Vaal в 07:07, 2 июня 2017

2017-06-02T07:07:03Z

Vaal: Новая страница: «`'''shred'''` is a Unix command that can be used to securely delete files and devices so that they can be recovered only with great…»

2017-04-05T13:32:39Z

Новая страница: «<tt>'''shred'''</tt> is a Unix command that can be used to securely delete files and devices so that they can be recovered only with great…»

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<tt>'''shred'''</tt> is a [[Unix]] command that can be used to [[data remanence|securely delete]] files and devices so that they can be recovered only with great difficulty with specialised hardware, if at all.{{ref|1|1}} It is a part of [[GNU Core Utilities]].

==Background==
For efficiency, the process of erasing a file from [[data storage device | storage]] usually only erases the file's [[file system | file-system]] entry while keeping the content of the file intact. This frequently allows commonly available software to recover the "erased" file's data. Even if the file is overwritten, residual magnetic fields may allow data recovery using [[data remanence|specialist hardware equipment]]. To prevent this, <tt>shred</tt> overwrites the contents of a file multiple times, using patterns chosen to maximize destruction of the residual data.

==Features==
<tt>shred</tt> can be invoked either on ordinary files or on devices (such as hard disk partitions), which are represented as files in Unix. By default, the command overwrites the file three times with multiple patterns, but the number is user configurable. It has an option to do an additional final overwrite with zeroes, which may help to hide the fact that it was used.

By default, shred also shreds [[fragmentation (computer)#Internal fragmentation|file slack]] (unused space in file allocations). For example, a 5 KB file on a file system with 4 KB clusters actually requires 8 KB of storage. Shred has an option to overwrite only the file itself, as well as an option to delete the file after it has completed operation.

==Limitations==
A limitation of <tt>shred</tt> when invoked on ordinary files is that it only overwrites the data in place without overwriting other copies of the file. Copies can manifest themselves in a variety of ways, such as through manual and automatic backups, file system snapshots, copy-on-write filesystems, [[wear leveling]] on [[solid-state drive|flash drive]]s, caching such as [[Network File System (protocol)|NFS]] caching, and [[Journaling file system|journaling]]. All limitations imposed by the file system can be overcome by shredding every device on which the data resides instead of specific files. However, since wear leveled devices do not guarantee a fixed relationship between logical blocks addressable through the interface and the physical locations in which the data is stored, shredding may not provide adequate security. If available, the SATA secure erase command, issued through [[hdparm]] or a similar utility, may be helpful in this situation. Even for magnetic devices, SATA secure erase will be faster and more reliable than shredding. Physical destruction may be necessary to securely erase devices such as [[memory card]]s and unusable hard disks.

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−	<tt>'''shred'''</tt> is a [[Unix]] command that can be used to [[data remanence\|securely delete]] files and devices so that they can be recovered only with great difficulty with specialised hardware, if at all.~~{{ref\|1\|1}}~~ It is a part of [[GNU Core Utilities]].	+	<tt>'''shred'''</tt> is a [[Unix]] command that can be used to [[data remanence\|securely delete]] files and devices so that they can be recovered only with great difficulty with specialised hardware, if at all. It is a part of [[GNU Core Utilities]].

	==Background==		==Background==

Shred - История изменений

Vaal в 07:07, 2 июня 2017

Vaal: Новая страница: «'''shred''' is a Unix command that can be used to securely delete files and devices so that they can be recovered only with great…»

Vaal: Новая страница: «`'''shred'''` is a Unix command that can be used to securely delete files and devices so that they can be recovered only with great…»