Time Machine (macOS)

Last updated

Time Machine
Developer(s) Apple Inc.
Operating system macOS 10.5 or newer
Type Backup software
License Proprietary
Website support.apple.com/en-us/HT201250

Time Machine is the backup mechanism of macOS, the desktop operating system developed by Apple. The software is designed to work with both local storage devices and network-attached disks, and is commonly used with external disk drives connected using either USB or Thunderbolt. It was first introduced in Mac OS X 10.5 Leopard, which appeared in October 2007 and incrementally refined in subsequent releases of macOS. Time Machine was revamped in macOS 11 Big Sur to support APFS, thereby enabling "faster, more compact, and more reliable backups" than were possible previously. [1] [2]

Contents

Overview

Time Machine creates incremental backups of files that can be restored at a later date. [3] It allows the user to restore the whole system or specific files. It also works within a number of applications such as Mail and iWork, making it possible to restore individual objects (e.g. emails, contacts, text documents, presentations) without leaving the application.

For backups to a network drive, Time Machine allows the user to back up Mac computers over the network, and supports backing up to certain network attached storage devices or servers, depending on the version of Time Machine. Earlier versions worked with a wide variety of NAS servers, but later versions require the server to support a recent version of Apple's Apple Filing Protocol (AFP) or a recent version of the Server Message Block (SMB) protocol, and Time Machine no longer works with servers using earlier versions of SMB. [4] Some of the legacy support can be re-enabled by using hand-tuned configuration options, accessed through the Terminal. Apple's Time Capsule, which was introduced in 2008 and discontinued in 2018, acted as a network storage device specifically for Time Machine backups, allowing both wired and wireless backups to the Time Capsule's internal hard drive. Time Machine may also be used with other external or internal volumes.

Time Machine saves hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month until the volume runs out of space. At that point, Time Machine deletes the oldest weekly backup. [5]

Revamp in macOS Big Sur

Time Machine was overhauled in macOS 11 Big Sur to utilize APFS, Apple's modern file system first introduced in 2016. Specifically, the new version of Time Machine makes use of APFS's snapshot technology. [1] [6] [7] According to Apple, this enables "faster, more compact, and more reliable backups" than were possible previously with HFS+-formatted drives. [1] [2] An independent evaluation of this claim found that macOS 11's Time Machine implementation in conjunction with APFS was 2.75-fold faster upon initial local backup and 4-fold faster upon subsequent backups relative to macOS 10.15's Time Machine implementation using HFS+. [2] A more modest yet nevertheless significant advantage was noted as well for backups to network-attached disks. [2]

New local (i.e. USB- or Thunderbolt-connected) and network-connected Time Machine backup destinations are formatted as APFS by default, though Time Machine can continue backing up to existing HFS+ backup volumes." [1] There is no option to convert existing, HFS+-based backups to APFS; instead, users who want to benefit from the advantages of the new, APFS-based implementation of Time Machine need to start with a fresh volume. [2]

At least in some circumstances, encryption appears to be required (instead of merely optional) in the new version of Time Machine. [2]

User interface

Time Machine's user interface when retrieving a file uses Apple's Core Animation API. Upon its launch, Time Machine "floats" the active Finder or application window from the user's desktop to a backdrop depicting the user's blurred desktop wallpaper. Behind the current active window are stacked windows, with each window representing a snapshot of how that folder or application looked on the given date and time in the past. When toggling through the previous snapshots, the stacked windows extend backwards, giving the impression of flying through a "time tunnel." While paging through these "windows from the past", a previous version of the data (or currently deleted data) may be retrieved.

Storage

Time Machine works with locally connected storage disks, which must be formatted in the APFS or HFS+ volume formats. Support for backing up to APFS volumes was added with macOS 11 Big Sur and since then APFS is the default volume format.

Time Machine also works with remote storage media shared from other systems, including Time Capsule, via the network. When using remote storage, Time Machine uses sparse bundles. This acts as an isolation layer, which makes the storage neutral to the actual file system used by the network server, and also permits the replication of the backup from one storage medium to another. Sparse bundles are mounted by macOS like any other device, presenting their content as a HFS+ formatted volume, functionally similar to a local storage.

Requirements

Time Machine places strict requirements on the backup storage medium. The only officially supported configurations are: [8]

On a Time Capsule, the backup data is stored in an HFS+ disk image and accessed via Apple Filing Protocol. Although it is not officially supported, users and manufacturers have also configured FreeBSD and Linux servers and network-attached storage systems to serve Time Machine-enabled Macs. There are also a few software tools available on the market that can copy files inside Time Machine backups in Windows machines. [9] [10] [11] [12] [13] [14] [15] [16]

Operation

Time Machine creates a folder on the designated Time Machine volume (local or inside a remote sparse image) into which it copies the directory tree of all locally attached storage drives, except for files and directories that the user has specified to omit, including the Time Machine volume itself. Every hour thereafter, it creates a new subordinate folder and copies only files that have changed since the last backup and creates (in the case of HFS+ volumes) hard links to files that already exist on the backup drive. A user can browse the directory hierarchy of these copies as if browsing the primary disk. [17]

Some other backup utilities save deltas for file changes, much like version control systems. Such an approach permits more frequent backups of minor changes, but can often complicate the interaction with the backup volume. By contrast, it is possible to manually browse a Time Machine backup volume without using the Time Machine interface; Time Machine presents each backup to the user as a complete disk copy. [17]

Time Machine on HFS+ volumes creates multiple hard links to unmodified directories. [17] Multiple linking of directories is a peculiar feature for HFS+, and is not supported on modern Unix file systems including Apple's own APFS. [18] As a result, tools like rsync cannot be used to replicate a Time Machine volume; replication can only reliably be done by imaging the entire filesystem.

Apple system events record when each directory is modified on the hard drive. This means that instead of examining every file's modification date when it is activated, Time Machine only needs to scan the directories that changed for files to copy. This differs from the approach taken by similar backup utilities rsync and FlyBack, which examine modification dates of all files during backup.

Time Machine is also available in the macOS installation process. One of the features in the Migration Assistant interface is to restore the contents of a Time Machine backup. In other words, a hard drive can be restored from a Time Machine backup in the event of a catastrophic crash.

OS X Mountain Lion introduced the ability to use multiple volumes simultaneously for Time Machine operations. When the user specifies more than one volume to use, macOS rotates among the desired volumes each time it does a backup. [19]

Exclusion

Time Machine supports two forms of exclusion: one based on a user-configured list of paths (plus a set of system defaults), the other based on the extended file attribute com.apple.metadata:com_apple_backup_excludeItem dependencies. Since the attribute is applied to the file or directory directly, moving or copying will not affect the exclusion. The attribute should contain the string com.apple.backup in any property list format. Writing com.apple.MobileBackup instead sets the exclusion for iOS backups. [20]

Google Chrome is known to use the attribute to exclude its histories. [20] Third-party backup applications that respect this setting include CrashPlan and Arq. [21] Apple wraps the attribute into the tmutil command-line utility [20] as well as a CoreServices API. [22]

See also

Related Research Articles

Hierarchical File System (HFS) is a proprietary file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. HFS is also referred to as Mac OS Standard, while its successor, HFS Plus, is also called Mac OS Extended.

<span class="mw-page-title-main">AirPort</span> Discontinued line of products by Apple Inc.

AirPort is a discontinued line of wireless routers and network cards developed by Apple Inc. using Wi-Fi protocols. In Japan, the line of products was marketed under the brand AirMac due to previous registration by I-O Data.

A resource fork is a fork of a file on Apple's classic Mac OS operating system that is used to store structured data. It is one of the two forks of a file, along with the data fork, which stores data that the operating system treats as unstructured. Resource fork capability has been carried over to the modern macOS for compatibility.

FileVault is a disk encryption program in Mac OS X 10.3 Panther (2003) and later. It performs on-the-fly encryption with volumes on Mac computers.

<span class="mw-page-title-main">Multi-booting</span> Act of installing multiple operating systems on a single computer

Multi-booting is the act of installing multiple operating systems on a single computer, and being able to choose which one to boot. The term dual-booting refers to the common configuration of specifically two operating systems. Multi-booting may require a custom boot loader.

The Apple Filing Protocol (AFP), formerly AppleTalk Filing Protocol, is a proprietary network protocol, and part of the Apple File Service (AFS), that offers file services for macOS, classic Mac OS, and Apple II computers. In OS X 10.8 Mountain Lion and earlier, AFP was the primary protocol for file services. Starting with OS X 10.9 Mavericks, Server Message Block (SMB) was made the primary file sharing protocol, with the ability to run an AFP server removed later in macOS 11 Big Sur. AFP supports Unicode file names, POSIX and access-control list permissions, resource forks, named extended attributes, and advanced file locking.

Macintosh File System (MFS) is a volume format created by Apple Computer for storing files on 400K floppy disks. MFS was introduced with the original Apple Macintosh computer in January 1984.

HFS Plus or HFS+ is a journaling file system developed by Apple Inc. It replaced the Hierarchical File System (HFS) as the primary file system of Apple computers with the 1998 release of Mac OS 8.1. HFS+ continued as the primary Mac OS X file system until it was itself replaced with the Apple File System (APFS), released with macOS High Sierra in 2017. HFS+ is also one of the formats supported by the iPod digital music player.

<span class="mw-page-title-main">File system</span> Computer filing system

In computing, a file system or filesystem governs file organization and access. A local file system is a capability of an operating system that services the applications running on the same computer. A distributed file system is a protocol that provides file access between networked computers.

The following tables compare general and technical information for a number of file systems.

A sparse image is a type of disk image file used on macOS that grows in size as the user adds data to the image, taking up only as much disk space as stored in it. Encrypted sparse image files are used to secure a user's home directory by the FileVault feature in Mac OS X Snow Leopard and earlier. Sparse images can be created using Disk Utility.

NTBackup is the first built-in backup utility of the Windows NT family. It was introduced with Windows NT 3.51. NTBackup comprises a GUI (wizard-style) and a command-line utility to create, customize, and manage backups. It takes advantage of Shadow Copy and Task Scheduler. NTBackup stores backups in the BKF file format on external sources, e.g., floppy disks, hard drives, tape drives, and Zip drives. When used with tape drives, NTBackup uses the Microsoft Tape Format (MTF), which is also used by BackupAssist, Backup Exec, and Veeam Backup & Replication and is compatible with BKF.

<span class="mw-page-title-main">AirPort Time Capsule</span> Wireless router by Apple

The AirPort Time Capsule is a wireless router which was sold by Apple Inc., featuring network-attached storage (NAS) and a residential gateway router, and is one of Apple's AirPort products. They are, essentially, versions of the AirPort Extreme with an internal hard drive. Apple describes it as a "Backup Appliance", designed to work in tandem with the Time Machine backup software utility introduced in Mac OS X 10.5.

<span class="mw-page-title-main">Apple Disk Image</span> File format developed by Apple and used by macOS

AppleDisk Image is a disk image format commonly used by the macOS operating system. When opened, an Apple Disk Image is mounted as a volume within the Finder.

macOS Sierra Thirteenth major release of macOS

macOS Sierra is the thirteenth major release of macOS, Apple Inc.'s desktop and server operating system for Macintosh computers. The name "macOS" stems from the intention to unify the operating system's name with that of iOS, watchOS and tvOS. Sierra is named after the Sierra Nevada mountain range in California and Nevada. Its major new features concern Continuity, iCloud, and windowing, as well as support for Apple Pay and Siri.

Apple File System (APFS) is a proprietary file system developed and deployed by Apple Inc. for macOS Sierra (10.12.4) and later, iOS 10.3, tvOS 10.2, watchOS 3.2, and all versions of iPadOS. It aims to fix core problems of HFS+, APFS's predecessor on these operating systems. APFS is optimized for solid-state drive storage and supports encryption, snapshots, and increased data integrity, among other capabilities.

macOS Big Sur 17th major version of the macOS operating system

macOS Big Sur is the seventeenth major release of macOS, Apple Inc.'s operating system for Macintosh computers. It was announced at Apple's Worldwide Developers Conference (WWDC) on June 22, 2020, and was released to the public on November 12, 2020.

<span class="mw-page-title-main">Carbon Copy Cloner</span> Backup software

Carbon Copy Cloner is a backup and disk cloning utility for macOS made by Bombich.

References

  1. 1 2 3 4 "macOS Big Sur 11.0.1 Release Notes". Apple. Retrieved December 13, 2020.
  2. 1 2 3 4 5 6 Cunningham, Andrew (November 12, 2022). "macOS 11.0 Big Sur: The Ars Technica review". Ars Technica. Retrieved March 6, 2021.
  3. ↑ Apple. "Apple - Mac OS X Leopard - Features - Time Machine" . Retrieved December 21, 2007.
  4. 1 2 "Time Machine over SMB Specification". Documentation Archive. Apple Inc. September 13, 2016. Retrieved April 24, 2019.
  5. ↑ Tiwari, Saurabh (May 7, 2018). "Create a backup with Time Machine on Mac". Techi Bhai. Retrieved February 16, 2022.
  6. ↑ Owen, Malcolm (June 27, 2020). "APFS changes affect Time Machine in macOS Big Sur, encrypted drives in iOS 14". Apple Insider. Retrieved August 6, 2020.
  7. ↑ Oakley, Howard (June 20, 2020). "APFS changes in Big Sur: how Time Machine backs up to APFS, and more". The Eclectic Light Company. Retrieved August 6, 2020.
  8. ↑ "Backup disks you can use with Time Machine". Apple Support. Apple Inc. Retrieved November 30, 2020.
  9. ↑ Matthias Kretschmann. "HowTo: Make Ubuntu A Perfect Mac File Server And Time Machine Volume" . Retrieved September 11, 2009.
  10. ↑ MKurtz. "NSLU2-Linux - HowTo / TimeMachineBackups" . Retrieved September 11, 2009.
  11. ↑ harryd71 (November 23, 2009). "Mac OS X Time Machine and FreeNAS 0.7" . Retrieved January 17, 2010.{{cite web}}: CS1 maint: numeric names: authors list (link)
  12. ↑ QNAP Systems Inc. "QNAP NAS support for Apple Time Machine" . Retrieved November 30, 2020.
  13. ↑ Bastian Bechtold. "Using a Raspberry Pi as a Time Capsule for Mountain Lion" . Retrieved August 23, 2012.
  14. ↑ Alonso, Noel. "Using Netatalk: AFP Services on a Linux Server". AFP548.com. Retrieved November 1, 2013. Also see slowfranklin's comment and its replies. To add the guest UAM, add AFPD_UAMLIST="-U uams_guest.so" to the [Global] section in afp.conf.
  15. ↑ Bas van de Wiel. "Ironclad Time Machine backups on FreeBSD" . Retrieved March 18, 2016.
  16. ↑ Amar Ilindra (November 21, 2018). "How to Access and Restore Time Machine Backup Files on Windows".
  17. 1 2 3 Pond, James (August 31, 2013). "How Time Machine Works its Magic". Apple OSX and Time Machine Tips. baligu.com. File System Event Store, Hard Links. Retrieved May 19, 2019.
  18. ↑ Butts, Jeff (September 25, 2017). "Time Machine and APFS: What You Need to Know". The Mac Observer. Retrieved April 23, 2019.
  19. ↑ Caldwell, Serenity (February 21, 2012). "Ten exciting system changes in Mountain Lion". Mac-world. Retrieved April 29, 2012.
  20. 1 2 3 Bobby, Brant. "macos - On OS X, what files are excluded by rule from a Time Machine backup?". Ask Different.
  21. ↑ "Feature Request: Honor com_apple_backup_excludeItem on MacOS · Issue #478 · gilbertchen/duplicacy". GitHub.
  22. ↑ "CSBackupSetItemExcluded - Core Services". Apple Developers Documentation.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.