Just edit the file /etc/proftpd/proftpd.conf and add these 2 lines:

UseReverseDNS off
IdentLookups off

Lesson learned: I should read manuals more often.

First you could try to install the default Debian package to check whether you need to recompile PureFTPD. This can be done via:

apt-get install pure-ftpd-common pure-ftpd

The following steps are needed to recompile the package with the necessary options to make it run on a virtual server. You only need to do these steps if you find the following message in your syslog when trying to connect to the ftp server:

 pure-ftpd: (?@?) [ERROR] Unable to switch capabilities : Operation not permitted

In that case, make sure that you have enabled the Debian source repositories in your /etc/apt/sources.list and fetch the source files via:

apt-get source pure-ftpd

The source files have now been downloaded to your current directory. There should now some new files and a directory pure-ftpd-1.0.21. Enter this directory and edit the file debian/rules you should change the line starting with optflags and add --without-capabilities to that line, so that it looks like:

optflags=--with-everything --with-largefile --with-pam --with-privsep --with-tls --without-capabilities

Now grab the dependencies needed to build the source and compile the Debian installation package:

apt-get build-dep pure-ftpd
dpkg-buildpackage -uc -b

The resulting Debian package should now have been built without errors and you can install it via:

dpkg -i ../pure-ftpd_1.0.1-8_i386.deb

The filename of the package might vary depending on the current patch level in the Debian repository.

When installing the package you will be asked whether to use a chrooted setup which you should do and if you prefer a standalone installation or inetd-based operation. For low volume sites I would prefer the inetd installation.

Now let’s get on to the configuration of PureFTPD. I prefer a setup using virtual users which are mapped to a central user account on the server. So I usually create a new account without a shell or home directory which belongs to the Apache user group to have access to hosted webs:

useradd -g www-data -d /dev/null -s /bin/false ftpuser

You can also use the existing user www-data instead. In that case you need to enable that user account (on Debian/Ubuntu it has the user id 33) in the PureFTP config:

echo 33 > /etc/pure-ftpd/conf/MinUID

The configuration of PureFTP is done via distinct files in the directory /etc/pure-ftpd/conf. Each file contains a single configuration setting and we can setup a decent configuration with the following commands:

cd /etc/pure-ftpd/conf
echo yes > ChrootEveryone
echo no > PAMAuthentication
echo no > UnixAuthentication
echo 1 > TLS
cd ../auth
ln -s ../conf/PureDB 50pure

With the above settings we disable all authentication methods except the internal PureFTPD user database. We also lock down each user into a chroot-environment and enable secure authentication via TLS. PureFTPD excepts a certificate in the file /etc/ssl/private/pure-ftpd.pem. You could copy your apache certificate to that file, or generate a new one via:

openssl req -new -x509 -days 4312 -nodes -keyout /etc/ssl/private/pure-ftpd.pem -out /etc/ssl/private/pure-ftpd.pem

The user administration and setup is now done with the PureFTPD tool pure-pw. You can add a new user via:

pure-pw useradd myusername -u ftpuser -d /path/to/homedir

The above command will ask you for a password and register the user which is mapped to the system user ftpuser within PureFTPD. Every time you modify the user database you need to rebuild the PureFTPD user configuration via:

pure-pw mkdb

Now you should be able to connect to your server with secure authorization with the newly created user.