A 'standard' deb-based install of DTC breaks pure ftp on Debian. This is a known bug, and following is how to fix it under Debian 4. It assumes you've already followed teh Debian Express Setup.
First, make sure you have src repositories in your /etc/apt/sources.list
(in general, the same as the normal repositories, but with deb-src not deb at the beginning of the line).
First, update your apt-get db and make a directory for the work, and cd into it:
apt-get update
mkdir pureftp
cd pureftp
Get the source for the package (downloaded to current directory) then cd into its directory, then the debian directory
apt-get source pure-ftpd
cd pure-ftpd-1.0.21/
cd debian
Edit the `rules` file, and add `--without-capabilites` to the end of the line full of other --xxxxxxx-xxx (replace `vim` with your favourite text editor).
vim rules
Build the dependencies:
apt-get build-dep pure-ftpd
wait
wait some more
Build the ftp server
dpkg-buildpackage pure-ftpd
wait
ditto
cd back to the directory you first got the source into, and install the appropriae deb file
cd ..
cd ..
dpkg -i pure-ftpd-mysql_1.0.21-8_amd64.deb
