Incorrect password entered: When switching users, the password of the target user needs to be entered. If the password is incorrect, the user switch will fail.
Insufficient user permissions: Only users with superuser permissions (root) can use the su command to switch to another user. If the current user does not have enough permissions to switch to the target user, the user switch will fail.
Switching users will fail if the target user does not exist.
The su command is disabled: Some system administrators disable the su command to enhance the security of the system. If the su command is disabled, switching users will fail.
The file permissions are set incorrectly: the su command requires special file permissions, so if the permissions of the relevant files are not set correctly, switching users will fail.
The su command has been tampered with: If the su command is maliciously tampered with, it may result in switching users failing or causing other issues.
Insufficient system resources, such as memory and CPU, can cause user switching to fail.
System error or malfunction: In some cases, system errors or malfunctions may prevent users from switching successfully.
Other security restrictions: In some systems, there may be additional security policies or limitations, such as the configuration of PAM (Pluggable Authentication Modules) modules, which could result in user switching failures.
