Slow FTP running ProFTPD on Parallels for Mac

My current web development server is a Debian GNU/Linux 5.0.5 machine running under Parallels for Mac (which I’m trialling right now). It was all working great until I tried to access the FTP server running on it from my Macbook Pro over the Airport. It worked but maaaaan was it slow! The Debian server is running ProFTPD, one of the many free FTP server options out there.

Thankfully the solution to the slow FTP access is very simple.  There isn’t a DNS server running here as it’s not something I need for local development (although it would’ve solved this problem, too).  The problem was caused by reverse DNS lookups failing – this is something ProFTPD has enabled by default if you use apt-get install proftpd to install ProFTPD.

Turn off Reverse DNS lookups

Turning off reverse DNS lookups in ProFTPD is as simple as checking /etc/proftpd/proftpd.conf for the following lines.

  • IdentLookups off
  • UseReverseDNS off

The IdentLookups line may already be set to ‘off’ – that’s fine and you can leave it that way.  The UseReverseDNS value may not exist at all – if that’s the case just added it to the proftpd.conf file and set the value to ‘off’ by following the format of the other configuration lines:

UseReverseDNS in ProFTPD

Restart ProFTPD

While logged in with appropriate privileges the following command (from the Terminal) should restart ProFTPD.  Rebooting your Debian GNU/Linux server will also restart ProFTPD but the whole point of running Linux is so you hardly ever have to reboot … right?

Restart ProFTPD:

/etc/init.d/proftpd restart

Obviously your own configuration may differ so only follow these instructions if it won’t break everything – be warned!