FTP

To provide an FTP service, Plesk uses the ProFTPD FTP server. Plesk
includes the following two packages:

• psa-proftpd which contains the main component.
• psa-proftpd-xinetd which contains patches and configurations to
  work with xinetd .

FTP Startup

The ProFTPD is started by the xinetd every time the server receives
an FTP request. In the case of authorized access, the FTP service is
started on behalf of the user whose request is to be processed. For
anonymous users, the service is started with the UID of the psaftp
user.

FTP Users

The FTP server allows for document access of authenticated users that
are listed in the /etc/passwd and /etc/shadow files. The first
one defines the user name, group membership, home directory, and active
access method. The second one stores password hash values. Let us look
at FTP users created during the virtual hosting setup procedure. The
following are some /etc/passwd lines defining FTP user parameters.

# grep ftp /etc/passwd
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
psaftp:x:2524:2522:anonftp psa user:/:/bin/false
ftpuser:x:10006:10001::/var/www/vhosts/domain.tst:/bin/false
ftpuser55:x:10010:10001::/var/www/vhosts/domainXX.tst:/bin/false

The first two lines are default FTP users. The psaftp is the user on
behalf of whom the FTP service is started when the Plesk server receives
an anonymous FTP request.

The last two lines define typical FTP users. The group ID 10001
refers to the psacln group that contains FTP users. The psacln is added
to the /etc/ftpchroot file. For every FTP user logged into the
Plesk, a “chroot” procedure is executed, which ensures the user cannot
see files owned by other users.

Plesk stores all FTP user accounts in a single database; therefore, FTP
users cannot have the same names even if they are created for…