Troubleshooting of SSH server logon failures

Troubleshooting of SSH server logon failures-Linux Enterprise Application-Linux server application information. For details, refer to the following section. Analysis and troubleshooting: When the ssh client logs on to the server using the port and IP address, we should follow the steps below when we encounter the problem that such services cannot be linked.

1. First, determine whether the service is normal before a problem occurs? Can I log on to a server with the same network segment? (Eliminate network problems, Check network devices or contact relevant Departments)

2. Can I ping the local loopback address? (Exclude local hardware issues)

3. Have the configuration file been changed? View logs and history operation records in the/var/log directory (exclude human error)

4. Exclude the preceding assumptions and then check the service processes and ports of the linux system. Two commands are used to judge:

Ps? Ef | grep sshd and netstat? Anp | grep sshd;

Ps? Ef | grep sshd displays "sshd" service process records

Netstat? Anp | grep sshd displays the port used by sshd.

The reason for this check is that many people may forget to modify the port value of/etc/ssh/sshd_config, so that they still use port 22 to log on when using the ssh tool, resulting in login failure.

5. If no service process or port is found, use service sshd restart to restart the service (the problem will be solved at this time)

6. If the service fails to be started, follow the error prompt and/var/log/messages logs to troubleshoot the problem.