Question: I forgot my password and I decided to reinstall Ubuntu with the last version. Now, how can I get rid of the old version? I use VM Virtualbox as emulator.

I must say that I am and old COBOL developer and everything is new here for me.

Answer: 
I always use `Ctrl`+`Shift`+`C` and `Ctrl`+`Shift`+`V` to copy and paste in my (non tmux) terminal.  

You can change these keyboard shortcuts in the keyboard preferences of your (non-tmux) terminal.

If however you want to keep using tmux you can also change the keyboard shortcuts of tmux by adding commands to `~/.tmux.conf`. simply add the following in that file:

```
bind-key -n [shortcut. for example Ctrl+v is C-v] [what you want to do. for example 'new-window' etc]

```

It will look like this

```
bind-key -n C-t new-window

```

You don't need the command prefix key to execute the commands in the `~/.tmux.conf` file.

For more info about the things available for `~/.tmux.conf` check [this link](http://www.hamvocke.com/blog/a-guide-to-customizing-your-tmux-conf/)

Very rudimentary copying and pasting can be done using this however for a bit more usefulness I recommend using a Vim-style copy/paste config.  

Enabling a Vim-style of copy/paste can be done with [this config file](http://jasonwryan.com/blog/2011/06/07/copy-and-paste-in-tmux/) or [another config file](https://gist.github.com/justin808/9493723). These do however require the use of the prefix key.  

Someone even made a [tmux extension](https://github.com/tmux-plugins/tmux-yank) to simplify the copy/paste action to the system clipboard in tmux. It might be worth a look.

If you want an alternative for Tmux you might try dvtm (`sudo apt-get install dvtm dtach`). I haven't used it myself but it looks like it has similar options.
It can be done with emacs.

1. Open emacs
2. `Alt`-`X` + `term`: opens a terminal in a new emacs buffer
3. `Ctrl`-`C`+`Ctrl`-`J`: enter line mode (more details on the modes below)
4. Select the desired text
5. `Alt`-`W`: copy the text
6. `Ctrl`-`C`+`Ctrl`-`K`: go back to char mode
7. `Ctrl`-`Y`: paste

**Remarks on line-mode and char-mode**

In char-mode, each character you type is sent to the terminal (like in any terminal) and most emacs shortcuts are disabled (to enable terminal shortcuts). In particular, don't be surprised if shortcuts to change the buffer do not work. To change the buffer, you must first enter line mode. In line mode emacs behave like in a normal emacs buffer. More details [here](https://www.masteringemacs.org/article/running-shells-in-emacs-overview).