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0053_auto_sd_resize.md

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auto sd resize

分析SD卡自动resize功能

参考文档

init resize

当你将下载的镜像烧录到SD卡之后，查看SD卡boot分区内容可以看到如下情况

  • /boot/cmdline.txt 
    dwc_otg.lpm_enable=0 console=serial0,115200 console=tty1 root=PARTUUID=7ee80803-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet init=/usr/lib/raspi-config/init_resize.sh
  • init=/usr/lib/raspi-config/init_resize.sh

init_resize.sh

  • usr/lib/raspi-config/init_resize.sh 
    #!/bin/sh

[...省略]

main () {
  get_variables

  if ! check_variables; then
    return 1
  fi

  check_kernel

  if [ "$NOOBS" = "1" ] && [ "$NEW_KERNEL" != "1" ]; then
    BCM_MODULE=$(grep -e "^Hardware" /proc/cpuinfo | cut -d ":" -f 2 | tr -d " " | tr '[:upper:]' '[:lower:]')
    if ! modprobe "$BCM_MODULE"; then
      FAIL_REASON="Couldn't load BCM module $BCM_MODULE"
      return 1
    fi
  fi

  if [ "$ROOT_PART_END" -eq "$TARGET_END" ]; then
    reboot_pi
  fi

  if [ "$NOOBS" = "1" ]; then
    if ! parted -m "$ROOT_DEV" u s resizepart "$EXT_PART_NUM" yes "$TARGET_END"; then
      FAIL_REASON="Extended partition resize failed"
      return 1
    fi
  fi

  if ! parted -m "$ROOT_DEV" u s resizepart "$ROOT_PART_NUM" "$TARGET_END"; then
    FAIL_REASON="Root partition resize failed"
    return 1
  fi

  partprobe "$ROOT_DEV"
  fix_partuuid

  return 0
}

mount -t proc proc /proc
mount -t sysfs sys /sys
mount -t tmpfs tmp /run
mkdir -p /run/systemd

mount /boot
mount / -o remount,rw

sed -i 's| init=/usr/lib/raspi-config/init_resize\.sh||' /boot/cmdline.txt
sed -i 's| sdhci\.debug_quirks2=4||' /boot/cmdline.txt

if ! grep -q splash /boot/cmdline.txt; then
  sed -i "s/ quiet//g" /boot/cmdline.txt
fi
sync

echo 1 > /proc/sys/kernel/sysrq

if ! check_commands; then
  reboot_pi
fi

if main; then
  whiptail --infobox "Resized root filesystem. Rebooting in 5 seconds..." 20 60
  sleep 5
else
  sleep 5
  whiptail --msgbox "Could not expand filesystem, please try raspi-config or rc_gui.\n${FAIL_REASON}" 20 60
fi

reboot_pi