A2enmod

a2enmod

is a shell script provided on Debian, and Debian-based Linux systems for quickly enabling extension modules of the Apache web server.

From the manual: a2enmod is a script that enables the specified module within the apache2 configuration. It does this by creating symlinks within /etc/apache2/mods-enabled. Likewise, a2dismod disables a module by removing those symlinks. It is not an error to enable a module which is already enabled, or to disable one which is already disabled.

If you've never looked at a shell script before, and tutorials seem too basic, then here is an example of a more complete shell script:

/usr/sbin/a2enmod

#!/bin/sh -e

SYSCONFDIR='/etc/apache2'

if [ -z $1 ]; then
        echo "Which module would you like to enable?"
        echo -n "Your choices are: "
        ls /etc/apache2/mods-available/*.load | \
        sed -e "s,$SYSCONFDIR/mods-available/,,g" | sed -e 's/\.load$//g;' | xargs echo
        echo -n "Module name? "
        read MODNAME
else
        MODNAME=$1
fi

#figure out if we are on a prefork or threaded mpm
if [ -x /usr/sbin/apache2 ]; then
        PREFORK=`/usr/sbin/apache2 -l | grep -E 'prefork|itk' || true`
fi

if [ "$MODNAME" = "cgi" ] && [ -z $PREFORK ]; then
        MODNAME="cgid"
        echo "Your MPM seems to be threaded. Selecting cgid instead of cgi."
fi

if [ -e $SYSCONFDIR/mods-enabled/$MODNAME.load ]; then
        echo "This module is already enabled!"
        exit 0
fi

if ! [ -e $SYSCONFDIR/mods-available/$MODNAME.load ]; then
        echo "This module does not exist!" >&2
        exit 1
fi

DEPENDS=`grep "# Depends:" $SYSCONFDIR/mods-available/$MODNAME.load|cut -f2 -d:`
if [ ! -z "$DEPENDS" ]; then
        for i in $DEPENDS; do
                echo "Enabling $i as a dependency"
                /usr/sbin/a2enmod "$i";
        done
fi