The /var directory was only part of my testing what was possible, but thank you for your comments. This was an interesting challenge, and more by luck than good judgement I found the settings you mentioned a few hours before your post.
If any other reader doesn't know (and I didn't at first), go to Sites and select the domain of interest. On its Options tab you will find a page on which you can enter a few of your own custom settings,
one of which is the open_basedir declaration. This field starts life with an ISPConfig default and it was this default upsetting my trial. After some experimenting, here's some things I discovered:
1. The default includes 10 directory paths. When I changed it to just the 3 I wanted everything I tested worked fine on a medium sized Drupal site with lots of symlinks - so I don't know why the default has so many paths. Legacy thing that hasn't been reviewed lately perhaps?
2. If you delete all the defaults, maybe as part of your own testing, be aware that ISPConfig will reinstate all 10 default paths again. I don't like any software being that dictatorial, but the key here is that it will only reinstate the defaults if you leave the field empty, so put something in there to suppress this unwelcome feature.
And the reason I described it as a challenge to find is because of an odd thing. Whatever appears in this field does not seem to be written to any standard apache conf file that I could find - hence my original post. The odd thing is that this Options page includes a panel for you to enter your own Apache Directives. Anything you add here is written out to the vhost configuration file for this domain.
Yes, it's odd that one of your custom fields finds its way into a standard config file but another doesn't - not just odd, but confusingly inconsistent. Perhaps it might be good if all the user changeable fields on this Options page could be treated in a consistent manner - preferrably all written out to config files.
Last edited by markshorter; 22nd January 2013 at 06:11.