As octal says, to a degree, it depends upon which Linux you're using. But there will almost certainly be a few in your repositories.
I just did a quick search in my Debian repositories and came up with about six possibilities. keepassx seems to be one of the more popular ones, which suggests to me it's probably easy to use.
I can't personally verify that, as I don't use one. But in all honesty, it's something I've been thinking about for a while. And having had my credit card flagged as stolen recently (even though I'm still in possession of it), did make me wonder if the passwords I was using were as safe as I thought. Complex passwords with a master key manager, would make sense, unless the master gets compromised.
Security (both on and off-line) is a mind-blowing exercise and one if you're not careful, one can become over-paranoid about. That's certainly not dismissing security out of hand, just simply trying to get a reasonable perspective on it.