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Chattr
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 Fil ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chmod
In Unix and Unix-like operating systems, is the command and system call used to change the access permissions and the special mode flags (the ''setuid'', ''setgid'', and ''sticky'' flags) of file system objects ( files and directories). Collectively these were originally called its modes, and the name was chosen as an abbreviation of ''change mode''. History A command first appeared in AT&T UNIX version 1, along with the system call. As systems grew in number and types of users, access-control lists were added to many file systems in addition to these most basic modes to increase flexibility. The version of bundled in GNU coreutils was written by David MacKenzie and Jim Meyering. The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities. The command has also been ported to the IBM i operating system. Command syntax Throughout this section, ''ser'' refers to the ow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E2fsprogs
e2fsprogs (sometimes called the e2fs programs) is a set of utilities for maintaining the ext2, ext3 and ext4 file systems. Since those file systems are often the default for Linux distributions, it is commonly considered to be essential software. List of utilities Included with e2fsprogs, ordered by ASCIIbetical order, are: ;badblocks : search a device for bad blocks ;blkid : locate/print block device attributes ;chattr : change file attributes on a Linux file system ;debugfs : used to manually view or modify internal structures of the file system ;dumpe2fs : which prints superblock and block group information. ;e2freefrag : report free space fragmentation information ;e2fsck : an fsck program that checks for and corrects inconsistencies ;e2image : save critical ext2/ext3/ext4 filesystem metadata to a file ;e2label : change the label on an ext2/ext3/ext4 filesystem ;e2undo : replay an undo log for an ext2/ext3/ext4 filesystem ;e4defrag : online defragmenter for ext4 filesystem ... [...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] |
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-o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stat (Unix)
is a Unix system call that returns file attributes about an inode. The semantics of vary between operating systems. As an example, Unix command uses this system call to retrieve information on files that includes: * atime: time of last access () * mtime: time of last modification () * ctime: time of last status change () stat appeared in Version 1 Unix. It is among the few original Unix system calls to change, with Version 4's addition of group permissions and larger file size. stat() functions The C POSIX library header , found on POSIX and other Unix-like operating systems, declares the stat() functions, as well as related functions called fstat() and lstat(). The functions take a struct stat buffer argument, which is used to return the file attributes. On success, the functions return zero, and on error, −1 is returned and errno is set appropriately. The stat() and lstat() functions take a filename argument. If the file is a symbolic link, stat() returns attributes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Btrfs
Btrfs (pronounced as "better F S", "butter F S", "b-tree F S", or simply by spelling it out) is a computer storage format that combines a file system based on the copy-on-write (COW) principle with a logical volume manager (not to be confused with Linux's LVM), developed together. It was initially designed at Oracle Corporation in 2007 for use in Linux, and since November 2013, the file system's on-disk format has been declared stable in the Linux kernel. According to Oracle, Btrfs "is not a true acronym". Btrfs is intended to address the lack of pooling, snapshots, checksums, and integral multi-device spanning in Linux file systems. Chris Mason, the principal Btrfs author, stated that its goal was "to let inuxscale for the storage that will be available. Scaling is not just about addressing the storage but also means being able to administer and to manage it with a clean interface that lets people see what's being used and makes it more reliable". History The core data ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount (Unix)
In computing, mount is a command in various operating systems. Before a user can access a file on a Unix-like machine, the file system on the device which contains the file needs to be mounted with the mount command. Frequently mount is used for SD card, USB storage, DVD and other removable storage devices. The command is also available in the EFI shell. Overview The mount command instructs the operating system that a file system is ready to use, and associates it with a particular point in the overall file system hierarchy (its ''mount point'') and sets options relating to its access. Mounting makes file systems, files, directories, devices and special files available for use and available to the user. Its counterpart umount instructs the operating system that the file system should be disassociated from its mount point, making it no longer accessible and may be removed from the computer. It is important to umount a device before removing it since changes to files may have ... [...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 records b blocksizeC cachesize D dumpdates d density -P pipecommand h 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 operatin ... References External linksHome page of the Linux Ext2 filesystem d ... [...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 ... [...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] |
OCFS2
The Oracle Cluster File System (OCFS, in its second version OCFS2) is a shared disk file system developed by Oracle Corporation and released under the GNU General Public License. The first version of OCFS was developed with the main focus to accommodate Oracle's database management system that used cluster computing. Because of that it was not a POSIX-compliant file system. With version 2 the POSIX features were included. OCFS2 (version 2) was integrated into the version 2.6.16 of Linux kernel. Initially, it was marked as "experimental" (Alpha-test) code. This restriction was removed in Linux version 2.6.19. With kernel version 2.6.29 in late 2008, more features were included into ocfs2, such as access control lists and quotas. OCFS2 used a distributed lock manager which resembles the OpenVMS DLM but is much simpler. Oracle announced version 1.6 in November 2010 which included a copy on write feature called reflink. See also * GlusterFS * GFS2 * General Parallel File S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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