My wife's PC, running CentOS 6, suddenly quit connecting to the Net. Autodidact that I am, I fumbled with all the hard- and software I could find or dared try, but did no good.
So we lugged it down to our favorite shop. While there, she bought a laptop, and asked them to install CentOS and copy all her files from the PC (including two books she's written and is trying to market).
They called to ask whether I wanted to specify a username & password, or just use their default dummies. I chose the dummies -- and realized in the night that I've never changed a username before.
I think, repeat think, I could hack it with mv and chown, but I had enough sense to try a few manuals and duckduckgo searches. Those eventually led me to usermod, and I took a look at 'man usermod'. It seems to be fairly powerful -- and therefore dangerous as well as apposite.
So I ask here: are there caveats, gotchas, and/or other entities of their ilk that I need be wary of?