1)In your AWS Ec2 console, In the navigation pane, choose Instances.

Select the instance and choose Instance state, Reboot instance.

Alternatively, select the instance and choose Actions, Manage instance state. In the screen that opens, choose Reboot, and then Change state.

Choose Reboot when prompted for confirmation.

The instance remains in the "running" state. 2) The other problem might be from kernel (sudo yum update kernel or if i miss out any additional commands you can look in google .I dont remmeber now ) end, you might need to reboot . Also check the system logs are located at /var/log/messages or /var/log/syslog depending on your OS distribution.

3)Also check your reboot history to determine if a user or an application inside the server initiated the reboot:

grep reboot /home/*/.bash_history

grep reboot /root/.bash_history

history | grep -i reboot

history | grep -i init

last reboot

4)The other area in cloudtrial- Event histroy -Select Event name from the filter dropdown list, and then enter RebootInstances.

create an Amazon CloudWatch alarm that automatically recovers instances experiencing underlying hardware issues resulting in reboot.

Hope this helps.