Two ways of accomplishing this come to mind.
First, you could construct/use a separate AuthUserFile
, and in that file, you define an entry for your user, and that user the UID of 0. This will effectively make your user a root user -- but only for FTP logins. Note that if you use this approach, you will also need to allow root logins (which ProFTPD rejects by default) using:
RootLogin on
in your proftpd.conf
.
Alternatively, you could use the UserOwner
directive, and specify that user "root" should be used, but only in designated directories. For example:
<Directory /path/to/some/dir>
# In this directory, file uploads/writes happen as the root user
UserOwner root
</Directory>
This second approach can be used with all of your FTP clients, rather than just specific users, but can be restricted to specific users if need be.
Hope this helps!