适用于：
环 境：
vmare 15 proubuntu 18.04qemu 6.2.0测试虚拟主板 ：vexpress-a9 （ARM Versatile Express for Cortex-A9）
源码下载：
qemu : https://download.qemu.orgu-boot: ftp://ftp.denx.de/pub/u-boot/buildroot: https://buildroot.org/downloads/需要的支持库：
apt-get install libpixman-1-dev sudo apt-get install zlib1g-dev sudo apt-get install libglib2.0-0 sudo apt-get install libglib2.0-dev
大概步骤：
一、下载安装qemu二、下载安装交叉编译器三、下载、编译u-boot (bootloader)四、下载、编译、安装文件系统（buildroot制作）五、内核zImage启动测试：(方法一，sd参数)六、启动内核方法二（initrd参数）七、启动内核方法三：(先启动u-boot - 加载内核到DRAM - bootz启动)八、启动内核方法四：tftp - 手动九、启动内核方法五：nfs - 手动十、启动内核方法七：自动用tftp加载内核到DRAM并启动十一、启动内核方法七：自动用nfs加载内核到DRAM并启动安装qemu ：
安装方法一：
命令：sudo apt-get install qemu
biren@ubuntu:~$ sudo apt-get install qemu The following additional packages will be installed: binfmt-support cpu-checker ibverbs-providers ipxe-qemu ipxe-qemu-256k-compat-efi-roms libaio1 libcacard0 libfdt1 libibverbs1 libiscsi7 libnl-route-3-200 librados2 librbd1 librdmacm1 libsdl1.2debian libspice-server1 libusbredirparser1 libxen-4.9 libxenstore3.0 msr-tools qemu-block-extra qemu-slof qemu-system qemu-system-arm qemu-system-common qemu-system-mips qemu-system-misc qemu-system-ppc qemu-system-s390x qemu-system-sparc qemu-system-x86 qemu-user qemu-user-binfmt qemu-utils seabios sharutils Suggested packages: qemu-user-static samba vde2 qemu-efi openbios-ppc openhackware openbios-sparc sgabios ovmf debootstrap sharutils-doc bsd-mailx | mailx 0 upgraded, 37 newly installed, 0 to remove and 148 not upgraded. Need to get 62.4 MB of archives. After this operation, 341 MB of additional disk space will be used. Do you want to continue? [Y/n]
此种安装方法的缺点是不能自主确定安装的版本。
安装方法二：
从qemu官网下载源码文件qemu-6.2.0.tar.xz
解压：
biren@ubuntu:~$ tar -xvf qemu-6.2.0.tar.xz
编 译：
命令：./configure --prefix=/usr/local/qemu6.2.0
错误一 ：
ERROR: pkg-config binary 'pkg-config' not found
biren@ubuntu:~$ cd qemu-6.2.0/ biren@ubuntu:~/qemu-6.2.0$ ./configure --prefix=/usr/local/qemu6.2.0 ERROR: pkg-config binary 'pkg-config' not found
解决：
安装pkg-config
biren@ubuntu:~/qemu-6.2.0$ sudo apt-get install pkg-config The following NEW packages will be installed: pkg-config 0 upgraded, 1 newly installed, 0 to remove and 235 not upgraded. Need to get 45.0 kB of archives. After this operation, 185 kB of additional disk space will be used. Get:1 http://mirrors.aliyun.com/ubuntu bionic/main amd64 pkg-config amd64 0.29.1-0ubuntu2 [45.0 kB] Fetched 45.0 kB in 0s (176 kB/s) Selecting previously unselected package pkg-config. (Reading database ... 140996 files and directories currently installed.) Preparing to unpack .../pkg-config_0.29.1-0ubuntu2_amd64.deb ... Unpacking pkg-config (0.29.1-0ubuntu2) ... Setting up pkg-config (0.29.1-0ubuntu2) ... Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
问题二：ERROR: Cannot find ninja
biren@ubuntu:~/qemu-6.2.0$ ./configure --prefix=/usr/local/qemu6.2.0 Using './build' as the directory for build output ERROR: Cannot find Ninja
解决：
安装ninja-build
biren@ubuntu:~/qemu-6.2.0$ sudo apt-get install ninja-build
问题三：ERROR: glib-2.56 gthread-2.0 is required to compile QEMU
biren@ubuntu:~/qemu-6.2.0$ ./configure --prefix=/usr/local/qemu6.2.0 Using './build' as the directory for build output ERROR: glib-2.56 gthread-2.0 is required to compile QEMU
解决：
biren@ubuntu:~/qemu-6.2.0$ sudo apt-get install libglib2.0 Note, selecting 'libglib2.0-cil-dev' for regex 'libglib2.0' Note, selecting 'libglib2.0-tests' for regex 'libglib2.0' Note, selecting 'libglib2.0-0-dbg' for regex 'libglib2.0' Note, selecting 'libglib2.0-dev-bin' for regex 'libglib2.0' Note, selecting 'libglib2.0-bin' for regex 'libglib2.0' Note, selecting 'libglib2.0-cil' for regex 'libglib2.0' Note, selecting 'libglib2.0-dev' for regex 'libglib2.0' Note, selecting 'libglib2.0-doc' for regex 'libglib2.0' Note, selecting 'libglib2.0-data' for regex 'libglib2.0' Note, selecting 'libglib2.0-0' for regex 'libglib2.0' The following additional packages will be installed: binfmt-support ca-certificates-mono cli-common libmono-corlib4.5-cil libmono-i18n-west4.0-cil libmono-i18n4.0-cil libmono-security4.0-cil libmono-system-configuration4.0-cil libmono-system-security4.0-cil libmono-system-xml4.0-cil libmono-system4.0-cil mono-4.0-gac mono-gac mono-runtime mono-runtime-common mono-runtime-sgen Suggested packages: monodoc-gtk2.0-manual devhelp libmono-i18n4.0-all libgamin0 The following NEW packages will be installed: binfmt-support ca-certificates-mono cli-common libglib2.0-cil libglib2.0-cil-dev libglib2.0-dev libglib2.0-dev-bin libglib2.0-doc libglib2.0-tests libmono-corlib4.5-cil libmono-i18n-west4.0-cil libmono-i18n4.0-cil libmono-security4.0-cil libmono-system-configuration4.0-cil libmono-system-security4.0-cil libmono-system-xml4.0-cil libmono-system4.0-cil mono-4.0-gac mono-gac mono-runtime mono-runtime-common mono-runtime-sgen The following packages will be upgraded: libglib2.0-0 libglib2.0-bin libglib2.0-data 3 upgraded, 22 newly installed, 0 to remove and 232 not upgraded. Need to get 10.1 MB/10.2 MB of archives. After this operation, 56.2 MB of additional disk space will be used. Do you want to continue? [Y/n]
问题四：ERROR: Dependency "pixman-1" not found
Run-time dependency appleframeworks found: NO (tried framework) Found pkg-config: /usr/bin/pkg-config (0.29.1) Run-time dependency pixman-1 found: NO (tried pkgconfig) ../meson.build:415:2: ERROR: Dependency "pixman-1" not found, tried pkgconfig A full log can be found at /home/biren/qemu-6.2.0/build/meson-logs/meson-log.txt ERROR: meson setup failed
解决：
biren@ubuntu:~/qemu-6.2.0$ sudo apt-get install libpixman-1-dev The following NEW packages will be installed: libpixman-1-dev 0 upgraded, 1 newly installed, 0 to remove and 232 not upgraded. Need to get 244 kB of archives. After this operation, 959 kB of additional disk space will be used.
继续安装qemu...：
biren@ubuntu:~/qemu-6.2.0$ ./configure --prefix=/usr/local/qemu6.2.0 biren@ubuntu:~/qemu-6.2.0$ make -j4 biren@ubuntu:~/qemu-6.2.0$ make install
将bin目录添加到环境变量PATH：
biren@ubuntu:~$ export PATH=$PATH:/usr/local/qemu6.2.0/bin 或在home目录下的.bashrc文件里加入上面这句。
qemu安装完成。
查看支持的主板：qemu-system-arm -machine help
biren@ubuntu:~$ qemu-system-arm -machine help Supported machines are: akita Sharp SL-C1000 (Akita) PDA (PXA270) ast2500-evb Aspeed AST2500 EVB (ARM1176) ast2600-evb Aspeed AST2600 EVB (Cortex-A7) borzoi Sharp SL-C3100 (Borzoi) PDA (PXA270) canon-a1100 Canon PowerShot A1100 IS (ARM946) cheetah Palm Tungsten|E aka. Cheetah PDA (OMAP310) collie Sharp SL-5500 (Collie) PDA (SA-1110) connex Gumstix Connex (PXA255) cubieboard cubietech cubieboard (Cortex-A8) emcraft-sf2 SmartFusion2 SOM kit from Emcraft (M2S010) fp5280g2-bmc Inspur FP5280G2 BMC (ARM1176) fuji-bmc Facebook Fuji BMC (Cortex-A7) g220a-bmc Bytedance G220A BMC (ARM1176) highbank Calxeda Highbank (ECX-1000) imx25-pdk ARM i.MX25 PDK board (ARM926) integratorcp ARM Integrator/CP (ARM926EJ-S) kudo-bmc Kudo BMC (Cortex-A9) kzm ARM KZM Emulation Baseboard (ARM1136) lm3s6965evb Stellaris LM3S6965EVB (Cortex-M3) lm3s811evb Stellaris LM3S811EVB (Cortex-M3) mainstone Mainstone II (PXA27x) mcimx6ul-evk Freescale i.MX6UL Evaluation Kit (Cortex-A7) mcimx7d-sabre Freescale i.MX7 DUAL SABRE (Cortex-A7) microbit BBC micro:bit (Cortex-M0) midway Calxeda Midway (ECX-2000) mps2-an385 ARM MPS2 with AN385 FPGA image for Cortex-M3 mps2-an386 ARM MPS2 with AN386 FPGA image for Cortex-M4 mps2-an500 ARM MPS2 with AN500 FPGA image for Cortex-M7 mps2-an505 ARM MPS2 with AN505 FPGA image for Cortex-M33 mps2-an511 ARM MPS2 with AN511 DesignStart FPGA image for Cortex-M3 mps2-an521 ARM MPS2 with AN521 FPGA image for dual Cortex-M33 mps3-an524 ARM MPS3 with AN524 FPGA image for dual Cortex-M33 mps3-an547 ARM MPS3 with AN547 FPGA image for Cortex-M55 musca-a ARM Musca-A board (dual Cortex-M33) musca-b1 ARM Musca-B1 board (dual Cortex-M33) musicpal Marvell 88w8618 / MusicPal (ARM926EJ-S) n800 Nokia N800 tablet aka. RX-34 (OMAP2420) n810 Nokia N810 tablet aka. RX-44 (OMAP2420) netduino2 Netduino 2 Machine (Cortex-M3) netduinoplus2 Netduino Plus 2 Machine (Cortex-M4) none empty machine npcm750-evb Nuvoton NPCM750 Evaluation Board (Cortex-A9) nuri Samsung NURI board (Exynos4210) orangepi-pc Orange Pi PC (Cortex-A7) palmetto-bmc OpenPOWER Palmetto BMC (ARM926EJ-S) quanta-gbs-bmc Quanta GBS (Cortex-A9) quanta-gsj Quanta GSJ (Cortex-A9) quanta-q71l-bmc Quanta-Q71l BMC (ARM926EJ-S) rainier-bmc IBM Rainier BMC (Cortex-A7) raspi0 Raspberry Pi Zero (revision 1.2) raspi1ap Raspberry Pi A+ (revision 1.1) raspi2b Raspberry Pi 2B (revision 1.1) realview-eb ARM RealView Emulation Baseboard (ARM926EJ-S) realview-eb-mpcore ARM RealView Emulation Baseboard (ARM11MPCore) realview-pb-a8 ARM RealView Platform Baseboard for Cortex-A8 realview-pbx-a9 ARM RealView Platform Baseboard Explore for Cortex-A9 romulus-bmc OpenPOWER Romulus BMC (ARM1176) sabrelite Freescale i.MX6 Quad SABRE Lite Board (Cortex-A9) smdkc210 Samsung SMDKC210 board (Exynos4210) sonorapass-bmc OCP SonoraPass BMC (ARM1176) spitz Sharp SL-C3000 (Spitz) PDA (PXA270) stm32vldiscovery ST STM32VLDISCOVERY (Cortex-M3) supermicrox11-bmc Supermicro X11 BMC (ARM926EJ-S) swift-bmc OpenPOWER Swift BMC (ARM1176) (deprecated) sx1 Siemens SX1 (OMAP310) V2 sx1-v1 Siemens SX1 (OMAP310) V1 tacoma-bmc OpenPOWER Tacoma BMC (Cortex-A7) terrier Sharp SL-C3200 (Terrier) PDA (PXA270) tosa Sharp SL-6000 (Tosa) PDA (PXA255) verdex Gumstix Verdex (PXA270) versatileab ARM Versatile/AB (ARM926EJ-S) versatilepb ARM Versatile/PB (ARM926EJ-S) vexpress-a15 ARM Versatile Express for Cortex-A15 vexpress-a9 ARM Versatile Express for Cortex-A9 virt-2.10 QEMU 2.10 ARM Virtual Machine virt-2.11 QEMU 2.11 ARM Virtual Machine virt-2.12 QEMU 2.12 ARM Virtual Machine virt-2.6 QEMU 2.6 ARM Virtual Machine virt-2.7 QEMU 2.7 ARM Virtual Machine virt-2.8 QEMU 2.8 ARM Virtual Machine virt-2.9 QEMU 2.9 ARM Virtual Machine virt-3.0 QEMU 3.0 ARM Virtual Machine virt-3.1 QEMU 3.1 ARM Virtual Machine virt-4.0 QEMU 4.0 ARM Virtual Machine virt-4.1 QEMU 4.1 ARM Virtual Machine virt-4.2 QEMU 4.2 ARM Virtual Machine virt-5.0 QEMU 5.0 ARM Virtual Machine virt-5.1 QEMU 5.1 ARM Virtual Machine virt-5.2 QEMU 5.2 ARM Virtual Machine virt-6.0 QEMU 6.0 ARM Virtual Machine virt-6.1 QEMU 6.1 ARM Virtual Machine virt QEMU 6.2 ARM Virtual Machine (alias of virt-6.2) virt-6.2 QEMU 6.2 ARM Virtual Machine witherspoon-bmc OpenPOWER Witherspoon BMC (ARM1176) xilinx-zynq-a9 Xilinx Zynq Platform Baseboard for Cortex-A9 z2 Zipit Z2 (PXA27x)
安装交叉编译器：
命令：sudo apt-get install gcc-arm-linux-gnueabi
biren@ubuntu:~$ sudo apt-get install gcc-arm-linux-gnueabi The following additional packages will be installed: binutils binutils-arm-linux-gnueabi binutils-common binutils-x86-64-linux-gnu cpp-7-arm-linux-gnueabi cpp-arm-linux-gnueabi gcc-7-arm-linux-gnueabi gcc-7-arm-linux-gnueabi-base gcc-7-cross-base gcc-8-cross-base libasan4-armel-cross libatomic1-armel-cross libbinutils libc6-armel-cross libc6-dev-armel-cross libcilkrts5-armel-cross libgcc-7-dev-armel-cross libgcc1-armel-cross libgomp1-armel-cross libstdc++6-armel-cross libubsan0-armel-cross linux-libc-dev-armel-cross Suggested packages: binutils-doc gcc-7-locales cpp-doc gcc-7-multilib-arm-linux-gnueabi gcc-7-doc libgcc1-dbg-armel-cross libgomp1-dbg-armel-cross libitm1-dbg-armel-cross libatomic1-dbg-armel-cross libasan4-dbg-armel-cross liblsan0-dbg-armel-cross libtsan0-dbg-armel-cross libubsan0-dbg-armel-cross libcilkrts5-dbg-armel-cross libmpx2-dbg-armel-cross libquadmath0-dbg-armel-cross gdb-arm-linux-gnueabi gcc-doc The following packages will be REMOVED: gcc-multilib The following NEW packages will be installed: binutils-arm-linux-gnueabi cpp-7-arm-linux-gnueabi cpp-arm-linux-gnueabi gcc-7-arm-linux-gnueabi gcc-7-arm-linux-gnueabi-base gcc-7-cross-base gcc-8-cross-base gcc-arm-linux-gnueabi libasan4-armel-cross libatomic1-armel-cross libc6-armel-cross libc6-dev-armel-cross libcilkrts5-armel-cross libgcc-7-dev-armel-cross libgcc1-armel-cross libgomp1-armel-cross libstdc++6-armel-cross libubsan0-armel-cross linux-libc-dev-armel-cross The following packages will be upgraded: binutils binutils-common binutils-x86-64-linux-gnu libbinutils 4 upgraded, 19 newly installed, 1 to remove and 228 not upgraded. Need to get 23.9 MB of archives. After this operation, 69.9 MB of additional disk space will be used. Do you want to continue? [Y/n]
也可以直接下载对应文件后配置：
下载地址：
http://releases.linaro.org/components/toolchain/binaries/https://launchpad.net/gcc-arm-embedded/+download查询安装情况：
biren@ubuntu:~$ arm-linux-gnueabi- arm-linux-gnueabi-addr2line arm-linux-gnueabi-gcov-7 arm-linux-gnueabi-ar arm-linux-gnueabi-gcov-dump arm-linux-gnueabi-as arm-linux-gnueabi-gcov-dump-7 arm-linux-gnueabi-c++filt arm-linux-gnueabi-gcov-tool arm-linux-gnueabi-cpp arm-linux-gnueabi-gcov-tool-7 arm-linux-gnueabi-cpp-7 arm-linux-gnueabi-gprof arm-linux-gnueabi-dwp arm-linux-gnueabi-ld arm-linux-gnueabi-elfedit arm-linux-gnueabi-ld.bfd arm-linux-gnueabi-gcc arm-linux-gnueabi-ld.gold arm-linux-gnueabi-gcc-7 arm-linux-gnueabi-nm arm-linux-gnueabi-gcc-ar arm-linux-gnueabi-objcopy arm-linux-gnueabi-gcc-ar-7 arm-linux-gnueabi-objdump arm-linux-gnueabi-gcc-nm arm-linux-gnueabi-ranlib arm-linux-gnueabi-gcc-nm-7 arm-linux-gnueabi-readelf arm-linux-gnueabi-gcc-ranlib arm-linux-gnueabi-size arm-linux-gnueabi-gcc-ranlib-7 arm-linux-gnueabi-strings arm-linux-gnueabi-gcov arm-linux-gnueabi-strip
下载、编译uboot :
下载地址：ftp://ftp.denx.de/pub/u-boot/
解压：
biren@ubuntu:~$ tar -xvf u-boot-2019.10.tar.bz2 biren@ubuntu:~$ cd u-boot-2019.10/ biren@ubuntu:~/u-boot-2019.10$ ll configs/vexp* -rw-rw-r-- 1 biren biren 1251 Oct 8 2019 configs/vexpress_aemv8a_juno_defconfig -rw-rw-r-- 1 biren biren 1120 Oct 8 2019 configs/vexpress_aemv8a_semi_defconfig -rw-rw-r-- 1 biren biren 963 Oct 8 2019 configs/vexpress_ca15_tc2_defconfig -rw-rw-r-- 1 biren biren 905 Oct 8 2019 configs/vexpress_ca5x2_defconfig -rw-rw-r-- 1 biren biren 936 Oct 8 2019 configs/vexpress_ca9x4_defconfig
以vexpress_ca9x4_defconfig为示例
编译u-boot :
biren@ubuntu:~/u-boot-2019.10$ make vexpress_ca9x4_defconfig # # configuration written to .config # biren@ubuntu:~/u-boot-2019.10$ make CROSS_COMPILE=arm-linux-gnueabi- all
结果：
产生的主要文件：u-boot , u-boot.bin ...
biren@ubuntu:~/u-boot-2019.10$ ls api doc Kbuild README u-boot.cfg.configs arch Documentation Kconfig scripts u-boot.lds board drivers lib System.map u-boot.map cmd dts Licenses test u-boot-nodtb.bin common env MAINTAINERS tools u-boot.srec config.mk examples Makefile u-boot u-boot.sym configs fs net u-boot.bin disk include post u-boot.cfg
测试u_boot启动：
命令：qemu-system-arm -M vexpress-a9 -m 512M -kernel ~/u-boot-2019.10/u-boot -nographic
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ qemu-system-arm -M vexpress-a9 -m 512M -kernel ~/u-boot-2019.10/u-boot -nographic U-Boot 2019.10 (Jun 23 2022 - 22:56:12 +0800) DRAM: 512 MiB WARNING: Caches not enabled Flash: 128 MiB MMC: MMC: 0 *** Warning - bad CRC, using default environment In: serial Out: serial Err: serial Net: smc911x-0 Hit any key to stop autoboot: 0 MMC Device 1 not found no mmc device at slot 1 Card did not respond to voltage select! smc911x: MAC 52:54:00:12:34:56 smc911x: detected LAN9118 controller smc911x: phy initialized smc911x: MAC 52:54:00:12:34:56 BOOTP broadcast 1 DHCP client bound to address 10.0.2.15 (5 ms) *** Warning: no boot file name; using '0A00020F.img' Using smc911x-0 device TFTP from server 10.0.2.2; our IP address is 10.0.2.15 Filename '0A00020F.img'. smc911x: MAC 52:54:00:12:34:56 。。。。。。 Wrong Image Format for bootm command ERROR: can't get kernel image! （此时还不能启动内核） =>
打印环境变量：
=> printenv arch=arm baudrate=38400 board=vexpress board_name=vexpress boot_a_script=load ${devtype} ${devnum}:${distro_bootpart} ${scriptaddr} ${prefix}${script}; source ${scriptaddr} boot_extlinux=sysboot ${devtype} ${devnum}:${distro_bootpart} any ${scriptaddr} ${prefix}${boot_syslinux_conf} boot_prefixes=/ /boot/ boot_script_dhcp=boot.scr.uimg boot_scripts=boot.scr.uimg boot.scr boot_syslinux_conf=extlinux/extlinux.conf boot_targets=mmc1 mmc0 pxe dhcp bootargs=root=/dev/sda1 rw console=ttyAMA0,38400n8 mem=1024M mtdparts=armflash:1M@0x800000(uboot),7M@0x1000000(kernel),24M@0x2000000(initrd) mmci.fmax=190000 devtmpfs.mount=0 vmalloc=256M bootcmd=run distro_bootcmd; run bootflash bootcmd_dhcp=if dhcp ${scriptaddr} ${boot_script_dhcp}; then source ${scriptaddr}; fi; bootcmd_mmc0=devnum=0; run mmc_boot bootcmd_mmc1=devnum=1; run mmc_boot bootcmd_pxe=dhcp; if pxe get; then pxe boot; fi bootdelay=2 自动启动内核延时 bootfile=boot.scr.uimg bootflash=run flashargs; cp ${ramdisk_addr} ${ramdisk_addr_r} ${maxramdisk}; bootm ${kernel_addr} ${ramdisk_addr_r} console=ttyAMA0,38400n8 cpu=armv7 distro_bootcmd=for target in ${boot_targets}; do run bootcmd_${target}; done dram=1024M ethact=smc911x-0 ethaddr=52:54:00:12:34:56 flashargs=setenv bootargs root=${root} console=${console} mem=${dram} mtdparts=${mtd} mmci.fmax=190000 devtmpfs.mount=0 vmalloc=256M kernel_addr=0x44100000 内核地址 kernel_addr_r=0x80008000 loadaddr=0x80008000 maxramdisk=0x1800000 mmc_boot=if mmc dev ${devnum}; then devtype=mmc; run scan_dev_for_boot_part; fi mtd=armflash:1M@0x800000(uboot),7M@0x1000000(kernel),24M@0x2000000(initrd) pxefile_addr_r=0x88000000 ramdisk_addr=0x44800000 根文件系统地址 ramdisk_addr_r=0x61000000 root=/dev/sda1 rw 。。。
启动成功
退出qemu或u-boot命令模式：
ctrl + a, 然后按x另一终端窗口中输入killall qemu-system-armpoweroff=====================================
下载、编译、安装文件系统（buildroot制作）：
下载：https://buildroot.org/downloads/
(buildroot可用于制作交叉编译、根文件系统、kernel内核、设备树dtb等)
解压：
biren@ubuntu:~ $ tar -xvf buildroot-2019.11-rc1.bz2
制作根文件、kernel方法一：自定义配置
配置：
biren@ubuntu:~$ cd buildroot-2019.11-rc1/ biren@ubuntu:~/buildroot-2019.11-rc1$ make menuconfig
Target options --->
Toolchain --->
System configuration --->
Filesystem images --->
......
执行make:
biren@ubuntu:~/buildroot-2019.11-rc1$ make -j4
制作根文件、kernel方法二：用预定义的配置
biren@ubuntu:~/buildroot-2019.11-rc1$ make qemu_arm_vexpress_defconfig biren@ubuntu:~/buildroot-2019.11-rc1$ make -j4 。。。。。。 mke2fs 1.45.4 (23-Sep-2019) Creating regular file /home/biren/buildroot-2019.11-rc1/output/images/rootfs.ext2 Creating filesystem with 61440 1k blocks and 15360 inodes Filesystem UUID: 0bb88659-037f-4f5e-be71-e6117cb08767 Superblock backups stored on blocks: 8193, 24577, 40961, 57345 Allocating group tables: done Writing inode tables: done Copying files into the device: done Writing superblocks and filesystem accounting information: done
buildroot编译结果：
生成关键的三个文件：rootfs.ext2(根文件系统), vexpress-v2p-ca9.dtb（设备树）, zImage（kernel内核）
biren@ubuntu:~/buildroot-2019.11-rc1$ ls arch Config.in DEVELOPERS linux package toolchain board Config.in.legacy dl Makefile README utils boot configs docs Makefile.legacy support CHANGES COPYING fs output system biren@ubuntu:~/buildroot-2019.11-rc1$ ls output build host images staging target biren@ubuntu:~/buildroot-2019.11-rc1$ ll output/images/ total 7884 -rw-r--r-- 1 biren biren 62914560 Jun 25 11:37 rootfs.ext2 -rw-r--r-- 1 biren biren 14430 Jun 25 11:37 vexpress-v2p-ca9.dtb -rw-r--r-- 1 biren biren 4134576 Jun 25 11:37 zImage
====================================
内核zImage启动测试：(方法一，用到-sd, mmcblk0参数)
启动命令：qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -nographic -sd rootfs.ext2 -append "root=/dev/mmcblk0 rw console=ttyAMA0 init=/linuxrc"
参数说明 ：
-kernel : 指定内核文件-dtb: 指定设备树文件-sd : 指定sd设备文件（此处存放根文件系统），类似有-hda(对应root=/dev/sda)-nographic : 非图形模式-append : 即bootargs启动命令行配置，root指定根文件系统挂载点，console指定输出接口，init指定启动后运行的第一个命令（程序 ）-m : 内存大小-M : 指定虚拟主板biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -append "root=/dev/mmcblk0 console=tty0 init=/linuxrc" -nographic -sd rootfs.ext2 WARNING: Image format was not specified for 'rootfs.ext2' and probing guessed raw. Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. Specify the 'raw' format explicitly to remove the restrictions. qemu-system-arm: Invalid SD card size: 60 MiB SD card size has to be a power of 2, e.g. 64 MiB. You can resize disk images with 'qemu-img resize <imagefile> <new-size>' (note that this will lose data if you make the image smaller than it currently is).
出现错误 ：SD card size has to be a power of 2, e.g. 64 MiB.
即SD文件的大小应是2的n次方
解决：修改文件大小
命令：qemu-img resize <imagefile> <new-size>
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ cp rootfs.ext2 rootfs-copy.ext2 biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ qemu-img resize rootfs.ext2 64M Image resized.
或者用dd命令新建一个64M的rootfs.img镜像文件，然后将数据复制进去：
dd if=/dev/zero of=rootfs.img bs=1M count=64
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ dd if=/dev/zero of=rootfs.img bs=1M count=64 64+0 records in 64+0 records out 67108864 bytes (67 MB, 64 MiB) copied, 0.134254 s, 500 MB/s biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ mkfs.ext2 rootfs.img mke2fs 1.44.1 (24-Mar-2018) Discarding device blocks: done Creating filesystem with 65536 1k blocks and 16384 inodes Filesystem UUID: 01d8344a-685d-420e-82f6-6b6d24c6d2d7 Superblock backups stored on blocks: 8193, 24577, 40961, 57345 Allocating group tables: done Writing inode tables: done Writing superblocks and filesystem accounting information: done biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ mkdir tmpfs biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo mount rootfs-copy.ext2 tmpfs biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo mount -o loop rootfs.img /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo cp -a tmpfs/* /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo umount tmpfs biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo umount /mnt
新的文件：
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ ll total 174457 -rw-r--r-- 1 biren biren 62914560 Jun 30 17:04 rootfs-copy.ext2 -rw-r--r-- 1 biren biren 67108864 Jun 30 16:54 rootfs.ext2 新的文件 -rw-rw-r-- 1 biren biren 67108864 Jun 30 17:03 rootfs.img 新的文件 -rw-rw-r-- 1 biren biren 134217728 Jun 28 16:49 sdcard.img drwxr-xr-x 18 root root 1024 Jun 25 11:37 tmpfs/ -rw-r--r-- 1 biren biren 14430 Jun 25 11:37 vexpress-v2p-ca9.dtb -rw-r--r-- 1 biren biren 4134576 Jun 25 11:37 zImage
重新启动内核zImage：
根文件系统用rootfs.img或rootfs.ext2都行
（有些是没有dtb的，编译内核时有参数指定）
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -nographic -sd rootfs.img -append "root=/dev/mmcblk0 console=ttyAMA0 init=/linuxrc" WARNING: Image format was not specified for 'rootfs.img' and probing guessed raw. Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. Specify the 'raw' format explicitly to remove the restrictions. Welcome to Buildroot 正常启动。。。。。。 buildroot login: root （无密码） # # pwd /root # ls / bin lib lost+found opt run tmp dev lib32 media proc sbin usr etc linuxrc mnt root sys var
警告：Image format was not specified for 'rootfs.img' and probing guessed raw.
可以用 -drive format=raw,file=rootfs.img解决
==================================
启动内核方法二：（用到-initrd,ram0参数）
命令：
qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -initrd rootfs.ext3 -nographic -append "root=/dev/ram0 rw console=ttyAMA0 init=/linuxrc"
与前面区别：这里没有用-sd选项，用的是-initrd rootfs.ext3
另外挂载点改为：root=/dev/ram0或root=/dev/ram
（此处的rootfs.ext3是从rootfs.ext2复制过来重新制成ext3格式，大小4M,可用dd制作）
（rootfs.ext3, rootfs.ext3.gz, rootfs.ext3.ramdisk都可用）
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ ll rootfs.ext3* -rw-rw-r-- 1 biren biren 4194304 Jul 13 22:29 rootfs.ext3 -rw-rw-r-- 1 biren biren 789675 Jul 6 10:47 rootfs.ext3.gz gzip压缩文件 -rw-rw-r-- 1 biren biren 4194368 Jul 6 11:24 rootfs.ext3.ramdisk 用mkimage制成的，加64字节头
值得注意的是编译内核时需要选上支持ram disk的相关选项：
配置buildroot:
命令：make qemu_arm_vexpress_defconfig
biren@ubuntu:~/buildroot-2019.11-rc1$ make qemu_arm_vexpress_defconfig biren@ubuntu:~/buildroot-2019.11-rc1$ make menuconfig
> Filesystem images :
ext2/3/4 root filesystem(60M) exact size 根文件系统的大小为60M（实际只占用几百K）配置内核：
命令：make linux-menuconfig
biren@ubuntu:~/buildroot-2019.11-rc1$ make linux-menuconfig
> General setup :
Initial RAM filesystem and RAM disk (initramfs/initrd) supportSupport initial ramdisk/ramfs compressed using gzip> Device Drivers > Block devices :
Default RAM disk size (kbytes) 指定ramdisk的大小，启动时在-initrd参数中指定的文件大小不能超过此值
> File systems :
Second extended fs support（ext2） ...
启动内核方法三：从MMC加载内核
(先启动u-boot - 加载内核到RAM - bootz启动)
一、先制作sdcard.img文件
创建128M文件格式化为vfat挂载到/mnt复制zImage、rootfs.ext2、vexpress-v2p-ca9.dtb到/mnt取消挂载点/mntbiren@ubuntu:~/buildroot-2019.11-rc1/output/images$ dd if=/dev/zero of=sdcard.img bs=4096 count=32768 25600+0 records in 25600+0 records out 104857600 bytes (134 MB, 128 MiB) copied, 0.818929 s, 128 MB/s biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ mkfs.vfat sdcard.img mkfs.fat 4.1 (2017-01-24) biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo mount -rw -o loop sdcard.img /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo cp zImage /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo cp rootfs.ext2 /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo cp vexpress-v2p-ca9.dtb /mnt biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ ll /mnt total 65514 -rwxr-xr-x 1 root root 62914560 Jun 28 16:44 rootfs.ext2* -rwxr-xr-x 1 root root 14430 Jun 28 16:44 vexpress-v2p-ca9.dtb* -rwxr-xr-x 1 root root 4134576 Jun 28 16:44 zImage* biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo umount /mnt
二、启动u-boot
命令：qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd sdcard.img -nographic
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -nographic -sd sdcard.img WARNING: Image format was not specified for 'sdcard.img' and probing guessed raw. Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. Specify the 'raw' format explicitly to remove the restrictions. U-Boot 2019.10 (Jun 23 2022 - 22:56:12 +0800) DRAM: 512 MiB WARNING: Caches not enabled Flash: 128 MiB MMC: MMC: 0 *** Warning - bad CRC, using default environment In: serial Out: serial Err: serial Net: smc911x-0 Hit any key to stop autoboot: 0 MMC Device 1 not found no mmc device at slot 1 switch to partitions #0, OK mmc0 is current device ** Invalid partition 1 ** smc911x: MAC 52:54:00:12:34:56 smc911x: detected LAN9118 controller smc911x: phy initialized smc911x: MAC 52:54:00:12:34:56 。。。 TFTP error: trying to overwrite reserved memory... smc911x: MAC 52:54:00:12:34:56 Wrong Image Format for bootm command ERROR: can't get kernel image! （此时还没有启动内核） =>
三、将zImage、rootfs.ext2、vexpress-v2p-ca9.dtb从sd中加载到DRAM内存中：
命令：fatload mmc 0:0 0x62008000 zImage
(加载地址自拟，只要不重叠即可)
=> fatload mmc 0:0 0x62008000 zImage 4134576 bytes read in 2344 ms (1.7 MiB/s) => fatload mmc 0:0 0x62A08000 rootfs.ext2 62914560 bytes read in 36366 ms (1.6 MiB/s) => fatload mmc 0:0 0x68E08000 vexpress-v2p-ca9.dtb 14430 bytes read in 40 ms (351.6 KiB/s)
四、启动内核
命令：bootz [addr [initrd[:size]] [fdt]]
如：bootz 62008000 62A08000 68E08000
无initrd时用“-”代替
如：bootz 62008000 - 68E08000
=> bootz 62008000 62A08000 68E08000 Kernel image @ 0x62008000 [ 0x000000 - 0x3f16b0 ] Wrong Ramdisk Image Format Ramdisk image is corrupt or invalid
错误 ：Wrong Ramdisk Image Format
解决：使用mkimage命令将根文件系统制成uImage格式的文件
命令：mkimage -n 'uboot ext2 ramdisk rootfs' -A arm -O linux -T ramdisk -C none -d rootfs.ext2 rootfs.ext2.ramdisk
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ mkimage -n 'uboot ext2 ramdisk rootfs' -A arm -O linux -T ramdisk -C none -d rootfs.ext2 rootfs.ext2.ramdisk Image Name: uboot ext2 ramdisk rootfs Created: Tue Jul 5 19:58:27 2022 Image Type: ARM Linux RAMDisk Image (uncompressed) Data Size: 62914560 Bytes = 61440.00 KiB = 60.00 MiB Load Address: 00000000 Entry Point: 00000000 biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ ll -rwxr-xr-x 1 biren biren 62914560 Jun 28 16:44 rootfs.ext2* -rw-rw-r-- 1 biren biren 62914624 Jul 5 19:58 rootfs.ext2.ramdisk -rw-rw-r-- 1 biren biren 134217728 Jul 5 19:57 sdcard.img drwxr-xr-x 2 root root 16384 Jan 1 1970 tmpfs/ -rw-r--r-- 1 biren biren 14430 Jun 25 11:37 vexpress-v2p-ca9.dtb -rw-r--r-- 1 biren biren 4134576 Jun 25 11:37 zImage
新的根文件系统文件：rootfs.ext2.ramdisk
将rootfs.ext2.ramdisk存入sdcard.img中：
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo mount -o loop sdcard.img tmpfs biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo cp rootfs.ext2.ramdisk tmpfs biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo umount tmpfs
再运行二到四步：
qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd sdcard.img -nographic fatload mmc 0:0 0x62008000 zImage;fatload mmc 0:0 0x62A08000 rootfs.ext2.ramdisk;fatload mmc 0:0 0x68E08000 vexpress-v2p-ca9.dtb setenv bootargs root=/dev/ram rw console=ttyAMA0,115200 init=/linuxrc bootz 62008000 62A08000 68E08000
启动内核方法四：用tftp加载内核
先进行qemu网络功能配置：
查看tun是否安装：
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ grep CONFIG_TUN= /boot/config-`uname -r` CONFIG_TUN=y 或用如下查询 ： biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ ll /dev/net/tun crw-rw-rw- 1 root root 10, 200 Jul 17 10:51 /dev/net/tun 如果没有tun则用如下命令增加： mknod /dev/net/tun c 10 200
ubuntu里安装桥接工具：
命令：sudo apt-get install uml-utilities bridge-utils
ubuntu里创建tap0 ：
查看当前网络：
命令：ip addr 或ip a 或ip address
或用：ifconfig
biren@ubuntu:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 00:0c:29:ad:94:63 brd ff:ff:ff:ff:ff:ff inet 192.168.153.146/24 brd 192.168.153.255 scope global dynamic noprefixroute ens33 valid_lft 1657sec preferred_lft 1657sec inet6 fe80::1800:85cd:fb23:2de/64 scope link noprefixroute valid_lft forever preferred_lft forever
网口名是ens33，ip是192.168.153.146
虚拟机ubuntu与win10连接用的是NAT方式
创建tap0命令：
sudo ip tuntap add dev tap0 mode tapsudo ip link set dev tap0 upsudo ip address add dev tap0 192.168.153.170/24biren@ubuntu:~$ sudo ip tuntap add dev tap0 mode tap biren@ubuntu:~$ sudo ip link set dev tap0 up biren@ubuntu:~$ sudo ip address add dev tap0 192.168.153.170/24 biren@ubuntu:~$ ifconfig ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.153.146 netmask 255.255.255.0 broadcast 192.168.153.255 inet6 fe80::1800:85cd:fb23:2de prefixlen 64 scopeid 0x20<link> ether 00:0c:29:ad:94:63 txqueuelen 1000 (Ethernet) RX packets 2430 bytes 3084008 (3.0 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 1452 bytes 118503 (118.5 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen 1000 (Local Loopback) RX packets 207 bytes 16767 (16.7 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 207 bytes 16767 (16.7 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 tap0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 192.168.153.170 netmask 255.255.255.0 broadcast 0.0.0.0 ether be:6a:b3:80:db:9d txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
配置TFTP服务器：
一、在主机ubuntu上搭建tftp服务器
安装tftp-hpa、 tftpd-hpa、 xinetd三个包文件
biren@ubuntu:~$ sudo apt-get install tftp-hpa tftpd-hpa xinetd
二、建立ftp文件夹,并修改为777权限
biren@ubuntu:~$ mkdir tftpFile biren@ubuntu:~$ chmod 777 tftpFile
三、修改/etc/default/tftpd-hpa
将
# /etc/default/tftpd-hpa TFTP_USERNAME="tftp" TFTP_DIRECTORY="/var/lib/tftpboot" TFTP_ADDRESS=":69" TFTP_OPTIONS="--secure"
修改为：
# /etc/default/tftpd-hpa TFTP_USERNAME="tftp" TFTP_DIRECTORY="/home/biren/tftpFile" TFTP_ADDRESS=":69" TFTP_OPTIONS="--secure"
四、新建/etc/xinetd.d/tftp文件，内容如下：
server tftp { protocol = udp flags = IPv4 socket_type = dgram user = root server = /usr/sbin/in.tftpd server_args = -s /home/biren/tftpFile wait = yes disable = no per_source = 11 cps = 100 2 }
五、启动tftp服务
sudo service tftpd-hpa start 出现tftp>命令符正常： biren@ubuntu:~$ tftp localhost tftp>
六、将zImage、rootfs.ext3.ramdisk、vexpress-v2p-ca9.dtb复制到/home/biren/tftpFile/里
biren@ubuntu:~/tftpFile$ pwd /home/biren/tftpFile biren@ubuntu:~/tftpFile$ ll total 8296 drwxrwxrwx 2 biren biren 4096 Aug 18 18:59 ./ drwxr-xr-x 32 biren biren 4096 Aug 18 16:15 ../ -rw-rw-r-- 1 biren biren 4194368 Jul 6 11:24 rootfs.ext3.ramdisk -rw-r--r-- 1 biren biren 14430 Jul 13 17:24 vexpress-v2p-ca9.dtb -rw-r--r-- 1 biren biren 4268720 Jul 13 17:24 zImage
带网络参数的启动u-boot :
命令：sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd sdcard.img -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no
参数说明：
-net nic 建立虚拟网卡-net tap,ifname=tap0 在host上产生一个tap0接口script, donwscript指定启动时的网络配置脚本，如果不指定时则会自动查找/etc/qemu-ifup和/etc/qemu-ifdown来运行启动后，设置qemu的ip为192.168.153.160 ，
设置serverip为192.168.153.170 ：
=> setenv ipaddr 192.168.153.160 => setenv serverip 192.168.153.170 => ping 192.168.153.170 smc911x: MAC 52:54:00:12:34:56 smc911x: detected LAN9118 controller smc911x: phy initialized smc911x: MAC 52:54:00:12:34:56 Using smc911x-0 device smc911x: MAC 52:54:00:12:34:56 host 192.168.153.170 is alive =>
设置启动参数：
=> setenv bootargs 'root=/dev/mmcblk0 rw console=ttyAMA0 init=/linuxrc'
用tftp命令加载启动文件到内存：
源：192.168.153.170:/home/biren/tftpFile/
目的地：qemu的起始地址为0x62008000、0x62508000、0x62a08000的内存处
命令：
tftp 62008000 zImage 从/home/biren/tftpFile/加载内核tftp 62508000 rootfs.ext3.ramdisk 加载根文件系统tftp 62a08000 vexpress-v2p-ca9.dtb 加载设备树=> tftp 62008000 zImage smc911x: MAC 52:54:00:12:34:56 smc911x: detected LAN9118 controller smc911x: phy initialized smc911x: MAC 52:54:00:12:34:56 Using smc911x-0 device TFTP from server 192.168.153.170; our IP address is 192.168.153.160 Filename 'zImage'. Load address: 0x62008000 Loading: ######################### 1.4 MiB/s done Bytes transferred = 4268720 (4122b0 hex) smc911x: MAC 52:54:00:12:34:56 => tftp 62508000 rootfs.ext3.ramdisk => tftp 62a08000 vexpress-v2p-ca9.dtb
启动内核：
=> bootz 62008000 62508000 62a08000
启动到最后时出现错误：
can't open /dev/ttyAMA0: No such file or directory
解决方法一：
将启动bootargs参数
setenv bootargs 'root=/dev/mmcblk0 rw console=ttyAMA0 init=/linuxrc'
改为：
setenv bootargs 'root=/dev/ram rw console=ttyAMA0 init=/linuxrc'
解决方法二：
将启动命令：
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd sdcard.img -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no
改为：(即用-sd挂载根文件系统)
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd rootfs.ext3 -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no
将启动内核命令改为即可：
bootz 62008000 - 62a08000
另一个可能的原因是：
没有勾选devtmpfs filesystem
通过以下方式选中并重新编译
biren@ubuntu:~/buildroot-2019.11-rc1$ make linux-menuconfig
Device Drivers ---> Generic Driver Options --->
[*] Maintain a devtmpfs filesystem to mount at /dev
[*] Automount devtmpfs at /dev, after the kernel mounted the rootfs
启动内核方法五：用nfs加载内核（自动）
1、安装nfs-kernel-server , nfs-common
命令：sudo apt-get install nfs-kernel-server nfs-common
2、创建共享文件夹：
biren@ubuntu:~$ mkdir nfsFile biren@ubuntu:~/nfsFile$ pwd /home/biren/nfsFile
3、在/etc/exports中加入一行：
/home/biren/nfsFile *(rw,sync,no_root_squash)
4、重启nfs服务：
sudo service nfs-kernel-server restart
5、配置tap0网络命令（ubuntu）：
sudo ip tuntap add dev tap0 mode tapsudo ip link set dev tap0 upsudo ip address add dev tap0 192.168.153.170/24也可以使用以下命令：
sudo tunctl -u $USER -t tap0 （生成一个tap0接口） sudo ifconfig tap0 192.168.153.170 删除tap0接口： sudo tunctl -d tap0 sudo ifconfig tap0 192.168.153.170 down 卸载网卡 删除网桥： sudo brctl delbr br0
6、启动仿真qemu
命令：sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -sd sdcard.img -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no -append "root=/dev/nfs rw nfsroot=192.168.153.170:/home/biren/nfsFile ip=192.168.153.160:192.168.153.170::::eth0:off console=ttyAMA0 init=/linuxrc"
错误一：
VFS: Cannot open root device "nfs" or unknown-block(2,0): error -6
VFS: Unable to mount root fs via NFS, trying floppy. VFS: Cannot open root device "nfs" or unknown-block(2,0): error -6 Please append a correct "root=" boot option; Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(2,0)
原因：
内核的nfs版本要与ubuntu中的server nfs版本一致
内核支持的nfs版本：
> File systems > Network File Systems
ubuntu server nfs版本查询命令：nfsstat
解决：
在启动命令上加入nfs版本v3
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel zImage -dtb vexpress-v2p-ca9.dtb -sd sdcard.img -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no -append "root=/dev/nfs rw nfsroot=192.168.153.170:/home/biren/nfsFile,v3 ip=192.168.153.160:192.168.153.170::::eth0:off console=ttyAMA0 init=/linuxrc" -rtc base=localtime,clock=host
错误二：
devtmpfs: error mounting -2
end Kernel panic - not syncing: Requested init /linuxrc failed (error -2)
解决方法一：
将根文件系统挂载到nfsFile目录下：
biren@ubuntu:~$ sudo mount buildroot-2019.11-rc1/output/images/rootfs.ext3 ./nfsFile
或者直接将根文件系统里所有的资料都复制到/home/biren/nfsFile里面
biren@ubuntu:~$ sudo mount buildroot-2019.11-rc1/output/images/rootfs.ext3 ./nfsFile/ biren@ubuntu:~$ ls ./nfsFile/ bin etc lib32 lost+found mnt proc run sys usr dev lib linuxrc media opt root sbin tmp var
解决方法二：（可能的原因之一）
重新将busybox编译成静态的：
biren@ubuntu:~/buildroot-2019.11-rc1$ make qemu_arm_vexpress_defconfig
biren@ubuntu:~/buildroot-2019.11-rc1$ make help （查看可用的命令）
biren@ubuntu:~/buildroot-2019.11-rc1$ make busybox-menuconfig
位置：Settings ---> [*] Build static binary (no shared libs)
biren@ubuntu:~/buildroot-2019.11-rc1$ make -j4
启动内核方法五：用nfs加载内核（手动）
1、将rootfs.ext3 vexpress-v2p-ca9.dtb zImage复制到nfsFile目录里
2、tap0设置：与前同
3、启动u-boot命令：
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no -rtc base=localtime,clock=host
4、设置网址（以下在虚拟qemu里操作）
=> setenv ipaddr 192.168.153.160
=> setenv serverip 192.168.153.170
5、加载内核到DRAM内存
=> nfs 62008000 192.168.153.170:/home/biren/nfsFile/zImage
=> nfs 62a08000 192.168.153.170:/home/biren/nfsFile/vexpress-v2p-ca9.dtb
6、ubuntu里挂载根文件系统rootfs.ext3到nfsFile
biren@ubuntu:~$ sudo mount buildroot-2019.11-rc1/output/images/rootfs.ext3 ./nfsFile/
7、设置bootcmd/bootargs
=> setenv bootargs 'root=/dev/nfs rw nfsroot=192.168.153.170:/home/biren/nfsFile,v3 ip=192.168.153.160:192.168.153.170::::eth0:off console=ttyAMA0 init=/linuxrc'
8、启动内核：
=> bootz 62008000 - 62a08000
启动内核方法六：自动用tftp加载内核到DRAM并启动
1、修改/home/biren/u-boot-2019.10/include/configs/vexpress_common.h，加入以下内容：
#define CONFIG_BOOTCOMMAND "tftp 0x62008000 zImage; tftp 0x62508000 rootfs.ext3.ramdisk; tftp 0x62a08000 vexpress-v2p-ca9.dtb; setenv bootargs 'root=/dev/ram rw console=ttyAMA0 init=/linuxrc'; bootz 0x62008000 0x62508000 0x62a08000;" #define CONFIG_IPADDR 192.168.153.160 #define CONFIG_NETMASK 255.255.255.0 #define CONFIG_SERVERIP 192.168.153.170
重新编译u-boot:
biren@ubuntu:~/u-boot-2019.10$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- -j4
2、tap0设置：与前同
3、启动u-boot（同时自动启动内核）命令：
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no -rtc base=localtime,clock=host
启动内核方法七：自动用nfs加载内核到DRAM并启动
1、修改/home/biren/u-boot-2019.10/include/configs/vexpress_common.h，加入以下内容：
#define CONFIG_BOOTCOMMAND "nfs 62008000 192.168.153.170:/home/biren/nfsFile/zImage; nfs 62508000 192.168.153.170:/home/biren/nfsFile/rootfs.ext3.ramdisk; nfs 62a08000 192.168.153.170:/home/biren/nfsFile/vexpress-v2p-ca9.dtb; setenv bootargs 'root=/dev/ram rw console=ttyAMA0 init=/linuxrc'; bootz 0x62008000 0x62508000 0x62a08000;" #define CONFIG_IPADDR 192.168.153.160 #define CONFIG_NETMASK 255.255.255.0 #define CONFIG_SERVERIP 192.168.153.170
2、其它与“方法六”一样
==================================
问题说明 ：
问题一：
end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block
可能原因：
root=/dev/ram（mmcblk0, sda, vda等）设置出错编译内核时参数设置错误启动时缺乏dtb参数等...... VFS: Cannot open root device "(null)" or unknown-block(0,0): error -6 Please append a correct "root=" boot option; here are the available partitions: 1f00 131072 mtdblock0 (driver?) 1f01 32768 mtdblock1 (driver?) Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.16 #1 Hardware name: ARM-Versatile Express [<80110dbc>] (unwind_backtrace) from [<8010c9f8>] (show_stack+0x10/0x14) [<8010c9f8>] (show_stack) from [<806a8a80>] (dump_stack+0x88/0x9c) [<806a8a80>] (dump_stack) from [<80120bf8>] (panic+0xf0/0x25c) [<80120bf8>] (panic) from [<809015e8>] (mount_block_root+0x210/0x2bc) [<809015e8>] (mount_block_root) from [<809017b4>] (mount_root+0x120/0x13c) [<809017b4>] (mount_root) from [<80901920>] (prepare_namespace+0x150/0x198) [<80901920>] (prepare_namespace) from [<80901190>] (kernel_init_freeable+0x354/0x364) [<80901190>] (kernel_init_freeable) from [<806bcee0>] (kernel_init+0x8/0x110) [<806bcee0>] (kernel_init) from [<801010e8>] (ret_from_fork+0x14/0x2c) Exception stack(0x9f48ffb0 to 0x9f48fff8) ffa0: 00000000 00000000 00000000 00000000 ffc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ffe0: 00000000 00000000 00000000 00000000 00000013 00000000 ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---
问题二：
/etc/qemu-ifup failed with status 256
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd rootfs.ext3 -nographic -net nic -net tap,ifname=tap0 WARNING: Image format was not specified for 'rootfs.ext3' and probing guessed raw. Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. Specify the 'raw' format explicitly to remove the restrictions. qemu-system-arm: -net tap,ifname=tap0: network script /usr/local/qemu6.2.0/bin/../etc/qemu-ifup failed with status 256
原因：是qemu-system-arm启动时会去查找/etc/qemu-ifup和/etc/qemu-ifdown并执行，这两个文件缺失或配置错误导致。
解决：
加上script=no,downscript=no参数即可
sudo /usr/local/qemu6.2.0/bin/qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd rootfs.ext3 -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no
问题三：
sudo: qemu-system-arm: command not found
biren@ubuntu:~/buildroot-2019.11-rc1/output/images$ sudo qemu-system-arm -M vexpress-a9 -m 512M -kernel /home/biren/u-boot-2019.10/u-boot -sd rootfs.ext3 -nographic -net nic -net tap,ifname=tap0,script=no,downscript=no sudo: qemu-system-arm: command not found
原因：
是配置网络需要root权限，所以要用上sudo，而sudo是默认开启了- -with-secure-path选项
解决：
方法一：qemu-system-arm加上绝对路径
方法二：修改/etc/sudoers文件，将qemu-system-arm所在的目录加入Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"中
问题四：
qemu-system-arm: -net tap,ifname=tap0: could not configure /dev/net/tun (tap0): Operation not permitted
解决：在命令前加上sudo
问题五：
Unknown command 'nfs' - try 'help'
=> nfs 62008000 192.168.153.170:/home/biren/nfsFile/zImage Unknown command 'nfs' - try 'help' => help nfs Unknown command 'nfs' - try 'help' without arguments for list of all known commands
原因：
编译u-boot时没选上nfs
解决：
选上nfs选项后重新编译u-boot
biren@ubuntu:~/u-boot-2019.10$ make vexpress_ca9x4_defconfig
biren@ubuntu:~/u-boot-2019.10$ make menuconfig
位置：Command line interface --> Network commands
重新编译即可：
make CROSS_COMPILE=arm-linux-gnueabi- all
=====================================
其它说明 ：
initrd（initial ramdisk）是在系统引导过程中挂载的一个临时根文件系统 ，用来支持两阶段的引导过程。initrd文件中包含了各种可执行程序和驱动程序，一般被用来临时的引导硬件到实际内核vmlinuz能够接管并继续引导的状态,也可以用来挂载实际的根文件系统，然后再将这个 initrd RAM 磁盘卸载，并释放内存。在很多嵌入式Linux 系统中，initrd 就是最终的根文件系统。
接口：tty0, ttyAMA0, ttySAC0, ttyS0
AMA：是Advanced Microcontroller Bus Architecture的缩写，是ARM的一种 UART设备（ARM AMBA PL011）
设置：mknod /dev/ttyAMA0 c 204 64
编译内核命令：
make zImage //编译生成zImage镜像文件make dtbs //编译生成设备树镜像文件make LOADADDR=0x60003000 uImage -j4 指定uImage的加载地址ubuntu中重启网络命令:
sudo service networking restart 或 sudo service network-manager restart 或 /etc/init.d/networking restart 或 sudo ifdown -a && sudo ifup -a
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