Linux Basics - Revision history

J: /* The "su" command */ added the "sudo" command

2008-07-14T19:46:05Z

‎The "su" command: added the "sudo" command

J: /* Delete */ added warning about 'rm -rf'

2008-07-14T19:38:08Z

‎Delete: added warning about 'rm -rf'

J: /* ls */ added info about -sh

2008-07-14T19:31:52Z

‎ls: added info about -sh

J: spelling, simple updates

2007-10-28T21:53:36Z

spelling, simple updates

Show changes

J: /* Technical Overview */ re-described monolithic kernel

2007-10-28T21:18:58Z

‎Technical Overview: re-described monolithic kernel

J at 23:08, 2 May 2007

2007-05-02T23:08:35Z

J: /* Conclusion */

2007-05-02T23:07:34Z

‎Conclusion

J: /* About Commands */

2007-05-02T23:00:11Z

‎About Commands

J: /* Delete */

2007-05-02T22:52:44Z

‎Delete

J: /* VNC Server */

2007-05-02T22:31:05Z

‎VNC Server

← Older revision		Revision as of 19:46, 14 July 2008
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	''su'' also has some argument that can be passed. The most interesting is the "-l" argument for "login". This will actually set up the PATH variable for the user you're running commands as. For instance, root often has "/sbin/" in its PATH, where most users won't and shouldn't. This is very useful for system administrators to be able to test configurations of their users. More about PATH and how to look at it below.		''su'' also has some argument that can be passed. The most interesting is the "-l" argument for "login". This will actually set up the PATH variable for the user you're running commands as. For instance, root often has "/sbin/" in its PATH, where most users won't and shouldn't. This is very useful for system administrators to be able to test configurations of their users. More about PATH and how to look at it below.
		+	====The "sudo" command====
		+	''sudo'' allows you to run commands as root without logging in as root and without knowing the root password. This is kind of handy. Most distributions will automatically add your user to the "sudo-ers" list, so you can go ahead and use it right away. Some distributions hide the root password from you completely, making ''sudo'' the only way to run commands as root.
		+
		+	To use ''sudo'', simply put the command you want to run as root after ''sudo''. You'll be asked to enter your password (not the root password) and then the command will run. Your password is usually stored for a period of time, so you won't have to reenter it for each command.
		+	<pre>
		+	[user@computer ~]$ sudo vim somefile
		+	Password:
		+	</pre>
		+	This runs the ''vim'' text editor, as root, on "somefile". You can run any command you want using sudo.

	====About Commands====		====About Commands====

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 </pre>
 Ahh, much better - no prompts.  This option will also automatically skip errors - for instance, it won't tell you if the file you're trying to delete already doesn't exist.  This is useful in scripting, where a single error might crash your script.  More on that in a much much more advanced article.
 ====Text Editors====

@@ Line 286: / Line 286: @@
 [user@computer somedir]$
 </pre>
 ====Manipulating Files====

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 ===Technical Overview===
-Linux is a [[Wikipedia:Monolithic_kernel|Monolithic kernel]], which means that device drivers and the graphics engine are built into the kernel - they are not separate entities.  By design, everything running on a Linux system is very modular.  Most components of a Linux system are designed to be interchangable with other components that can provide the same functionality.  Many components are not required to be installed or running for the system to operate, which saves resources for the things that do need to be running.  This is true of many aspects of Linux software including graphical interfaces, network, server software, printing, and sound.
+Linux is a [[Wikipedia:Monolithic_kernel|Monolithic kernel]], which means that there is minimal layering within the kernel.  This maximizes performance by eliminating excessive abstraction, but can cause some low-level problems if developers aren't careful. By design, everything running on a Linux system is very modular.  Most components of a Linux system are designed to be interchangeable with other components that can provide the same functionality.  Many components are not required to be installed or running for the system to operate, which saves resources for the things that do need to be running.  This is true of many aspects of Linux software including graphical interfaces, network, server software, printing, and sound.
 <br><br>
 The Linux kernel has been ported to work on many common devices including routers (see [http://www.dd-wrt.com/ DD-WRT] for Linksys WRT routers), MP3 players (such as the [http://ipodlinux.org/Main_Page Apple iPod]), phones, and gaming systems (such as [http://playstation2-linux.com/ Sony PS2], [http://www.gc-linux.org/wiki/Main_Page Nintendo GameCube], [http://www.xbox-linux.org/wiki/Main_Page Microsoft XBox], and XBox 360).  Many embedded systems (such as [http://www.tivo.com TiVo] and older [http://www.linksys.com Linksys] routers) also use Linux based systems out of the box.

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 [[Category:Linux]]
 [[Category:How-To]]
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 ==Conclusion==
 So, that's how it works.  Good luck, have fun.
 ==Notes==

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 ====About Commands====
-When you type in a command, Linux looks in the ''PATH'' variable to find that command.  Generally, you don't have to worry about the PATH, but it's good to know about what's going on.  To see your ''PATH'':
+When you type in a command, Linux looks in the directories specified in the ''PATH'' variable to find that command.  Generally, you don't have to worry about the PATH, but it's good to know about what's going on.  To see your ''PATH'':
 <pre>
 [user@computer ~]$ echo $PATH

@@ Line 338: / Line 338: @@
 [user@computer ~]$
 </pre>
-Ahh, much better.  This option will also automatically skip errors - for instance, it won't tell you if the file you're trying to delete already doesn't exist.  This is useful in scripting, where a single error might crash your script.  More on that much much later.
+Ahh, much better.  This option will also automatically skip errors - for instance, it won't tell you if the file you're trying to delete already doesn't exist.  This is useful in scripting, where a single error might crash your script.  More on that in a much much more advanced article.
 ====Text Editors====

@@ Line 129: / Line 129: @@
 ====VNC Server====
-VNC is a network protocol for remote GUI sessions.  There are lots of different VNC server and viewer applications available, some with additional "non-protocol" features like file transfer or computer-to-computer instant messenging.  Like X, it is possible to run many sessions of VNC at the same time.  I use VNC because it's pretty easy to configure and I can run the same viewer to connect to Windows or Linux machines.  VNC also allows all your applications to continue running after you disconnect without any additional commands - when you reconnect, everything will be just as if you were working at a desktop machine, got up for a while, and then returned.
+VNC is a network protocol for remote GUI sessions.  There are lots of different VNC server and viewer applications available, some with additional "non-protocol" features like file transfer or computer-to-computer instant messenging.  Each VNC session actually connects to an already running X display session, so it's possible to have as many VNC sessions as you have X sessions.  I use VNC because it's pretty easy to configure and I can run the same viewer to connect to Windows or Linux machines.  VNC also allows all your applications to continue running after you disconnect without any additional commands - when you reconnect, everything will be just as if you were working at a desktop machine, got up for a while, and then returned.
-I'm not going to get into how to configure VNC servers here, that's for a later tutorial.  Assuming VNC is set up correctly on the server, all you need is a viewer client, such as [http://ultravnc.sourceforge.net/ Ultra VNC], the host name or IP of the machine you want to connect to, the display you want to connect to, and the password for the VNC connection.  Punch all the information into the client and it should work just fine.
+I'm not going to get into how to configure VNC servers here, that's for a later tutorial.  Assuming VNC is set up correctly on the server, all you need is a viewer client - such as [http://ultravnc.sourceforge.net/ Ultra VNC], the host name or IP of the machine you want to connect to, the display you want to connect to, and the password for the VNC connection.  Punch all the information into the client and it should work just fine.
 ===Understanding the Linux Filesystem===