如果您是第一次开始使用rsync，并且有多个大型硬盘驱动器要备份，那么在这个漫长的过程中使用一个或多个硬盘驱动器是否安全？今天的超级用户问答帖子回答了一位忧心忡忡的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

问题

超级用户读者都想知道在rsync运行时使用硬盘是否安全：

I plan to backup my collection of large hard drives using rsync and anticipate that it will take a few days. Is it safe to use the original hard drive (adding files) while rsync is working or it is better to leave the hard drives untouched until rsync is completely finished?

rsync运行时使用硬盘安全吗？

答案

超级用户贡献者Michael Kjorling为我们提供了答案：

As others have already pointed out, it is safe to read from the source disk or use the target disk outside of the target directory while rsync is running. It is also safe to read within the target directory, especially if the target directory is being populated exclusively by the rsync run.

What is not generally safe, however, is to write within the source directory while rsync is running. “Write” is anything that modifies the content of the source directory or any subdirectory thereof, so that includes file updates, deleti***, creation, etc.

Doing so will not actually break anything, but the change may or may not actually get picked up by rsync for copying to the target location. That depends on the type of change, whether rsync has scanned that particular directory yet, and whether rsync has copied the file or directory in question yet.

There is an easy way around that, however. Once rsync has finished, run it again with the same parameters (unless you have some funky deletion parameter; if you do, then be a bit more careful). Doing so will cause rsync to re-scan the source and transfer any differences that were not picked up during the original run.

The second run should transfer only differences that happened during the previous rsync run, and as such, will be completed much faster. Thus, you can feel free to use the computer normally during the first run, but should avoid making any changes as much as possible to the source during the second run. If you can, strongly c***ider remounting the source file system as read-only before starting the second rsync run (something like mount -o ro,remount /media/source should do).

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