{"id":177,"date":"2020-08-18T19:23:47","date_gmt":"2020-08-18T20:23:47","guid":{"rendered":"http:\/\/www.linux-tutorial.info\/?page_id=77"},"modified":"2020-08-22T19:26:41","modified_gmt":"2020-08-22T20:26:41","slug":"this-is-the-page-title-toplevel-11","status":"publish","type":"page","link":"http:\/\/www.linux-tutorial.info\/?page_id=177","title":{"rendered":"What Linux Does"},"content":{"rendered":"\nWhat Linux Does<\/title>\n<p>\nOn any <glossary>operating system<\/glossary>,\na core set of tasks is performed. On <glossary>multi-user<\/glossary>\nor server systems such as Linux, these tasks include adding and configuring\nprinters, adding and administering users, and adding new hardware to the system.\nEach of these tasks could take up an entire chapter in this book. In fact, I do\ncover all of these, and many others, in a fair bit of detail later on.\n<\/p>\n<p>\nI think it’s important to briefly cover all of the basic tasks that an\n<glossary>administrator<\/glossary> needs to perform in one place. There are a couple of reasons for\nthis. First, many administrators of Linux systems are not only novice\nadministrators, they are novice users. They get into the position as they are\nthe only ones in the company or department with computer experience. (They’ve\nworked with <glossary>DOS<\/glossary>\nbefore.) Second, by introducing the varied aspects of system\nadministration here, I hope to lay the foundation for later chapters. If you are not familar\nwith this issue, you may have trouble later.\n<\/p>\n<p>\nKeep in mind that depending on what packages are installed, any Linux\ndistribution can do a lot more. Here we will be discussing just the basic\nadministrative functions.\n<\/p>\n<p>\nThe average user may not want to get into the details that the later\nchapters provide. So here I give an overview of the more important components.\nHopefully, this will give you a better understanding of what goes into an\noperating system as well as just how complex the job is that your system\nadministrator does.\n<\/p>\n<p>\nThe first job of a system <glossary>administrator<\/glossary>\nis to add <glossary term=\"user\">users<\/glossary> to the system.\nAccess is gained to the system only through user accounts. Although it may be\nall that a normal user is aware of, these accounts consist of substantially more\nthan just a name and password. Each user must also be assigned one of the\n<glossary term=\"shell\">shells<\/glossary>, a <glossary>home directory<\/glossary>,\nand a set of privileges to access system resources.\n<\/p>\n<p>\nAlthough the system <glossary>administrator<\/glossary>\ncould create a single user <glossary>account<\/glossary>\nfor all users to use to log in, it ends up creating more problems than it solves. Each\nuser has his\/her own <glossary>password<\/glossary> and <glossary>home directory<\/glossary>.\nIf there were a single user,\neveryone’s files would be stored in the same place and everyone would have access\nto everyone else’s data. This may be fine in certain circumstances, but not in\nmost.\n<\/p>\n<p>\nUsers are normally added to the system through the adduser command. Here,\nwhen adding a user, you can input that user’s default <glossary>shell<\/glossary>,\nhis\/her home directory as well as his\/her access privileges.\n<\/p>\n<p>\nAnother very common function is the addition and configuration of system\nprinters. This includes determining what physical connection the printer has to\nthe system (e.g. parallel cable, USB, network), what characteristics the printer has (to choose the appropriate model printer) as well as making the printer available for printing.\nGenerically, all the files and programs that are used to access and manage\nprinters are called the print spool, although not all of them are in the spool\ndirectory.\n<\/p>\n<p>\nAdding a printer can be accomplished like in many <glossary>UNIX<\/glossary>\ndialects: you do it\nmanually with the primary configuration file, <file type=\"\">\/etc\/printcap<\/file> file. The printcap man-page lists all the capabilities that your version of Linux supports. You\nmust also add the appropriate directory and enable printing on the port. We’ll\nget into more detail about it as we move on.\n<\/p>\n<p>\nMost newer Linux distributions support the <glossary term=\"CUPS\">Common Unix Printing System<\/glossary> (CUPS). This provides a graphical interface (via web browser) to the printer configuration and makes the necessary changes when you add, modify or remove a printer.\n<\/p>\n<p>\nWhat happens when you want to remove a file and inadvertently end up\nremoving the wrong one (or maybe more than one)? If you are like me with my\nfirst computer, you’re in big trouble. The files are gone, never to show up\nagain. I learned the hard way about the need to do backups. If you have a good\nsystem <glossary>administrator<\/glossary>,\n he\/she has probably already learned the lesson and makes\nregular backups of your system.\n<\/p>\n<p>\nThere are several ways of making backups and several different utilities for\ndoing them. Which program to use and how often to make backups completely\ndepends on the circumstances. The system <glossary>administrator<\/glossary>\nneeds to take into account things like how much data needs to be backed up, how often the data are changed, how much can be lost, and even how much will fit on the backup\nmedia.\n<\/p>\n<p>\nThere are tasks that an <glossary>administrator<\/glossary>\nmay need to perform at regular\nintervals, such as backups, cleaning up temporary directories, or calling up\nremote sites to check for incoming mail. The system <glossary>administrator<\/glossary>\ncould have a\nchecklist of these things and a timer that goes off once a day or every hour to\nremind him\/her of these chores, which he\/she then executes manually.\n<\/p>\n<question id=\"25\" text=\"The cron facility is used to run programs at specific times.\" \/>\n<concept id=\"84\" description=\"You can start programs regularly at specific intervals using the cron daemon.\" \/>\n<p>\nFortunately, performing regular tasks can be automated. One basic utility in\nevery <glossary>UNIX<\/glossary>\nversion is <command>cron<\/command>. Cron (the “o” is short) is a program that\nsits in the background and waits for specific times. When these times are\nreached, it starts pre-defined programs to accomplish various, arbitrarily\ndefined tasks. These tasks can be set to run at intervals ranging from once a\nminute to once a year, depending on the needs of the system <glossary>administrator<\/glossary>.\n<\/p>\n<p>\nCron “jobs” (as they are called) are grouped together into files,\ncalled <em>cron tables<\/em>, or <em>crontabs<\/em> for short. There are several\nthat are created by default on your system and many users and even system\nadministrators can go quite a long time before they notice them. These monitor\ncertain aspects of system activity, clean up temporary files, and even check to\nsee if you have <glossary>UUCP<\/glossary>\njobs that need to be sent.\n<\/p>\n<p>\nWhat about a program that you only want to run one time at a specific time\nand then never again? Linux provides a mechanism: <command>at<\/command>. Like cron, at will run a\njob at a specific time, but once it has completed, the job is never run again.\n<\/p>\n<p>\nA third command that relates to cron and at, the <command>batch<\/command> command,\ndiffers from the other two in that batch runs the job you submit whenever it has time; that\nis, when the system load permits.\n<\/p>\n<p>\nLinux supports the idea of virtual consoles (VCs), like SCO. With this, the\nsystem console (the keyboard and monitor attached to the computer itself) can\nwork like multiple terminals. By default, the system is configured with at least\nfour VCs that you switch between by pressing the ALT key and one of the function\nkeys F1-F6. Note that this is in <i>addition<i> to any graphical login you might have.\n<\/p>\n<p>\nNormally, you will only find the first six VCs active. Also, if you are\nusing the <glossary>X<\/glossary>\nWindowing System, it normally starts up on VC 7. To switch from\nthe X-Windows screen to one of the virtual consoles, you need to press\nCTRL-ALT plus the appropriate function key.\n<\/p>\n<p>\nKeeping the data on your system safe is another important task for the system\nadministrator. Linux provides a couple of useful tools for this: tar and cpio.\nEach has its own advantages and disadvantages. Check out the details on the\nrespective <glossary>man-page<\/glossary>.\n<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What Linux Does On any operating system, a core set of tasks is performed. On multi-user or server systems such as Linux, these tasks include adding and configuring printers, adding and administering users, and adding new hardware to the system. … <a href=\"http:\/\/www.linux-tutorial.info\/?page_id=177\">Continue reading <span class=\"meta-nav\">→<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-177","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/177","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=177"}],"version-history":[{"count":1,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/177\/revisions"}],"predecessor-version":[{"id":792,"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=\/wp\/v2\/pages\/177\/revisions\/792"}],"wp:attachment":[{"href":"http:\/\/www.linux-tutorial.info\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=177"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}