2.3.3.5. Exceptions
Some commands don't have separate documentation, because they
are part of another command. cd, exit, logout and pwd are such exceptions. They are part of your shell
program and are called shell built-in commands. For
information about these, refer to the man or info page of your
shell. Most beginning Linux users have a Bash shell. See
Section 3.2.3.2 for more
about shells.
If you have been changing your original system configuration, it
might also be possible that man pages are still there, but not
visible because your shell environment has changed. In that case,
you will need to check the MANPATH
variable. How to do this is explained in
Section 7.2.1.2.
Some programs or packages only have a set of instructions or
references in the directory /usr/share/doc. See
Section 3.3.4 to display.
In the worst case, you may have removed the documentation from
your system by accident (hopefully by accident, because it is a
very bad idea to do this on purpose). In that case, first try to
make sure that there is really nothing appropriate left using a
search tool, read on in
Section 3.3.3. If so, you may
have to re-install the package that contains the command to which
the documentation applied, see
Section 7.5.