ResolutionFirst, the Plesk Debian repository should be added to the sources list. The link to the Plesk Debian repository is http://autoinstall.plesk.com/.
Open it in a web browser to see which Plesk versions are available.
Then add the repository record for your desired Plesk version into "/etc/apt/sources.list." For example, you would use the below line for Plesk 9.5.3 Etch:
deb http://autoinstall.plesk.com/PSA_9.5.3/ etch all
Next, update the cache packages list:
# apt-get update
Now you can install Plesk. For example, use the below line to install the base Plesk package:
# apt-get install psa