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从零开构建树莓派64位操作系统

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1. 首次安装树莓派

1.1 安装树莓派

1.1.1 下载树莓派镜像(可跳过)

从https://www.raspberrypi.org/software/operating-systems/ 下载树莓派镜像，为了快速下载，这里下载的是 Raspberry Pi OS Lite ，体积最小，后面主要在命令行环境使用。这里下载的版本是 2021-03-04-raspios-buster-armhf-lite.zip
准备2张SD卡，一张安装树莓派系统（这里取代号A卡），另外一张（B卡）用于我们自己的构建系统。

1.1.2 安装树莓派系统

在Ubuntu主机上安装树莓派烧写工具 rpi-imager

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sudo apt install rpi-imager

在命令行执行 rpi-imager 后会出现工具

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rpi-imager


选择刚才下载的zip文件：

或者直接选择需要安装的系统在线安装

选择A卡，点击烧录即可完成安装。

1.1.3 无屏幕键盘初始化树莓派

如果没有屏幕，可通过配置WIFI和SSH，通过SSH来连接树莓派。在烧录系统到A卡后，A卡上有2个分区 root rootfs ， root 分区上是包含树莓派引导文件已经Linux Kerne、设备数文件等等，具体的内容后面会详细介绍。
配置网络
如果有网线，直接插线就可以。连接WIFI需要以下操作：
在 root 分区新建 wpa_supplicant.conf 文件

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ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=US

network={
ssid="WIFI名称"
psk="WIFI密码"
key_mgmt=WPA-PSK
}

配置SSH
在root 分区新建名为SSH的文件即可。
将A卡插入树莓派即可启动树莓派系统。

1.2 树莓派系统初始化

1.2.1 SSH连接

通过SSH连接树莓派：

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ssh [email protected]

默认密码为：raspberry
到此即可通过SSH来使用树莓派。
修改密码：

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$ passwd
Changing password for pi.
Current password: 
New password: 
Retype new password:

输入默认密码 raspberry 和自己的密码。

1.2.2 树莓派系统配置和VNC连接(可选)

通过raspi-config可对树莓派进行设置，比如打来GPIO 端口，开启VNC 服务等

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sudo raspi-config


在 3 Interface Options / P3 VNC 中开启VNC 。
在Ubuntu中安装VNC客户端:
在 https://www.realvnc.com/en/connect/download/viewer/linux/ 中下载VNC View https://www.realvnc.com/download/file/viewer.files/VNC-Viewer-6.20.529-Linux-x64.deb
安装：

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sudo dpkg -i VNC-Viewer-6.20.529-Linux-x64.deb

打开vnc view，新建Connection 输入树莓派IP地址和用户名密码即可进入远程桌面。

至此完成了树莓派系统的初步安装。

2 从零构建树莓派

2.1 串口连接树莓派

这一步需要使用到USB转TTL串口的线，淘宝和京东有售。

2.1.2 串口接线

USB 串口工具

树莓派GPIO借口

1,2号pin是远离树莓派USB的那一端。

接线：
usb转串口工具的TX连接树莓派的RX，RX连接树莓派的TX，VCC与GND正常连接

通过 raspi-config 设置 3 Interface Options / P6 Serial Port 开启串口

2.1.2 Ubuntu上安装串口工具

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sudo apt-get install minicom

启动minicom

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sudo minicom -D /dev/ttyUSB0

-D 参数Device，ttyUSB0 即为电脑连接上的USB串口。

在接好线，插好USB，启动minicom后，接通树莓派电源，可看到minicom打印内核启动过程：

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sudo minicom -D /dev/ttyUSB0                  


Welcome to minicom 2.7.1

OPTIONS: I18n 
Compiled on Dec 23 2019, 02:06:26.
Port /dev/ttyUSB0, 20:27:33

Press CTRL-A Z for help on special keys

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 5.10.11-v7l+ (dom@buildbot) (arm-linux-gnueabihf-gcc-8 (Ubuntu/Linaro 8.4.0-3ubuntu1) 8.4.0, GNU ld (GNU Binutils f1
[    0.000000] CPU: ARMv7 Processor [410fd083] revision 3 (ARMv7), cr=30c5383d
[    0.000000] CPU: div instructions available: patching division code
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[    0.000000] OF: fdt: Machine model: Raspberry Pi 4 Model B Rev 1.2
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] Reserved memory: created CMA memory pool at 0x000000001ec00000, size 256 MiB
[    0.000000] OF: reserved mem: initialized node linux,cma, compatible id shared-dma-pool
[    0.000000] Zone ranges:
[    0.000000]   DMA      [mem 0x0000000000000000-0x000000002fffffff]
[    0.000000]   Normal   empty
[    0.000000]   HighMem  [mem 0x0000000030000000-0x00000000fbffffff]
[    0.000000] Movable zone start for each node
[    0.000000] Early memory node ranges
[    0.000000]   node   0: [mem 0x0000000000000000-0x0000000037ffffff]
[    0.000000]   node   0: [mem 0x0000000040000000-0x00000000fbffffff]
[    0.000000] Initmem setup node 0 [mem 0x0000000000000000-0x00000000fbffffff]
[    0.000000] percpu: Embedded 20 pages/cpu s50636 r8192 d23092 u81920
[    0.000000] Built 1 zonelists, mobility grouping on.  Total pages: 997120
[    0.000000] Kernel command line: coherent_pool=1M 8250.nr_uarts=1 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 video=HDMI-A-1:1t
[    0.000000] Kernel parameter elevator= does not have any effect anymore.
[    0.000000] Please use sysfs to set IO scheduler for individual devices.
[    0.000000] Dentry cache hash table entries: 131072 (order: 7, 524288 bytes, linear)
[    0.000000] Inode-cache hash table entries: 65536 (order: 6, 262144 bytes, linear)
[    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
[    0.000000] software IO TLB: mapped [mem 0x0000000017cc0000-0x000000001bcc0000] (64MB)
[    0.000000] Memory: 3602320K/3997696K available (10240K kernel code, 1354K rwdata, 3152K rodata, 2048K init, 890K bss, 133232K reserved, 2621)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[    0.000000] ftrace: allocating 33824 entries in 67 pages
[    0.000000] ftrace: allocated 67 pages with 3 groups
[    0.000000] rcu: Hierarchical RCU implementation.
[    0.000000]  Rude variant of Tasks RCU enabled.
[    0.000000]  Tracing variant of Tasks RCU enabled.
[    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 10 jiffies.
[    0.000000] NR_IRQS: 16, nr_irqs: 16, preallocated irqs: 16
[    0.000000] GIC: Using split EOI/Deactivate mode
[    0.000000] random: get_random_bytes called from start_kernel+0x3c8/0x59c with crng_init=0
[    0.000008] sched_clock: 32 bits at 1000kHz, resolution 1000ns, wraps every 2147483647500ns
[    0.000035] clocksource: timer: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275 ns
[    0.000099] bcm2835: system timer (irq = 25)
[    0.000743] arch_timer: cp15 timer(s) running at 54.00MHz (phys).
[    0.000765] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0xc743ce346, max_idle_ns: 440795203123 ns
[    0.000786] sched_clock: 56 bits at 54MHz, resolution 18ns, wraps every 4398046511102ns
[    0.000804] Switching to timer-based delay loop, resolution 18ns
[    0.001051] Console: colour dummy device 80x30
[    0.001772] printk: console [tty1] enabled
[    0.001840] Calibrating delay loop (skipped), value calculated using timer frequency.. 108.00 BogoMIPS (lpj=540000)
[    0.001894] pid_max: default: 32768 minimum: 301
[    0.002074] LSM: Security Framework initializing
[    0.002266] Mount-cache hash table entries: 2048 (order: 1, 8192 bytes, linear)
[    0.002311] Mountpoint-cache hash table entries: 2048 (order: 1, 8192 bytes, linear)
[    0.003882] Disabling memory control group subsystem
[    0.004016] CPU: Testing write buffer coherency: ok
[    0.004476] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[    0.005683] Setting up static identity map for 0x200000 - 0x20003c
[    0.005896] rcu: Hierarchical SRCU implementation.
[    0.006824] smp: Bringing up secondary CPUs ...
[    0.008018] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
[    0.009364] CPU2: thread -1, cpu 2, socket 0, mpidr 80000002
[    0.010646] CPU3: thread -1, cpu 3, socket 0, mpidr 80000003
[    0.010895] smp: Brought up 1 node, 4 CPUs
[    0.010927] SMP: Total of 4 processors activated (432.00 BogoMIPS).
[    0.010957] CPU: All CPU(s) started in HYP mode.
[    0.010984] CPU: Virtualization extensions available.
[    0.011809] devtmpfs: initialized
[    0.025623] VFP support v0.3: implementor 41 architecture 3 part 40 variant 8 rev 0
[    0.025866] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.025919] futex hash table entries: 1024 (order: 4, 65536 bytes, linear)
[    0.032638] pinctrl core: initialized pinctrl subsystem
[    0.033713] NET: Registered protocol family 16
[    0.037476] DMA: preallocated 1024 KiB pool for atomic coherent allocations
[    0.038273] audit: initializing netlink subsys (disabled)
[    0.038568] audit: type=2000 audit(0.030:1): state=initialized audit_enabled=0 res=1
[    0.039138] thermal_sys: Registered thermal governor 'step_wise'
[    0.039819] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers.
[    0.039873] hw-breakpoint: maximum watchpoint size is 8 bytes.
[    0.040268] Serial: AMBA PL011 UART driver
[    0.072212] bcm2835-mbox fe00b880.mailbox: mailbox enabled
[    0.090908] raspberrypi-firmware soc:firmware: Attached to firmware from 2021-01-27T22:19:57, variant start
[    0.100922] raspberrypi-firmware soc:firmware: Firmware hash is 99d9a48302e4553cff3688692bb7e9ac760a03fa
[    0.145578] bcm2835-dma fe007000.dma: DMA legacy API manager, dmachans=0x1
[    0.149725] vgaarb: loaded
[    0.150191] SCSI subsystem initialized
[    0.150419] usbcore: registered new interface driver usbfs
[    0.150507] usbcore: registered new interface driver hub
[    0.150595] usbcore: registered new device driver usb
[    0.151041] usb_phy_generic phy: supply vcc not found, using dummy regulator
[    0.153196] clocksource: Switched to clocksource arch_sys_counter
[    1.180263] VFS: Disk quotas dquot_6.6.0
[    1.180389] VFS: Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
[    1.180588] FS-Cache: Loaded
[    1.180789] CacheFiles: Loaded
[    1.181786] simple-framebuffer 3e6c7000.framebuffer: framebuffer at 0x3e6c7000, 0x500000 bytes, mapped to 0x(ptrval)
[    1.181830] simple-framebuffer 3e6c7000.framebuffer: format=a8r8g8b8, mode=1280x1024x32, linelength=5120
[    1.188675] Console: switching to colour frame buffer device 160x64
[    1.194941] simple-framebuffer 3e6c7000.framebuffer: fb0: simplefb registered!
[    1.204680] NET: Registered protocol family 2
[    1.205611] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 6144 bytes, linear)
[    1.205834] TCP established hash table entries: 8192 (order: 3, 32768 bytes, linear)
[    1.205979] TCP bind hash table entries: 8192 (order: 4, 65536 bytes, linear)
[    1.206114] TCP: Hash tables configured (established 8192 bind 8192)
[    1.206324] UDP hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.206423] UDP-Lite hash table entries: 512 (order: 2, 16384 bytes, linear)
[    1.206743] NET: Registered protocol family 1
[    1.207511] RPC: Registered named UNIX socket transport module.
[    1.207589] RPC: Registered udp transport module.
[    1.207652] RPC: Registered tcp transport module.
[    1.207714] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    1.207799] PCI: CLS 0 bytes, default 64
[    1.210729] Initialise system trusted keyrings
[    1.211026] workingset: timestamp_bits=14 max_order=20 bucket_order=6
[    1.219381] zbud: loaded
[    1.221358] FS-Cache: Netfs 'nfs' registered for caching
[    1.222193] NFS: Registering the id_resolver key type
[    1.222304] Key type id_resolver registered
[    1.222364] Key type id_legacy registered
[    1.222547] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
[    1.223725] Key type asymmetric registered
[    1.223789] Asymmetric key parser 'x509' registered
[    1.224032] bounce: pool size: 64 pages
[    1.224117] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 249)
[    1.224399] io scheduler mq-deadline registered
[    1.224465] io scheduler kyber registered
[    1.228738] brcm-pcie fd500000.pcie: host bridge /scb/pcie@7d500000 ranges:
[    1.231271] brcm-pcie fd500000.pcie:   No bus range found for /scb/pcie@7d500000, using [bus 00-ff]
[    1.233925] brcm-pcie fd500000.pcie:      MEM 0x0600000000..0x063fffffff -> 0x00c0000000
[    1.236493] brcm-pcie fd500000.pcie:   IB MEM 0x0000000000..0x00bfffffff -> 0x0400000000
[    1.295300] brcm-pcie fd500000.pcie: link up, 5.0 GT/s PCIe x1 (SSC)
[    1.298093] brcm-pcie fd500000.pcie: PCI host bridge to bus 0000:00
[    1.300511] pci_bus 0000:00: root bus resource [bus 00-ff]
[    1.302938] pci_bus 0000:00: root bus resource [mem 0x600000000-0x63fffffff] (bus address [0xc0000000-0xffffffff])
[    1.305532] pci 0000:00:00.0: [14e4:2711] type 01 class 0x060400
[    1.308205] pci 0000:00:00.0: PME# supported from D0 D3hot
[    1.314106] PCI: bus0: Fast back to back transfers disabled
[    1.316839] pci 0000:01:00.0: [1106:3483] type 00 class 0x0c0330
[    1.319343] pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x00000fff 64bit]
[    1.322172] pci 0000:01:00.0: PME# supported from D0 D3cold
[    1.328028] PCI: bus1: Fast back to back transfers disabled
[    1.330422] pci 0000:00:00.0: BAR 8: assigned [mem 0x600000000-0x6000fffff]
[    1.332810] pci 0000:01:00.0: BAR 0: assigned [mem 0x600000000-0x600000fff 64bit]
[    1.335291] pci 0000:00:00.0: PCI bridge to [bus 01]
[    1.337675] pci 0000:00:00.0:   bridge window [mem 0x600000000-0x6000fffff]
[    1.340468] pcieport 0000:00:00.0: enabling device (0140 -> 0142)
[    1.343081] pcieport 0000:00:00.0: PME: Signaling with IRQ 63
[    1.351160] Serial: 8250/16550 driver, 1 ports, IRQ sharing enabled
[    1.354458] bcm2835-aux-uart fe215040.serial: there is not valid maps for state default
[    1.359294] iproc-rng200 fe104000.rng: hwrng registered
[    1.361981] vc-mem: phys_addr:0x00000000 mem_base=0x3ec00000 mem_size:0x40000000(1024 MiB)
[    1.365371] gpiomem-bcm2835 fe200000.gpiomem: Initialised: Registers at 0xfe200000
[    1.380748] brd: module loaded
[    1.395318] loop: module loaded
[    1.399348] Loading iSCSI transport class v2.0-870.
[    1.404157] libphy: Fixed MDIO Bus: probed
[    1.407776] bcmgenet fd580000.ethernet: GENET 5.0 EPHY: 0x0000
[    1.423223] libphy: bcmgenet MII bus: probed
[    1.503347] unimac-mdio unimac-mdio.-19: Broadcom UniMAC MDIO bus
[    1.506805] usbcore: registered new interface driver r8152
[    1.509183] usbcore: registered new interface driver lan78xx
[    1.511502] usbcore: registered new interface driver smsc95xx
[    1.515385] xhci_hcd 0000:01:00.0: enabling device (0140 -> 0142)
[    1.517778] xhci_hcd 0000:01:00.0: xHCI Host Controller
[    1.520019] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus number 1
[    1.525563] xhci_hcd 0000:01:00.0: hcc params 0x002841eb hci version 0x100 quirks 0x0000030000000890
[    1.529114] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002, bcdDevice= 5.10
[    1.531401] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    1.533729] usb usb1: Product: xHCI Host Controller
[    1.536026] usb usb1: Manufacturer: Linux 5.10.11-v7l+ xhci-hcd
[    1.538319] usb usb1: SerialNumber: 0000:01:00.0
[    1.541333] hub 1-0:1.0: USB hub found
[    1.543716] hub 1-0:1.0: 1 port detected
[    1.546630] xhci_hcd 0000:01:00.0: xHCI Host Controller
[    1.548897] xhci_hcd 0000:01:00.0: new USB bus registered, assigned bus number 2
[    1.551175] xhci_hcd 0000:01:00.0: Host supports USB 3.0 SuperSpeed
[    1.553989] usb usb2: New USB device found, idVendor=1d6b, idProduct=0003, bcdDevice= 5.10
[    1.556309] usb usb2: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    1.558613] usb usb2: Product: xHCI Host Controller
[    1.560891] usb usb2: Manufacturer: Linux 5.10.11-v7l+ xhci-hcd
[    1.563206] usb usb2: SerialNumber: 0000:01:00.0
[    1.566198] hub 2-0:1.0: USB hub found
[    1.568559] hub 2-0:1.0: 4 ports detected
[    1.572456] dwc_otg: version 3.00a 10-AUG-2012 (platform bus)
[    1.575615] usbcore: registered new interface driver uas
[    1.577961] usbcore: registered new interface driver usb-storage
[    1.580371] mousedev: PS/2 mouse device common for all mice
[    1.584260] bcm2835-wdt bcm2835-wdt: Broadcom BCM2835 watchdog timer
[    1.589977] sdhci: Secure Digital Host Controller Interface driver
[    1.592240] sdhci: Copyright(c) Pierre Ossman
[    1.595223] sdhci-pltfm: SDHCI platform and OF driver helper
[    1.600204] ledtrig-cpu: registered to indicate activity on CPUs
[    1.602781] hid: raw HID events driver (C) Jiri Kosina
[    1.605191] usbcore: registered new interface driver usbhid
[    1.607409] usbhid: USB HID core driver
[    1.614965] Initializing XFRM netlink socket
[    1.617362] NET: Registered protocol family 17
[    1.619680] Key type dns_resolver registered
[    1.622214] Registering SWP/SWPB emulation handler
[    1.624581] registered taskstats version 1
[    1.626751] Loading compiled-in X.509 certificates
[    1.629732] Key type ._fscrypt registered
[    1.631899] Key type .fscrypt registered
[    1.634124] Key type fscrypt-provisioning registered
[    1.647476] uart-pl011 fe201000.serial: there is not valid maps for state default
[    1.649974] uart-pl011 fe201000.serial: cts_event_workaround enabled
[    1.652213] fe201000.serial: ttyAMA0 at MMIO 0xfe201000 (irq = 36, base_baud = 0) is a PL011 rev2
[    1.661041] bcm2835-aux-uart fe215040.serial: there is not valid maps for state default
[    1.664051] printk: console [ttyS0] disabled
[    1.666328] fe215040.serial: ttyS0 at MMIO 0xfe215040 (irq = 37, base_baud = 62500000) is a 16550
[    2.967163] printk: console [ttyS0] enabled
[    2.976253] bcm2835-power bcm2835-power: Broadcom BCM2835 power domains driver
[    2.989191] of_cfs_init
[    2.994060] of_cfs_init: OK
[    3.037147] mmc0: SDHCI controller on fe340000.emmc2 [fe340000.emmc2] using ADMA
[    3.048226] Waiting for root device PARTUUID=37dc5df3-02...
[    3.123239] usb 1-1: new high-speed USB device number 2 using xhci_hcd
[    3.148244] mmc0: new ultra high speed DDR50 SDHC card at address aaaa
[    3.157974] mmcblk0: mmc0:aaaa SC16G 14.8 GiB
[    3.170257]  mmcblk0: p1 p2
[    3.213492] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
[    3.224119] VFS: Mounted root (ext4 filesystem) readonly on device 179:2.
[    3.242393] devtmpfs: mounted
[    3.256691] Freeing unused kernel memory: 2048K
[    3.263934] Run /sbin/init as init process
[    3.305845] usb 1-1: New USB device found, idVendor=2109, idProduct=3431, bcdDevice= 4.21
[    3.316511] usb 1-1: New USB device strings: Mfr=0, Product=1, SerialNumber=0
[    3.326113] usb 1-1: Product: USB2.0 Hub
[    3.334293] hub 1-1:1.0: USB hub found
[    3.340665] hub 1-1:1.0: 4 ports detected
[    3.357666] random: fast init done
[    3.709677] systemd[1]: System time before build time, advancing clock.
[    3.820447] NET: Registered protocol family 10
[    3.828660] Segment Routing with IPv6
[    3.894632] systemd[1]: systemd 241 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYP)
[    3.922400] systemd[1]: Detected architecture arm.
[    4.013351] systemd[1]: Set hostname to <raspberrypi>.
[    4.784874] random: systemd: uninitialized urandom read (16 bytes read)
[    4.807407] random: systemd: uninitialized urandom read (16 bytes read)
[    4.821131] systemd[1]: Created slice system-systemd\x2dfsck.slice.
[    4.833750] random: systemd: uninitialized urandom read (16 bytes read)
[    4.843600] systemd[1]: Listening on udev Kernel Socket.
[    4.855139] systemd[1]: Reached target Swap.
[    4.866153] systemd[1]: Listening on Journal Socket.
[    4.886705] systemd[1]: Starting Restore / save the current clock...
[    4.900496] systemd[1]: Condition check resulted in Huge Pages File System being skipped.
[    4.912097] systemd[1]: Listening on initctl Compatibility Named Pipe.
[    5.179601] i2c /dev entries driver

Raspbian GNU/Linux 10 raspberrypi ttyS0

raspberrypi login:

从日志中我们可以看到，Linux内核为5.10.11-v7l 使用的是armv7l架构的版本，编译的gcc为arm，32位

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Linux version 5.10.11-v7l+ (dom@buildbot) (arm-linux-gnueabihf-gcc-8 (Ubuntu/Linaro 8.4.0-3ubuntu1) 8.4.0

在串口里面我们可以直接登录。
到这里，串口的部分结束了，为了和后面做对比，我们登录后，看一下/boot 下的这个2个文件。
**cmdline.txt**

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console=serial0,115200 console=tty1 root=PARTUUID=37dc5df3-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

cmdline.txt 是树莓派BootLoader启动Linux内核时，传给内核的启动参数
console=serial0,115200 设置串口控制台，波特率为115200
console=tty1 设置tty1控制台
root=PARTUUID=37dc5df3-02 rootfs目录挂在的位置，这里的PARTUUID=37dc5df3-02直接制定了分区号
rootfstype=ext4 rootfs的分区类型为ext4
elevator=``deadline 磁盘扫描算法为deadline
fsck.repair=true 开启磁盘修复能力
rootwait 等待root设备加载完毕，如果不设置，会出现加载完内核后，无法找到磁盘的情况

Linux启动参数后面会有更多介绍，这里暂时列出现有的。

**config.txt**

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[all]
start_x=0
gpu_mem=128
enable_uart=1

start_x 是否启动桌面
enable_uart 开启串口
gpu_mem 设置GPU内存
其他的配置暂时没列。

2.2 构建64位Linux系统

在准备完串口工具后，我们正式开始构建系统

2.2.1 编译U-boot（可选）

在树莓派有自己的BootLoader，可以直接加载Kernel，也可以先加载U-Boot再启动Kernel，这里选择编译一下U-Boot。
64位构建过程参考 https://www.cwiki.cn/archives/u-boot安装到树莓派

2.2.2 编译Linux Kernel

kernel 建议使用树莓派的，里面已经配置好了各种选项。

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git clone https://github.com/raspberrypi/linux.git
cd linux
make distclean
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcm2711_defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig # 可选择自己定制
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-  -j12 # 自己设置编译进程数

构建完成后，在arch/arm64/boot 目录下，可找到 Image Image.gz 镜像文件，其中Image 是未经压缩的Kernel文件，Image.gz 是gzip压缩过的镜像文件。64位的树莓派需要使用未经压缩的内核，即Image

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$ file Image 
Image: MS-DOS executable PE32+ executable (EFI application) Aarch64 (stripped to external PDB), for MS Windows
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$ file Image.gz 
Image.gz: gzip compressed data, max compression, from Unix, original size modulo 2^32 21043712

2.2.3 通过BusyBox构建文件系统（可选）

下载BusyBox https://busybox.net/ ，解压后，进入Busybox目录

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make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j12

选择静态编译 Settings  ---> / --- Build Options 下的 Build static binary (no shared libs) ，如果不选择静态编译，会带上很多so库，静态编译会方便一些。
编译后会有下面的显示，这个可以不用管，编译已经成功。

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Static linking against glibc, can't use --gc-sections
Trying libraries: crypt m resolv rt
 Library crypt is not needed, excluding it
 Library m is needed, can't exclude it (yet)
 Library resolv is needed, can't exclude it (yet)
 Library rt is not needed, excluding it
 Library m is needed, can't exclude it (yet)
 Library resolv is needed, can't exclude it (yet)
Final link with: m resolv

构建Busybox文件系统：

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make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- install

在busybox目录下生成 _install 目录。

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make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-  PREFIX=/path/sdcark/rootfs install

通过PREFIX参数可以制定安装位置，建议直接安装到需要的地方。具体参考 https://git.busybox.net/busybox/tree/INSTALL
在将BusyBox生成的install文件拷贝到rootfs目录后，进入rootfs目录，补充完所需目录。

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mkdir root dev etc bin sbin mnt sys proc lib home tmp var usr
mkdir usr/sbin usr/bin usr/lib usr/modules
mkdir mnt/usb mnt/nfs mnt/etc mnt/etc/init.d
mkdir lib/modules
sudo chmod 1777 tmp

创建必要设备

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cd dev
sudo mknod -m 660 console c 5 1
sudo mknod -m 660 null c 1 3
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cd etc
vim fstab

proc    /proc   proc    defaults    0   0
none    /tmp    ramfs   defaults    0   0
mdev    /dev    ramfs   defaults    0   0
sysfs   /sys    sysfs   defaults    0   0
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cd etc/init.d
vim rcS

#! /bin/sh

/bin/mount -a
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cd etc
vim inittab

::sysinit:/etc/init.d/rcS
::respawn:-/bin/sh
::restart:/sbin/init
::ctrlaltdel:/bin/umount -a -r
::shutdown:/bin/umount -a -r
::shutdown:/sbin/swapoff –a
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cd etc
vim group

root:*:0:
daemon:*:1:
bin:*:2:
sys:*:3:
adm:*:4:
tty:*:5:
disk:*:6:
lp:*:7:lp
mail:*:8:
news:*:9:
uucp:*:10:
proxy:*:13:
kmem:*:15:
dialout:*:20:
fax:*:21:
voice:*:22:
cdrom:*:24:
floppy:*:25:
tape:*:26:
sudo:*:27:
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cd etc 
vim profile

# /etc/profile: system-wide .profile file for the Bourne shells

echo
echo "FileSystem is Ready ..."
echo

USER="`id -un`"
LOGNAME=$USER
PS1='[\u@\h \W]\# '
PATH=$PATH
HOSTNAME=`/bin/hostname`

export USER LOGNAME PS1 PATH

至此完成了文件系统制作。也可以将这个文件系统打包成镜像，在Kernel启动时制定initrd

2.2.4 通过debootstrap构建基于Debian的文件系统（建议）

通过debootstrap制作文件系统就相当简单，建议以这种方式。debootstrap制作的文件系统包含了Debian所需的软件，文件系统完善，可直接使用apt等命令等。
在为了避免跨平台到来的麻烦，我们直接在树莓派现有系统上操作。
在树莓派上通过读卡器插入B卡

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sudo fdisk -l

找到B的的rootfs分区

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sudo mount /dev/sdb2 /mnt
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sudo apt install debootstrap
sudo debootstrap --arch=arm64 --foreign buster /mnt/ http://ftp.cn.debian.org/debian/
sudo chroot /mnt/
debootstrap/debootstrap --second-stage

设置清华源

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vim.tiny /etc/apt/sources.list

deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-updates main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-updates main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-backports main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian/ buster-backports main contrib non-free
deb https://mirrors.tuna.tsinghua.edu.cn/debian-security buster/updates main contrib non-free
# deb-src https://mirrors.tuna.tsinghua.edu.cn/debian-security buster/updates main contrib non-free

配置时区、串口、SSH、Vimd等等

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apt-get update
passwd
# localtime
ln -sf /usr/slocaltimehare/zoneinfo/Asia/Shanghai /etc/localtime
# serial port
ln -s /lib/systemd/system/serial-getty\@.service /etc/systemd/system/getty.target.wants/[email protected]

apt-get install vim ssh
apt-get install ifupdown net-tools
apt-get install udev sudo wget curl
apt-get install alsa-utils libasound2-dev

添加用户、设置网络、设置中文

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USER=pi
HOST=raspberry
useradd -G sudo -m -s /bin/bash $USER
passwd $USER

echo $HOST > /etc/hostname
echo "127.0.0.1    localhost.localdomain localhost" > /etc/hosts
echo "127.0.0.1    $HOST" >> /etc/hosts

cat <<EOF > /etc/network/interfaces.d/eth0
 auto eth0
 iface eth0 inet static
 address 192.168.1.9
 gateway 192.168.1.1
 netmask 255.255.255.0
EOF

apt-get install locales
dpkg-reconfigure locales

2.3 配置引导

拷贝编译好的Linux Kernel文件Image 到root分区，如果需要使用U-Boot引用，好需要将u-boot.bin 拷贝到root分区。

2.3.1 配置树莓派基本引导文件

将https://github.com/raspberrypi/firmware.git 中root目录下的文件拷贝到root分区，参考https://www.cwiki.cn/archives/u-boot安装到树莓派

2.3.2 配置启动内核Linux

修改cmdline.txt，这个文件里面是Linux启动参数

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console=ttyAMA0,115200 console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

修改config.txt为

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kernel=kernel8.img # 启动内核
arm_64bit=1 # 64位
enable_uart=1 # 打开串口

当设置位U-Boot启动时，设置为

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kernel=u-boot.bin  # 启动内核
arm_64bit=1 # 64位
enable_uart=1 # 打开串口

由于uboot编译的是树莓派的rpi_4_defconfig ，启动后自动加载配置，包括 cmdline.txt config.txt

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MESS:00:00:05.410376:0: arasan: arasan_emmc_open                                                         
MESS:00:00:05.578211:0: brfs: File read: /mfs/sd/config.txt                                              
MESS:00:00:05.581017:0: brfs: File read: 257 bytes                                                       
MESS:00:00:05.648806:0: brfs: File read: /mfs/sd/config.txt                                              
MESS:00:00:05.667051:0: brfs: File read: 257 bytes                                                       
MESS:00:00:06.147877:0: gpioman: gpioman_get_pin_num: pin DISPLAY_DSI_PORT not defined                   
MESS:00:00:06.155166:0: *** Restart logging                                                              
MESS:00:00:06.160428:0: hdmi: HDMI:hdmi_get_state is deprecated, use hdmi_get_display_state instead      
MESS:00:00:06.169785:0: hdmi: HDMI:hdmi_get_state is deprecated, use hdmi_get_display_state instead      
MESS:00:00:06.175719:0: HDMI0: hdmi_pixel_encoding: 300000000                                            
MESS:00:00:06.181188:0: HDMI1: hdmi_pixel_encoding: 300000000                                            
MESS:00:00:06.191390:0: dtb_file 'bcm2711-rpi-4-b.dtb'                                                   
MESS:00:00:06.198297:0: brfs: File read: /mfs/sd/bcm2711-rpi-4-b.dtb
MESS:00:00:06.201544:0: Loading 'bcm2711-rpi-4-b.dtb' to 0x100 size 0xbd2d
MESS:00:00:06.220694:0: brfs: File read: 48429 bytes
MESS:00:00:06.232960:0: brfs: File read: /mfs/sd/overlays/overlay_map.dtb
MESS:00:00:06.298769:0: brfs: File read: 1523 bytes
MESS:00:00:06.301317:0: brfs: File read: /mfs/sd/config.txt
MESS:00:00:06.311815:0: brfs: File read: 257 bytes
MESS:00:00:06.315176:0: brfs: File read: /mfs/sd/cmdline.txt
MESS:00:00:06.318896:0: Read command line from file 'cmdline.txt':
MESS:00:00:06.324775:0: 'console=serial0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait'
MESS:00:00:07.446637:0: brfs: File read: 115 bytes
MESS:00:00:08.020689:0: brfs: File read: /mfs/sd/kernel8.img
MESS:00:00:08.023242:0: Loading 'kernel8.img' to 0x80000 size 0x76f687
MESS:00:00:09.138881:0: Kernel relocated to 0x200000
MESS:00:00:09.140734:0: Device tree loaded to 0x2eff3d00 (size 0xc203)
MESS:00:00:09.148754:0: uart: Set PL011 baud rate to 103448.300000 Hz
MESS:00:00:09.156064:0: uart: Baud rate change done...
MESS:00:00:09.158083:0:[    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd083]
[    0.000000] Linux version 5.10.25-v8+ (zauther@zauther-MS-7B98) (aarch64-linux-gnu-gcc (GNU Toolchain for the A-profile Architecture 8.3-201

从串口中启动打印可以知道，u-boot启动时，会依次读取config.txt 配置，加载bcm2711-rpi-4-b.dtb 设备树描述文件， overlay_map.dtb 等。从cmdline.txt 中读取Linux Kernel启动参数，加载kernel8.img 默认文件名。加载kernel到内存位置 0x80000 ，重定位到0x200000 ；加载设备树到0x2eff3d00，设置串口波特率，并启动Kernel。
至此完成了Kernel的加载，并启动文件系统。
如果遇到文件系统出现损坏，为只读文件系统，可尝试切换到root用户，重新挂载根文件系统：

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mount -o remount rw /

由于之前配置的是静态IP，通过SSH即可连接到树莓派。

DONE.