In ubuntu 12.1 unable to locate package tree
 

From the bash shell I tried to use the tree command and was advised to enter this command "sudo apt-get install tree" when I tried I got this message "E: Unable to locate package tree". I'm running Ubuntu from a thumb drive I haven't installed it, could that be the reason for the problem?

Is it a Live session? If it is why are you trying to locate a package tree?

Also there is no such thing as Ubuntu 12.1. Ubuntu has .04 and .10 releases.

This error happens when the package is not part of any repository list installed on the distro, you need to add a repository that has the tree package, update the install list, then rerun the apt-get command to install the package.

Ok then all I have to do is seek out this install list and find out how to update it.

Nope, if you have not installed it, as you say in your OP, then you are running a live session and it doesn't matter if you are trying to update or anything the next time you start the Live session it will be gone. What you need to do is actually install Ubuntu and then work from there.

I ended up installing and I noticed the checkbox for updating so I did now all is working as I'd hoped. Thanks.