You can install Apache through APT or build it yourself from source code. The Apache source builds on just about any UNIX-like operating system and on Win32.
If you are about to install a new version of Apache, shut down the old server. Even if it’s unlikely that the old server will interfere with the installation procedure, shutting it down ensures that there will be no problems. If you do not know how to stop Apache, see the “Starting and Stopping Apache” section later in this chapter.