The default username for Linux instances is root.
To reset the ECS instance password
Enter the new password. Take note of the password complexity.
Select the ECS instance on which the password was changed and click Restart. Do note that restarting an instance may disrupt your business traffic.
There are two restart option: Restart and Force Restart.
The force restart operation is same as a power failure. Data in the instance operation system that is not written to the disk may be lost.