みんなやってると思うけど、日本語のブログとかgoogleさんに聞いてもヒットしなかったので備忘録です。
#nano etc/apache2/mods-available/alias.conf
<IfModule alias_module>
#
# Aliases: Add here as many aliases as you need (with no limit). The format is
# Alias fakename realname
#
# Note that if you include a trailing / on fakename then the server will
# require it to be present in the URL. So "/icons" isn't aliased in this
# example, only "/icons/". If the fakename is slash-terminated, then the
# realname must also be slash terminated, and if the fakename omits the
# trailing slash, the realname must also omit it.
#
# We include the /icons/ alias for FancyIndexed directory listings. If
# you do not use FancyIndexing, you may comment this out.
#
#Alias /icons/ "/usr/share/apache2/icons/" ※コメントアウト
#<Directory "/usr/share/apache2/icons"> ※念のためIndexesを-Indexesにしといてコメントアウト
# Options -Indexes MultiViews
# AllowOverride None
# Order allow,deny
# Allow from all
#</Directory>
</IfModule>