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Dar (disk Archiver)
dar (disk archive) is a computer program, a command-line archiving tool intended as a replacement for tar in Unix-like operating systems. Features * Support for slices, archives split over multiple files of a particular size * Option of deleting files from the system which are removed in the archive * Full backup * Differential backup * Incremental backup, * Decremental backup * Takes care of any type of inode (directory, plain files, symlinks, special devices, named pipes, sockets, doors, ...) * Takes care of hard-linked inodes (hard-linked plain files, char devices, block devices, hard-linked symlinks) * Takes care of sparse files * Takes care of Linux file Extended Attributes, * Takes care of Linux file ACL * Takes care of Mac OS X file forks * Takes care of some filesystem specific attributes like Birthdate of HFS+ filesystem and immutable, data-journaling, secure-deletion, no-tail-merging, undeletable, noatime attributes of ext2/3/4 filesystem. * Per-file comp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
GNU General Public License
The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was the first copyleft for general use and was originally written by the founder of the Free Software Foundation (FSF), Richard Stallman, for the GNU Project. The license grants the recipients of a computer program the rights of the Free Software Definition. These GPL series are all copyleft licenses, which means that any derivative work must be distributed under the same or equivalent license terms. It is more restrictive than the GNU Lesser General Public License, Lesser General Public License and even further distinct from the more widely used permissive software licenses BSD licenses, BSD, MIT License, MIT, and Apache License, Apache. Historically, the GPL license family has been one of the most popular software licenses in the free and open ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Named Pipe
In computing, a named pipe (also known as a FIFO for its behavior) is an extension to the traditional pipe concept on Unix and Unix-like systems, and is one of the methods of inter-process communication (IPC). The concept is also found in OS/2 and Microsoft Windows, although the semantics differ substantially. A traditional pipe is " unnamed" and lasts only as long as the process. A named pipe, however, can last as long as the system is up, beyond the life of the process. It can be deleted if no longer used. Usually a named pipe appears as a file, and generally processes attach to it for IPC. In Unix Instead of a conventional, unnamed, shell pipeline, a named pipeline makes use of the filesystem. It is explicitly created using mkfifo() or mknod(), and two separate processes can access the pipe by name — one process can open it as a reader, and the other as a writer. For example, one can create a pipe and set up gzip to compress things piped to it: mkfifo my_pipe gzip -9 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Suballocation
Block suballocation is a feature of some computer file systems which allows large blocks or allocation units to be used while making efficient use of empty space at the end of large files, space which would otherwise be lost for other use to internal fragmentation. In file systems that don't support fragments, this feature is also called tail merging or tail packing because it is commonly done by packing the "tail", or last partial block, of multiple files into a single block. Rationale File systems have traditionally divided the disk into equally sized blocks to simplify their design and limit the worst-case fragmentation. Block sizes are typically multiples of 512 bytes due to the size of hard disk sectors. When files are allocated by some traditional file systems, only whole blocks can be allocated to individual files. But as file sizes are often not multiples of the file system block size, this design inherently results in the last blocks of files (called tails) occupying ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Erasure
Data erasure (sometimes referred to as data clearing, data wiping, or data destruction) is a software-based method of overwriting the data that aims to completely destroy all electronic data residing on a hard disk drive or other digital media by using zeros and ones to overwrite data onto all sectors of the device in an irreversible process. By overwriting the data on the storage device, the data is rendered irrecoverable and achieves data sanitization. Ideally, software designed for data erasure should: #Allow for selection of a specific standard, based on unique needs, and #Verify the overwriting method has been successful and removed data across the entire device. Permanent data erasure goes beyond basic file deletion commands, which only remove direct pointers to the data disk sectors and make the data recovery possible with common software tools. Unlike degaussing and physical destruction, which render the storage media unusable, data erasure removes all information wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journaling File System
A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a "journal", which is usually a circular log. In the event of a system crash or power failure, such file systems can be brought back online more quickly with a lower likelihood of becoming corrupted. Depending on the actual implementation, a journaling file system may only keep track of stored metadata, resulting in improved performance at the expense of increased possibility for data corruption. Alternatively, a journaling file system may track both stored data and related metadata, while some implementations allow selectable behavior in this regard. History In 1990 IBM introduced JFS in AIX 3.1 as one of the first UNIX commercial filesystems that implemented journaling. The next year the idea was popularized in a widely cited paper on log-structured file systems. This was subsequently i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HFS Plus
HFS Plus or HFS+ (also known as Mac OS Extended or HFS Extended) 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. Compared to its predecessor HFS, also called ''Mac OS Standard'' or ''HFS Standard,'' HFS Plus supports much larger files (block addresses are 32-bit length instead of 16-bit) and using Unicode (instead of Mac OS Roman or any of several other character sets) for naming items. Like HFS, HFS Plus uses B-trees to store most volume metadata, but unlike most file systems that support hard links, HFS Plus supports hard links to directories. HFS Plus permits filenames up to 255 characters in length, and n-fork ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resource Fork
The resource fork is a fork (file system), fork or section of a computer file, file on Apple Inc., Apple's classic Mac OS operating system, which was also carried over to the modern macOS for compatibility, used to store structured data along with the unstructured data stored within the data fork. A resource fork stores information in a specific form, containing details such as icon bitmaps, the shapes of windows, definitions of menus and their contents, and application code (machine code). For example, a word processing file might store its text in the data fork, while storing any embedded images in the same file's resource fork. The resource fork is used mostly by executables, but every file is able to have a resource fork. The Macintosh file system Originally conceived and implemented by programmer Bruce Horn, the resource fork was used for three purposes with Hierarchical File System, Macintosh file system: * It was used to store all graphical data on disk until it was neede ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Access-control List
In computer security, an access-control list (ACL) is a list of permissions associated with a system resource (object). An ACL specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject and an operation. For instance, if a file object has an ACL that contains , this would give Alice permission to read and write the file and give Bob permission only to read it. Implementations Many kinds of operating systems implement ACLs or have a historical implementation; the first implementation of ACLs was in the filesystem of Multics in 1965. Filesystem ACLs A filesystem ACL is a data structure (usually a table) containing entries that specify individual user or group rights to specific system objects such as programs, processes, or files. These entries are known as access-control entries (ACEs) in the Microsoft Windows NT, OpenVMS, and Unix-like operating systems suc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extended File Attributes
Extended file attributes are file system features that enable users to associate computer files with metadata not interpreted by the filesystem, whereas regular attributes have a purpose strictly defined by the filesystem (such as permissions or records of creation and modification times). Unlike forks, which can usually be as large as the maximum file size, extended attributes are usually limited in size to a value significantly smaller than the maximum file size. Typical uses include storing the author of a document, the character encoding of a plain-text document, or a checksum, cryptographic hash or digital certificate, and discretionary access control information. In Unix-like systems, extended attributes are usually abbreviated as xattr. Implementations AIX In AIX, the JFS2 v2 filesystem supports extended attributes, which are accessible using the command. The , , , , and APIs support fetching, setting, listing, getting information about, and removing extended attribu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sparse File
In computer science, a sparse file is a type of computer file that attempts to use file system space more efficiently when the file itself is partially empty. This is achieved by writing brief information ( metadata) ''representing'' the empty blocks to the data storage media instead of the actual "empty" space which makes up the block, thus consuming less storage space. The full block size is written to the media as the actual size only when the block contains "real" (non-empty) data. When reading sparse files, the file system transparently converts metadata representing empty blocks into "real" blocks filled with null bytes at runtime. The application is unaware of this conversion. Most modern file systems support sparse files, including most Unix variants and NTFS. Apple's HFS+ does not provide support for sparse files, but in OS X, the virtual file system layer supports storing them in any supported file system, including HFS+. Apple File System (APFS), announced in June 2016 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block Device
In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions. Overview Device files usually provide simple interfaces to standard devices (such as printers and serial ports), but can also be used to access specific unique resources on those devices, such as disk partitions. Additionally, device files are useful for accessing system resources that have no connection with any actual device, such as data sinks and random number generators. There are two general kinds of device files in Unix-like operating systems, known as ''character ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Character Device
In Unix-like operating systems, a device file or special file is an interface to a device driver that appears in a file system as if it were an ordinary file. There are also special files in DOS, OS/2, and Windows. These special files allow an application program to interact with a device by using its device driver via standard input/output system calls. Using standard system calls simplifies many programming tasks, and leads to consistent user-space I/O mechanisms regardless of device features and functions. Overview Device files usually provide simple interfaces to standard devices (such as printers and serial ports), but can also be used to access specific unique resources on those devices, such as disk partitions. Additionally, device files are useful for accessing system resources that have no connection with any actual device, such as data sinks and random number generators. There are two general kinds of device files in Unix-like operating systems, known as ''character ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
