I already used SFTP (port 23) on a Debian 13 server. For this to work I had to disable FTPS in /etc/proftpd.conf (TLSEngine off).
For the Server SSL Certificate I used the ECDSA-256 (the default of ACME?)
After updating to the latest versions I ran into 2 problems, both causing ProFTPd not to be able to start.
○ proftpd.service - ProFTPD FTP Server
Loaded: loaded (/etc/systemd/system/proftpd.service; enabled; preset: enabled)
Active: inactive (dead) since Wed 2026-11-11 16:50:00 CET; 32s ago
Duration: 73ms
Invocation: 60ea87c2b4ec4d478c47b77bbc99a731
Process: 198634 ExecStartPre=/usr/sbin/proftpd --configtest (code=exited, status=0/SUCCESS)
Process: 198636 ExecStart=/usr/sbin/proftpd --nodaemon $PROFTPD_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 198636 (code=exited, status=0/SUCCESS)
Mem peak: 2.6M
CPU: 82ms
Nov 11 16:50:00 daintern systemd[1]: Starting proftpd.service - ProFTPD FTP Server...
Nov 11 16:50:00 daintern proftpd[198634]: Checking syntax of configuration file
Nov 11 16:50:00 daintern proftpd[198634]: 2026-11-11 16:50:00,074 daintern proftpd[198634]: mod_tls/2.9.2: certificate '/etc/exim.cert': expected RSA certificate, found EC
Nov 11 16:50:00 daintern proftpd[198634]: 2026-11-11 16:50:00,079 daintern proftpd[198634]: mod_tls/2.9.2: certificate '/etc/exim.cert': expected RSA certificate, found EC
Nov 11 16:50:00 daintern proftpd[198634]: 2026-11-11 16:50:00,094 daintern proftpd[198634] 188.200.21.232: mod_sftp/1.2.0: Server 'ProFTPd': cannot support both FTPS (TLSEngine on) and SFTP (SFTPEngine on) for the same host
Nov 11 16:50:00 daintern systemd[1]: Started proftpd.service - ProFTPD FTP Server.
Nov 11 16:50:00 daintern proftpd[198636]: 2026-11-11 16:50:00,148 daintern proftpd[198636]: mod_tls/2.9.2: certificate '/etc/exim.cert': expected RSA certificate, found EC
Nov 11 16:50:00 daintern proftpd[198636]: 2026-11-11 16:50:00,152 daintern proftpd[198636]: mod_tls/2.9.2: certificate '/etc/exim.cert': expected RSA certificate, found EC
Nov 11 16:50:00 daintern proftpd[198636]: 2026-11-11 16:50:00,168 daintern proftpd[198636] 188.200.21.232: mod_sftp/1.2.0: Server 'ProFTPd': cannot support both FTPS (TLSEngine on) and SFTP (SFTPEngine on) for the same host
Nov 11 16:50:00 daintern systemd[1]: proftpd.service: Deactivated successfully.
After generating a RSA 4096 Server Certificate, this problem was solved. Now I ran into the old problem, I had to disable FTPS again, because FTPS and SFTP can't run on the same installation.
○ proftpd.service - ProFTPD FTP Server
Loaded: loaded (/etc/systemd/system/proftpd.service; enabled; preset: enabled)
Active: inactive (dead) since Wed 2026-11-11 16:53:29 CET; 4s ago
Duration: 88ms
Invocation: 169df26187954caead6ac57355bd602f
Process: 200739 ExecStartPre=/usr/sbin/proftpd --configtest (code=exited, status=0/SUCCESS)
Process: 200741 ExecStart=/usr/sbin/proftpd --nodaemon $PROFTPD_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 200741 (code=exited, status=0/SUCCESS)
Mem peak: 2.3M
CPU: 84ms
Nov 11 16:53:28 daintern systemd[1]: Starting proftpd.service - ProFTPD FTP Server...
Nov 11 16:53:28 daintern proftpd[200739]: Checking syntax of configuration file
Nov 11 16:53:29 daintern proftpd[200739]: 2026-11-11 16:53:29,029 daintern proftpd[200739] 188.200.21.232: mod_sftp/1.2.0: Server 'ProFTPd': cannot support both FTPS (TLSEngine on) and SFTP (SFTPEngine on) for the same host
Nov 11 16:53:29 daintern systemd[1]: Started proftpd.service - ProFTPD FTP Server.
Nov 11 16:53:29 daintern proftpd[200741]: 2026-11-11 16:53:29,119 daintern proftpd[200741] 188.200.21.232: mod_sftp/1.2.0: Server 'ProFTPd': cannot support both FTPS (TLSEngine on) and SFTP (SFTPEngine on) for the same host
Nov 11 16:53:29 daintern systemd[1]: proftpd.service: Deactivated successfully.
Do I have to manually reconfigure proftpd on all my servers, because the update breaks the old one? Can this be solved in a different way?
Enrico