I experienced exactly the same problem for a week.
This evening I found out that a non-root user could not execute
sftp_server in /opt/libexec:
Couldn't open /dev/null: Permission denied$
As root I set the permissions for null:
# chmod og+rw null
# ls -al null
crw-rw-rw- 1 root root 1, 3 Jan 1 1970 null
And now a non-root user is able to connect with WinSCP!
--- In firstname.lastname@example.org, "bm1ll" <bm1ll@...> wrote:
> Unslung V2.3R63-uNSLUng-6.10-beta
> openssh-sftp-server - 4.9p1-1
> I can't seem to get sftp working for non-root users. Everything works
> fine for root, but just fails for non-root users. In WinSCP, I get
> the following error: "Cannot initialize SFTP protocol. Is the host
> running a SFTP server?" SSH'ing as non-root users works just fine.
> The /etc/passwd entry looks like this:
> wwwadm:rA.242xEI5vWQ:601:600:WWW Admin:/storage/www:/bin/sh
> Any help would be greatly appreciated. Thanks.