{"id":21,"date":"2017-06-29T11:50:51","date_gmt":"2017-06-29T11:50:51","guid":{"rendered":"https:\/\/www.coimbatorewebhosting.com\/blog\/?p=21"},"modified":"2017-07-21T13:50:28","modified_gmt":"2017-07-21T08:20:28","slug":"what-is-an-operating-systemlinux","status":"publish","type":"post","link":"https:\/\/coimbatorewebhosting.com\/blog\/what-is-an-operating-systemlinux\/","title":{"rendered":"What is an Operating System(Linux):-"},"content":{"rendered":"<p class=\"western\" lang=\"zxx\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>What is an Operating System?<\/b><\/span><\/span><\/p>\n<p class=\"western\" lang=\"zxx\"><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">An operating system (OS) is a resource manager. It takes the form of a set of software routines that allow users and application programs to access system resources (e.g. the CPU, memory, disks, modems, printers network cards etc.) in a <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">safe,efficient and abstract way.<\/span><\/span><\/span><\/p>\n<p class=\"western\" lang=\"zxx\"><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">For example, an OS ensures <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">safe<\/span><\/span><\/span><b> <\/b><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">access to a printer by allowing only one application program to send data directly to the printer at any one time.<\/span><\/span><\/span><\/p>\n<p class=\"western\" lang=\"zxx\"><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">An OS encourages <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">efficient <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">use of the CPU by suspending programs that are waiting for I\/O operations to complete to make way for programs that can use the CPU more productively. An OS also provides convenient <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">abstractions<\/span><\/span><\/span><b> <\/b><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(such as files rather than disk locations) which isolate application programmers and users from the details of the underlying hardware.<\/span><\/span><\/span><\/p>\n<p lang=\"zxx\"><a href=\"https:\/\/www.coimbatorewebhosting.com\/blog\/wp-content\/uploads\/2017\/06\/Untitledp.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-22 size-full\" src=\"https:\/\/www.coimbatorewebhosting.com\/blog\/wp-content\/uploads\/2017\/06\/Untitledp.jpg\" alt=\"\" width=\"350\" height=\"304\" srcset=\"https:\/\/coimbatorewebhosting.com\/blog\/wp-content\/uploads\/2017\/06\/Untitledp.jpg 350w, https:\/\/coimbatorewebhosting.com\/blog\/wp-content\/uploads\/2017\/06\/Untitledp-300x261.jpg 300w\" sizes=\"auto, (max-width: 350px) 100vw, 350px\" \/><\/a><\/p>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><i>Fig. shows: General operating system architecture<\/i><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Fig. &nbsp;presents the architecture of a typical operating system and shows how an OS succeeds in presenting users and application programs with a uniform interface without regard to the details of the underlying hardware. We see that:<\/span><\/span><\/p><\/blockquote>\n<ul>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">The operating system <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">kernel <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">is in direct control of the underlying hardware. The kernel provides low-level device, memory and processor management functions (e.g. dealing with interrupts from hardware devices, sharing the processor among multiple programs, allocating memory for programs etc.)<\/span><\/span><\/span><\/p><\/blockquote>\n<\/li>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Basic hardware-independent kernel services are exposed to higher-level programs through a library of <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">system calls<\/span><\/span><\/span><b> <\/b><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(e.g. services to create a file, begin execution of a program, or open a logical network connection to another computer).<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Application programs<\/span><\/span><\/span><b> <\/b><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(e.g. word processors, spreadsheets) and <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">system<\/span><\/span><\/span> <span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">utility programs <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(simple but useful application programs that come with the operating system, e.g. programs which find text inside a group of files) make use of system calls. Applications and system utilities are <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">launched using a shell (a textual command line interface) or a graphical user interface that provides direct user interaction.<\/span><\/span><\/span><\/p><\/blockquote>\n<\/li>\n<\/ul>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Operating systems (and different flavors of the same operating system) can be distinguished from one another by the system calls, system utilities and user interface they provide, as well as by the resource scheduling policies implemented by the kernel.<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Architecture of the Linux Operating System:-<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Linux has all of the components of a typical OS (at this point you might like to refer back to Fig :<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-size: large;\"><strong><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\">Kernel<\/span><\/span><\/strong><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><br \/>\nThe Linux kernel includes device driver support for a large number of PC hardware devices (graphics cards, network cards, hard disks etc.), advanced processor and memory management features, and support for many different types of filesystems (including DOS floppies and the ISO9660 standard for CDROMs).<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">In terms of the services that it provides to application programs and system utilities, the kernel implements most BSD and SYSV system calls, as well as the system calls described in the POSIX.1 specification.<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">The kernel (in raw binary form that is loaded directly into memory at system startup time) is typically found in the file \/boot\/vmlinuz, while the source files can usually be found in \/usr\/src\/linux. The latest version of the Linux kernel sources can be downloaded from &nbsp;<\/span><\/span><\/span><span style=\"color: #000080;\"><span lang=\"zxx\"><u><a href=\"http:\/\/www.kernel.org\/\" rel=\"nofollow noopener\" target=\"_blank\"><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">http:\/\/www.kernel.org<\/span><\/span><\/span><\/a><\/u><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">.<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Shells and GUIs<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Linux supports two forms of command input: through textual command line shells similar to those found on most UNIX systems (e.g. sh - the Bourne shell, bash - the Bourne again shell and csh - the C shell) and through graphical interfaces (GUIs) such as the KDE and GNOME window managers. If you are connecting remotely to a server your access will typically be through a command line shell.<br \/>\n<\/span><\/span><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>System Utilities:-<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote lang=\"zxx\">\n<ul>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Virtually every system utility that you would expect to find on standard implementations of UNIX (including every system utility described in the POSIX.2 specification) has been ported to Linux. <\/span><\/span><\/p><\/blockquote>\n<\/li>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">This includes commands such as <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">ls, cp, grep, awk, sed, bc, wc, more<\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">, and so on. These system utilities are designed to be powerful tools that do a single task extremely well (e.g. <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">grep <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">finds text inside files while <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">wc <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">counts the number of words, lines and bytes inside a file). <\/span><\/span><\/span><\/p><\/blockquote>\n<\/li>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Users can often solve problems by interconnecting these tools instead of writing a large monolithic application program.<\/span><\/span><\/p><\/blockquote>\n<\/li>\n<\/ul>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Like other UNIX flavours, Linux's system utilities also include server programs called <\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">daemons<\/span><\/span><\/span><b> <\/b><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">which provide remote network and administration services (e.g <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">telnetd <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">and <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">sshd <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">provide remote login facilities, <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">lpd <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">provides printing services, <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">httpd <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">serves web pages, <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">crond <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">runs regular system administration tasks automatically). <\/span><\/span><\/span><\/p><\/blockquote>\n<ul>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">A daemon (probably derived from the Latin word which refers to a beneficient spirit who watches over someone, or perhaps short for \"Disk And Execution MONitor\") is usually spawned automatically at system startup and spends most of its time lying dormant (lurking?) waiting for some event to occur.<\/span><\/span><\/p><\/blockquote>\n<\/li>\n<\/ul>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Application programs<\/b><\/span><\/span><\/p><\/blockquote>\n<ul>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Linux distributions typically come with several useful application programs as standard. <\/span><\/span><\/p><\/blockquote>\n<\/li>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Examples include the <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">emacs <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">editor,<\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">xv <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(an image viewer), <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">gcc <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(a C compiler), <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">g++ <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(a C++ compiler), <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">xfig <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(a drawing package), <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">latex <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(a powerful typesetting language) and <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">soffice <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">(StarOffice, which is an MS-Office style clone that can read and write Word, Excel and PowerPoint&nbsp;<\/span><\/span><\/span><\/span><span style=\"font-size: large; font-family: 'Times New Roman', serif; color: #000000;\">files).<\/span><\/p><\/blockquote>\n<\/li>\n<li>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Redhat Linux also comes with <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">rpm<\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">, the Redhat Package Manager which makes it easy to install and uninstall application programs.<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Logging into (and out of) UNIX Systems<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Text-based (TTY) terminals<\/b><\/span><\/span><\/span><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">:<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">When you connect to a UNIX computer remotely (using telnet) or when you log in locally using a text-only terminal, you will see the prompt:<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">login:<\/span><\/span><\/span><\/tt><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">At this prompt, type in your usename and press the enter\/return\/ key. Remember that UNIX is case sensitive (i.e. Will, WILL and will are all different <a href=\"https:\/\/www.coimbatorewebhosting.com\/blog\/steps-to-redirecting-the-url-by-using-htaccess\/\" title=\"logins).\" alt=\"logins).\">logins).<\/a>) You should then be prompted for your password:<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">login: will<\/span><\/span><\/span><\/tt><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">password:<\/span><\/span><\/span><\/tt><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Type your password in at the prompt and press the enter\/return\/ key. Note that your password will not be displayed on the screen as you type it in.<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">If you mistype your username or password you will get an appropriate message from the computer and you will be presented with the <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">login: <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">prompt again. Otherwise you should be presented with a shell prompt which looks something like this:<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">$<\/span><\/span><\/span><\/tt><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">To log out of a text-based UNIX shell, type \"exit\" at the shell prompt (or if that doesn't work try \"logout\"; if that doesn't work press ctrl-d).<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Graphical terminals:<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">If you're logging into a UNIX computer locally, or if you are using a remote login facility that supports graphics, you might instead be presented with a graphical prompt with login and password fields. Enter your user name and password in the same way as above (N.B. you may need to press the TAB key to move between fields).<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Once you are logged in, you should be presented with a graphical window manager that looks similar to the Microsoft Windows interface. To bring up a window containing a shell prompt look for menus or icons which mention the words \"shell\", \"xterm\", \"console\" or \"terminal emulator\".<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">To log out of a graphical window manager, look for menu options similar to \"Log out\" or \"Exit\".<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>Changing your password:-<\/b><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">One of the things you should do when you log in for the first time is to change your password.<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">The UNIX command to change your password is <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">passwd<\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">:<\/span><\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">$ passwd<\/span><\/span><\/span><\/tt><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">The system will prompt you for your old password, then for your <a href=\"https:\/\/www.coimbatorewebhosting.com\/blog\/how-to-register-your-own-domain-name\/\" title=\"new password\" alt=\"new password\">new password<\/a>. To eliminate any possible typing errors you have made in your new password, it will ask you to reconfirm your new password.<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Remember the following points when choosing your password:<\/span><\/span><\/p><\/blockquote>\n<ul>\n<li style=\"list-style-type: none;\">\n<ul>\n<li>\n<p class=\"western\" lang=\"zxx\" align=\"justify\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Avoid characters which might not appear on all keyboards, e.g. '\u00a3'.<\/span><\/span><\/p>\n<\/li>\n<li>\n<p class=\"western\" lang=\"zxx\" align=\"justify\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">The weakest link in most computer security is user passwords so keep your password a secret, don'<a href=\"https:\/\/www.coimbatorewebhosting.com\/blog\/how-to-create-a-sudo-user-for-your-server-on-centos-7\/\" title=\"t write\" alt=\"t write\">t write<\/a> it down and don't tell it to anyone else. Also avoid dictionary words or words related to your personal details (e.g. your boyfriend or girlfriend's name or your login).<\/span><\/span><\/p>\n<\/li>\n<li>\n<p class=\"western\" lang=\"zxx\" align=\"justify\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Make it at least 7 or 8 characters long and try to use a mix of letters, numbers and punctuation.<\/span><\/span><\/p>\n<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p class=\"western\" lang=\"zxx\" align=\"justify\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\"><b>General format of UNIX commands:-<\/b><\/span><\/span><\/p>\n<blockquote class=\"western\" lang=\"zxx\"><p><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">A UNIX command line consists of the name of a UNIX command (actually the \"command\" is the name of a built-in shell command, a system utility or an application program) followed by its \"arguments\" (options and the target filenames and\/or expressions). The general syntax for a UNIX command is<\/span><\/span><\/p><\/blockquote>\n<blockquote class=\"western\" lang=\"zxx\"><p><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">$ command -options targets<\/span><\/span><\/span><\/tt><\/p>\n<p><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">Here <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">command <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">can be though of as a verb, <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">options <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">as an adverb and <\/span><\/span><\/span><tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">targets <\/span><\/span><\/span><\/tt><span style=\"color: #000000;\"><span style=\"font-family: 'Times New Roman', serif;\"><span style=\"font-size: large;\">as the direct objects of the verb. In the case that the user wishes to specify several options, these need not always be listed separately (the options can sometimes be listed altogether after a single dash).<\/span><\/span><\/span><\/p><\/blockquote>\n<\/li>\n<\/ul>\n<\/blockquote>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is an Operating System? An operating system (OS) is a resource manager. It takes the form of a set of software routines that allow users and application programs to access system resources (e.g. the CPU, memory, disks, modems, printers network cards etc.) in a safe,efficient and abstract way. For [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":22,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[3],"tags":[],"class_list":["post-21","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-linux"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/coimbatorewebhosting.com\/blog\/wp-content\/uploads\/2017\/06\/Untitledp.jpg","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/pa2YU7-l","_links":{"self":[{"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/posts\/21","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/comments?post=21"}],"version-history":[{"count":0,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/posts\/21\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/media\/22"}],"wp:attachment":[{"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/media?parent=21"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/categories?post=21"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coimbatorewebhosting.com\/blog\/wp-json\/wp\/v2\/tags?post=21"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}