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Chflags
is the command in Linux that allows a user to set certain attributes of a file. is the command that displays the attributes of a file. Most BSD-like systems, including macOS, have always had an analogous command to set the attributes, but no command specifically meant to display them; specific options to the command are used instead. The chflags command first appeared in 4.4BSD. Solaris has no commands specifically meant to manipulate them. and are used instead. Other Unix-like operating systems, in general, have no analogous commands. The similar-sounding commands (from HP-UX) and (from AIX) exist but have unrelated functions. Among other things, the command is useful to make files immutable so that password files and certain system files cannot be erased during software upgrades. In Linux systems ( and ) File system support The command line tools (to manipulate attributes) and (to list attributes) were originally specific to the Second Extended File ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Attribute
File attributes are a type of meta-data that describe and may modify how files and/or directories in a filesystem behave. Typical file attributes may, for example, indicate or specify whether a file is visible, modifiable, compressed, or encrypted. The availability of most file attributes depends on support by the underlying filesystem (such as FAT, NTFS, ext4) where attribute data must be stored along with other control structures. Each attribute can have one of two states: set and cleared. Attributes are considered distinct from other metadata, such as dates and times, filename extensions or file system permissions. In addition to files, folders, volumes and other file system objects may have attributes. DOS and Windows Traditionally, in DOS and Microsoft Windows, files and folders accepted four attributes: * Archive (A): When set, it indicates that the hosting file has changed since the last backup operation. Windows' file system sets this attribute on any file that has change ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hidden File And Hidden Directory
In computing, a hidden folder (sometimes hidden directory) or hidden file is a folder (computing), folder or computer file, file which filesystem utilities do not display by default when showing a Directory (computing), directory listing. They are commonly used for storing user preferences or preserving the state of a utility and are frequently created implicitly by using various utilities. They are not a security mechanism because access is not restricted – usually the intent is simply to not "clutter" the display of the contents of a directory listing with files the user did not directly create. Unix and Unix-like environments In Unix-like operating systems, any file or folder that starts with a full stop, dot character (for example, ), commonly called a dot file or dotfile, is to be treated as hidden – that is, the ls command does not display them unless the -a or -A command-line argument, flags (ls -a or ls -A) are used. In most command line, command-line shell (computi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which includes the kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name "GNU/Linux" to emphasize the importance of GNU software, causing some controversy. Popular Linux distributions include Debian, Fedora Linux, and Ubuntu, the latter of which itself consists of many different distributions and modifications, including Lubuntu and Xubuntu. Commercial distributions include Red Hat Enterprise Linux and SUSE Linux Enterprise. Desktop Linux distributions include a windowing system such as X11 or Wayland, and a desktop environment such as GNOME or KDE Plasma. Distributions intended for ser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
JFS (file System)
Journaled File System (JFS) is a 64-bit journaling file system created by IBM. There are versions for AIX, OS/2, eComStation, ArcaOS and Linux operating systems. The latter is available as free software under the terms of the GNU General Public License (GPL). HP-UX has another, different filesystem named JFS that is actually an OEM version of Veritas Software's VxFS. In the AIX operating system, two generations of JFS' exist, which are called ''JFS'' (''JFS1'') and ''JFS2'' respectively. In other operating systems, such as OS/2 and Linux, only the second generation exists and is called simply ''JFS''. This should not be confused with JFS in AIX that actually refers to JFS1. History IBM introduced JFS with the initial release of AIX version 3.1 in February 1990. This file system, now called ''JFS1 on AIX'', was the premier file system for AIX over the following decade and was installed in thousands or millions of customers' AIX systems. Historically, the JFS1 file system is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LILO (boot Loader)
LILO (Linux Loader) is a boot loader for Linux and was the default boot loader for most Linux distributions in the years after the popularity of loadlin. Today, many distributions use GRUB as the default boot loader, but LILO and its variant ELILO are still in wide use. Further development of LILO was discontinued in December 2015 along with a request by Joachim Wiedorn for potential developers. ELILO For EFI-based PC hardware the now orphaned ELILO boot loader was developed, originally by Hewlett-Packard for IA-64 systems made, but later also for standard i386 and amd64 hardware with EFI support. On any version of Linux running on Intel-based Apple Macintosh hardware, ELILO is one of the available bootloaders. It supports network booting using TFTP/DHCP. See also * /boot/ * Comparison of boot loaders The following tables compare general and technical information for a number of available bootloaders. General information Technical information Note: The column MB ... [...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] |
Orlov Block Allocator
The Orlov block allocator is an algorithm to define where a particular file will reside on a given file system (blockwise), so as to speed up disk operations. Etymology The scheme is named after its creator Grigoriy Orlov, who first posted, in 2000, a brief description and implementation for OpenBSD of the technique, which was later used in the BSD Fast Filesystem kernel variants. Background The performance of a file system is dependent on many things; one of the crucial factors is just how that filesystem lays out files on the disk. In general, it is best to keep related items together. The Linux ext2 and ext3 filesystems, for instance, have tried to spread directories on the cylinders of the disk. Imagine setting up a system with users' home directories in /home: if all the first-level directories within /home (i.e. the home directories for numerous users) are placed next to each other, there may be no space left for the contents of those directories. User files thus end up b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Remanence
Data remanence is the residual representation of digital data that remains even after attempts have been made to remove or erase the data. This residue may result from data being left intact by a nominal file deletion operation, by reformatting of storage media that does not remove data previously written to the media, or through physical properties of the storage media that allow previously written data to be recovered. Data remanence may make inadvertent disclosure of sensitive information possible should the storage media be released into an uncontrolled environment (''e.g.'', thrown in the bin (trash) or lost). Various techniques have been developed to counter data remanence. These techniques are classified as clearing, purging/sanitizing, or destruction. Specific methods include overwriting, degaussing, encryption, and media destruction. Effective application of countermeasures can be complicated by several factors, including media that are inaccessible, media that ... [...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] |
HTree
An HTree is a specialized tree data structure for directory indexing, similar to a B-tree. They are constant depth of either one or two levels, have a high fanout factor, use a hash of the filename, and do not require balancing. The HTree algorithm is distinguished from standard B-tree methods by its treatment of hash collisions, which may overflow across multiple leaf and index blocks. HTree indexes are used in the ext3 and ext4 Linux filesystems, and were incorporated into the Linux kernel around 2.5.40. HTree indexing improved the scalability of Linux ext2 based filesystems from a practical limit of a few thousand files, into the range of tens of millions of files per directory. History The HTree index data structure and algorithm were developed by Daniel Phillips in 2000 and implemented for the ext2 filesystem in February 2001. A port to the ext3 filesystem by Christopher Li and Andrew Morton in 2002 during the 2.5 kernel series added journal based crash consistency. With ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extent (file Systems)
In computing, an extent is a contiguous area of storage reserved for a file in a file system, represented as a range of block numbers, or tracks on count key data devices. A file can consist of zero or more extents; one file fragment requires one extent. The direct benefit is in storing each range compactly as two numbers, instead of canonically storing every block number in the range. Also, extent allocation results in less file fragmentation. Extent-based file systems can also eliminate most of the metadata overhead of large files that would traditionally be taken up by the block-allocation tree. But because the savings are small compared to the amount of stored data (for all file sizes in general) but make up a large portion of the metadata (for large files), the overall benefits in storage efficiency and performance are slight. In order to resist fragmentation, several extent-based file systems do allocate-on-flush. Many modern fault-tolerant file systems also do copy-on-wr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dump (Unix)
The dump command is a program on Unix and Unix-like operating systems used to back up file systems. It operates on blocks, below filesystem abstractions such as files and directories. Dump can back up a file system to a tape or another disk. It is often used across a network by piping its output through bzip2 then SSH. A dump utility first appeared in Version 6 AT&T UNIX. A dump command is also part of ASCII's ''MSX-DOS2 Tools'' for MSX-DOS version 2. Usage dump 0123456789acLnSuB recordsb blocksize C cachesize D dumpdates d density -P pipecommandh level s feetT datefilesystem $ dump -W , -w See also *restore (program) *tar (file format) *cpio *rsync rsync is a utility for efficiently transferring and synchronizing files between a computer and a storage drive and across networked computers by comparing the modification times and sizes of files. It is commonly found on Unix-like opera ... References External linksHome page of the Linux Ext2 filesystem du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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