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Umask
umask is a shell command that reports or sets the mask value that limits the file permissions for newly created files in many Unix and Unix-like file systems. A system call with the same name, , provides access to the mask value stored in the operating system (OS), and the command provides shell user access to the system call. Additionally, the mask value, formally ''file mode creation mask'', is often referred to as the ''umask''. When a new file is created, its access permissions are restricted by the stored umask mask value. The file's permission bits that each grant access are cleared by corresponding bits of the mask that are set. Set bits of the mask disallow the permission and clear bits of the mask allow the permission. The otherwise default value of a file's permissions is defined elsewhere. The mask just prevents corresponding bits of the default. The mask acts as a last-stage filter that strips away permissions as a file is created; each bit that is set strips away ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chmod
is a shell command for changing access permissions and special mode flags of files (including special files such as directories). The name is short for ''change mode'' where ''mode'' refers to the permissions and flags collectively. The command originated in AT&T Unix version 1 and was exclusive to Unix and Unix-like operating systems until it was ported to other operating systems such as Windows (in UnxUtils) and IBM i. In Unix and Unix-like operating systems, a system call with the same name as the command, , provides access to the underlying access control data. The command exposes the capabilities of the system call to a shell user. As the need for enhanced file-system permissions grew, access-control lists were added to many file systems to augment the modes controlled via . The implementation of bundled in GNU coreutils was written by David MacKenzie and Jim Meyering. Use Although the syntax of the command varies somewhat by implementation, it generally acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fmask
fstab (after '' file systems table'') is a system file commonly found in the directory /etc on Unix and Unix-like computer systems. The /etc/fstab file is used by utilities from the util-linux package (such as mount and findmnt), but it's not limited to them — it is also processed by systemd via systemd-fstab-generator for automatic mounting during boot. The fstab file typically lists all available disk partitions and other types of file systems and data sources that may not necessarily be disk-based, and indicates how they are to be initialized or otherwise integrated into the larger file system structure. The fstab file is read by the mount command, which happens automatically at boot time to determine the overall file system structure, and thereafter when a user executes the mount command to modify that structure. It is the duty of the system administrator to properly create and maintain the fstab file. While fstab is used for basic system configuration, for other uses, it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fstab
fstab (after '' file systems table'') is a system file commonly found in the directory /etc on Unix and Unix-like computer systems. The /etc/fstab file is used by utilities from the util-linux package (such as mount and findmnt), but it's not limited to them — it is also processed by systemd via systemd-fstab-generator for automatic mounting during boot. The fstab file typically lists all available disk partitions and other types of file systems and data sources that may not necessarily be disk-based, and indicates how they are to be initialized or otherwise integrated into the larger file system structure. The fstab file is read by the mount command, which happens automatically at boot time to determine the overall file system structure, and thereafter when a user executes the mount command to modify that structure. It is the duty of the system administrator to properly create and maintain the fstab file. While fstab is used for basic system configuration, for other uses, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chmod
is a shell command for changing access permissions and special mode flags of files (including special files such as directories). The name is short for ''change mode'' where ''mode'' refers to the permissions and flags collectively. The command originated in AT&T Unix version 1 and was exclusive to Unix and Unix-like operating systems until it was ported to other operating systems such as Windows (in UnxUtils) and IBM i. In Unix and Unix-like operating systems, a system call with the same name as the command, , provides access to the underlying access control data. The command exposes the capabilities of the system call to a shell user. As the need for enhanced file-system permissions grew, access-control lists were added to many file systems to augment the modes controlled via . The implementation of bundled in GNU coreutils was written by David MacKenzie and Jim Meyering. Use Although the syntax of the command varies somewhat by implementation, it generally acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File Permissions
Typically, a file system maintains permission settings for each stored item commonly files and directories that either grant or deny the ability to manipulate file system items. Often the settings allow controlling access based on function such as read, change, navigate, and execute and to different users and groups of users. One well-established technology was developed for Unix and later codified by POSIX. Another common technology is an access-control list (ACL) with multiple variants implemented in file systems and one codified by POSIX. Since POSIX defines both the older Unix-based technology as well as ACLs, the former is called ''traditional POSIX permissions'' for clarity even though it is not a well-known term. A permission-driven user interface tailors the functionality available to the user based on file system item permissions. For example, the interface might hide menu options that are not allowed based on the permissions stored for an item. Examples File sy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Setgid
The Unix and Linux access rights flags setuid and setgid (short for ''set user identity'' and ''set group identity'') allow users to run an executable with the file system permissions of the executable's owner or group respectively and to change behaviour in directories. They are often used to allow users on a computer system to run programs with temporarily elevated privileges to perform a specific task. While the assumed user id or group id privileges provided are not always elevated, at a minimum they are specific. The flags setuid and setgid are needed for tasks that require different privileges than what the user is normally granted, such as the ability to alter system files or databases to change their login password. Some of the tasks that require additional privileges may not immediately be obvious, though, such as the ping command, which must send and listen for control packets on a network interface. File modes The setuid and setgid bits are normally represented as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Setuid
The Unix and Linux access rights flags setuid and setgid (short for ''set user identity'' and ''set group identity'') allow users to run an executable with the file system permissions of the executable's owner or group respectively and to change behaviour in directories. They are often used to allow users on a computer system to run programs with temporarily elevated privileges to perform a specific task. While the assumed user id or group id privileges provided are not always elevated, at a minimum they are specific. The flags setuid and setgid are needed for tasks that require different privileges than what the user is normally granted, such as the ability to alter system files or databases to change their login password. Some of the tasks that require additional privileges may not immediately be obvious, though, such as the ping command, which must send and listen for control packets on a network interface. File modes The setuid and setgid bits are normally represented a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mask (computing)
In computer science, a mask or bitmask is data that is used for bitwise operations, particularly in a bit field. Using a mask, multiple bits in a byte, nibble, Word (computer architecture), word, etc. can be set either on or off, or inverted from on to off (or vice versa) in a single bitwise operation. An additional use of masking involves Predication (computer architecture), predication in vector processing, where the bitmask is used to select which element operations in the vector are to be executed (mask bit is enabled) and which are not (mask bit is clear). Common bitmask functions Masking bits to 1 To turn certain bits on, the Logical disjunction, bitwise OR operation can be used, following Logical disjunction#Bitwise operation, the principle that for an individual bit Y, Y OR 1 = 1 and Y OR 0 = Y. Therefore, to make sure a bit is on, OR can be used with a 1. To leave a bit unchanged, OR is used with a 0. Example: Masking ''on'' the higher nibble (bits 4, 5, 6, 7) while l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
POSIX
The Portable Operating System Interface (POSIX; ) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines application programming interfaces (APIs), along with command line shells and utility interfaces, for software compatibility (portability) with variants of Unix and other operating systems. POSIX is also a trademark of the IEEE. POSIX is intended to be used by both application and system developers. As of POSIX 2024, the standard is aligned with the C17 language standard. Name Originally, the name "POSIX" referred to IEEE Std 1003.1-1988, released in 1988. The family of POSIX standards is formally designated as IEEE 1003 and the ISO/IEC standard number is ISO/ IEC 9945. The standards emerged from a project that began in 1984 building on work from related activity in the ''/usr/group'' association. Richard Stallman suggested the name ''POSIX'' to the IEEE instead of the former ''IEEE-IX''. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unix SUS2008 Utilities
Unix (, ; trademarked as UNIX) is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and others. Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley ( BSD), Microsoft (Xenix), Sun Microsystems (SunOS/ Solaris), HP/ HPE ( HP-UX), and IBM ( AIX). The early versions of Unix—which are retrospectively referred to as " Research Unix"—ran on computers such as the PDP-11 and VAX; Unix was commonly used on minicomputers and mainframes from the 1970s onwards. It distinguished itself from its predecessors as the first portable operating system: almost the entire operating system is written in the C programming language (in 1973), which allows Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Kernel
The Linux kernel is a Free and open-source software, free and open source Unix-like kernel (operating system), kernel that is used in many computer systems worldwide. The kernel was created by Linus Torvalds in 1991 and was soon adopted as the kernel for the GNU operating system (OS) which was created to be a free software, free replacement for Unix. Since the late 1990s, it has been included in many Linux distributions, operating system distributions, many of which are called Linux. One such Linux kernel operating system is Android (operating system), Android which is used in many mobile and embedded devices. Most of the kernel code is written in C (programming language), C as supported by the GNU compiler collection (GCC) which has extensions beyond standard C. The code also contains assembly language, assembly code for architecture-specific logic such as optimizing memory use and task execution. The kernel has a Modular programming, modular design such that modules can be inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
