I'm running Ubuntu 20 and have installed Pure-FTPd. When I SFTP on port 22 with FileZilla the log shows "We claim SSH-2.0 FileZilla ... Remote version SSH-2.0 OpenSSH..." On login with FileZilla, auth.log shows an ssh2 connection.
I'm confused about why I don't see something like "Welcome to Pure-FTPd [privsep] [TLS]". The service is running. I haven't read anywhere that we need to do anything to tell OpenSSH to hand over SFTP requests to another process. I'm guessing that something else needs to be set under /etc/ssh/sshd_config.d ?
It doesn't look like the PureFTPd service is processing these requests at all, with its own user db or other settings.
Thanks.
SSHD runs on port 22 by default. There is no handing over, when a process is started and a port is allocated, that port belongs to that application until it stops running or is terminated.
You need to set a different port for sftp, or disable sshd.
To test this quickly, simply kill sshd and start ftpd.
ps -ef | grep sshd
kill -9
Where is the process id of the sshd process.