This document introduces how to troubleshoot problems when you cannot connect to a Linux instance, exploring the primary factors that may cause the inability to connect to Linux instances, and a guide through the steps of troubleshooting, locating, and solving the problems.
Possible Reasons
The main reasons for being unable to log in to Linux instance include:
- SSH issue prevents log-in
- Unable to log in due to password problem
- High bandwidth usage
- High server load
- Remote port configuration error
- Improper security group rules
Troubleshooting
Log-in via VNC
Log in by Converge Cloud VNC log-in and you can locate the cause of the fault with it.
- Log in to the CVM console.
On the instance management page, select the instance you want to log in to and click Log In. - In the pop-up Log in to Linux Instance window, select Other methods (VNC) and click Log in now.
If you forget your password during the log-in, you can reset the password for the instance in the console. For specific operations, refer to [Reset Instance Password](/document/product/221286/16566).
- In the dialog box that pops up, enter your username and password to complete the log-in process.
SSH issue prevents log-in
Fault Phenomena: When you use SSH to log in to a Linux instance, an error message indicating unable to connect or connection failure appears.
Directions: Refer to Unable to Log in to Linux Instance via SSH for troubleshooting.
Unable to log in due to password problem
Fault Phenomenon: Log-in failed due to incorrect password input, forgotten password, or failed password reset.
Solution: Reset the password of the instance in the console and restart the instance.
Directions: For how to reset the instance password, refer to Reset the Instance Password.
High bandwidth usage
Fault Phenomenon: The self-diagnosis tool shows that the problem is high bandwidth utilization.
Directions:
- Log in to the instance via VNC log-in.
- See High Bandwidth Usage Prevents Log-in, track the bandwidth usage of the instance and address faults.
High server load
Fault Phenomenon: Self-service checking tools or cloud monitoring shows that the high server CPU load causes the failure of remote system access or significant access latency.
Possible Causes: Viruses, Trojans, third-party antivirus software, application anomalies, driver anomalies, or automatic updates in the backend of the software. All the factors above can cause high CPU usage, resulting in problems such as being unable to log in to the CVM or slow access.
Directions:
- Log in to the instance via VNC log-in.
- See Linux Instance: High CPU and Memory Usage Causes Log-in Failure and locate high-load processes in the System Monitor.
Remote port configuration error
Fault Phenomenon: Remote connection is unavailable, the remote access port is not the default port, has been modified, or port 22 is not open.
Diagnostic Method: Whether you can ping the public IP address of the instance and use the telnet command to check whether the port is open.
Directions: For specific operations, refer to Port Problem Leads to Failure of Remote Log-in.
Improper security group rules
Fault Phenomenon: After checking with the self-service checking tools, it was found that the security group rules were set incorrectly, resulting in log-in failure.
Directions: If it is determined that the problem is with the security group port settings, the feature One-click Release in the tool can be used to open the port.
If you need to customize security group rules, reconfigure the security group rules.
Other Solutions
If you still cannot connect to the Linux instance after the above troubleshooting, please save the self-diagnosis results and submit a ticket for feedback.