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42-465: Note: On macOS, files in /Library are not loaded at boot time when booting into Safe Mode. The System Folder is normally located directly below the root directory in the filesystem hierarchy, but does not need to be. The Mac OS identifies the "System Folder" by undocumented characteristics that are independent of its name (it has different names in non-English versions of the Mac OS), or its location in

84-449: A computer file system , and primarily used in the Unix and Unix-like operating systems , the root directory is the first or top-most directory in a hierarchy. It can be likened to the trunk of a tree , as the starting point where all branches originate from. The root file system is the file system contained on the same disk partition on which the root directory is located; it

126-408: A different partition from the replaceable OS system files. Another scenario involves a drive-level failure, such as a compromised file system or drive partition, or a hard disk drive failure . In any of these cases, the data is not easily read from the media devices. Depending on the situation, solutions involve repairing the logical file system, partition table, or master boot record , or updating

168-433: A hard disk drive can be unreadable due to damage to the partition table or file system , or to (intermittent) media errors. In the majority of these cases, at least a portion of the original data can be recovered by repairing the damaged partition table or file system using specialized data recovery software such as TestDisk ; software like ddrescue can image media despite intermittent errors, and image raw data when there

210-454: A hard disk drive, it is generally assumed that the previous data are no longer possible to recover. In 1996, Peter Gutmann , a computer scientist, presented a paper that suggested overwritten data could be recovered through the use of magnetic force microscopy . In 2001, he presented another paper on a similar topic. To guard against this type of data recovery, Gutmann and Colin Plumb designed

252-430: A hard drive, even in cases where a head crash has occurred, does not necessarily mean there will be a permanent loss of data. The techniques employed by many professional data recovery companies can typically salvage most, if not all, of the data that had been lost when the failure occurred. Of course, there are exceptions to this, such as cases where severe damage to the hard drive platters may have occurred. However, if

294-439: A map of bad sectors and tuning parameters) and other information required to properly access data on the drive. Replacement boards often need this information to effectively recover all of the data. The replacement board may need to be reprogrammed. Some manufacturers (Seagate, for example) store this information on a serial EEPROM chip, which can be removed and transferred to the replacement board. Each hard disk drive has what

336-539: A method of irreversibly scrubbing data, known as the Gutmann method and used by several disk-scrubbing software packages. Substantial criticism has followed, primarily dealing with the lack of any concrete examples of significant amounts of overwritten data being recovered. Gutmann's article contains a number of errors and inaccuracies, particularly regarding information about how data is encoded and processed on hard drives. Although Gutmann's theory may be correct, there

378-564: A new volume, the copy is "blessed" as well. On a system with more than one disk volume, it is thus easy to create functioning backups of a system simply by dragging the folder. It is also easy to maintain older and newer versions of the OS "in parallel", each on its own volume, and revert to the old one if problems are encountered with the new one. This degree of flexibility distinguishes the classic Mac OS from most other operating systems, including macOS. All versions of Mac OS permit multiple copies of

420-425: A secluded environment to run software that requires legacy libraries and sometimes to simplify software installation and debugging. Chroot is not meant to be used for enhanced security as the processes inside can break out. Some Unix systems support a directory below the root directory. Normally, "/.." points back to the same inode as "/", however, under MUNIX  [ de ] , this can be changed to point to

462-403: A super-root directory, where remote trees can be mounted. If, for example, two workstations "pcs2a" and "pcs2b" were connected via "connectnodes" and "uunite" startup script, "/../pcs2b" could be used to access the root directory of "pcs2b" from "pcs2a". Under DOS , OS/2 , and Microsoft Windows , each partition has a drive letter assignment (e.g. the C partition is labeled C:\ ) and there

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504-401: A very simple or technical challenge. This is why there are specific software companies specialized in this field. The most common data recovery scenarios involve an operating system failure, malfunction of a storage device, logical failure of storage devices, accidental damage or deletion, etc. (typically, on a single-drive, single- partition , single-OS system), in which case the ultimate goal

546-505: Is a process of retrieving deleted, inaccessible, lost, corrupted, damaged, or formatted data from secondary storage , removable media or files , when the data stored in them cannot be accessed in a usual way. The data is most often salvaged from storage media such as internal or external hard disk drives (HDDs), solid-state drives (SSDs), USB flash drives , magnetic tapes , CDs , DVDs , RAID subsystems, and other electronic devices . Recovery may be required due to physical damage to

588-557: Is acquired and saved on a reliable medium, the image can be safely analyzed for logical damage and will possibly allow much of the original file system to be reconstructed. A common misconception is that a damaged printed circuit board (PCB) may be simply replaced during recovery procedures by an identical PCB from a healthy drive. While this may work in rare circumstances on hard disk drives manufactured before 2003, it will not work on newer drives. Electronics boards of modern drives usually contain drive-specific adaptation data (generally

630-438: Is called a system area or service area ; this portion of the drive, which is not directly accessible to the end user, usually contains drive's firmware and adaptive data that helps the drive operate within normal parameters. One function of the system area is to log defective sectors within the drive; essentially telling the drive where it can and cannot write data. The sector lists are also stored on various chips attached to

672-421: Is no practical evidence that overwritten data can be recovered, while research has shown to support that overwritten data cannot be recovered. Solid-state drives (SSD) overwrite data differently from hard disk drives (HDD) which makes at least some of their data easier to recover. Most SSDs use flash memory to store data in pages and blocks, referenced by logical block addresses (LBA) which are managed by

714-427: Is no public root directory on it. On many Unixes , there is also a directory named /root (pronounced "slash root"). This is the home directory of the 'root' superuser . On many Mac and iOS systems this superuser home directory is /var/root . A home page 's URL usually points to the root of the respective website 's domain name . Disk Partition Recovery In computing , data recovery

756-520: Is partition table or file system damage. This type of data recovery can be performed by people without expertise in drive hardware as it requires no special physical equipment or access to platters. Sometimes data can be recovered using relatively simple methods and tools; more serious cases can require expert intervention, particularly if parts of files are irrecoverable. Data carving is the recovery of parts of damaged files using knowledge of their structure. After data has been physically overwritten on

798-576: Is simply to copy all important files from the damaged media to another new drive. This can be accomplished using a Live CD , or DVD by booting directly from a ROM or a USB drive instead of the corrupted drive in question. Many Live CDs or DVDs provide a means to mount the system drive and backup drives or removable media, and to move the files from the system drive to the backup media with a file manager or optical disc authoring software. Such cases can often be mitigated by disk partitioning and consistently storing valuable data files (or copies of them) on

840-457: Is the filesystem on top of which all other file systems are mounted as the system boots up. Unix abstracts the nature of this tree hierarchy entirely and in Unix and Unix-like systems the root directory is denoted by the / (slash) sign. Though the root directory is conventionally referred to as / , the directory entry itself has no name – its path is the "empty" part before

882-402: Is used to recover/restore the data files. In the list of logical failures of hard disks, a logical bad sector is the most common fault leading data not to be readable. Sometimes it is possible to sidestep error detection even in software, and perhaps with repeated reading and statistical analysis recover at least some of the underlying stored data. Sometimes prior knowledge of the data stored and

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924-414: The firmware or drive recovery techniques ranging from software-based recovery of corrupted data, to hardware- and software-based recovery of damaged service areas (also known as the hard disk drive's "firmware"), to hardware replacement on a physically damaged drive which allows for the extraction of data to a new drive. If a drive recovery is necessary, the drive itself has typically failed permanently, and

966-609: The flash translation layer (FTL). When the FTL modifies a sector it writes the new data to another location and updates the map so the new data appear at the target LBA. This leaves the pre-modification data in place, with possibly many generations, and recoverable by data recovery software. Sometimes, data present in the physical drives (Internal/External Hard disk, Pen Drive , etc.) gets lost, deleted and formatted due to circumstances like virus attack, accidental deletion or accidental use of SHIFT+DELETE. In these cases, data recovery software

1008-497: The PCB, and they are unique to each hard disk drive. If the data on the PCB do not match what is stored on the platter, then the drive will not calibrate properly. In most cases the drive heads will click because they are unable to find the data matching what is stored on the PCB. The term "logical damage" refers to situations in which the error is not a problem in the hardware and requires software-level solutions. In some cases, data on

1050-602: The System or Finder files from it, which are the two files required for booting. (New World Macintoshes also need the Mac OS ROM file.) Some versions of the classic Mac OS, 8.5 and upwards, check the blessed System Folder before shutdown and warn the user if the System Folder is missing any of the key system files, to prevent them from inadvertently rendering the hard drive unbootable. An alternative to manually blessing

1092-503: The computer gets encrypted or hidden due to reasons like virus attacks which can only be recovered by some computer forensic experts. A wide variety of failures can cause physical damage to storage media, which may result from human errors and natural disasters. CD-ROMs can have their metallic substrate or dye layer scratched off; hard disks can suffer from a multitude of mechanical failures, such as head crashes , PCB failure, and failed motors; tapes can simply break. Physical damage to

1134-466: The directory hierarchy. The Macintosh Finder displays this "blessed" folder with a special icon. A "live" System Folder can freely be moved to any location in the directory hierarchy while the OS is operating, and it will continue to operate with no problems after the folder has been moved and after the system is restarted with the folder in its new location. When the Finder copies a "blessed" folder to

1176-427: The error detection and correction codes can be used to recover even erroneous data. However, if the underlying physical drive is degraded badly enough, at least the hardware surrounding the data must be replaced, or it might even be necessary to apply laboratory techniques to the physical recording medium. Each of the approaches is progressively more expensive, and as such progressively more rarely sought. Eventually, if

1218-480: The final, physical storage medium has indeed been disturbed badly enough, recovery will not be possible using any means; the information has irreversibly been lost. Recovery experts do not always need to have physical access to the damaged hardware. When the lost data can be recovered by software techniques, they can often perform the recovery using remote access software over the Internet, LAN or other connection to

1260-436: The focus is rather on a one-time recovery, salvaging whatever data can be read. In a third scenario, files have been accidentally " deleted " from a storage medium by the users. Typically, the contents of deleted files are not removed immediately from the physical drive; instead, references to them in the directory structure are removed, and thereafter space the deleted data occupy is made available for later data overwriting. In

1302-445: The hard drive can be repaired and a full image or clone created, then the logical file structure can be rebuilt in most instances. Most physical damage cannot be repaired by end users. For example, opening a hard disk drive in a normal environment can allow airborne dust to settle on the platter and become caught between the platter and the read/write head . During normal operation, read/write heads float 3 to 6   nanometers above

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1344-407: The initial directory separator character ( / ). All file system entries, including mounted file systems are "branches" of this root. In UNIX-like operating systems, each process has its own idea of what the root directory is. For most processes this is the same as the system's actual root directory, but it can be changed by calling the chroot system call . This is typically done to create

1386-538: The mind of end users , deleted files cannot be discoverable through a standard file manager, but the deleted data still technically exists on the physical drive. In the meantime, the original file contents remain, often several disconnected fragments , and may be recoverable if not overwritten by other data files. The term "data recovery" is also used in the context of forensic applications or espionage , where data which have been encrypted , hidden, or deleted, rather than damaged, are recovered. Sometimes data present in

1428-412: The more reputable ones using class 100 dust- and static-free cleanrooms . Recovering data from physically damaged hardware can involve multiple techniques. Some damage can be repaired by replacing parts in the hard disk. This alone may make the disk usable, but there may still be logical damage. A specialized disk-imaging procedure is used to recover every readable bit from the surface. Once this image

1470-472: The operating system on a single volume. Mac OS 9 added formal support for this by permitting the user to select from multiple copies of the system on the same volume via the Startup Disk control panel, primarily used for selecting which volume to boot from. Prior to this, one would have to manually bless the copy of the System Folder that they wished to use. A folder can be de-blessed by removing either

1512-426: The physical location of the damaged media. The process is essentially no different from what the end user could perform by themselves. Remote recovery requires a stable connection with an adequate bandwidth. However, it is not applicable where access to the hardware is required, as in cases of physical damage. Usually, there are four phases when it comes to successful data recovery, though that can vary depending on

1554-531: The platter surface, and the average dust particles found in a normal environment are typically around 30,000   nanometers in diameter. When these dust particles get caught between the read/write heads and the platter, they can cause new head crashes that further damage the platter and thus compromise the recovery process. Furthermore, end users generally do not have the hardware or technical expertise required to make these repairs. Consequently, data recovery companies are often employed to salvage important data with

1596-455: The storage devices or logical damage to the file system that prevents it from being mounted by the host operating system (OS). Logical failures occur when the hard drive devices are functional but the user or automated-OS cannot retrieve or access data stored on them. Logical failures can occur due to corruption of the engineering chip, lost partitions, firmware failure, or failures during formatting/re-installation. Data recovery can be

1638-510: The system folders in the Mac OS was to use a utility like System Picker . Blessing is continued for mactel machines running macOS with an EFI system, albeit in a mostly different manner. See EFI system partition § macOS and the two types of booting for Apple's BootX bootloader. The System Folder is less protected than the equivalent folders on macOS, in that the contents are all viewable and most files and folders are editable. However it

1680-507: The type of data corruption and recovery required. The Windows operating system can be reinstalled on a computer that is already licensed for it. The reinstallation can be done by downloading the operating system or by using a "restore disk" provided by the computer manufacturer. Eric Lundgren was fined and sentenced to U.S. federal prison in April 2018 for producing 28,000 restore disks and intending to distribute them for about 25 cents each as

1722-672: Was made more convenient when Apple implemented the Extensions Manager , itself a Control Panel that was originally a shareware utility by Ricardo Batista. This allowed activation and deactivation of Control Panels, Extensions, Startup Items and Shutdown Items, and could be invoked fairly early in the boot process by holding down the space bar on the keyboard. One notable absence was the managements of Fonts . For this, Apple allowed Third-party development of font management programs such as Extensis Suitcase, Adobe Type Manager and AlSoft MasterJuggler . Root directory In

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1764-630: Was possible to prevent inexperienced users from accidentally altering the contents by using the Protect System Folder Contents checkbox in the General Controls Control Panel. The Startup and Shut Down programs, Appearance themes, control panels, fonts, and extensions, as well as items in the Apple Menu , are controlled by adding or removing items from folders in the System Folder. This process

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