psa name_PSA：即使未插入备份驱动器，也可以使用Time Machine

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Time Machine, macOS’s built-in back up utility, is one of the simplest backup programs around. Here’s a tip that a lot of people don’t know, though: even if your Time Machine drive isn’t connected to your Mac, it can still protect your files.

macOS的内置备份实用程序Time Machine是周围最简单的备份程序之一。 不过，这是很多人不知道的提示：即使您的Time Machine驱动器未连接到Mac，它仍然可以保护您的文件。

If you have a laptop, you probably don’t have it connected to an external drive at all hours of the day. So what happens when you accidentally delete a file, but don’t have your backup drive plugged in? Time Machine’s local snapshots come to the rescue.

如果您有一台笔记本电脑，则可能一天之中都不会将其连接到外部驱动器。 那么，当您意外删除文件但没有插入备份驱动器时会发生什么呢？ Time Machine的本地快照可以解救。

Time Machine的本地快照 (Time Machine’s Local Snapshots)

Time Machine keeps a collection of hourly, daily, and weekly backups. Hourly backups are kept for 24 hours, daily backups are kept for a month, and weekly backups are kept indefinitely, as long as there is space on your Time Machine drive.

Time Machine收集每小时，每天和每周的备份。 只要Time Machine驱动器上有空间，每小时备份将保留24小时，每天备份将保留一个月，并且每周备份将无限期保留。

When your backup disk isn’t connected, Time Machine can’t save any information, so it stores the backup data on your startup disk as a Local Snapshot. When you connect your Time Machine drive, the backups are copied across to it.

当您的备份磁盘未连接时，Time Machine无法保存任何信息，因此它将备份数据作为本地快照存储在启动磁盘上。 连接Time Machine驱动器时，备份将复制到其中。

Since OS X Lion, MacBooks will keep Local Snapshots while there is enough free space on the startup disk. As long as the hard drive is less than 80% full, Time Machine will keep as many Snapshots as it can. If the hard drive gets more than 80% full, Time Machine will start deleting the oldest backups. The fuller the startup disk, the more aggressively Time Machine deletes older backups.

从OS X Lion开始，MacBook会在启动磁盘上有足够可用空间时保留本地快照。 只要硬盘驱动器的可用空间不足80％，Time Machine就会保留尽可能多的快照。 如果硬盘驱动器的可用空间超过80％，Time Machine将开始删除最早的备份。 启动盘越完整，Time Machine越积极地删除较早的备份。

Local Snapshots aren’t a true backup, of course, since the information is all stored on the same disk. If your hard drive gets damaged, they’ll vanish along with every other bit of data.

当然，本地快照不是真正的备份，因为所有信息都存储在同一磁盘上。 如果您的硬盘驱动器损坏，它们将与其他所有数据一起消失。

But, Local Snapshots can still be useful for restoring corrupted or accidentally deleted files. If a Word document goes bad while you’re working on it—which is the data disaster that inspired this article—you can jump into Time Machine and restore a version that is, at most, an hour old.

但是，本地快照对于恢复已损坏或意外删除的文件仍然有用。 如果在处理Word文档时出现问题(这是引起本文的数据灾难)，则可以跳入Time Machine并还原最多一个小时的版本。

如何从本地快照恢复文件 (How to Recover Files from Local Snapshots)

To recover a file from a Local Snapshot, click the Time Machine menubar icon and select Enter Time Machine.

要从本地快照恢复文件，请单击Time Machine菜单栏图标，然后选择Enter Time Machine。

A Finder window will appear that you can use to browse your Mac’s file system. You can go back to previous backups by clicking on the arrows or on a specific date in the sidebar.

将出现一个Finder窗口，可用于浏览Mac的文件系统。 您可以通过单击箭头或侧边栏中的特定日期来返回以前的备份。

Without your Time Machine drive connected, you’ll only be able to browse backups that exist as a Local Snapshot. If you keep a relatively empty hard drive, these could go back for months.

在没有连接Time Machine驱动器的情况下，您将只能浏览作为本地快照存在的备份。 如果您保留相对空的硬盘驱动器，则这些驱动器可能会再使用几个月。

To restore a file or folder from an older version, select it and click the Restore button, just like you would in any other Time Machine session.

要从旧版本还原文件或文件夹，请选择它并单击“还原”按钮，就像在任何其他Time Machine会话中一样。

Local Snapshots are a nice extra fallback, but they’re not something that should be relied on. It’s just another safety net behind your regular backups. My Mac is almost maxed out on storage space, so I only had a couple of Local Snapshots to work from. (And if you’d rather have that free space, you can always delete the Local Snapshots too.) If you need to go back an hour or two, you should be fine; just don’t count on a file you deleted last month still being around.

本地快照是一个很好的额外后备，但它不是值得依赖的。 这只是常规备份的另一个安全网。 我的Mac的存储空间几乎已用完，因此只能使用几个本地快照。 (如果您希望有可用空间，也可以随时删除“本地快照” 。)如果需要返回一两个小时，就可以了。 只是不要指望您上个月删除的文件仍然存在。

翻译自: https://www.howtogeek.com/276196/you-can-use-time-machine-even-if-your-backup-drive-isnt-plugged-in/

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