Why do the Snort logs appear to be empty

So I was following this guide on how to install Snort, Barnyard 2 and the like.

I've set up Snort so it would run automatically, by editing the rc.local file:

ifconfig eth1 up

/usr/local/snort/bin/snort -D -u snort -g snort \
-c /usr/local/snort/etc/snort.conf -i eth1
/usr/local/bin/barnyard2 -c /usr/local/snort/etc/barnyard2.conf \
-d /var/log/snort \
-f snort.u2 \
-w /var/log/snort/barnyard2.waldo \
-D

And I then restarted the computer. Snort was able to run and detect the attack, but the log files (including barnyard2.waldo) remained blank, even if a new log entry was created for each attack.

I'm not sure what went wrong here, since it's supposed to log any attacks and store it in the log directory, right?

Then, I tried changing the parameter to:

    /usr/local/snort/bin/snort -D -b -u snort -g snort \
-c /usr/local/snort/etc/snort.conf -i eth1

And when I checked the log file, there are two log files, one in u2 and another in tcpdump format, but they're both blank and is approximately 0 bytes.

So I thought I'd run it from the console to see if it would work from there, using this command:

/usr/local/snort/bin/snort -A full -u snort -g snort \

-c /usr/local/snort/etc/snort.conf -i eth1

and I then checked the log file to see if it would log the attack, and it still doesn't.