On Linux, I did it like this - works fine.

1. Stop crowd
2. useradd -c "Atlassian Crowd" crowd
3. chown -R crowd:root /opt/atlassian/crowd
4. chown -R crowd:root /var/atlassian/crowd
5. find /opt/atlassian/crowd -type d -exec chmod 750 {} \;
6. cd /opt/atlassian/crowd/atlassian-crowd-2.7.0
7. cp start_crowd.sh ORIG_start_crowd.sh
8. cp stop_crowd.sh ORIG_stop_crowd.sh

9. Edit start_crowd.sh. Replace with:
#!/bin/sh

PRGDIR=`dirname "$0"`

su -m crowd -c "$PRGDIR/apache-tomcat/bin/startup.sh $@"

10. Edit stop_crowd.sh
#!/bin/sh
PRGDIR=`dirname "$0"`
su -m crowd -c "$PRGDIR/apache-tomcat/bin/shutdown.sh $@"

11.Start crowd using start_crowd.sh

That's it. Easy.

I have updated documentation so that it is possible to run Crowd as an unprivileged user.

Unfortunately achieving this out of the box would require a dedicated installer, which we would have to maintain for multiple operating systems and variations of operating systems. I would suggest creating a new issue for a dedicated installer if this feature is important for you.

I have updated the permission change script in the Running Crowd as an Unprivileged User section at http://confluence.atlassian.com/display/CROWD/Setting+Crowd+to+Run+Automatically+and+Use+an+Unprivileged+System+User+on+UNIX to work correctly with the latest Crowd version.

The permission change script alone is not enough to run Crowd automatically as a specified user. In order to do that, a start-up script should be created using the instructions in Getting Crowd to Start Automatically section at http://confluence.atlassian.com/display/CROWD/Setting+Crowd+to+Run+Automatically+and+Use+an+Unprivileged+System+User+on+UNIX.

Olli has updated the page. See diff:
http://confluence.atlassian.com/pages/diffpages.action?pageId=211649189&originalId=236585785

Thanks Olli!

Hallo Martijn
Thanks for pointing this out! I've asked the development team to take a look at that page.
Cheers, Sarah