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Microsoft Previews Serial Console Recovery Tool for Azure Virtual Machines

Microsoft on Monday announced a preview of a new Serial Console command-line tool for recovering Linux and Windows virtual machines (VMs) running on Azure infrastructure.

The Serial Console tool is used to access Azure VMs that are stuck, which can happen because of operating system misconfigurations, such as having incorrect file systems table (fstab) syntax or incorrect firewall rules. Alternatively, network changes could have been made that locked out the Remote Desktop Protocol port, precluding access.

Linux users accessing VMs on-premises were used to having direct access to VMs in such situations, and Microsoft wanted to provide a similar experience when using Azure VMs, according to a video chat between Corey Sanders, corporate vice president of Microsoft Azure Compute, and Hariharan Jayaraman, principal program manager on the Azure Linux Team.

The Serial Console tool was a "highly requested" feature, according to Sanders. It's bidirectional and uses the same log-in and password as Secure Shell (SSH) for Linux users. They can directly fix a problem with an Azure VM without having to separately dig through log files, since the console shows the VM's boot diagnostics log. The recovery tool apparently is named after the COM1 serial port of a VM, according to Microsoft's documentation.

"It's like having a keyboard plugged into the server in our datacenter but in the comfort of your office or home," Sanders explained regarding the Serial Console tool in an announcement.

While it's a command-line tool, the Serial Console preview can only be accessed right now through the Azure Portal. Users of Serial Console need to have VM Contributor or higher management status to use this tool.

The Serial Console tool is already configured for many Linux distros supported on Azure VMs. Those distros include CentOS, CoreOS, Oracle Linux, Red Hat, SUSE and Ubuntu, according to Microsoft's documentation.

The Serial Console preview tool also works with Windows-based Azure VMs. It requires a "few additional steps" to enable Serial Console for Windows, as described in Microsoft's documentation.

On the Windows side, Serial Console connects with the VM using the Special Administration Console (SAC), a command-line tool that's been present in the server operating system since Windows Server 2003, according to Jayaraman in a video talk with Scott Hanselman of Microsoft's Web Platform Team. Microsoft has roadmap plans to make the Serial Console tool also available through the Azure Command Line Interface tool, according to the talk. SAC is just available through Windows Server, and is enabled by default for "newer Windows Server images," according to the documentation.

About the Author

Kurt Mackie is senior news producer for the 1105 Enterprise Computing Group.

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