@Domhnall Currie Jeremy Davis 

This post related to the v18 (not the 18  rc1)

You might want to change this config as it is a bit 'misconfigured'.  When you work "fast" in redmin. You get an error in your Browser, and hit the anti DOS protection.  Happend many times here.

Log reads as: May 16 17:26:11 redmine mod_evasive[1098]: Couldn't open logfile /var/log/apache2/dos-xxx.xxx.xxx.xxx: Permission denied

Have solved this by editing this file:

/etc/apache2/mods-available/evasive.conf

<IfModule mod_evasive20.c>
    #DOSHashTableSize    3097
    #DOSPageCount        2
    #DOSSiteCount        50
    #DOSPageInterval     1
    #DOSSiteInterval     1
    #DOSBlockingPeriod   10
    #DOSEmailNotify      you@yourdomain.com
    #DOSSystemCommand    "su - someuser -c '/sbin/... %s ...'"
    DOSLogDir           "/var/log/apache2"
</IfModule>

The # says those settings are not configured, so by default it uses the default ones.

For my Local lan Usage i Added; DosWhiteList IPADRESS, and that solved the issue for me. 

Restart Apache to apply changes.

However i think this should be configured correctly in the ISO so new uses won't encounter this, A bit loser restricions then default.

Also, there is an issue with Kernal values, happening every startup, would be nice if that could be solved to:
May 16 11:51:51 redmine systemd[1]: Failed to start systemd-sysctl.service - Apply Kernel Variables.
May 16 11:51:51 redmine systemd-sysctl[390]: Couldn't write '"1 4 1 7"' to 'kernel/printk': Invalid argument
May 16 11:51:50 redmine systemd-sysctl[363]: Couldn't write '"1 4 1 7"' to 'kernel/printk': Invalid argument
May 16 11:51:50 redmine systemd[1]: Failed to start systemd-sysctl.service - Apply Kernel Variables.

However not found a solutions for that Yet.

This weekend i will test the RC1.. Then i will write also a migration document how to migrate the data to a new server.