Quota errors

If you receive aquota error when you try to startan instance, you must request additional CPU quota. For more information, seetheVM instances section of theCompute Engine allocation quotas documentation.

Boot disks

If your instance does not start and you are unable to connect to it or log inthrough the interactive serial console, identify the reason why the boot disk isnot completing the boot and startup process.

Identify the reason why the boot disk isn't booting

• Verify that your boot disk is not full.

  If your boot disk is completely full and your operating system does notsupport automatic resizing, you won't be able to connect to your instance.You must create a new instance and recreate the boot disk. For moreinformation, seeRecoveringVMs or full boot disks.

• Examine your virtual machine instance's serial port output.

  An instance's BIOS, bootloader, and kernel prints their debug messages intothe instance's serial port output, providing valuable information about anyerrors or issues that the instance experienced. If youenable serial portoutput logging to Cloud Logging, you can access this information even when your instance isnot running.

• Enable interactive access to the serial console.

  You can enable interactive access to an instance's serial console, so youcan log in and debug boot issues from within the instance without requiringyour instance to be fully booted. For more information, seeTroubleshootingusing the serial console.

• Verify that boot disk cloning is not in progress

  Ifcloningof the boot disk is in progress, you can't start the VM and you see an errorsimilar to the following.

  Failed to start example-vm: The instance resource 'projects/example-project/zones/us-central1-b/instances/example-vm' is already being used by 'projects/example-project/zones/us-central1-b/disks/clone'

  Wait for the clone to complete, then start the VM.

• Verify that snapshot of the boot disk is not in progress

  If asnapshotof the boot disk is in progress, you can't start the VM and you see an errorsimilar to the following:

  The instance resource 'projects/example-project/zones/asia-east1-b/instances/example-vm' is already being used by 'projects/example-project/global/snapshots/example-vm-prod-asia-east1-b-abc'

  Wait for the snapshot to complete, then start the VM.

• Verify that your disk has a valid file system.

  If your file system is corrupted or otherwise invalid, you won't be able tolaunch your instance. Validate your disk's file system:

  1. Detach the disk in question from any instance it is attached to, ifapplicable:

     gcloud compute instances delete old-instance --keep-disks boot

  2. Start a new instance with the latest Google-provided image:

     gcloud compute instances create debug-instance

  3. Attach your disk as a non-boot disk, but don't mount it. ReplaceDISKwith the name of the disk that won't boot. Note the device name thatidentifies the disk on the instance:

     gcloud compute instances attach-disk debug-instance \    --diskDISK \    --device-name debug-disk

  4. Connect to the instance:

     gcloud compute ssh debug-instance

  5. Look up the root partition of the disk, which is identified with thepart1 notation. In this case, the root partition of the disk is at/dev/sdb1:

     ls -l /dev/disk/by-idtotal 0lrwxrwxrwx 1 root root  9 Jan 22 17:09 google-debug-disk -> ../../sdblrwxrwxrwx 1 root root 10 Jan 22 17:09 google-debug-disk-part1 -> ../../sdb1lrwxrwxrwx 1 root root  9 Jan 22 17:02 google-persistent-disk-0 -> ../../sdalrwxrwxrwx 1 root root 10 Jan 22 17:02 google-persistent-disk-0-part1 -> ../../sda1lrwxrwxrwx 1 root root  9 Jan 22 17:09 scsi-0Google_PersistentDisk_debug-disk -> ../../sdblrwxrwxrwx 1 root root 10 Jan 22 17:09 scsi-0Google_PersistentDisk_debug-disk-part1 -> ../../sdb1lrwxrwxrwx 1 root root  9 Jan 22 17:02 scsi-0Google_PersistentDisk_persistent-disk-0 -> ../../sdalrwxrwxrwx 1 root root 10 Jan 22 17:02 scsi-0Google_PersistentDisk_persistent-disk-0-part1 -> ../../sda1

  6. Run a file system check on the root partition:

     sudo fsck /dev/sdb1fsck from util-linux 2.20.1e2fsck 1.42.5 (29-Jul-2012)/dev/sdb1: clean, 19829/655360 files, 208111/2621184 blocks

  7. Mount your file system:

     sudo mkdir /mydisk

     sudo mount /dev/sdb1 /mydisk

  8. Check that the disk has kernel files:

     ls /mydisk/boot/vmlinuz-*/mydisk/boot/vmlinuz-3.2.0-4-amd64

• Verify that the disk has a validmaster boot record (MBR).

  Run the following command on the debug instance that has the attachedpersistent boot disk, such as/dev/sdb:

  sudo parted /dev/sdb print

  If your MBR is valid, it lists information about the file system:

  Disk /dev/sdb: 10.7GBSector size (logical/physical): 512B/4096BPartition Table: msdosDisk Flags:Number  Start   End     Size    Type     File system  Flags 1      2097kB  10.7GB  10.7GB  primary  ext4         boot

Correct the boot issue

After you identify where the boot and startup process is failing, you cancorrect the issue by completing one of the following actions:

• Use your imported image tocreate a standalone boot disk

• Start over andimport the boot disk image again

Creating a standalone boot disk

Mount your imported image on a secondary disk that is attached to a temporary VMinstance. Use the Google Cloud console or the gcloud CLI tocreate a standalone disk from the image that you uploaded and create a temporaryVM with the standalone disk attached. You can use this instance to modify fileson the standalone disk and fix issues that cause that image to fail to start.

gcloud compute disks createDISK_NAME \    --zone=ZONE \    --image=IMAGE_NAME

gcloud compute instances createINSTANCE_NAME \    --zone=ZONE \    --disk name=DISK_NAME

After you create the instance with the attached standalone disk, you have avirtual environment where you can modify the bootloader from your originalboot disk image.

Configuring the boot disk

Connect to the instance, mount the standalone disk, and configure the bootloaderso that it boots properly on Compute Engine.

1. Connect to the temporary instanceby using SSH-in-browser or thegcloud compute ssh command.

2. Use theblkid command to identify the disk that you want to modify andthe partitions that you need to mount. In this example,/dev/sdb is thedisk that you imported.

   lsblk

   NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTsda      8:0    0   10G  0 disk└─sda1   8:1    0   10G  0 part /sdb      8:16   0  100G  0 disk├─sdb1   8:17   0   96G  0 part├─sdb2   8:18   0    1K  0 part└─sdb5   8:21   0    4G  0 part

3. Mount the root partition from the standalone disk to the/tmp directory.In this example/dev/sdb1 is the root partition and the other partitionsdo not require any modifications. Your partition scheme might require youto mount multiple partitions before you can access all of the files that youneed to change.

   sudo mount /dev/sdb1 /tmp

4. Edit files that might cause the disk to fail the boot process. For moreinformation, see thebootloader configuration instructions.

5. Unmount the boot disk from the temporary instance.

   sudo umount /tmp

Using the boot disk

When you have finished configuring this disk, detach it, and use it as the bootdisk for new instance.

gcloud compute instances detach-diskINSTANCE_NAME \    --disk name=DISK_NAME

gcloud compute instances createINSTANCE_NAME \    --zoneZONE \    --disk name=DISK_NAME,boot=yes

Test the instance that you created using the modified boot disk. If you arestill unable to connect to the instance,view the serial port outputagain to identify where the boot process is failing. Repeat thetroubleshooting process until youcorrect the issues with the boot disk image.