> For the complete documentation index, see [llms.txt](https://open-rt.gitbook.io/open-surfacert/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://open-rt.gitbook.io/open-surfacert/surface-rt/linux/booting/uefi-boot.md).

# UEFI boot

Boot an EFI-based Linux kernel on your Surface RT.

## Prerequisites

* A Surface RT with secure boot disabled. Visit [Yahallo](/open-surfacert/common/boot-sequence/uefi/secure-boot/disable-secureboot.md) for more information on how to disable it.
* A USB drive, formatted as FAT32 with either MBR or GPT. The partition doesn't require being marked as EFI system partition. Be aware that [FAT32 isn't FAT32](/open-surfacert/common/boot-sequence/uefi/fat32-isnt-fat32.md).
* A root filesystem/distro on your SD card (recommended)/internal storage/USB. \
  See [root filesystem](/open-surfacert/surface-rt/linux/root-filesystem.md).

## Preparing the files

{% hint style="info" %}
There is a premade ZIP below.

There are [prebuilt binaries](/open-surfacert/surface-rt/linux/kernel/prebuilt-binaries.md).
{% endhint %}

Most people use UEFI shell to chainload an EFI linux kernel. Using UEFI shell gives the option to easily specify and modify the kernel command line.

{% file src="/files/-MeH0KWUIYWAW2iObAa1" %}
UEFI shell
{% endfile %}

You may want to use different bootloaders, like [GRUB](/open-surfacert/surface-rt/uefi/compiling-grub2.md).

Place UEFI shell onto your bootable USB drive (as efi/boot/bootarm.efi) and place the zImage and the tegra30-microsoft-surface-rt-efi.dtb files onto the root of your usb drive.

You will need to create a startup script for UEFI shell:

{% code title="startup.nsh" %}

```
fs0:
# add initrd=<initrd.img-filename> if you want to boot a ramdisk image
# replace console=tty0 with console=ttyS0,115200 if you want serial output on UART A
zImage dtb=tegra30-microsoft-surface-rt-efi.dtb root=/dev/mmcblk1p2 console=tty0 cpuidle.off=1

# shutdown if something went wrong
reset -s
```

{% endcode %}

You may want to change the line that begins with `zImage`. It is the kernel command line. `root=/dev/mmcblk1p2` is the second partition of the sdcard, change this if you want to use a different device/partition. [RPI OS](/open-surfacert/surface-rt/linux/root-filesystem/distros/raspberry-pi-os.md) is a recommended distro, as it runs smooth

`root=/dev/mmcblk0p2` is a location set to internal storage (eMMC) second partition, set it to this after cloning the installation over to internal storage.

`root=/dev/sda2` is a second partition for USB only boot, set it to this if you want to USB boot only

{% hint style="info" %}
See [Kernel parameters](/open-surfacert/surface-rt/linux/booting/kernel-parameters.md) for further information.
{% endhint %}

### Premade ZIP

{% file src="/files/-Miv387j-uOAVCFsjVDJ" %}

Extract this ZIP to your USB, and add your zImage and device tree to it. You can find precompiled binaries [here](/open-surfacert/surface-rt/linux/kernel/prebuilt-binaries.md).

## Booting linux

With the USB drive set up, a distro installed and secure boot disabled, you are ready to boot linux.

1. Shut the device off
2. Plug in your USB drive
3. Boot from the USB
   1. Hold the volume down button
   2. Press the power button for a second
   3. Wait until the surface logo appears
   4. Release volume down
4. You should see kernel logs onscreen (after a short while (15 seconds), wait for 1 minute if nothing happens try again)

If you have any issues, feel free to contact us on [discord](https://discord.gg/tAxvvVC).

## Installing boot files on internal storage

With the method shown above, you will need your USB always on hand to boot linux. You can also install these boot files on the internal storage.

The easiest method is to just clean the windows boot files from the EFI partition, and replace them with the contents of your USB drive.

{% hint style="danger" %}
This will make you unable to boot Windows!
{% endhint %}

{% hint style="info" %}
It is possible to make Windows and Linux dual-boot. For example, you can use GRUB.
{% endhint %}

### Using UEFI shell to copy the files

Replace the contents of your startup.nsh on the USB with the following:

```
fs0:

cp fs1:\efi/boot/bootarm.efi fs1:\efi/boot/bootarm.efi.backup >> log.txt
cp efi/boot/bootarm.efi fs1:\efi/boot/bootarm.efi >> log.txt
cp tegra30-microsoft-surface-rt-efi.dtb fs1: >> log.txt
cp zImage fs1: >> log.txt
cp startup-system.nsh fs1:\startup.nsh >> log.txt

reset -s
```

After booting, it will copy the devicetree, zImage and the startup-system.nsh over to the EFI partition on the internal storage. Fill your startup-system.nsh with the linux boot commands. (The commands you normally have in your startup.nsh)

This method is also useful for updating the device tree and zImage, if you already have existing linux files there.