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Overview

The “Boot Images” page is a library of Linux boot files you can reuse across servers. A boot image is either a Unified Kernel Image (UKI) or a Linux kernel with its initramfs and a kernel command line. A server set to measured direct boot starts straight from these files instead of the bootloader on its disk, with SEV-SNP launch measurement. This is an advanced, experimental feature for people building confidential computing setups. If you just want to install an operating system from your own installer, use a custom ISO instead. See ISO Mounting. Open the Ascienth console at https://console.advinservers.com and click “Boot Images” under “Setup” in the left sidebar.
Measured boot is not offered everywhere yet. If the page shows Uploads unavailable, you can still see your library, but you cannot upload or delete images until it is available.

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Limits

A UKI must be an x86-64 image with one kernel, one initramfs and one command line built in. Multi-profile images, separate microcode, device trees and firmware sections are not supported.
Only upload public boot code. Never put passwords, keys or other secrets in the files or the command line.

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Uploading a Boot Image

1

Open the upload form

On the “Boot Images” page, click Upload Image.
2

Name it and choose the source

Enter a Name of up to 80 characters. Then choose a Source: Unified Kernel Image (UKI) or Kernel + initramfs.
3

Add the files and their checksums

For a UKI, choose the UKI file and enter its UKI SHA-256. The kernel, initramfs and command line are read from inside the UKI.For a kernel and initramfs, choose the Linux kernel and Initramfs files, enter the Kernel SHA-256 and Initramfs SHA-256, and enter the Exact kernel command line.You can get a checksum with sha256sum <file> on Linux. If a checksum does not match the file you uploaded, the upload is refused with The SHA-256 checksum does not match the uploaded file.
4

Upload

Click Upload Image. The form shows the upload progress. When it finishes, the image appears in the list.
To see an image’s checksums and command line later, click the menu at the end of its row and choose View Boot Inputs. These checksums identify the boot files. They are not an SNP launch measurement.

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Using an Image on a Server

1

Prepare the server

Open the server, click its “Settings” tab, and open “Measured Boot”. Turn on SEV-SNP there, and set UEFI firmware in the “Hardware” section.
2

Choose the image

Turn on Enable measured direct boot, then pick your image under Boot image. You can also upload a kernel and initramfs for just this server instead.
3

Save and restart fully

Click Save Boot Configuration. The new boot files take effect after a full shutdown and start of the server, not a reboot from inside the operating system.
To go back to booting from the disk, turn off Enable measured direct boot and save. Make sure your disk still has a working bootloader first.
A saved boot configuration is not proof that the server is running a verified operating system.

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Deleting a Boot Image

Click the menu at the end of the image’s row and choose Delete. To confirm, type the image’s name and click Delete. Servers already set to boot from the image keep their own copy and are not changed. To use the image on another server later, you need to upload it again.

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Team Permissions

Boot images belong to the team you are working in. The team owner can always manage them. Members need these permissions in their role: Choosing an image for a server also needs the Change server settings permission. See Team Members and Roles.