I added some variables to /etc/profile:
# Customisation by Nick for OpenNMS:
if ! echo $PATH | /bin/grep -q "/usr/java/jdk1.3.1/bin" ; then
    PATH="$PATH:/usr/java/jdk1.3.1/bin"
fi

if [ -z "$TOMCAT_HOME" ]; then
        TOMCAT_HOME=/var/tomcat4
fi


if [ -z "$JAVA_HOME" ]; then
        JAVA_HOME=/usr/java/jdk1.3.1
fi
export PATH TOMCAT_HOME JAVA_HOME

I did not install the postgresql with OpenNMS, as suggested by the
release notes.

I found that the automounter on /usr/local caused problems with many
things, including installation of jdk, tomcat,...

My solution was to add /usr/local /etc/auto.home to /etc/auto.master.
I made an empty /etc/auto.home (probably unnecessary), and restarted
autofs.  It's necessary to do this before installing the software.

I installed all the other packages except perl-DBI-Pg, since the RH
7.2 version looked recent enough.

There are a number of main things to watch out for:

1. /etc/profile.d/opennms.sh is horribly broken, and needs fixing to
   avoid stomping all over the PATH.
2. /etc/tomcat4/conf/tomcat4.conf has JAVA_HOME hardcoded to the wrong
   value.  Comment it out.
3. postgresql needs its configuration file
   /var/lib/pgsql/data/postgresql.conf changing; see the release
   notes under Red Hat 7.2 in
   http://www.opennms.org/users/docs/docs/html/release.html
4. The log files are in /opt/OpenNMS/logs and /var/tomcat4/logs.
5. I turned off nautilus.  The instructions for this are in the Gnome
   manual, and it was quite easy to do.