Lubuntu 14.04 was working really great. . .until I messed up and had to do a complete fresh reinstall.

Now I receive error messages when I input commands into the Terminal, even after immediately completing the fresh install.

For example I type:

sudo leafpad ?/etc/default/

or sudo leafpad ?/etc/default/grub

I get:

sudo: leafpad: command not found

I type:

sudo update-initramfs ?-u

or sudo update-grub

I get:

sudo: update-initramfs: command not found

or sudo: update-grub: command not found

If I use the command mkdir I get:

mkdir: command not found

I also get this same exact error message, command not found, with sudo apt-get and wget

In other words I can't do anything that I was able to do when inputting commands into the terminal.

So I cannot add any repositories or update anything at all. I am not really sure what is causing the problem(s).

It appeared to me that Lubuntu installed and booted up OK. However just as soon as I enter anything into the Terminal I immediately get the above error messages. I have tried to do the reinstall three times, same error messages.

If anyone can suggest any fixes I would really appreciate it very much. Thank you!