安装qemu工具：
$ sudo apt install qemu-system-arm到buildroot.org官网下载相应的压缩包：buildroot-2020.02.6.tar.gz 。
解压源码包：
$ tar xzvf buildroot-2017.05.2.tar.gz也可以用git抓取：
$ git clone https://git.buildroot.net/buildroot（1）选择虚拟qemu配置（详细配置查看configs目录）：
book@bc7c3ac008b2:~/buildroot-2020.02.6$ make qemu_arm_vexpress_defconfig mkdir -p /home/buildroot-2020.02.6/output/build/buildroot-config/lxdialog PKG_CONFIG_PATH="" make CC="/usr/bin/gcc" HOSTCC="/usr/bin/gcc" \ obj=/home/buildroot-2020.02.6/output/build/buildroot-config -C support/kconfig -f Makefile.br conf make[1]: Entering directory '/home/buildroot-2020.02.6/support/kconfig' /usr/bin/gcc -DCURSES_LOC="<ncurses.h>" -DLOCALE -I/home/buildroot-2020.02.6/output/build/buildroot-config -DCONFIG_=\"\" -MM *.c > /home/buildroot-2020.02.6/output/build/buildroot-config/.depend 2>/dev/null || : /usr/bin/gcc -DCURSES_LOC="<ncurses.h>" -DLOCALE -I/home/buildroot-2020.02.6/output/build/buildroot-config -DCONFIG_=\"\" -c conf.c -o /home/buildroot-2020.02.6/output/build/buildroot-config/conf.o /usr/bin/gcc -DCURSES_LOC="<ncurses.h>" -DLOCALE -I/home/buildroot-2020.02.6/output/build/buildroot-config -DCONFIG_=\"\" -I. -c /home/buildroot-2020.02.6/output/build/buildroot-config/zconf.tab.c -o /home/buildroot-2020.02.6/output/build/buildroot-config/zconf.tab.o /usr/bin/gcc -DCURSES_LOC="<ncurses.h>" -DLOCALE -I/home/buildroot-2020.02.6/output/build/buildroot-config -DCONFIG_=\"\" /home/buildroot-2020.02.6/output/build/buildroot-config/conf.o /home/buildroot-2020.02.6/output/build/buildroot-config/zconf.tab.o -o /home/buildroot-2020.02.6/output/build/buildroot-config/conf rm /home/buildroot-2020.02.6/output/build/buildroot-config/zconf.tab.c make[1]: Leaving directory '/home/buildroot-2020.02.6/support/kconfig' # # configuration written to /home/buildroot-2020.02.6/.config #（2）开始编译：
book@bc7c3ac008b2:~/buildroot-2020.02.6$ make（3）编译完成：
Creating regular file /home/book/buildroot-2020.02.6/output/images/rootfs.ext2 Creating filesystem with 61440 1k blocks and 15360 inodes Filesystem UUID: 7d89a22b-8f0a-47dc-93d0-fb818e671192 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 ln -snf /home/book/buildroot-2020.02.6/output/host/arm-buildroot-linux-uclibcgnueabihf/sysroot /home/book/buildroot-2020.02.6/output/staging编译结果在output/images下生成zImage、vexpress-v2p-ca9.dtb、rootfs.ext2三个文件，分别是内核、DeviceTree文件和文件系统：
book@bc7c3ac008b2:~/buildroot-2020.02.6/output/images$ ls -al total 7896 drwxr-xr-x 2 book book 4096 Oct 4 15:00 . drwxrwxr-x 6 book book 4096 Oct 4 15:00 .. -rw-r--r-- 1 book book 62914560 Oct 4 15:00 rootfs.ext2 -rw-r--r-- 1 book book 14430 Oct 4 15:00 vexpress-v2p-ca9.dtb -rw-r--r-- 1 book book 4149024 Oct 4 15:00 zImage（4）启动buildroot：
执行如下命令：
$ qemu-system-arm -M vexpress-a9 -smp 4 -m 1024M -kernel output/images/zImage -append "root=/dev/mmcblk0 \ console=ttyAMA0 loglevel=8" -dtb output/images/vexpress-v2p-ca9.dtb -sd output/images/rootfs.ext2 -nographic以下是启动过程的打印信息：
book@bc7c3ac008b2:~/buildroot-2020.02.6$ qemu-system-arm -M vexpress-a9 -smp 4 -m 1024M -kernel output/images/zImage -append "root=/dev/mmcblk0 console=ttyAMA0 loglevel=8" -dtb output/images/vexpress-v2p-ca9.dtb -sd output/images/rootfs.ext2 -nographic WARNING: Image format was not specified for 'output/images/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. ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' Booting Linux on physical CPU 0x0 Linux version 4.19.91 (book@bc7c3ac008b2) (gcc version 8.4.0 (Buildroot 2020.02.6)) #1 SMP Sun Oct 4 14:49:19 +09 2020 CPU: ARMv7 Processor [410fc090] revision 0 (ARMv7), cr=10c5387d CPU: PIPT / VIPT nonaliasing data cache, VIPT nonaliasing instruction cache OF: fdt: Machine model: V2P-CA9 Memory policy: Data cache writealloc On node 0 totalpages: 262144 Normal zone: 2048 pages used for memmap Normal zone: 0 pages reserved Normal zone: 262144 pages, LIFO batch:63 random: get_random_bytes called from start_kernel+0x98/0x470 with crng_init=0 percpu: Embedded 16 pages/cpu s32780 r8192 d24564 u65536 pcpu-alloc: s32780 r8192 d24564 u65536 alloc=16*4096 pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3 Built 1 zonelists, mobility grouping on. Total pages: 260096 Kernel command line: root=/dev/mmcblk0 console=ttyAMA0 loglevel=8 log_buf_len individual max cpu contribution: 4096 bytes log_buf_len total cpu_extra contributions: 12288 bytes log_buf_len min size: 16384 bytes log_buf_len: 32768 bytes early log buf free: 15064(91%) Dentry cache hash table entries: 131072 (order: 7, 524288 bytes) Inode-cache hash table entries: 65536 (order: 6, 262144 bytes) Memory: 1029432K/1048576K available (6144K kernel code, 397K rwdata, 1400K rodata, 1024K init, 156K bss, 19144K reserved, 0K cma-reserved) Virtual kernel memory layout: vector : 0xffff0000 - 0xffff1000 ( 4 kB) fixmap : 0xffc00000 - 0xfff00000 (3072 kB) vmalloc : 0xc0800000 - 0xff800000 (1008 MB) lowmem : 0x80000000 - 0xc0000000 (1024 MB) modules : 0x7f000000 - 0x80000000 ( 16 MB) .text : 0x(ptrval) - 0x(ptrval) (7136 kB) .init : 0x(ptrval) - 0x(ptrval) (1024 kB) .data : 0x(ptrval) - 0x(ptrval) ( 398 kB) .bss : 0x(ptrval) - 0x(ptrval) ( 157 kB) SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1 rcu: Hierarchical RCU implementation. rcu: RCU event tracing is enabled. rcu: RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4. rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=4 NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16 L2C: platform modifies aux control register: 0x02020000 -> 0x02420000 L2C: DT/platform modifies aux control register: 0x02020000 -> 0x02420000 L2C-310 enabling early BRESP for Cortex-A9 L2C-310 full line of zeros enabled for Cortex-A9 L2C-310 dynamic clock gating disabled, standby mode disabled L2C-310 cache controller enabled, 8 ways, 128 kB L2C-310: CACHE_ID 0x410000c8, AUX_CTRL 0x46420001 sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns clocksource: arm,sp804: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275 ns Failed to initialize '/smb@4000000/motherboard/iofpga@7,00000000/timer@12000': -22 smp_twd: clock not found -2 Console: colour dummy device 80x30 Calibrating local timer... 89.61MHz. Calibrating delay loop... 511.18 BogoMIPS (lpj=2555904) pid_max: default: 32768 minimum: 301 Mount-cache hash table entries: 2048 (order: 1, 8192 bytes) Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes) CPU: Testing write buffer coherency: ok CPU0: Spectre v2: using BPIALL workaround CPU0: thread -1, cpu 0, socket 0, mpidr 80000000 Setting up static identity map for 0x60100000 - 0x60100060 rcu: Hierarchical SRCU implementation. smp: Bringing up secondary CPUs ... CPU1: thread -1, cpu 1, socket 0, mpidr 80000001 CPU1: Spectre v2: using BPIALL workaround CPU2: thread -1, cpu 2, socket 0, mpidr 80000002 CPU2: Spectre v2: using BPIALL workaround CPU3: thread -1, cpu 3, socket 0, mpidr 80000003 CPU3: Spectre v2: using BPIALL workaround smp: Brought up 1 node, 4 CPUs SMP: Total of 4 processors activated (1430.06 BogoMIPS). CPU: All CPU(s) started in SVC mode. devtmpfs: initialized VFP support v0.3: implementor 41 architecture 3 part 30 variant 9 rev 0 clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns futex hash table entries: 1024 (order: 4, 65536 bytes) NET: Registered protocol family 16 DMA: preallocated 256 KiB pool for atomic coherent allocations cpuidle: using governor ladder hw-breakpoint: debug architecture 0x4 unsupported. Serial: AMBA PL011 UART driver 10009000.uart: ttyAMA0 at MMIO 0x10009000 (irq = 29, base_baud = 0) is a PL011 rev1 console [ttyAMA0] enabled 1000a000.uart: ttyAMA1 at MMIO 0x1000a000 (irq = 30, base_baud = 0) is a PL011 rev1 1000b000.uart: ttyAMA2 at MMIO 0x1000b000 (irq = 31, base_baud = 0) is a PL011 rev1 1000c000.uart: ttyAMA3 at MMIO 0x1000c000 (irq = 32, base_baud = 0) is a PL011 rev1 OF: amba_device_add() failed (-19) for /smb@4000000/motherboard/iofpga@7,00000000/wdt@f000 OF: amba_device_add() failed (-19) for /memory-controller@100e0000 OF: amba_device_add() failed (-19) for /memory-controller@100e1000 OF: amba_device_add() failed (-19) for /watchdog@100e5000 irq: type mismatch, failed to map hwirq-75 for interrupt-controller@1e001000! SCSI subsystem initialized libata version 3.00 loaded. usbcore: registered new interface driver usbfs usbcore: registered new interface driver hub usbcore: registered new device driver usb Advanced Linux Sound Architecture Driver Initialized. clocksource: Switched to clocksource arm,sp804 NET: Registered protocol family 2 tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes) TCP established hash table entries: 8192 (order: 3, 32768 bytes) TCP bind hash table entries: 8192 (order: 4, 65536 bytes) TCP: Hash tables configured (established 8192 bind 8192) UDP hash table entries: 512 (order: 2, 16384 bytes) UDP-Lite hash table entries: 512 (order: 2, 16384 bytes) NET: Registered protocol family 1 RPC: Registered named UNIX socket transport module. RPC: Registered udp transport module. RPC: Registered tcp transport module. RPC: Registered tcp NFSv4.1 backchannel transport module. hw perfevents: enabled with armv7_cortex_a9 PMU driver, 5 counters available workingset: timestamp_bits=30 max_order=18 bucket_order=0 squashfs: version 4.0 (2009/01/31) Phillip Lougher jffs2: version 2.2. (NAND) © 2001-2006 Red Hat, Inc. 9p: Installing v9fs 9p2000 file system support io scheduler noop registered (default) io scheduler mq-deadline registered io scheduler kyber registered clcd-pl11x 1001f000.clcd: PL111 designer 41 rev2 at 0x1001f000 clcd-pl11x 1001f000.clcd: clcd@1f000 hardware, 640x480@59 display Console: switching to colour frame buffer device 80x30 clcd-pl11x 10020000.clcd: PL111 designer 41 rev2 at 0x10020000 clcd-pl11x 10020000.clcd: clcd@10020000 hardware, 1024x768@59 display 40000000.flash: Found 2 x16 devices at 0x0 in 32-bit bank. Manufacturer ID 0x000000 Chip ID 0x000000 Intel/Sharp Extended Query Table at 0x0031 Using buffer write method erase region 0: offset=0x0,size=0x40000,blocks=256 40000000.flash: Found 2 x16 devices at 0x0 in 32-bit bank. Manufacturer ID 0x000000 Chip ID 0x000000 Intel/Sharp Extended Query Table at 0x0031 Using buffer write method erase region 0: offset=0x0,size=0x40000,blocks=256 Concatenating MTD devices: (0): "40000000.flash" (1): "40000000.flash" into device "40000000.flash" libphy: Fixed MDIO Bus: probed smsc911x 4e000000.ethernet: Linked as a consumer to regulator.1 libphy: smsc911x-mdio: probed smsc911x 4e000000.ethernet eth0: MAC Address: 52:54:00:12:34:56 isp1760 4f000000.usb: bus width: 32, oc: digital isp1760 4f000000.usb: NXP ISP1760 USB Host Controller isp1760 4f000000.usb: new USB bus registered, assigned bus number 1 isp1760 4f000000.usb: Scratch test failed. isp1760 4f000000.usb: can't setup: -19 isp1760 4f000000.usb: USB bus 1 deregistered usbcore: registered new interface driver usb-storage rtc-pl031 10017000.rtc: rtc core: registered pl031 as rtc0 mmci-pl18x 10005000.mmci: Got CD GPIO mmci-pl18x 10005000.mmci: Got WP GPIO mmci-pl18x 10005000.mmci: Linked as a consumer to regulator.1 mmci-pl18x 10005000.mmci: mmc0: PL181 manf 41 rev0 at 0x10005000 irq 25,26 (pio) ledtrig-cpu: registered to indicate activity on CPUs usbcore: registered new interface driver usbhid usbhid: USB HID core driver ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory ALSA lib confmisc.c:767:(parse_card) cannot find card '0' ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory ALSA lib confmisc.c:392:(snd_func_concat) error evaluating strings ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory ALSA lib confmisc.c:1246:(snd_func_refer) error evaluating name ALSA lib conf.c:4732:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory ALSA lib conf.c:5220:(snd_config_expand) Evaluate error: No such file or directory ALSA lib pcm.c:2642:(snd_pcm_open_noupdate) Unknown PCM default alsa: Could not initialize DAC alsa: Failed to open `default': alsa: Reason: No such file or directory audio: Failed to create voice `lm4549.out' input: AT Raw Set 2 keyboard as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10006000.kmi/serio0/input/input0 aaci-pl041 10004000.aaci: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24 aaci-pl041 10004000.aaci: FIFO 512 entries oprofile: using arm/armv7-ca9 NET: Registered protocol family 17 9pnet: Installing 9P2000 support Registering SWP/SWPB emulation handler mmc0: new SD card at address 4567 mmcblk0: mmc0:4567 QEMU! 60.0 MiB rtc-pl031 10017000.rtc: setting system clock to 2020-10-04 14:21:32 UTC (1601821292) ALSA device list: #0: ARM AC'97 Interface PL041 rev0 at 0x10004000, irq 24 input: ImExPS/2 Generic Explorer Mouse as /devices/platform/smb@4000000/smb@4000000:motherboard/smb@4000000:motherboard:iofpga@7,00000000/10007000.kmi/serio1/input/input2 random: fast init done EXT4-fs (mmcblk0): mounted filesystem without journal. Opts: (null) VFS: Mounted root (ext4 filesystem) readonly on device 179:0. devtmpfs: mounted Freeing unused kernel memory: 1024K Run /sbin/init as init process random: crng init done EXT4-fs (mmcblk0): re-mounted. Opts: (null) Starting syslogd: OK Starting klogd: OK Running sysctl: OK Saving random seed: OK Starting network: Generic PHY 4e000000.ethernet-ffffffff:01: attached PHY driver [Generic PHY] (mii_bus:phy_addr=4e000000.ethernet-ffffffff:01, irq=POLL) smsc911x 4e000000.ethernet eth0: SMSC911x/921x identified at 0xc1290000, IRQ: 22 udhcpc: started, v1.31.1 udhcpc: sending discover udhcpc: sending discover udhcpc: sending select for 10.0.2.15 udhcpc: lease of 10.0.2.15 obtained, lease time 86400 deleting routers adding dns 10.0.2.3 OK Welcome to Buildroot buildroot login:（5）输入root进入系统并打印目录：
buildroot login: root # cd / # ls bin lib lost+found opt run tmp dev lib32 media proc sbin usr etc linuxrc mnt root sys var（6）停止qemu执行如下命令：
$ killall qemu-system-arm
