Aborted install

Plone Unified Installer version 5.0b3 on:

Debian 8.1
i5
Hard disk space – lots
16 GB RAM

The installer was stopping and returning missing dependency errors all of which where easily fixed. However, after fixing libjpeg-dev the error was: /opt/plone/zinstance already exists; aborting install which required me to run the rm command (see below).

#******************* run install

Root install method chosen. Will install for use by users:
ZEO & Client Daemons: plone_daemon
Code Resources & buildout: plone_buildout

Detailed installation log being written to /home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller/install.log
Installing Plone 5.0b3 at /opt/plone

Using useradd and groupadd to create users and groups.
plone_group already exists; no need to create it.
User plone_daemon already exists. No need to create it.
Adding user plone_daemon to group plone_group.
User plone_buildout already exists. No need to create it.
Adding user plone_buildout to group plone_group.
Instance target /opt/plone/zinstance already exists; aborting install.
root@Death-Star:/home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller#
root@Death-Star:/home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller#
root@Death-Star:/home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller#
root@Death-Star:/home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller#
root@Death-Star:/home/kevin/Downloads/Plone-5.0b3-UnifiedInstaller# rm -rf /opt/plone

#*******************

IMHO might be something that shouldn't happen. Just saying.

Do you mean the part about not overwriting your installation? That's arguable. I'd much rather have to do it myself than to risk having the installer do it automatically. It could be that you're running the installer and have given it the wrong target directory.