How would you search the entire file system for a file named today.odt?

Answer 1

correction: This is in Linux.

Answer 2

Try
find / today.odt
it will search all directories under root, including links.
For more options, type
man find
to read about the command find on Linux (man for manual).

Answer 3

Would this also work: find / -name "today.odt " -print

Answer 4

Yes it would.
The quotes are used to delimit regular expressions, for example if you want to find all files ending with .h or .c, you would type in
find / "*.[ch]" -print
If you don't put any metacharacters for regular expressions, it will be interpreted as is.