Hello li shaoyong,
It seems that sshd server process on your target board is not set up, please check whether sshd is running with the following command.
root@localhost:~# ps aux | grep sshd
root 3767 0.0 0.1 10412 5020 ? Ss 15:58 0:00 /usr/sbin/sshd -D
root 4778 0.0 0.0 2708 440 ttyS0 S+ 16:07 0:00 grep --color=auto sshd
If no, please generate Ubuntu rootfs filesystem with the following command in LSDK.
$ flex-builder -i mkrfs -r ubuntu:main
For details, please refer to the section "LSDK userland" in LSDK 19.09 document.
Thanks,
Yiping
