It’s a career reboot that requires more than just a new pair of boots.

In 2008, Darius Rucker, formerly of soft-rock band Hootie & the Blowfish, released a twangy solo album. Today, he’s enjoying another summer on the road as an A-list country star.

In April, R&B great Lionel Richie scored his first No. 1 album since the Reagan administration with “Tuskegee,” a batch of his vintage hits reimagined as duets with country A-listers, including Rucker. It’s currently the highest-selling album released in 2012.

But if it looks as if Nashville’s tent is getting bigger, look again.

“The genre is not friendly to newcomers,” says Aaron Lewis, the latest refugee to set his sights on the country charts. After 16 years spent fronting the multi-platinum rock group Staind, Lewis released his first solo EP last year, a collection of country tunes called “Town Line.”

Supportive Staind fans quickly pushed “Town Line” to the top of Billboard’s country albums chart. Its first single, “Country Boy,” featured guest turns from country royals George Jones and Charlie Daniels and was nominated for prizes at the CMT and ACM awards.

But radio wouldn’t touch it. Dyed-in-the-denim country fans kept their distance.

“It hasn’t been easy in any way, shape or form,” says Lewis. “The biggest thing that I run up against is, ‘He’s not country.’ … It’s frustrating.”

Alison Bonaguro, who writes about country music for CMT.com, says it’s typical. Despite the unlikely triumphs of Rucker and Richie, the industry isn’t rolling out red carpets for any old artist hoping to hit reset in Nashville.

“It’s not as hospitable as you’d think,” Bonaguro says. “I think there’s a little clique-iness, a feeling that it’s almost not fair that there’s so many people wanting a piece of that pie.”

If Lewis wants to score a slice, his upcoming album, “The Road,” due Sept. 11, will have to resonate with fans and radio programmers the way Rucker’s 2008 solo debut did.

Other outsiders haven’t had the same good luck. In 2008, pop singer Jessica Simpson’s country debut, “Do You Know,” debuted at No. 1 but quickly vanished from the airwaves. She left her label a year later.

Meantime, Broadway singer Laura Bell Bundy has fared even worse. Her 2010 country disc, “Achin’ and Shakin’,” failed to make a noticeable dent on the charts.

That might be because, fabricated or not, credibility is still a leading virtue in country music. During his promotional tour for “Tuskegee,” even Richie had to prove his bona fides.

“I was born in the country, country radio was radio when I was growing up,” the Alabama native told CNN’s Piers Morgan in an interview televised in March. “I’m just going back to claim my kids.”

Lewis has a similar story. The 40-year-old singer grew up in Massachusetts but spent his summers listening to country music with his grandfather. For him, this isn’t a reinvention so much as rediscovery of what’s always been there.

“I write music on an acoustic guitar,” Lewis says, citing “It’s Been Awhile” and other slow-churning hits he penned for Staind. “If I had brought those same exact songs to Nashville and colored them country, they would be right in line and right on point with the stuff I’m working on now.”

But even if he brings new ears to the genre, the blanket skepticism that so many country fans reserve for outsiders remains a huge obstacle.

It all reminds Bonaguro of “Gone Country,” a 1994 song by Alan Jackson that takes a jab at musicians looking for a shortcut to stardom by way of Music City:

He’s gone country / Look at them boots.

He’s gone country / Oh, back to his roots.

“That’s an old song, but God, it’s still so true,” says Bonaguro. “For some people in the industry, it’s a philosophy.”