feat: add network boot guide

- With network boot, we can load rootfs more easily
So we can debug more easily, painless

Author: initdc

.gitignore

@@ -3,10 +3,13 @@
 *.fd
 *.efi
 *.EFI
+*.gz
+*vmlin*
+*initrd*
+Image*
 
 boot.scr
 dtb
-Image
 
 /test
 /rootfs

Makefile

@@ -79,9 +79,23 @@ uboot-efi:
 	-device virtio-blk-device,drive=hd0 \
 	$(EXTRA_ARG)
 
+tftp:
+	qemu-system-aarch64 -m 4096 -smp 2 -cpu cortex-a57 -M virt -nographic \
+	-bios u-boot.bin \
+	-device virtio-net,netdev=net0 -netdev user,id=net0,tftp=./,net=192.168.1.0/24,hostfwd=tcp::8080-:80 \
+	-device virtio-net,netdev=net1 -netdev user,id=net1,net=100.0.0.0/24
+
+tftp-env:
+	qemu-system-aarch64 -m 4096 -smp 2 -cpu cortex-a57 -M virt -nographic \
+	-bios u-boot.bin \
+ 	-device loader,file=u-boot/boot.scr,addr=0x40200000 \
+	-drive file=fat:rw:u-boot \
+	-device virtio-net,netdev=net0 -netdev user,id=net0,tftp=./,net=192.168.1.0/24,hostfwd=tcp::8080-:80 \
+	-device virtio-net,netdev=net1 -netdev user,id=net1,net=100.0.0.0/24
+
 parted-list:
 	parted $(ARGS) unit MiB print
 
-boot.src:
+boot.scr:
 	mkimage -A arm64 -O linux -T script -C none \
 	-d u-boot/boot.txt u-boot/boot.scr

README.md

@@ -31,6 +31,7 @@ pkill -f qemu-system-aarch64
   openwrt-24.10.5-armsr-armv8-generic-kernel.bin
   openwrt-24.10.5-armsr-armv8-generic-squashfs-combined-efi.img
   openwrt-24.10.5-armsr-armv8-generic-squashfs-rootfs.img
+  openwrt-24.10.5-armsr-armv8-rootfs.cpio.gz
   u-boot.bin
   ```
 
@@ -51,7 +52,7 @@ pkill -f qemu-system-aarch64
   make uefi-shell
   ```
 
-- U-Boot boot.src (as a disk partition)
+- U-Boot `boot.scr` (as a disk partition)
 
   ```sh
   mkdir -p u-boot/boot
@@ -64,12 +65,10 @@ pkill -f qemu-system-aarch64
   fatload virtio 1 ${kernel_addr_r} /boot/Image
   setenv bootargs root=fe00
   booti ${kernel_addr_r} - ${fdtcontroladdr}
-
-  echo "Boot failed!"
   ```
 
   ```sh
-  make boot.src
+  make boot.scr
   make uboot-env
 
   # enter u-boot
@@ -81,9 +80,16 @@ pkill -f qemu-system-aarch64
   CONFIG_BOOTCOMMAND="source ${scriptaddr}"
   ```
 
+### Network Boot
+
+- [Network Boot](network-boot.md)
+
 ### Guide
 
-https://openwrt.org/docs/guide-user/virtualization/qemu
+- https://openwrt.org/docs/guide-user/virtualization/qemu
+- https://linuxkernel.org.cn/doc/html/latest/admin-guide/nfs/nfsroot.html
+- https://linuxkernel.org.cn/doc/html/latest/filesystems/ramfs-rootfs-initramfs.html
+- https://linuxkernel.org.cn/doc/html/latest/admin-guide/initrd.html
 
 ### License
 

network-boot.md

@@ -0,0 +1,39 @@
+## Network Boot
+
+### Prepare
+
+  Rebuild the [kernel](https://github.com/initdc/openwrt-qemu/releases) which should support `/dev/ram0`
+
+  ```sh
+  CONFIG_BLK_DEV_RAM=y
+  CONFIG_BLK_DEV_RAM_COUNT=16
+  CONFIG_BLK_DEV_RAM_SIZE=4096 # change size as you need
+  ```
+
+  ```sh
+  export ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
+
+  make defconfig
+  make menuconfig
+  make Image -j$(nproc)
+
+  file arch/arm64/boot/Image
+  Image: Linux kernel ARM64 boot executable Image, little-endian, 4K pages
+  ```
+
+### Run and test
+
+  then `make tftp`
+
+  ```sh
+  # enter u-boot
+  dhcp
+
+  tftp ${kernel_addr_r} Image
+  tftp ${ramdisk_addr_r} openwrt-24.10.5-armsr-armv8-rootfs.cpio.gz
+
+  setenv bootargs root=/dev/ram0
+  booti ${kernel_addr_r} ${ramdisk_addr_r}:${filesize} ${fdtcontroladdr}
+  ```
+
+  you can compile it as `boot.scr`, then `make tftp-env`