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Passwd
passwd is a command on Unix, Plan 9, Inferno, and most Unix-like operating systems used to change a user's password. The password entered by the user is run through a key derivation function to create a hashed version of the new password, which is saved. Only the hashed version is stored; the entered password is not saved for security reasons. When the user logs on, the password entered by the user during the log on process is run through the same key derivation function and the resulting hashed version is compared with the saved version. If the hashes are identical, the entered password is considered to be correct, and the user is authenticated. In theory, it is possible for two different passwords to produce the same hash. However, cryptographic hash functions are designed in such a way that finding any password that produces the same hash is very difficult and practically infeasible, so if the produced hash matches the stored one, the user can be authenticated. The passw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User (computing)
A user is a person who uses a computer or network service. A user often has a user account and is identified to the system by a username (or user name). Some software products provide services to other systems and have no direct end users. End user End users are the ultimate human users (also referred to as operators) of a software product. The end user stands in contrast to users who support or maintain the product such as sysops, database administrators and computer technicians. The term is used to abstract and distinguish those who only use the software from the developers of the system, who enhance the software for end users. In user-centered design, it also distinguishes the software operator from the client who pays for its development and other stakeholders who may not directly use the software, but help establish its requirements. This abstraction is primarily useful in designing the user interface, and refers to a relevant subset of characteristics t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
User Identifier (Unix)
Unix-like operating systems identify a user by a value called a user identifier, often abbreviated to user ID or UID. The UID, along with the group identifier (GID) and other access control criteria, is used to determine which system resources a user can access. The password file maps textual user names to UIDs. UIDs are stored in the inodes of the Unix file system, running processes, tar archives, and the now-obsolete Network Information Service. In POSIX-compliant environments, the shell command id gives the current user's UID, as well as more information such as the user name, primary user group and group identifier (GID). Process attributes The POSIX standard introduced three different UID fields into the process descriptor table, to allow privileged processes to take on different roles dynamically: Effective user ID The effective UID (euid) of a process is used for most access checks. It is also used as the owner for files created by that process. The effective GID (egid) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Network Information Service
The Network Information Service, or NIS (originally called Yellow Pages or YP), is a client–server directory service protocol (computing), protocol for Distributed computing, distributing system configuration data such as User (computing), user and host names between computers on a computer network. Sun Microsystems developed the NIS; the technology is Software license, licensed to virtually all other Unix vendors. Because British Telecom PLC owned the name "Yellow Pages" as a registered trademark in the United Kingdom for its paper-based, commercial telephone directory, Sun changed the name of its system to NIS, though all the commands and functions still start with "yp". A NIS/YP system maintains and distributes a central directory of user and group information, hostnames, e-mail aliases and other text-based tables of information in a computer network. For example, in a common Unix, UNIX environment, the list of users for Identification (information), identification is placed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptographic Hash Function
A cryptographic hash function (CHF) is a hash algorithm (a map (mathematics), map of an arbitrary binary string to a binary string with a fixed size of n bits) that has special properties desirable for a cryptography, cryptographic application: * the probability of a particular n-bit output result (hash value) for a random input string ("message") is 2^ (as for any good hash), so the hash value can be used as a representative of the message; * finding an input string that matches a given hash value (a ''pre-image'') is infeasible, ''assuming all input strings are equally likely.'' The ''resistance'' to such search is quantified as security strength: a cryptographic hash with n bits of hash value is expected to have a ''preimage resistance'' strength of n bits, unless the space of possible input values is significantly smaller than 2^ (a practical example can be found in ); * a ''second preimage'' resistance strength, with the same expectations, refers to a similar problem of f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Logname
In computer software, logname (stands for Login Name) is a program in Unix and Unix-like operating systems that prints the name of the user who is currently logged in on the terminal. It usually corresponds to the LOGNAME variable in the system-state environment (but this variable could have been modified). History The logname system call and command appeared for the first time in UNIX System III. The author of the version of logname bundled in GNU coreutils is unknown. The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports Ports collections (or ports trees, or just ports) are the sets of makefiles and Patch (Unix), patches provided by the BSD-based operating systems, FreeBSD, NetBSD, and OpenBSD, as a simple method of installing software or creating binary packages. T ... of common GNU Unix-like utilities. Usage $ logname --help Usage: logname PTIONPrint the name of the current user. --help di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Colon (punctuation)
The colon, , is a punctuation mark consisting of two equally sized dots aligned vertically. A colon often precedes an explanation, a list, or a quoted sentence. It is also used between hours and minutes in time, between certain elements in medical journal citations, between chapter and verse in Bible citations, between two numbers in a ratio, and, in the US, for salutations in business letters and other formal letters. History In Ancient Greek, in rhetoric and prosody, the term (', 'limb, member of a body') did not refer to punctuation, but to a member or section of a complete thought or passage; see also '' Colon (rhetoric)''. From this usage, in palaeography, a colon is a clause or group of clauses written as a line in a manuscript.''Oxford English Dictionary'', 1st ed. "colon, ''n.2''" Oxford University Press (Oxford), 1891. In the 3rd century BC, Aristophanes of Byzantium is alleged to have devised a punctuation system, in which the end of such a was thought to oc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Line (text File)
In computing, a line is a unit of organization for text files. A line consists of a sequence of zero or more characters, usually displayed within a single horizontal sequence. The term comes directly from physical printing, where a line of text is a horizontal row of characters. Depending on the file system or operating system being used the number of characters on a line may either be predetermined or fixed, or the length may vary from line to line. Fixed-length lines are sometimes called records. With variable-length lines, the end of each line is usually indicated by the presence of one or more special end-of-line characters. These include line feed, carriage return, or combinations thereof. A blank line usually refers to a line containing zero characters (not counting any end-of-line characters); though it may also refer to any line that does not contain any visible characters (consisting only of whitespace). Some tools that operate on text files (e.g., editors) p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Text File
A text file (sometimes spelled textfile; an old alternative name is flat file) is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists stored as data within a computer file system. In operating systems such as CP/M, where the operating system does not keep track of the file size in bytes, the end of a text file is denoted by placing one or more special characters, known as an end-of-file (EOF) marker, as padding after the last line in a text file. In modern operating systems such as DOS, Microsoft Windows and Unix-like systems, text files do not contain any special EOF character, because file systems on those operating systems keep track of the file size in bytes. Some operating systems, such as Multics, Unix-like systems, CP/M, DOS, the classic Mac OS, and Windows, store text files as a sequence of bytes, with an end-of-line delimiter at the end of each line. Other operating systems, such as OpenVMS and OS/360 an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superuser
In computing, the superuser is a special user account used for system administration. Depending on the operating system (OS), the actual name of this account might be root, administrator, admin or supervisor. In some cases, the actual name of the account is not the determining factor; on Unix-like systems, for example, the user with a user identifier (UID) of zero is the superuser .e., uid=0 regardless of the name of that account; and in systems which implement a r model, any user with the role of superuser (or its synonyms) can carry out all actions of the superuser account. The principle of least privilege recommends that most users and applications run under an ordinary account to perform their work, as a superuser account is capable of making unrestricted, potentially adverse, system-wide changes. Unix and Unix-like In Unix-like computer OSes (such as Linux), ''root'' is the conventional name of the user who has all rights or permissions (to all files and programs) in all mod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
File System 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] |
Passwd (database)
The Name Service Switch (NSS) is a feature found in the standard C library of various Unix-like operating systems that connects a computer with a variety of sources of common configuration databases and name resolution mechanisms. These sources include local operating system files (such as , , and ), the Domain Name System (DNS), the Network Information Service (NIS, NIS+), and LDAP. nsswitch.conf A system administrator usually configures the operating system's name services using the file . This file lists databases (such as passwd, shadow and group), and one or more sources for obtaining that information. Examples for sources are ''files'' for local files, ''ldap'' for the Lightweight Directory Access Protocol, ''nis'' for the Network Information Service, ''nisplus'' for NIS+, ''dns'' for the Domain Name System (DNS), and ''wins'' for Windows Internet Name Service. The nsswitch.conf file has line entries for each service consisting of a database name in the first ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
