last year, apart from two weeks last autumn, said he was looking forward to welcoming his customers back.
However, Joe Gunning said he has mixed feelings about some of the Government guidelines and it would be "better" if the Government came up with something that was easier to manage.
Meanwhile, the Restaurants Association of Ireland said it expects that a quarter of Irish businesses will not reopen for indoor dining immediately, because they are unwilling to operate under the latest guidelines.
Among them is Volpe Nera in Blackrock, Dublin. General manager Darren D'Arcy said they took the decision to keep just outdoor dining "a number of weeks ago".