As actions on the file’s attributes and its xattrs are recorded in FSEvents, they will normally result in a fresh backup being made of the file, even though its data hasn’t been changed. Instead of looking at file modification dates, it looks in a database stored on each volume which records all the events which occur in the file system, FSEvents. As changing permissions or xattrs doesn’t affect file modification dates, those actions won’t cause the file to be backed up again. ![]() If that date is more recent than the last backup, that file will be backed up in the next backup. Most third-party tools, like ChronoSync, look at file modification dates to determine whether a file needs to be backed up. This all depends on the method that the backup system uses to determine which files need to be backed up. But the same doesn’t happen when you use a third-party backup app instead of Time Machine. This is a particular concern when you change a lot of permissions, by resetting or repairing Home folder permissions, or tag a large folder using Dintch. Some users have noticed that changing permissions or xattrs does normally trigger a fresh copy of that file to be made when Time Machine next performs a back up. In fact, unless you look at the xattrs using a utility such as my xattr editor xattred, you won’t even notice what’s happened. So adding or changing a xattr won’t change the date of modification, nor the date that the file was last opened. Xattrs aren’t even stored in the main data area of a volume, but apart, in the file system metadata. In Dintch’s case, it calculates the SHA256 digest (checksum) of a file and writes that to a custom xattr.Ĭhanging a file’s xattrs doesn’t alter the data in the file itself. Some apps, including my utility for checking the integrity of files, Dintch, don’t touch the data in a file, or its regular attributes like datestamps or permissions, but instead write to xattrs. ![]() As you do that without even opening the file, changing permissions alone won’t affect the Last opened date either. If you were to change some of that file’s attributes (metadata), such as its permissions, that also doesn’t alter the date of modification. This large PDF file hasn’t been modified since it was created almost seven years ago, but macOS also tracks when it was last opened, through an extended attribute (xattr) of type, and the datestamp there is used for the Last opened field. When you change the data within a file, its date of last modification is also altered. This article explains a bit more about some of these which could readily confuse. It’s not always clear which of these should be expected to change when different parts of a file change. Use AppleScripts to automate the process even further.Files in macOS have a lot of attributes, or metadata, which provide important information, such as the date that they were last modified.Launch ChronoSync at system startup and have it run in the background.Schedule synchronizations to occur at launch, termination, once, or any repetitive time frame desired.Automate synchronization with a full-featured scheduler.A complete transaction log maintains a complete history of all synchronizations run with options for exporting and printing.Special options that ignore invisible files, resolve alias, preserve folder attributes and synchronize deletions.Run trial synchronizations to check results before committing.Compare files before and after synchronizations to see the status of every file. ![]() Establish simple, intermediate, or advanced rules to include or exclude files by name, size, date, extension, plus other more advanced options.Synchronize files in any direction or bi-directionally.All synchronization settings are stored in separate, self-contained, double-click- able documents that can be run or modified at any time.ChronoSync easily synchronizes or backs-up files and folders in a variety of ways.Synchronize files between folders, hard drives, removable media, laptops, file servers, or any computer, not just a Mac.
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