If you plan to write or edit any documentation with emacs, install a customized emacs configuration file with DocBook commands in the skeleton directory, so it will be used for all new users. The file also fixes the backspace -> help mis-mapping that often occurs in terminals.
cp /tmp/openacs-5.9.0/packages/acs-core-docs/www/files/emacs.txt /etc/skel/.emacscp: overwrite `/etc/skel/.emacs'?
apt-get install psgml
Note: The new nxml mode for emacs, when used in combination with psgml, provides a pretty good set of functionality that makes DocBook editing much less painless. In particular, nxml does syntax testing in real-time so that you can see syntax errors immediately instead of in the output of the xsltproc hours or days later. For Debian,
apt-get install nxml.