Grub display menu debugging12/19/2023 ![]() ![]() ![]() The GRUB menu displays during the boot process. This can be useful when troubleshooting a failing instance. From the GRUB menu, you can select which kernel to boot into, or modify menu entries to change how the kernel will boot. The GRUB menu appears when you press and hold Shift during the boot process. GRUB is the default boot-loader for most Linux operating systems. Now that you have an idea of example cases where you might run into system failure, let’s walk through how EC2 serial console with GRUB can help you fix the issue. You will later use GRUB to access a rescue kernel to resolve the start-up failure. Before you rename the kernel, you must ensure that GRUB is configured to read and write to the virtual serial port of your EC2 Instance. You can simulate the same scenario by renaming the Linux kernel. The following screenshot shows an example of this error. Access to the serial port using EC2 Serial Console shows you that the kernel is no longer available. In this scenario, you must revert back to the last known stable kernel. After rebooting, the missing kernel will fail to load correctly. In the software update scenario you might have upgraded the Linux kernel, and in the process might have inadvertently deleted the wrong kernel. The following screenshot from EC2 Serial Console shows the boot process of an instance that had both the / etc/fstab and network configuration files deleted. You can view the entire boot sequence using EC2 Serial Console via the AWS Management Console. In both cases, the only way to troubleshoot the misconfigured instance is to view the boot sequence. Or you might have misconfigured the Ethernet configuration, resulting in an instance that boots without network connectivity. You do not need to have direct network connectivity to the instance in order to access it using the virtual serial port.Ĭonfiguration changes or software updates are two examples out of many that could result in an Amazon EC2 instance start-up failure.įor example, in the configuration change scenario, you might have made an error to the file systems table (/etc/fstab), which controls how disks are mounted. ![]() The EC2 Serial Console can establish connection to an instance even when a user is not able to connect using other methods such as Secure Shell (SSH) or Remote Desktop Protocol (RDP). The EC2 Serial Console provides a secure and dedicated way to connect to the serial port (ttyS0 or COM1) of your Amazon EC2 instance. While this post focuses on Amazon Linux 2, you can use a similar workflow with other Linux distributions in addition to as on Windows instances to troubleshoot and fix boot-failure. We demonstrate how you can access the GNU GRand Unified Bootloader (GRUB) using Amazon EC2 Serial Console to fix the problem. In this post, we walk you through a scenario where an Amazon EC2 instance fails to start. On March 30,2021, AWS announced the EC2 Serial Console, a simple, and secure way for system and network administrators to interactively troubleshoot boot and network connectivity issues by establishing a virtual serial connection to your Amazon EC2 instances. In the past Amazon Elastic Compute Cloud (Amazon EC2) customers could only view console output using the GetConsoleOutput API to identify that a network or boot failure has occurred. ![]() In the AWS Cloud, the administrator has no access to the data center. When an instance fails to start up on premises or can no longer connect to the network, an administrator can walk up to the server in a data center and use the serial port of the server to resolve the problem. Menuentry 'First custom entry' -class red -class gnu-linux -class gnu -class os $menuentry_id_option 'gnulinux-4.2. post is written by Pallavi Ravishankar a Senior Product Manager and Jason Nicholls an Enterprise Solutions Architect.ĭebugging and fixing infrastructure is one of the key responsibilities of system and network administrators. # menu entries you want to add after this comment. # This file provides an easy way to add custom menu entries.
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