Q) Help! Does vsftpd support virtual users?
A) Yes, via PAM integration. Set "guest_enable=YES" in /etc/vsftpd.conf. This
has the effect of mapping every non-anonymous successful login to the local
username specified in "guest_username". Then, use PAM and (e.g.) its pam_userdb
module to provide authentication against an external (i.e. non-/etc/passwd)
repository of users.
Note - currently there is a restriction that with guest_enable enabled, local
users also get mapped to guest_username.
There is an example of virtual users setup in the "EXAMPLE" directory.