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[分享]一键恢复 之 原理
使用 LLM 解释/回答一下
“一键恢复”技术的核心，在于对备份分区系统的引导。
计算机在启动时总是通过MBR引导已激活的主分区（在同一块硬盘上，最多只能有三个主分区）。只要在MBR中驻留一段特定的程序，就可以控制激活哪一个分区，引导哪一个系统了。
在同一块硬盘上设置两个主分区，一个装Windows XP，一个装DOS。在Windows XP崩溃时，激活DOS系统所在的分区。通过CONFIG.SYS和AUTOEXEC.BAT两个文件，自动完成GHOST镜像文件到分区的装载，就完成了恢复的功能。
根据硬盘的结构，备份分区的位置应是整块硬盘的末分区。因为这里是磁头不常访问的区域，远离系统分区，不容易产生坏道，保证了备份文件的安全。这就对用作备份的DOS系统提出了更高的要求。通常，DOS系统必须安装在硬盘的第一主分区，而目前的条件要求DOS系统必须被安装在末主分区。这样的DOS系统，只能有求于MS-DOS 7.0了（Windows 98 下的DOS）。同时，DOS所在的分区的文件系统必须是FAT32格式。
我们现在使用的系统多为Windows XP，再加上必备的驱动程序、常用的应用软件等等，其大小也要2GB以上。使用GHOST高度压缩（最大约为50%），其镜像文件大约在1GB以上。为了保证数据的安全性，备份区的大小就要在2GB左右。如果要备份多系统，就一定要量体裁衣，决定其对应的空间大小。
而为了对备份的数据更进一步的保护，就要求该分区在系统恢复时显现，而在平时不可见，无论是DOS下，还是Windows下。
实际上，这正是IBM的专用恢复程序BMGR的原理与硬件的设置要求。恢复程序BMGR驻留在MBR内，在开机时会给出以下提示：
To Start the IBM Product Recovery Program, press F11
在出现该提示2秒内，按下F11键，就可以激活恢复系统（上文的DOS系统），进行自动的系统恢复。而重新启动计算机后，该分区又被隐藏了来。
“一键恢复”原理至此完结。
The core of the "one-click recovery" technology lies in the boot of the backup partition system.
When a computer starts, it always boots the activated primary partition through the MBR (on the same hard drive, there can be at most three primary partitions). As long as a specific program is resident in the MBR, it can control which partition is activated and which system is booted.
Set two primary partitions on the same hard drive, one with Windows XP and the other with DOS. When Windows XP crashes, activate the partition where the DOS system is located. Through the two files CONFIG.SYS and AUTOEXEC.BAT, the GHOST image file is automatically loaded to the partition, and the recovery function is completed.
According to the structure of the hard drive, the location of the backup partition should be the last partition of the entire hard drive. Because this is an area where the magnetic head is not often accessed, far from the system partition, it is not easy to generate bad sectors, ensuring the safety of the backup file. This puts higher requirements on the DOS system used for backup. Usually, the DOS system must be installed in the first primary partition of the hard drive, but the current condition requires that the DOS system must be installed in the last primary partition. Such a DOS system can only rely on MS-DOS 7.0 (the DOS under Windows 98). At the same time, the file system of the partition where DOS is located must be in FAT32 format.
The system we use now is mostly Windows XP, plus necessary drivers, common application software, etc., and its size is also more than 2GB. Using GHOST for high compression (up to about 50%), the image file is about more than 1GB. In order to ensure the security of data, the size of the backup area should be about 2GB. If you want to back up multiple systems, you must tailor it to determine the corresponding space size.
And in order to further protect the backed-up data, it is required that the partition is visible during system recovery and invisible at ordinary times, whether in DOS or in Windows.
In fact, this is exactly the principle and hardware setting requirements of IBM's dedicated recovery program BMGR. The recovery program BMGR is resident in the MBR, and the following prompt will be given when booting:
To Start the IBM Product Recovery Program, press F11
Press the F11 key within 2 seconds after this prompt appears, and the recovery system (the above-mentioned DOS system) can be activated to perform automatic system recovery. And after restarting the computer, the partition is hidden again.
The principle of "one-click recovery" is completed here.
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