I'm working on a new FTP server with Very Simple FTP (vsftp) and wondering how exactly the anonymous user works in vsftp. The Archwiki doesn't seem to give a good explanation of what it is, only that it can be used for login. Similarly,
man vsftpd.conf doesn't explain it. Both seem to assume a working knowledge of this "anonymous user."
I got the FTP server working with the anonymous login (and had to guess username/password until I found out that the username is "anonymous" and password is arbitrary -- is this documented somewhere?), so my question is not about how to set it up (which the manuals explain well) but rather what the anonymous user is.
It doesn't seem to the
ftp user (and not in the
ftp group) which was my initial guess, because changing the permissions of the ftp directory to something like
550 doesn't allow the anonymous user to view it anymore. Similarly, options like
anon_other_write_enable can change its permissions.
Is it a true Linux user?
vsftp doesn't show up in
/etc/passwd, so I would guess not. If not, what is it and how does it work?