This document describes possible causes of Linux instance login failures and troubleshooting methods, helping you detect, locate and resolve problems.
Tencent Cloud provides a diagnosis tool to help you determine whether the problem is due to common bandwidth, firewall, or security group configurations issues. More than 70% of the problems can be located by this tool. You can locate problems that result in login failures based on the detected causes.
You can use TAT to send commands to an instance for troubleshooting and problem locating. The directions are as follows:
df -THand click Execute command to view the result of an instance without logging in to it.
If you cannot troubleshoot with the diagnosis tool, we recommend you log in to the CVM instance via VNC and follow the instructions.
Common login failure reasons:
If you cannot log in to the Linux instance by using Webshell or remote login software, you can try log in with VNC for troubleshooting.
If you forgot the password for the instance, you can reset it in the console. For more information, see Resetting Instance Password.
Problem: During login to a Linux instance using SSH, a message appears indicating that the connection is unavailable or failed.
Steps: See Unable to Use the SSH Method to Log in to a Linux Instance to perform troubleshooting.
Problem: The login attempt failed because you forgot the password, entered an incorrect password, or failed to reset your password.
Solution: Reset the password for this instance in the CVM console and restart the instance.
Procedure: See Resetting Instance Password for the detailed procedure.
Problem: The self-diagnosis tool shows that bandwidth utilization is too high.
Problem: The self-diagnosis tool or Cloud Monitor shows that server CPU workload is too high, and the system is unable to perform remote connection or access is slow.
Possible cause: Viruses, trojans, third-party antivirus software, application exceptions, driver exceptions, and automatic updates of software on the backend may lead to high CPU utilization, causing CVM login failures or slow access.
Problems: The self-diagnosis tool shows that the security group rule configuration is improper, leading to login failures.
Procedure: Troubleshoot with the security group (port) verification tool.
If the problem is caused by a port issue of the security group, you can use the Open all ports feature to open all ports.
To define a custom rule for the security group, see Adding Security Group Rules.
If you still cannot connect to the Linux instance, save your self-diagnosis results and submit a ticket for assistance.