Cancel a command
Ctrl+U, Ctrl+X, or @
Change the working directory to /usr
cd /usr
Change the working directory back to your home directory
cd
Copy a file
cp oldfile newfile
Copy a file to another directory
cp oldfile dirname
Copy a bunch of files (e.g. filename1, filename2, ...) to another directory
cp filename* dirname
Copy all the files in this directory and in all its subdirectories
cp -r * newdir
Erase a file
rm filename
Rename a file
mv oldname newname
Move a file to another directory
mv oldfile dirname
List filenames
ls
List filenames with sizes and dates
ls -l
List hidden files too
ls -al
List files and pause when screen is full
ls | more
Look at a text file
cat filename
Look at a long text file
more filename
Make a new link (name) for a file
ln oldname newname
Make new links (names) for files in a directory
ln dirname/* newdir
Combine two files
cat file1 file2 > newfile
Compare two files
diff file1 file2
Look at the manual page for the ls command
man ls
Change your password
passwd