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![]() GRUB DISPLAY MENU SERIALUbuntu 12.04 will allow access to serial console but does not offer the ability to interact.Ĭreate a file called /etc/init/nf containing the following text: # ttyS0 - getty etc/default/grub and observe a 3-second timeout to hit EscĬomment out these two lines: #GRUB_HIDDEN_TIMEOUT=0Īnd add this line: GRUB_TIMEOUT_STYLE=countdown Similar behavior can be experienced by making changes to the file Option 2 - Allows for Esc to be pressed before booting You are not required to hit Esc as GRUB will be displayed immediately. GRUB DISPLAY MENU UPDATEUpdate the file /etc/default/grub.d/50-cloudimg-settings.cfg to keep the GRUB menu on screen for the specified TIMEOUT. Option 1 - Forces GRUB to be displayed on Screen The system should log a reset message such as thisīy default you should be able to access GRUB by holding down Esc key during the VM boot, if the GRUB menu is not presented you can force and keep the GRUB menu on screen in the Azure Serial Console by using one of these options. Once completed, you can then try accessing sysrq and should see that a reboot is possible. Sysctl -w kernel.sysrq=1 echo kernel.sysrq = 1 > /etc/nf Using the Azure portal Operations -> Run Command -> RunShellScript feature, requires the waagent process be healthy you can then inject this command to enable sysrq ![]() This method can be beneficial if the sudoers.d/waagent file has become broken or has been deleted. You can enable sysrq in this scenario using the Azure portal. If you do not have root access or sudo is broken, it will not be possible configure sysrq from a shell prompt. To configure the kernel parameter dynamically To configure the VM to accept a reboot via SysRq commands on the Azure portal, you will need to set a value of 1 for the kernel parameter kernel.sysrqįor this configuration to persist a reboot, add an entry to the file nfĮcho kernel.sysrq = 1 > /etc/nf The VM must be configured to accept a value of 1 for the kernel parameter, which enables all functions of sysrq or 128, which allows reboot/poweroff The SysRq feature is useful for rebooting a crashed or non-responding VM directly from the Azure Serial Console, also helpful in gaining access to the GRUB menu, alternatively restarting a VM from another portal window or ssh session might drop your current console connection thus expiring GRUB Timeouts to which are used to display the GRUB menu. On older distros, it might be disabled completely. The sysrq key is enabled on some newer Linux distros by default, although on others it might be configured for accepting values only for certain SysRq functions. GRUB DISPLAY MENU HOW TOHow to configure Linux VM to accept SysRq keys In this article, we'll review various Linux distributions and document configurations on how to make GRUB available. Some older distros such as SLES 11 are not configured to display Login prompt in the Azure Serial Console Not all Linux Azure VMs are configured by default for GRUB access and neither are they all configured to be interrupted with the sysrq commands. If you do not have access to GRUB watch this video and see, how you can easily automate the disk swap procedure to recover your VM Challenges You could even force the VM to boot from an alternative kernel should you have multiple kernels on disk in the scenario where your primary kernel becomes corrupt.ĭisk Swap – can be automated using either: GRUB DISPLAY MENU PASSWORDOther extensions such as Custom Script are available however these options require that the Linux waagent be up and in a healthy state which is not always the case.Įnsuring you have access to the Azure Serial Console and GRUB means that a password change or an incorrect configuration can be rectified in a matter of minutes instead of hours. ![]() The Reset Password feature is known as an Extension and communicates with the Linux Guest agent. The method of recovery depends on the problem being experienced, for example a lost or misplaced password can be reset through Azure portal options -> Reset Password. The more experienced Linux/Unix sys admins will appreciate the single user and emergency modes that are accessible via the Azure Serial Console making Disk Swap and VM deletion for many recovery scenarios redundant. You can manipulate many configuration files including how the kernel will boot. With the Azure Serial Console, you can interact with your Linux VM as if you were at a system's console. Progress is being made continually to tooling and features to ensure services are recovered quickly. In a Cloud environment, this process has been challenging. There are a number of methods to help recovery of Linux VMs. Watch this video below to see how you can quickly recover your Linux VM once you have access to GRUB Ensure you take backups of files before making changes ![]()
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