在极少数情况下，您的 iPhone 或 iPad 可能会遇到严重问题（可能是在软件更新不佳之后），而您无法通过标准故障排除解决这些问题。然而，在将设备带到Apple Store之前，您应该尝试最后一件事——将 iPhone 或 iPad 重置为DFU（设备固件更新(Device Firmware Update)）模式(Mode)。
iPhone 上的DFU 模式(DFU Mode)是一种高级恢复环境 - 类似于恢复模式 -(Recovery Mode—that)从头开始重新安装 iPhone 或 iPad 的系统软件。但它也更进一步，恢复了设备的固件，有可能解决硬件级别的损坏程序问题。
何时应进入 DFU 模式
如果您的 iPhone 或 iPad 出现故障，您必须先在恢复模式下更新或重置它(update or reset it in Recovery Mode)。仅在设备继续执行以下操作的情况下才使用DFU 模式：(DFU Mode)
- 卡在 Apple 标志(stuck at the Apple logo)上。
- 陷入连续的引导循环(stuck in a continuous boot loop)。
- 无法响应触摸(respond to touch)。
- 无法响应按钮按下。
- 遇到随机冻结。
- 体验快速的电池耗尽问题(battery draining issues)。
- 导致错误代码（例如错误 4013(error 4013)）
在DFU 模式下(DFU Mode)重置 iPhone 或 iPad将永久删除其中的所有数据。如果您有最近的 iCloud 或 iTunes/Finder 备份，您可以在重置过程后恢复丢失的数据。您还可以稍后通过登录Apple ID(Apple ID)取回您设置为与 iCloud 同步的任何数据，例如照片和联系人。
如果设备在连接到Mac或 PC 时出现在 iTunes/Finder 中，最好在 iPhone 上进入和使用DFU 模式之前(DFU Mode)在线或本地创建新备份。(create a fresh backup online or locally)
进入 DFU 模式需要什么
您需要Mac或 PC 才能在 iPhone 或 iPad 上通过iTunes 或Finder应用程序进入(Finder)DFU 模式(DFU Mode—via)并与之交互。您还应该使用兼容的USB电缆将故障设备物理连接到计算机。
注意：(Note:)在 PC 上，您必须手动下载并安装iTunes（如果您尚未安装）。Mac预装了 iTunes，但它已被从 macOS Catalina 开始的Finder应用程序所(Catalina)取代(Finder)。
但是，没有理由使用您以前用于备份或同步目的的Mac或 PC。(Mac)DFU 模式(DFU Mode)不需要访问 iPhone 或 iPad 上的任何文件，因此任何 macOS 或 Windows 10 设备都应该足够好。
但最好更新 iTunes 或Finder应用程序，以确保您在使用DFU 模式(DFU Mode)时不会遇到问题。您可以通过System Preferences > Software Update应用最新的系统软件更新来更新(Software Update)Mac上的iTunes/ Finder。在 PC 上，转至Microsoft Store >下载和更新(Downloads and updates)。
如何进入 DFU 模式
要在 iPhone 或 iPad 上进入DFU 模式(DFU Mode)，您必须按下根据设备的品牌和型号而变化的各种按钮。下面的步骤一开始可能会让人感到困惑和棘手，因此您可能会在正确完成之前失败几次。
与恢复模式(Recovery Mode)不同，iPhone 或 iPad 上的屏幕在DFU 模式下(DFU Mode)将保持空白。如果您在步骤结束时看到任何内容（例如“插入(Plug)Mac/PC”指示符），则必须重试。
注意：(Note:)以下说明适用于 iPhone 或 iPad，无论它是开机还是关机(Off)。
iPhone 8 Series and Later | iPads Without Home Button
1. 将您的 iPhone 或 iPad 连接到Mac或 PC。
2. 打开 iTunes 或 Finder 应用程序。
3. 按下并快速松开iPhone 或 iPad 上的提高音量按钮。(Volume Up)
4. 按下并快速松开降低音量(Volume Down)按钮。
5. 快速按住侧边(Side)/顶部(Top)按钮，直到屏幕变黑。或者，等到Apple标志出现并再次消失。
6. 立即按住降低音量(Volume Down )按钮而不松开侧面(Side )按钮。
7. 等待 5 秒。
8. 松开侧面(Side )按钮，但继续按住降低音量(Volume Down )按钮。
9.一旦设备出现在 iTunes 或Finder中，松开(Finder)降低音量(Volume Down)按钮。
iPhone 7 系列(iPhone 7 Series)
1. 将您的 iPhone 或 iPad 连接到您的Mac或 PC。
2. 打开 iTunes 或 Finder 应用程序。
3. 按住 iPhone 的侧边(Side )和降低音量(Volume Down)按钮。
4. 等待 8-10 秒。与此同时，屏幕应该关闭，或者Apple标志应该出现然后消失。
5.按住降低音量按钮的同时松开(Volume Down)侧面(Side )按钮。
6.一旦您在 iTunes 或Finder中看到设备，请松开降低音量(Volume Down)按钮。
iPhone 6s Series and Earlier | iPads With Home Button
1. 将您的 iPhone 连接到您的Mac或 PC。
2. 打开 iTunes 或 Finder 应用程序。
3. 按住iPhone 或 iPad 上 的Side/Top 和主页按钮。(Home)
4. 等待 8-10 秒。
4. 松开Side/Top 按钮，但继续按住主页(Home )按钮。
5.在 iTunes 或Finder中看到设备后松开Home按钮。
如何在 iPhone 和 iPad 上使用DFU 模式(DFU Mode)
在 DFU 模式下，选择恢复 iPhone(Restore iPhone)或恢复 iPad(Restore iPad )以开始重置 iPhone 或 iPad。iTunes/Finder 将自动下载最新版本的 iOS/iPadOS 系统软件（通常为 5-6GB）并将其安装在您的 iPhone 或 iPad 上。它还将恢复固件。
注意：(Note:)假设您的 iPhone 或 iPad在下载阶段自动退出DFU模式。(DFU)在这种情况下，您必须重新按下按钮并等待 iTunes/Finder 完成下载。
当 iTunes/Finder 正在重新安装系统软件和固件时，请勿断开您的 iPhone 或 iPad。这将使设备完全无法使用。
如果DFU模式成功完成，请在设置 iPhone 或 iPad 以restore data from an iCloud or iTunes/Finder backup从 iCloud 备份(Restore from iCloud Backup)恢复或从 Mac 或 PC 恢复(Restore from Mac or PC)选项。
如何在 iPhone 和 iPad 上退出DFU 模式(DFU Mode)
如果您想在不重置 iPhone 或 iPad 的情况下退出DFU 模式(DFU Mode)，则必须强制重启设备。
iPhone 8 Series and Later | iPads Without Home Button
1. 按下并快速松开音量调高(Volume Up )按钮。
2. 按下并快速松开降低音量(Volume Down )按钮。
3. 快速按住侧边(Side)/顶部(Top )按钮，直到您在屏幕上看到Apple标志。(Apple)
iPhone 7 系列(iPhone 7 Series)
按住侧边(Side )按钮和降低音量(Volume Down)按钮，直到Apple标志出现在屏幕上。
iPhone 6s Series and Earlier | iPads With Home Button
按住侧边(Side)/顶部(Top)和主页(Home)按钮，直到Apple标志出现在屏幕上。
下一步行动
在DFU 模式下(DFU Mode)执行重置并不能保证您最终会修复您的 iPhone 或 iPad。某些问题（尤其是与故障硬件相关的问题）无法通过恢复系统软件和固件来解决。
如果您无法在 iPhone 或 iPad 上进入DFU 模式(DFU Mode)，或者在执行重置后同样的问题不断出现，您别无选择，只能将设备取出进行维修或更换。
How to Use DFU Mode on iPhone and iPad
On rare occasions, уоur iPhone or iPad can run into serious issues—pеrhaps after a botched sоftware update—that you can’t fix with standard troubleshoоting. Before takіng the dеvice to an Apple Store, however, there’s one last thing you should try—resetting the iPhоne or iPad in DFU (Device Firmware Update) Mode.
DFU Mode on iPhone is an advanced recovery environment—similar to Recovery Mode—that reinstalls the iPhone or iPad’s system software from scratch. But it also goes a step beyond and restores the device’s firmware, potentially resolving problems with corrupt programming at the hardware-level.
When You Should Enter DFU Mode
If you have a malfunctioning iPhone or iPad, you must first update or reset it in Recovery Mode. Only resort to using DFU Mode in instances where the device continues to:
Resetting your iPhone or iPad in DFU Mode will permanently erase all data on it. If you have a recent iCloud or iTunes/Finder backup, you can restore the lost data after the reset procedure. You can also get back any data—such as photos and contacts—that you’ve set to sync with iCloud by signing into your Apple ID later on.
If the device shows up in iTunes/Finder when you connect it to a Mac or PC, it’s a good idea to create a fresh backup online or locally before entering and using DFU Mode on your iPhone.
What You Need to Enter DFU Mode
You need a Mac or PC to enter and interact with DFU Mode—via the iTunes or Finder apps—on the iPhone or iPad. You should also have a compatible USB cable to connect the malfunctioning device to the computer physically.
Note: On the PC, you must download and install iTunes manually (if you haven’t already). The Mac comes with iTunes pre-installed, but it’s replaced by the Finder app starting with macOS Catalina.
However, there’s no reason to use a Mac or PC that you’ve previously used for backup or sync purposes. DFU Mode does not require access to any files on the iPhone or iPad, so any macOS or Windows 10 device should be good enough.
But it’s a great idea to update iTunes or the Finder apps to ensure that you don’t run into hitches while using DFU Mode. You can update iTunes/Finder on Mac by applying the latest system software updates via System Preferences > Software Update. On the PC, go to Microsoft Store > Downloads and updates instead.
How to Enter DFU Mode
To enter DFU Mode on the iPhone or iPad, you must press various buttons that change depending on the device’s make and model. The steps below may appear confusing—and tricky—to time correctly at first, so you may fail a few times before getting them right.
Unlike Recovery Mode, the screen on your iPhone or iPad will remain blank in DFU Mode. If you see anything (such as a “Plug into Mac/PC” indicator) at the end of the steps, you must try again.
Note: The following instructions work on an iPhone or iPad regardless of whether it’s powered On or Off.
iPhone 8 Series and Later | iPads Without Home Button
1. Connect your iPhone or iPad to a Mac or PC.
2. Open iTunes or the Finder app.
3. Press and quickly release the Volume Up button on the iPhone or iPad.
4. Press and quickly release the Volume Down button.
5. Quickly press and hold the Side/Top button until the screen turns black. Or, wait until the Apple logo shows up and disappears again.
6. Immediately hold down the Volume Down button without releasing the Side button.
7. Wait for 5 seconds.
8. Release the Side button but keep holding the Volume Down button.
9. Release the Volume Down button once the device shows up in iTunes or Finder.
iPhone 7 Series
1. Connect your iPhone or iPad to your Mac or PC.
2. Open iTunes or the Finder app.
3. Press and hold the iPhone’s Side and Volume Down buttons.
4. Wait for 8-10 seconds. In the meantime, the screen should turn off, or the Apple logo should show up and disappear.
5. Release the Side button while holding the Volume Down button.
6. Release the Volume Down button once you see the device in iTunes or Finder.
iPhone 6s Series and Earlier | iPads With Home Button
1. Connect your iPhone to your Mac or PC.
2. Open iTunes or the Finder app.
3. Press and hold the Side/Top and Home buttons on the iPhone or iPad.
4. Wait for 8-10 seconds.
4. Release the Side/Top button but keep holding down the Home button.
5. Release the Home button once you see the device in iTunes or Finder.
How to Use DFU Mode on iPhone and iPad
In DFU Mode, select Restore iPhone or Restore iPad to begin resetting the iPhone or iPad. iTunes/Finder will automatically download the latest version of the iOS/iPadOS system software (which typically amounts to 5-6GB) and install it on your iPhone or iPad. It will also restore the firmware.
Note: Suppose your iPhone or iPad automatically exits DFU mode during the download phase. In that case, you must perform the button presses all over again and wait for iTunes/Finder to finish the download.
Do not disconnect your iPhone or iPad while iTunes/Finder is actively re-installing the system software and firmware. That will make the device completely unusable.
If DFU mode completes successfully, select the Restore from iCloud Backup or the Restore from Mac or PC option while setting up your iPhone or iPad to restore data from an iCloud or iTunes/Finder backup.
How to Exit DFU Mode on iPhone and iPad
If you want to exit DFU Mode without resetting your iPhone or iPad, you must force-restart the device.
iPhone 8 Series and Later | iPads Without Home Button
1. Press and quickly release the Volume Up button.
2. Press and quickly release the Volume Down button.
3. Quickly press and hold the Side/Top button until you see the Apple logo on the screen.
iPhone 7 Series
Press and hold both the Side and Volume Down buttons until the Apple logo appears on the screen.
iPhone 6s Series and Earlier | iPads With Home Button
Press and hold both the Side/Top and the Home buttons until the Apple logo appears on the screen.
The Next Course of Action
Performing a reset in DFU Mode does not guarantee that you’ll end up fixing your iPhone or iPad. Some issues—specifically those related to faulty hardware—are impossible to resolve by restoring the system software and firmware.
If you can’t enter DFU Mode on your iPhone or iPad, or if the same problem keeps recurring after performing the reset, you have no recourse but to take the device out for a repair or replacement.
