Can I change the shortname only?

[Gabri]

Can I change the shortname only without changing the home folder name?

I found a way but I'm not sure about it http://osxdaily.com/2011/05/20/change-short-name-user-mac-os-x/

 

[robgendreau]

If you're "not sure" don't do it. It can change permissions and access to stuff that's probably pretty critical to you, so unless you understand the implications of the instructions you've cited I would leave it alone. Apple recommends the names match, and unless you know why you shouldn't change that.