can't connect to Linux VM serial console

Question

can't connect to Linux VM serial console

Jack Li Admin 0

I have Ubuntu Linux server, I have upgraded it from version 22 to 24, server was rebooted after upgrade, it never came back, and I can't even connect to the serial console.

Ankit Yadav 4,060 Reputation points Microsoft External Staff Moderator

2025-10-17T16:58:04.29+00:00
Hello @Jack Li Admin ,

Can you please answer our below queries about the VM so that we can understand the issue better:

Did you reboot the VM manually or was it done as part of the upgrade, inside the VM?

Is the VM in running state and the agent is in ready state?

What error you see from the serial console?

Can you share what do you observe from Boot Diagnostics for the VM? (from screenshot and serial log)?

Additionally, I've asked some PII information related to the case in the Private message, kindly review and answer them
Himanshu Shekhar 1,095 Reputation points Microsoft External Staff Moderator

2025-10-21T07:52:11.0566667+00:00

Hello @Jack Li Admin ,

Could you please provide an update on this post?

Kindly let us know if the suggested steps helps or you need further assistance on this issue.
Ankit Yadav 4,060 Reputation points Microsoft External Staff Moderator

2025-10-25T11:03:36.38+00:00

Hello @Jack Li Admin ,

If the query has been resolved, please take a moment to accept answers and upvote it 👍 to make it helpful to the community.

Thank you for helping to improve Microsoft Q&A!!

1 answer

Your answer

Ankit Yadav 4,060 Reputation points Microsoft External Staff Moderator

2025-10-17T16:58:04.29+00:00

Hello @Jack Li Admin ,

Can you please answer our below queries about the VM so that we can understand the issue better:

Did you reboot the VM manually or was it done as part of the upgrade, inside the VM?

Is the VM in running state and the agent is in ready state?

What error you see from the serial console?

Can you share what do you observe from Boot Diagnostics for the VM? (from screenshot and serial log)?

Additionally, I've asked some PII information related to the case in the Private message, kindly review and answer them
Himanshu Shekhar 1,095 Reputation points Microsoft External Staff Moderator

2025-10-21T07:52:11.0566667+00:00

Hello @Jack Li Admin ,

Could you please provide an update on this post?

Kindly let us know if the suggested steps helps or you need further assistance on this issue.
Ankit Yadav 4,060 Reputation points Microsoft External Staff Moderator

2025-10-25T11:03:36.38+00:00

Hello @Jack Li Admin ,

If the query has been resolved, please take a moment to accept answers and upvote it 👍 to make it helpful to the community.

Thank you for helping to improve Microsoft Q&A!!

Answer 1

Hello @Jack Li Admin ,

Sharing some quick checks for the Serial Console connection failure:

“Connection timed out” or blank screen : Ensure Boot diagnostics is enabled under VM → Support + Troubleshooting → Boot diagnostics, and that the diagnostics storage account is accessible.
Reference: https://free.blessedness.top/en-us/troubleshoot/azure/virtual-machines/linux/serial-console-linux
“Access denied” message : Verify you or your VM user has the VM Contributor or higher role that has permission to the diagnostics storage account.
Stuck at GRUB prompt or kernel panic: Use the Azure VM repair commands (az vm repair create) to attach the OS disk to a rescue VM and inspect /etc/fstab, kernel, or GRUB issues.
Reference: https://free.blessedness.top/en-us/troubleshoot/azure/virtual-machines/linux/repair-linux-vm-using-azure-virtual-machine-repair-commands
Serial console shows nothing at all: Check that the VM’s configuration includes the proper kernel parameters (console=ttyS0,115200n8). You can add or fix this via rescue mode if necessary.
Reference: https://free.blessedness.top/en-us/troubleshoot/azure/virtual-machines/linux/boot-error-troubleshoot-linux

Let me know if this helps to solve your issue!

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can't connect to Linux VM serial console

1 answer

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