作者：张华 发表于：2024-07-20
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try ubuntu core on qemu

#ovmf is to ensure compatibility with the required UEFI features in ubuntu core
sudo apt install qemu-kvm ovmf
kvm-ok
#swtpm is to provide a TPM emulator
sudo snap install --edge test-snapd-swtpm
#Download ubuntu core - https://ubuntu.com/core/docs/supported-platforms
wget https://cdimage.ubuntu.com/ubuntu-core/24/stable/current/ubuntu-core-24-amd64.img.xz
xz -d ubuntu-core-24-amd64.img.xz
#With TPM emulation and full disk encryption
sudo qemu-system-x86_64 -enable-kvm -smp 1 -m 2048 -machine q35 -cpu host -global ICH9-LPC.disable_s3=1 \
 -net nic,model=virtio -net user,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80  \
 -drive file=/usr/share/OVMF/OVMF_CODE.secboot.fd,if=pflash,format=raw,unit=0,readonly=on \
 -drive file=/usr/share/OVMF/OVMF_VARS.ms.fd,if=pflash,format=raw,unit=1 \
 -drive "file=/images/kvm/ubuntu-core-24-amd64.img",if=none,format=raw,id=disk1 \
 -device virtio-blk-pci,drive=disk1,bootindex=1 -serial mon:stdio
#https://login.ubuntu.com  and https://login.ubuntu.com/ssh-keys
ssh <your-name>@localhost -p 8022

try ubuntu core on raspberry pi

#download image from https://ubuntu.com/core/docs/supported-platforms , eg: ubuntu-core-24-arm64+raspi.img.xz
xz -d ubuntu-core-24-arm64+raspi.img.xz
sudo dd if=ubuntu-core-24-arm64+raspi.img of=/dev/sdb status=progress; sync

try ubuntu core on x64 computer

#dd to usb or disk
sudo dd if=/images/kvm/ubuntu-core-24-amd64.img of=/dev/sdb status=progress; sync

树霉派上的linux启动流程理论分析

注意：下面的过程只是我从网上做的一个理论分析，并没有做实验，只是想让自己大致心里清楚有些大致的步骤。

树莓派4b启动流程：romboot–>uboot–>kernel–>rootfs
1, 第一阶段bootloader, 上电后，加载bootrom(固化在芯片内部，4b之前通过EEPROM加载SD上的bootcode.bin)到GPU中运行来初始化PLL, DDR等
2, 第二阶段bootloader, 从SD/网络/USB等加载start4.elf, 接着读取config.txt去进行uboot的启动流程
3, 启动kernel

通过JTAG将uboot引导安装到开发板Nor Flash/BIOS中，有两类，一类是并口，一类是USB代替并口(/dev/ttyUSB0)
通过uboot将OS(如tftp)引导安装到开发板NAND Flash中
打开Raspberry Pi Imager烧录镜（romboot）像到SD中， 默认串口没有输出，需修改config.txt在末尾添加enable_uart=1

1, 交叉编译工具的安装与uboot的编译

wget https://releases.linaro.org/components/toolchain/binaries/latest-7/aarch64-linux-gnu/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu.tar.xz
tar -xvf gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu.tar.xz -C /bak/soft/arm
alias crosscompiler='export KERNEL=kernel8;export ARCH=arm64;export CROSS_COMPILE=/bak/soft/arm/gcc-linaro-7.5.0-2019.12-x86_64_aarch64-linux-gnu/bin/aarch64-linux-gnu-'
git clone https://github.com/u-boot/u-boot.git
cp ./u-boot <your-sd>
git checkout v2020.04-rc3
sudo apt install u-boot-tools bison bc make flex libssl-dev ncurses-* -y
crosscompiler
make rpi_4_defconfig
make -j $(nproc)
cat << EOF |tee ./config.txt
ls u-boot.bin
arm_control=0x200  #64 bits
kernel=u-boot.bin
dtoverlay=disable-bt #If serial debugging is enabled, Bluetooth cannot be used
EOF

下面是一个客户使用的config.txt, 本来无法进入ubuntu core内核，但改为dtoverlay=vc4-kms-v3d就修复了
[cm4]
otg_mode=1
[pi4]
kernel=uboot_rpi_4.bin
dtoverlay=vc4-fkms-v3d,cma-128
dtoverlay=dwc2,dr_mode=host
[pi3]
kernel=uboot_rpi_3.bin
dtoverlay=vc4-fkms-v3d,cma-128
max_framebuffers=2
[all]
arm_64bit=1
enable_uart=1

2, 编译树莓派Linux源代码， 并通过tftp加载kernel

git clone --branch rpi-5.6.y https://github.com/raspberrypi/linux
mkdir rpi_hw
make O=rpi_hw bcm2711_defconfig
make O=rpi_hw menuconfig
make O=rpi_hw -j $(nproc)
ls rpi_hw/arch/arm64/boot
sudo cp rpi_hw/arch/arm64/boot/Image /bak/tftp/

进入u-boot命令窗口(就像进入bios一样的, 可能需要在出现“Hit any key to stop autoboot: 3”时，按下空格键）后运行

sudo minicom -D /dev/ttyUSB0 -b 115200  #press power key
setenv ipaddr 10.1.1.100 #设置开发板的静态地址(自定义)
setenv serverip 10.1.1.160 #设置根文件系统的nfs服务器地址
setenv netmask 255.255.255.0
saveenv
reset
setenv kernel_addr_r 0x8000
setenv kernel Image
setenv netboot 'tftp ${kernel_addr_r} ${kernel} && booti ${kernel_addr_r} - ${fdtcontroladdr}'
setenv bootcmd 'run netboot'
setenv bootargs 'console=ttyAMA0'
saveenv
reset

设置cmdline, 可以用下列的u-boot命令设置，也可以在/run/mnt/ubuntu-seed/cmdline.txt中设置

setenv nfsroot /opt/nfs/
setenv bootargs "console=ttyAMA0,115200 root=/dev/nfs rw nfsroot=${serverip}:${nfsroot},v3,tcp ip=$ipaddr:$serverip::$netmask::eth0:off"
saveenv

搭建tftp服务器的步骤：

#windows client is Tftp64
sudo apt install tftpd-hpa tftp-hpa -y  
cat << EOF |tee /etc/default/tftpd-hpa
# /etc/default/tftpd-hpa
TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/bak/tftp"
TFTP_ADDRESS=":69"
TFTP_OPTIONS="--secure --create"
EOF
sudo chown tftp:tftp /bak/tftp
sudo systemctl restart tftpd-hpa
echo 'test' |sudo tee /bak/tftp/test.txt
tftp 127.0.0.1 -c get test.txt

3, 从nfs文件系统中挂载根文件系统

sd里有两个分区，一个rootfs一个boot, 将boot分区的所有文件拷到file路径下
sudo cp <rootfs_in_sd> /opt/nfs/ -R
sudo mkdir -p /opt/nfs/file
sudo cp <all-files-in-boot> /opt/nfs/file/
sudo vim etc/fstab
 10.1.1.160:/opt/nfs/file /boot nfs defaults,vers=4.1,proto=tcp 0 0

Reference

[1] https://ubuntu.com/core/docs/testing-with-qemu
[2] https://blog.csdn.net/quqi99/article/details/80425722
[3] https://cloud.tencent.com/developer/article/1806436