There are over 300 staffers Trump doesn't choose when he enters the White House - and they're the ones he'll see every day

On Friday, January 20, Donald Trump will be inaugurated as the 45th President of the US.

In preparation for this day, Trump and his transition team have been working expeditiously to fill the roughly 4,000 positions that will be vacant when the Obama administration leaves.

But there are a few lesser-known staff positions that Trump will not choose: White House permanent residence staffers.

These are the butlers, chefs, valets, groundskeepers, and more that keep the White House running smoothly from day to day. They prepare state dinner banquet rooms, feed the first family, and are available for any request, small or large, that may arise.

And unlike policy staff, they aren't replaced when a new first family enters the White House. In fact, some stay for decades, assisting one president to the next. Eugene Allen, for example, was a butler from 1952 to 1986, and was the inspiration for the 2013 film "The Butler."

The group is characteristically tight-lipped about what it's like to work for the president and their family. The clearest glimpse into the life of a residence staffer comes from the 2015 book "The Residence: Inside the Private World of the White House," by Kate Brower.

Brower interviewed more than 100 (primarily former) staff members for her book, noting how rare it was to get such intimate details about the job. "There's an unwritten rule that they stay in the background," Brower told The Washington Post in 2015. "Unlike a lot of people in Washington, they don't talk about their jobs," she said.

There are 96 full-time and 250 part-time residence staffers, according to Bower. They work throughout the 132-room White House, which contains 28 different fireplaces, eight staircases, six floors, and two below-ground levels.

And their jobs are incredibly demanding, a former White House executive chef explained in the book.

"You work for the same people every day, you don't have any personal life, family, social life, you work what we used to call 'White House flex time'-that is, you choose any eighty-five hours you want to work each week," he said.

Still, they are incredibly devoted to the families in the White House, regardless of the candidate from whom they voted.

"I was an independent Republicrat," former White House usher Worthington White told Brower in a Vanity Fair article published last April. "I would say I voted for the president, no matter who it was," White, who worked as an usher from 1980 to 2012, said.

And some of their toughest work comes on Friday, when they will have about five or six hours to completely turn over the White House for the incoming president. Michelle and Barack Obama will head to the the inauguration and at 12:00 p.m., the White House is no longer their home.

Still, being a permanent staffer at the White House doesn't mean that there is no risk of being replaced. Their employment is still at the discretion of the president.

Trump's team may be willing to shake up long-term staff. For example, they dismissed inauguration announcer Charles Brotman earlier in January via email.

"I looked at at my email, then I got the shock of my life," Brotman told CNN. "I felt like Muhammad Ali had hit me in the stomach."

Brotman has been the announcer for the past 11 presidents, at every inauguration parade since 1957.

Some staffers apparently worried in April about the fate of their jobs should Trump win the election, according to Brower's Vanity Fair article. Former top pastry chef Roland Mesnier told Brower that he would be nervous if he was still working there.

"If the Donald makes it to the White House I think there's going to be a lot of changes," Mesnier, who served five presidents from Jimmy Carter to George W. Bush, said. "I think the White House as we know it and the kitchen will be totally different."