Time Machine (Apple software)
Encyclopedia
Time Machine is a backup utility
developed by Apple. It is included with Mac OS X
and was introduced with the 10.5 "Leopard" release of Mac OS X. The software is designed to work with the Time Capsule
as well as other internal or external drives.
, iLife
, and several other compatible programs, making it possible to restore individual objects (e.g.: photos, contacts, calendar events) without leaving the application. According to Apple support personnel:
For backups to a network drive, Time Machine allows the user to back up Apple Macintosh computers through Apple's AirPort
networking, and supports backing up to normal network attached storage
devices or servers without the use of hand-tuned configuration options, accessed through the Terminal. Apple's Time Capsule
acts 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 alternatively be used with any external or internal volume.
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.
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 a galaxy and star field. 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 presently deleted data) may be retrieved.
s to files that already exist on the remote drive. A user can browse these "versions" of the primary drive and see each file as if it were right where it was left.
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; the software's use of hard links makes each backup session appear to the user like a full backup, rather than an incremental or "delta" backup.
Time Machine appears to create multiple hard links to unmodified directories. Multiple linking of
directories is quite different from conventional UNIX.
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 (the remainder being hard-linked). 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 Leopard, Snow Leopard, and Lion
installation process. One of the features in the Migration Assistant interface is to re-install 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.
, Address Book, iPhoto
'08 or newer and GarageBand
'08 or newer.
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 configured Linux servers and network-attached storage
systems to serve Time Machine-enabled Macs.
Backup software
Backup software are computer programs used to perform backup; they create supplementary exact copies of files, databases or entire computers. These programs may later use the supplementary copies to restore the original contents in the event of data loss....
developed by Apple. It is included with Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
and was introduced with the 10.5 "Leopard" release of Mac OS X. The software is designed to work with the Time Capsule
Time Capsule (Apple)
The Time Capsule is a wireless network-attached storage device combined with a wireless residential gateway router made by Apple Inc. It is described as a "Backup Appliance", designed to work in tandem with the Time Machine backup utility, introduced in Mac OS X 10.5 "Leopard".The device includes a...
as well as other internal or external drives.
Overview
Time Machine creates incremental backups of files that can be restored at a later date. It allows the user to restore the whole system (from the OS X Install DVD), multiple files, or a single file. It works within iWorkIWork
iWork is an office suite of desktop applications created by Apple for the Mac OS X and iOS operating systems. The first version of iWork, iWork '05, was released in 2005. The suite originally bundled Keynote, a presentation program which had previously been sold as a standalone application, and...
, iLife
ILife
iLife is a suite of software applications developed by Apple for organizing, editing, and publishing photos, movies, and music. The suite comprises five applications: iPhoto, iMovie, iDVD, GarageBand, and iWeb, all of which run on the Mac OS X operating system....
, and several other compatible programs, making it possible to restore individual objects (e.g.: photos, contacts, calendar events) without leaving the application. According to Apple support personnel:
"Time Machine is a backup utility, not an archival utility, it is not intended as offline storage. Time Machine captures the most recent state of your data on your disk. As snapshots age, they are prioritized progressively lower compared to your more recent ones."
For backups to a network drive, Time Machine allows the user to back up Apple Macintosh computers through Apple's AirPort
AirPort
AirPort and AirPort Extreme are local area wireless networking products from Apple Inc. based on the IEEE 802.11 standard ....
networking, and supports backing up to normal network attached storage
Network-attached storage
Network-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
devices or servers without the use of hand-tuned configuration options, accessed through the Terminal. Apple's Time Capsule
Time Capsule (Apple)
The Time Capsule is a wireless network-attached storage device combined with a wireless residential gateway router made by Apple Inc. It is described as a "Backup Appliance", designed to work in tandem with the Time Machine backup utility, introduced in Mac OS X 10.5 "Leopard".The device includes a...
acts as a network storage
Network-attached storage
Network-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
device specifically for Time Machine backups, allowing both wired and wireless backups to the Time Capsule's internal hard drive. Time Machine may alternatively be used with any external or internal volume.
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.
User interface
Time Machine's user interfaceUser interface
The user interface, in the industrial design field of human–machine interaction, is the space where interaction between humans and machines occurs. The goal of interaction between a human and a machine at the user interface is effective operation and control of the machine, and feedback from the...
when retrieving a file uses Apple's Core Animation
Core Animation
Core Animation is a data visualization API used by Mac OS X 10.5 and later as well as iOS to produce animated user interfaces.-Overview:Core Animation provides a way for developers to produce animated user interfaces via an implicit animation model as well as an "explicit" model...
API
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
. Upon its launch, Time Machine "floats" the active Finder or application window from the user's desktop to a backdrop depicting a galaxy and star field. Behind the current active window
Active window
An active window is the currently focused window in the current window manager or explorer. Different window managers indicate the currently-active window in different ways and allow the user to switch between windows in different ways. For example, in Microsoft Windows, if both Notepad and...
are stacked windows, with each window representing a snapshot
Snapshot (computer storage)
In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems....
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 presently deleted data) may be retrieved.
How it works
Time Machine creates a folder on the designated Time Machine volume which is named the current date and time. It then copies all locally attached drives (except for files and directories that it has specifically been told not to copy, including the Time Machine volume itself) to the folder. Every hour thereafter, it creates a new folder on the remote drive using the same naming scheme, but instead of making another complete copy of the primary hard drive, Time Machine instead only backs up files that have changed and creates hard linkHard link
In computing, a hard link is a directory entry that associates a name with a file on a file system. . The term is used in file systems which allow multiple hard links to be created for the same file. This has the effect of creating multiple names for the same file, causing an aliasing effect: e.g...
s to files that already exist on the remote drive. A user can browse these "versions" of the primary drive and see each file as if it were right where it was left.
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; the software's use of hard links makes each backup session appear to the user like a full backup, rather than an incremental or "delta" backup.
Time Machine appears to create multiple hard links to unmodified directories. Multiple linking of
directories is quite different from conventional UNIX.
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 (the remainder being hard-linked). This differs from the approach taken by similar backup utilities rsync
Rsync
rsync is a software application and network protocol for Unix-like and Windows systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar...
and FlyBack
FlyBack
FlyBack is an open source backup utility for Linux based on Git and modeled loosely after Apple's Time Machine.-Overview:FlyBack creates incremental backups of files which can be restored at a later date...
, which examine modification dates of all files during backup.
Time Machine is also available in the Leopard, Snow Leopard, and Lion
Mac OS X Lion
Mac OS X Lion is the eighth and current major release of Mac OS X, Apple's desktop and server operating system for Macintosh computers....
installation process. One of the features in the Migration Assistant interface is to re-install 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.
Time Machine-aware applications
Some Mac OS X applications work with Time Machine, such as Finder, MailMail (application)
Mail is an email program included with Apple Inc.'s Mac OS X operating system. Originally developed by NeXT as NeXTMail, a part of their NeXTSTEP operating system, it was adapted, following Apple's acquisition of NeXT, to become OS X's Mail application.Mail uses the SMTP, POP3, and IMAP protocols,...
, Address Book, iPhoto
IPhoto
iPhoto is a digital photograph manipulation software application developed by Apple Inc. and released with every Macintosh personal computer as part of the iLife suite of digital life management applications...
'08 or newer and GarageBand
GarageBand
GarageBand is a software application for Mac OS X and iOS that allows users to create music or podcasts. It is developed by Apple Inc. as a part of the iLife software package on Mac OS X.-Audio recording:...
'08 or newer.
Requirements
Time Machine places strict requirements on the backup storage medium. The only officially supported configurations are:- A non-booting hard drive or partition connected directly to the computer, either internally or by a bus like USB or FireWire, and formatted as journaledJournaling file systemA journaling file system is a file system that keeps track of the changes that will be made in a journal before committing them to the main file system...
HFS+HFS PlusHFS Plus or HFS+ is a file system developed by Apple Inc. to replace their Hierarchical File System as the primary file system used in Macintosh computers . It is also one of the formats used by the iPod digital music player...
. - A folder on a journaled HFS+ file system shared by another Mac on the same network running at least Leopard.
- A drive shared by an Apple Time CapsuleTime Capsule (Apple)The Time Capsule is a wireless network-attached storage device combined with a wireless residential gateway router made by Apple Inc. It is described as a "Backup Appliance", designed to work in tandem with the Time Machine backup utility, introduced in Mac OS X 10.5 "Leopard".The device includes a...
on the same network.
On a Time Capsule, the backup data is stored in an HFS+ disk image
Disk image
A disk image is a single file or storage device containing the complete contents and structure representing a data storage medium or device, such as a hard drive, tape drive, floppy disk, CD/DVD/BD, or USB flash drive, although an image of an optical disc may be referred to as an optical disc image...
and accessed via Apple Filing Protocol
Apple Filing Protocol
The Apple Filing Protocol is a network protocol that offers file services for Mac OS X and original Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block , Network File System , File Transfer Protocol , and WebDAV...
. Although it is not officially supported, users and manufacturers have configured Linux servers and network-attached storage
Network-attached storage
Network-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
systems to serve Time Machine-enabled Macs.
See also
- MobileMe BackupBackup (software)Backup is a backup utility made by Apple for Mac OS X. It is available through Apple's MobileMe collection of Internet services...
- List of backup software
- Revision controlRevision controlRevision control, also known as version control and source control , is the management of changes to documents, programs, and other information stored as computer files. It is most commonly used in software development, where a team of people may change the same files...
- Time Capsule (Apple)Time Capsule (Apple)The Time Capsule is a wireless network-attached storage device combined with a wireless residential gateway router made by Apple Inc. It is described as a "Backup Appliance", designed to work in tandem with the Time Machine backup utility, introduced in Mac OS X 10.5 "Leopard".The device includes a...
- System RestoreSystem RestoreSystem Restore is a component of Microsoft's Windows Me, Windows XP, Windows Vista and Windows 7, but not Windows 2000, operating systems that allows for the rolling back of system files, registry keys, installed programs, etc., to a previous state in the event of system malfunction or failure.The...