Linux ECS instance fails to start with a

Symptoms

When you start a Linux ECS instance, its operating system fails to start. When you connect to the instance by using the VNC console, the "UEFI Interactive Shell" screen is displayed.

UEFI Interactive Shell v2.2
EDK II
UEFI v2.70 (EDK II, 0x00010000)
Mapping table
      BLK2: Alias(s):
            PciRoot(0x0)/Pci(0x4,0x0)
      BLK3: Alias(s):
            PciRoot(0x0)/Pci(0x4,0x0)/HD(1,MBR,0x000B2D99,0x800,0x4FFCE25)
      BLK0: Alias(s):
            PciRoot(0x0)/Pci(0x1,0x0)/Floppy(0x0)
      BLK1: Alias(s):
            PciRoot(0x0)/Pci(0x1,0x0)/Floppy(0x1)
Press ESC in 1 seconds to skip startup.nsh or any other key to continue.
Shell> _

Causes

This error occurs for the following reasons:

The image does not support UEFI, but the instance's boot mode is set to UEFI. This typically happens with a custom image. To fix this, change the image's boot mode to BIOS. For more information, see Change the image's boot mode to BIOS.
The image supports UEFI, but its firmware is corrupted. To fix this, repair the UEFI firmware. For more information, see Repair the UEFI firmware.

Resolution

To resolve this issue, change the image's boot mode or repair the UEFI firmware as described in the following sections.

Change image boot mode to BIOS

If you do not require UEFI, or if the image does not support it, change the custom image's boot mode to BIOS and use the image to create a new instance.

Release the problematic ECS instance.

For more information, see Release an instance.
Change the boot mode of the image to BIOS.

For more information, see Modify the boot mode of an image.
Create an instance from the image.

For more information, see Create an instance by using a custom image.
Connect to the instance. If the connection is successful and the "UEFI Interactive Shell" error no longer appears, the issue is resolved.

For more information, see Connection methods overview.

Repair the UEFI firmware

If your instance type and image support UEFI and you want to use this boot mode, follow these steps to repair the firmware.

Detach the system disk from the problematic ECS instance and attach it as a data disk to a working ECS instance.
Check whether the required EFI packages are installed and the EFI firmware files in the /boot/efi/EFI/centos directory are complete.
1. Run the following command to check the installed EFI packages:
```
rpm -qa |grep -i efi
```
  The command returns output similar to the following:
```
[root@hostname ~]# rpm -qa |grep -i efi
grub2-efi-x64-2.02-0.87.el7.centos.6.x86_64
efibootmgr-17-2.el7.x86_64
efivar-libs-36-12.el7.x86_64
```
  Compare this output to the packages on a healthy instance running the same Linux distribution:
  - If the installed EFI packages match, proceed to step 2.b.
  - If any EFI packages are missing, run the sudo yum install command to install the corresponding package.
    
    For example, the following command installs the grub2-efi-x64 package:
```
sudo yum install grub2-efi-x64-2.02-0.87.el7.centos.6.x86_64
```
2. Run the following commands to check the EFI firmware files in the /boot/efi/EFI/centos directory:
```
cd /boot/efi/EFI/centos && ll
```
  The command returns output similar to the following:
```
[root@hostname centos]# ll
total 7020
-rwx------  1 root root     134 Jul 31  2020 BOOT.CSV
-rwx------  1 root root     134 Jul 31  2020 BOOTX64.CSV
drwx------  2 root root    4096 Jun 16  2021 fonts
-rwx------  1 root root    5184 Jun 16  2021 grub.cfg
-rwx------  1 root root    1024 Jun 16  2021 grubenv
-rwx------  1 root root 1122120 Mar 17  2021 grubx64.efi
-rwx------  1 root root 1154640 Jul 31  2020 mmx64.efi
-rwx------  1 root root 1154640 Jul 31  2020 MokManager.efi
-rwx------  1 root root 1243864 Jul 31  2020 shim.efi
-rwx------  1 root root 1237824 Jul 31  2020 shimx64-centos.efi
-rwx------  1 root root 1243864 Jul 31  2020 shimx64.efi
```
  Compare this output to the EFI firmware files on a healthy instance running the same Linux distribution:
  - If the EFI firmware files match, proceed to step 3.
  - If any EFI firmware files are missing, run the sudo yum install command to install the corresponding package.
    
    Reinstall the grub2-efi-x64 package by running the following command:
```
sudo yum install grub2-efi-x64-2.02-0.87.el7.centos.6.x86_64
```
Reattach the system disk to the original ECS instance.
Connect to the instance. If the connection is successful and the "UEFI Interactive Shell" error no longer appears, the issue is resolved.

For more information, see Connection methods overview.