Understanding Elastic Metal RV1 usage

Boot process

EM-RV1 servers do not support standard UEFI or BIOS boot, therefore the boot process might slightly differ from other servers. At boot, the bootloader expects the eMMC to be partitioned as GPT, and will look for a boot.itb file in the first or second partition. The partition that contains this boot file must be formatted as FAT32.

This boot.itb file is in fact a FIT Image that must contain the following sections:

• kernel: A Linux kernel image.
• fdt: A device tree.
• opensbi: The SBI as defined by RISC-V SBI specification.
• env: A text-based environment file that defines the following keys:
  • usr_bootargs: Command-line arguments to pass to the kernel.
  • usr_has_ramdisk: Set to 1 if we should load the ramdisk from the FIT image.
• ramdisk (optional): A ramdisk image.

The following section will explain in details how to create your own boot FIT image.

Boot a custom kernel

In this section, you will build a boot image based off a close-to-mainline Linux kernel.

Before you start

To complete the actions presented below, you must have:

• Installed an EM-RV1 server with Ubuntu
• Proficient knowledge of Linux systems
• A few hours of availability to build a Linux kernel

1. Connect to your EM-RV1 server using SSH.
2. Install the build dependencies.

   sudo apt update
   sudo apt install -y \
     autoconf bc bison dwarves flex gawk git make \
     libelf-dev libssl-dev \
     u-boot-tools device-tree-compiler
   

3. Clone the projects to build.

   git clone --depth=1 https://github.com/revyos/th1520-linux-kernel.git linux
   git clone https://github.com/revyos/thead-opensbi.git opensbi
   git clone https://github.com/scaleway/em-rv1.git
   

4. Build the Linux kernel.

   cd linux/
   make revyos_defconfig
   # This can take several hours.
   make -j
   sudo make modules_install
   cd ..
   

5. Build OpenSBI.

   cd opensbi/
   make PLATFORM=generic -j
   cd ..
   

6. Build and install the FIT image.

   cd em-rv1/fit/
   # Build the device tree
   cpp \
    -nostdinc \
    -I ../linux/arch/riscv/boot/dts/thead/ \
    -I ../linux/include/ \
    -undef \
    -x assembler-with-cpp \
    em-rv1-c4m16s128-a.dts \
    | dtc -o em-rv1-c4m16s128-a.dtb
   # Build the FIT image
   sudo mv /boot/boot.itb /boot/boot.itb.bak
   sudo mkimage -f em-rv1-c4m16s128-a-boot.its /boot/boot.itb
   cd -
   

7. Reboot the server to load the new kernel.