nve:~ # systemctl start sshd.service
Job for sshd.service failed because the control process exited with error code. See "systemctl status sshd.service" and "journalctl -xe" for details.
nve:~ # systemctl status sshd.service
● sshd.service - OpenSSH Daemon
Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor preset: disabled)
Active: failed (Result: start-limit) since Tue 2021-04-27 15:43:49 EDT; 17s ago
Process: 6576 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=0/SUCCESS)
Process: 12164 ExecStartPre=/usr/sbin/sshd -t $SSHD_OPTS (code=exited, status=255)
Process: 12161 ExecStartPre=/usr/sbin/sshd-gen-keys-start (code=exited, status=0/SUCCESS)
Main PID: 6576 (code=exited, status=0/SUCCESS)
Tasks: 6
CGroup: /system.slice/sshd.service
├─11434 sshd: admin@pts/0
├─11438 -bash
├─11939 sudo su
├─11942 su
├─11943 bash
└─12169 systemctl status sshd.service
Apr 27 15:43:48 nve systemd[1]: Failed to start OpenSSH Daemon.
Apr 27 15:43:48 nve systemd[1]: sshd.service: Unit entered failed state.
Apr 27 15:43:48 nve systemd[1]: sshd.service: Failed with result 'exit-code'.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Service RestartSec=100ms expired, scheduling restart.
Apr 27 15:43:49 nve systemd[1]: Stopped OpenSSH Daemon.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Start request repeated too quickly.
Apr 27 15:43:49 nve systemd[1]: Failed to start OpenSSH Daemon.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Unit entered failed state.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Failed with result 'start-limit'.
nve:~ # tail -n 30 /var/log/messages | grep ssh
Apr 27 15:43:48 nve systemd[1]: sshd.service: Service RestartSec=100ms expired, scheduling restart.
Apr 27 15:43:48 nve sshd-gen-keys-start[12161]: Checking for missing server keys in /etc/ssh
Apr 27 15:43:48 nve ssh-keygen[12162]: OWB:ERROR:BSAFELIB:func(112):reason(113):b_dsa.c:112
Apr 27 15:43:48 nve sshd-gen-keys-start[12161]: ssh-keygen: generating new host keys: DSA key_generate failed: error in libcrypto
Apr 27 15:43:48 nve sshd[12164]: /etc/ssh/sshd_config line 171: Directive 'kexalgorithms' is not allowed within a Match block
Apr 27 15:43:48 nve systemd[1]: sshd.service: Control process exited, code=exited status=255
Apr 27 15:43:48 nve systemd[1]: sshd.service: Unit entered failed state.
Apr 27 15:43:48 nve systemd[1]: sshd.service: Failed with result 'exit-code'.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Service RestartSec=100ms expired, scheduling restart.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Start request repeated too quickly.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Unit entered failed state.
Apr 27 15:43:49 nve systemd[1]: sshd.service: Failed with result 'start-limit'.NVE /etc/ssh/sshd_config 檔案包含 kexalgorithms 項目，在之前的 NVE 升級期間未移除。
nve:~ # cat /etc/ssh/sshd_config | grep -b2 kexalgorithms
Match Address ::1,127.0.0.1,127.0.0.1,127.0.0.2,::1,10.0.0.3,fe80::250:56ff:febb:58e7
PermitRootLogin yes
kexalgorithms diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,curve25519-sha256@libssh.org