I, too, wondered how to enable GZIP compression in Apache on Debian (Ubuntu 10.04). Here are my findings.
1.) Add directives to Apache configuration, e.g., to /etc/apache2/httpd.conf
Note: For versions of Apache <= 2.0.48, read the comments carefully; it is necessary to un-comment the last BrowserMatch directive.
Note: This above block comes straight from the Apache documentation.
# Insert filter
# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html
# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0 no-gzip
# MSIE masquerades as Netscape, but it is fine
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won't work. You can use the following
# workaround to get the desired effect:
# BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html
# Don't compress images
SetEnvIfNoCase Request_URI \
\.(?:gif|jpe?g|png)$ no-gzip dont-vary
# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary
2.) Enable the required modules; both mod_deflate
are required. (mod_headers is required for the last directive in the above snippet.)
# a2enmod deflate
# a2enmod headers
# service apache2 restart
Pages should now be served with GZIP compression. There are a number of utilities with which to test, e.g., http://www.whatsmyip.org/http-compression-test/