What Zould You Enter Qt Q Co qnd Pro pt to Start a New Bourne again Shell Session

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The Trounce and the GUI

You tin interact with SLES by using one of two methods. The offset method is the apply of a crush or console, and the second method is a Graphical User Interface (GUI). This section will explicate and discuss both environments and provide tips for using these two components of SLES.

The Trounce

The heart of the SLES operating organization is the Linux kernel. The kernel's primary responsibleness is to manage running processes and their interaction with the various hardware components of a computer. This includes direction of memory (RAM), processors (CPU), hard disks, and other hardware components. Left on its ain the kernel manages these components quite well. However, without the guidance of a user or administrator, the kernel certainly will not achieve much!

For an administrator, the ability to collaborate with the Linux kernel tin can be more of import than the kernel itself. One important style to facilitate interaction with the kernel is through the utilize of a "crush."

A shell is a programme designed to accept user input, validate that input based on certain criteria (such as syntax and permissions), and then pass instructions off to the kernel for processing. This beat out functionality is very like to the familiar DOS shells under Microsoft Windows environments. Linux shells, however, are much more powerful than traditional not-Unix shells and therefore tin exist more circuitous and difficult to master.

One reason for this complexity is the fact that several shells are available for use in Linux environments. Although the purpose of these shells is substantially the same across all variations, the implementations tin differ dramatically. These differences are typically manifest in syntax and feature-set capabilities, but each trounce can also be substantially dissimilar from a usability perspective also.

Table iii.7 offers a list of some of the shells normally found in Linux environments.

Tabular array 3.7 Mutual Linux Shells

Shell	Binary Program	Comments
Bourne Shell (SH)	/bin/sh	The standard command interpreter. On Linux, sh is frequently a symbolic link to /bin/bash.
GNU Bourne-Again Vanquish (BASH)	/bin/bash	An improved version of the Bourne Shell. Supports some avant-garde features of the C and Korn Shells. Excellent shell for new Linux users.
Public Domain Korn Vanquish	/bin/ksh	An open up source version of the Korn Shell. Among other things, supports advanced floating-point arithmetics features.
C Trounce	/bin/tcsh	Enhanced version of the Berkley Unix C shell. Features a C programming type of command-line syntax support.
The Z Beat out	/bin/zsh	An enhancement of the ksh trounce. Features such capabilities every bit command-line editing and spell checking.

Each beat has its own specific features and advantages. If yous already use ane of these shells, or some other shell, feel free to proceed to use that beat. If you are new to the Linux environment, the Bash trounce is usually the default beat and is an excellent vanquish for new users. Throughout this book, all shell command syntax will exist issued with BASH in listen, although other shells nearly always understand this syntax as well. The balance of this section will introduce you to concepts and features of the Bash shell.

Invoking the Crush

Although invoking the shell may seem similar a rather straightforward topic, there are a few important aspects of this topic that should be pointed out.

If no graphical surround was installed with SLES, subsequently server startup a login prompt should exist presented. Simply logging in every bit a valid user volition invoke that user's default beat out. This behavior will as well be encountered if the graphical surroundings is installed, only not configured for automatic startup. In either instance, following the login prompts will lead yous to a shell surroundings.

From within a graphical environs on Linux, at that place are a number of terminal programs that will invoke a shell. Common graphical shells are listed in Table 3.8.

Table three.8 Mutual Graphical Last Programs

Graphical Shell Program	Master Graphical Environment	Comments
Console	KDE	Full-featured graphical shell including tab back up for multiple windows, and customizable view profiles. Based on the Qt toolkit.
gnome-last	GNOME	Full-featured graphical vanquish including tab support for multiple windows and customizable view profiles. Based on the GTK+ toolkit.
Xterm	All	Minimalist graphical terminal window.

Launching a graphical shell is a simple chore of locating the respective shell icon and clicking on it, or entering the awarding command name in a "run command" blazon of dialog. This will typically start the trounce using the credentials of the currently logged-in user. A commonly establish graphical crush is the KDE-based Konsole, which is shown in Effigy three.5.

In addition to graphical terminals, another method used to gain shell admission is using the "Virtual Terminals" available in Linux environments.

Virtual Terminals are concluding sessions bound to a specialized device on Linux. Rather than being fastened to a physical hardware device, such as the connection of a serial cable to a COM port, connections to Virtual Terminals are achieved through bindings represented by the keyboard part keys. Typically, the offset six function keys (F1–F6) are bound to full-screen terminal sessions using the mingetty programme. Function key F7 is normally bound to the first graphical surround running on the Linux computer. It is as well possible to have a second graphical environment running and spring to the F8 part key.

Yous can access these Virtual Terminals by pressing a combination of command keys. In graphical environments such as KDE, this keystroke combination is Ctrl+Alt+Fn (where Fn is substituted for the desired terminal). When y'all have accessed a Virtual Terminal, you must enter valid user credentials prior to invoking a usable shell.

Another mutual style of invoking a control shell is through remote crush access via some other estimator. The bones method of invoking this admission is through a telnet session. Telnet connections tin be fabricated from nearly every operating environment to a Linux server. Still, telnet uses an insecure protocol and therefore telnet connections are not normally allowed to Linux servers. By default, SLES does not permit telnet connections. To alleviate security risks inherent with telnet, a Secure SHell (SSH) session tin can exist used for encrypted remote access.

Secure shell support on Linux servers is provided past the OpenSSH software programme. On SLES, OpenSSH is configured by default and is the recommended method of remote access. Connecting to the OpenSSH server is possible from other Linux machines using the ssh plan. Basic usage of ssh is as follows:

#ssh johndoe@192.168.1.56

Subsequently issuing the ssh command, the user is prompted for a countersign for the SSH session. Upon successfully entering the password, the default crush of the designated user is invoked.

The only potential drawback to SSH is the fact that SSH customer programs are not commonly available on non-Linux workstations. Table 3.9 lists a few commonly used programs that provide SSH client support in Windows environments.

Table 3.9 SSH Clients for Windows

SSH Client Program	Home Page	Comments
SecureShell for Windows	http://www.ssh.com/	Total-featured SSH client
PuTTY	http://world wide web.chiark.greenend.org.uk/~sgtatham/putty/	Free Telnet/SSH Client
SSHWindows	http://sshwindows.sourceforge.cyberspace/	SSH Server and Client implementation for Windows

Given the benefits of SSH remote shells, using one of these or other secure shell clients on non-Linux workstations is well worth the investment.

Using the Shell

Later on yous've invoked a shell, you can perform any number of actions. Control execution is the chief reason for invoking a vanquish, and for that execution to be successful, there are a few rules y'all need to be aware of:

• External commands (standalone programs, not built-in shell functions or aliases) tin can merely be executed if they are found within directories specified by your PATH environment variable. All other external commands can just be executed if the command is referenced using a valid path to the programme.

• The permissions on a file determine whether or not that file is executable. Virtually standalone applications and utilities should already accept a correct prepare of rights assigned to them. However, if you lot are working with shell scripts, be sure to assign the execute (10) flag to the script prior to attempting to execute the script.

• Linux shells are case sensitive. This ways that all filenames, commands, and command parameters are case sensitive. Often, control-line parameters differ dramatically based on the case used. Be sure to double-cheque all parameters earlier executing critical commands!

• Know the difference between relative and absolute paths. Many commands in Linux reference source or destination directories and files. When using these commands, it is disquisitional that you distinguish between a relative and an absolute path.

• Whatever path or filename reference beginning with a slash (/) is referring to the accented path to that file—from the root of the bulldoze. Relative path and filenames typically start with no path or with a unmarried period followed past a slash (./) indicating the electric current directory. The parent directory can be referenced using a double period followed by a slash (../).

• If relative and absolute paths are used incorrectly, files tin be inadvertently written to locations off the root of the bulldoze, rather than the intended location.

Before you begin post-obit these rules, there are a number of shell features you lot should know about that make working in a Linux shell a much more than effective do. A few important features are explained in this listing:

• Tab completion—Tab completion allows users to press the Tab key while working at a crush prompt and have Fustigate attempt to autocomplete the filename or path. If a beep is heard, multiple matches have been found. Pressing Tab a second fourth dimension volition display all matching items.

• History—The Bash shell automatically tracks commands entered by each user. These commands can exist accessed by pressing the Upwards and Down arrow keys. The history control can also be used to display the unabridged known history of the current user.

You can so result commands stored in your history using an assertion point (!) followed by the history number entry, or an exclamation point followed by the first few characters of the desired command. When using the beginning few characters of a command, the most contempo entry that matches those characters is executed.

• File globbing—File globbing is the process of the shell interpreting wildcard characters rather than the utility beingness called. When a command-line utility is executed, the shell itself searches and satisfies whatever wildcard characters and then executes the control using the matching parameters. For example, if the control ls /etc/is* was executed, the Fustigate shell would really determine all matches for /etc/is* and really execute ls /etc/consequence /etc/issue.net.

File globbing tin can be beneficial if used properly and quite harmful if used incorrectly. If you would like to prevent file globbing, exist certain to escape any wildcard characters by using a backslash or past enclosing the parameter containing the wildcard in quotation marks.

• I/O redirection—Linux uses built-in file descriptors to denote the standard input, standard output, and standard fault channels. These descriptors are numbered 0, one, and 2 respectively. Redirecting input or output to and from a command can be washed using the > and < metacharacters.

The less-than (<) metacharacter is used exclusively for redirecting input into a command from a file. The greater-than (>) metacharacter is used for redirecting either or both standard output and standard error channels to a file. To execute a control anstandard output and standard error to a file, the following syntax is used:

ls /etc/* > etc.dir

When redirecting both standard output to the aforementioned file, the following syntax is used:

true cat /etc/passwd /etc/passwd.bad > ok.txt 2> err.txt

To write both standard error andd log the output into a text file, the post-obit syntax would exist used:

true cat /etc/passwd /etc/passwd.bad > ok.txt ii>&1

• Command chaining—Control chaining allows the standard output of one command to exist redirected into the standard input channel of a 2d command. To perform this function, the 2 commands are separated on the aforementioned command line using the pipe (|) metacharacter. The following example shows the output of the cat command beingness redirected and used as input for the sort command:

Control chaining can exist used to chain a nearly unlimited number of commands together. The Bash shell processes these commands one at a time. After completing each command, the output of that command is and so passed as input to the next command.

With the preceding framework of required rules and shell tips, you are now ready to interact with files, run commands, and navigate the filesystem. Unfortunately, providing a list of all Fustigate commands y'all might need would require another consummate volume! Yet, some essential command-line tools are described in the "Finding Your Way" section of this affiliate. A more consummate list of the most essential commands used in Linux has also been compiled in Appendix B, "The Nearly Essential Linux Commands."

The SLES Graphical Surround

The SLES graphical environment is similar to most Linux-based workstations, such every bit the Novell Linux Desktop (NLD). These graphical environments tend to be rather complex and a complete understanding of each graphical component is necessary to thoroughly troubleshoot any issues that might arise. The following section provides an overview of these components.

XFree86

To provide a graphical environment, SLES uses the XFree86 implementation of the X Window System. This aforementioned graphical, or 10, server is used on Linux workstations and is not always installed in server environments, only SLES, past default, does install the graphical environment.

Your server may be configured to automatically start the graphical environment and provide for a graphical login, or it may start and prompt for a text-based login. To reduce operating overhead in a server surround, many configurations provide for text-based logins, but do allow the graphical environment on need. To start the graphical server from a text-based login, execute the startx command afterward logging in.

A consummate graphical environment on SLES consists of several layers of graphical components. These components and a brief description of them tin be found in Table iii.x.

Table 3.10 Components of the SLES Graphical Environment

Component	Description
Video hardware	The video card, monitor, and physical connections to these components.
X Server	The XFree86 X Server is responsible for passing graphical instructions from customer applications to the video bill of fare hardware.
Display Manager	The Display Manager is responsible for providing a graphical login to users in runlevel 5. Graphical environments starting from runlevel 3 practice not use a Display Managing director. SLES uses the One thousand Display Director (KDM) by default. The GNOME Display Manager (GDM) is also provided with SLES.
Window Manager	A Window Manager is responsible for providing window functionality to X clients. This functionality includes the minimize/maximize functionality, title bars, window resizing, and and then on. SLES uses the Yard Window Manager (KWin) past default. The Metacity Window Manager is used with GNOME desktop environments. (If the minimal graphical surroundings is selected during installation, the FVWM window managing director is installed to provide bones graphical functionality. No desktop environment is installed in this situation.)
Desktop Surround	A desktop environment's chief purpose is to provide all X clients with a common wait and feel. They accomplish this task through edge enhancement, color coordination, and context- sensitive menus. Desktop environments also normally provide taskbars and launcher menus used to facilitate admission to installed programs. SLES provides the K Desktop Surround (KDE) by default. The GNOME desktop tin also be selected every bit role of the SLES installation.
Ten Client Applications	Applications that rely on graphical libraries for displaying their interface, dialogs, menus, and so on. Examples of X clients include such things as OpenOffice, KCalc, and KMail.

Each component of the X Window Organization plays an important function in the overall goal of providing users with a complete graphical environment. Although some components are optional, all components rely on the base 10 server for graphical functionality by interacting with the video card and monitor.

The 10 server configuration is performed using the sax2 utility. This utility is automatically launched during the SLES installation if a graphical environment is selected for installation. Subsequently installation, sax2 can exist run from either the control line or the graphical environment to adapt graphical settings. Additional hardware configuration changes, such as selecting an advisable mouse, can exist performed from within the Hardware section of YaST.

Desktop Environments

When installing SLES, yous have the option of installing a KDE, GNOME, or minimal graphical environment. The minimal graphical environment is a bare-bones surroundings designed to provide an X server for graphical applications. On the other hand, KDE and GNOME are both desktop environments and offering a full graphical environment consummate with taskbars, application launchers, unified menus, screensavers, and many other components common to workstation environments.

K Desktop Surround (KDE)

The K Desktop Environment (KDE) is the default desktop for SLES 9. A typical desktop view is shown in Effigy 3.six. KDE is based on the Qt graphical toolkit and therefore most applications used nether KDE are also based on this toolkit. As long as required libraries are available, applications based on other graphical toolkits can notwithstanding run nether a KDE environment (such every bit running GNOME apps under KDE).

Effigy 3.6 The One thousand Desktop Surroundings (KDE) workspace.

KDE offers a complete desktop environs that includes the post-obit components:

• The Desktop—The desktop consists of the background and i or more than icons used to access mutual programs or utilities. Launching applications from the desktop is washed using a single mouse click on the advisable icon.

• The KDE Command Console or Kicker—The Kicker is known as a taskbar in other graphical environments. In KDE, the Kicker is used to provide immediate access to commonly used programs, a task manager for running programs, virtual desktops, and environment-specific applets (such as the clock). You tin configure the Kicker by right-clicking on the primary panel and selecting Configure Panel.

• The KDE menu—The KDE carte du jour is accessed using the green push with a red "N" on the left side of the Kicker. The KDE menu provides easy access to graphical programs installed on the local server. Right-clicking on the KDE menu provides a link to a tool for menu editing. This tool can be used to adjust or add icons to the menu easily.

• Virtual Desktops—KDE includes support for up to 16 virtual desktops. By default, only two virtual desktops are configured. You can access each desktop by using the center section of the Kicker panel. To configure the virtual desktop, right-click on the desktop and choose Configure Desktop, Multiple Desktops.

Primal to KDE is the Konqueror utility. Konqueror is an integrated file manager and web browser. In addition to performing those two tasks, Konqueror also offers extensive features such every bit accessing information through several different network protocols, interacting with local hardware devices, and providing the KDE help system.

Konqueror is the default spider web browser with KDE, only Mozilla and Firefox tin can both be installed as office of the SLES installation, and used in place of Konqueror. OES officially supports both the Mozilla and Konqueror browsers.

GNOME

During the SLES installation, the GNOME desktop tin exist installed either in addition to KDE or as a replacement for KDE. GNOME is based on the GTK+ graphical toolkit. Every bit with KDE, equally long as the required graphical libraries are available, all graphical applications tin can be used nether GNOME. Figure three.7 shows a GNOME desktop with common GNOME-based utilities.

GNOME offers a complete desktop surround that consists of the post-obit components:

• The Desktop—The desktop consists of the background and one or more icons used to access common programs or utilities. Different KDE, launching applications from the GNOME desktop is done using a double mouse click on the advisable icon.

• The Elevation Panel—The Top Panel is used to provide piece of cake access to available applications. This console is fully configurable and tin can be customized with boosted links to applications. By default, this panel includes links to the Nautilus file manager, a terminal emulation window, and applets for the clock and book command.

• The Bottom Console—The Lesser Panel is used to provide access to currently running programs through a task manager interface in the eye of this console. The Bottom Console also displays an icon for endmost all open windows and revealing the desktop. Accessing virtual workspaces is also accomplished using this panel.

• The Applications Menu—The Applications carte du jour is accessed using the Top Panel. This menu contains links for currently installed graphical applications.

• Virtual Workspaces—GNOME includes support for up to 36 virtual workspaces (called virtual desktops in KDE). By default, only iv virtual workspaces are configured. You lot tin access each workspace by using the correct department of the Bottom Panel. Correct-click on the Virtual Workspaces applet to configure the virtual workspace.

GNOME utilizes Nautilus as the master tool for file direction and Epiphany as the default spider web browser. The Epiphany web browser is also supported for OES web-based utilities. Every bit in KDE environments, both Mozilla and Firefox can be installed and used in place of Epiphany.

FVWM

In add-on to the two desktop environments of KDE and GNOME, the SLES installation likewise allows for the installation of a minimal graphical surround. This surroundings is based on the Feeble Virtual Windows Manager (FVWM) window maker (fvwm2). Equally shown in Effigy 3.8, this Desktop Environment certainly offers fewer features than KDE and GNOME.

FVWM is a powerful, notwithstanding minimalist window environment. Rather than employing large, retentivity-consuming menus and advanced window features, FVWM focuses on providing an efficient and powerful graphical environment. Due to this focus, new users may discover FVWM a difficult surroundings to chief. Other users capeesh the depression-resources footprint when using FVWM—specially in a server environment.

Features of FVWM include the following:

• The Desktop—The desktop of FVWM consists of just a background graphic. Different KDE and GNOME, there are no desktop icons in FVWM. Clicking on the desktop with the left mouse button volition invoke the "Work Bill of fare" pop-up. Clicking the right mouse button will invoke the "KDE Menu" pop-up.

• FvwmButtons—FvwmButtons create a group of buttons on the root desktop screen. The grouping of buttons includes such things every bit a clock, and links to SUSE and FVWM utilities. Links to shells and other utilities can also be found in the button grouping.

• KDE Menu—Accessed by clicking the right mouse button on the desktop, the KDE bill of fare contains links to applications configured in the KDE surround. Applications visible in this menu are determined by what is installed on the server.

• Work Bill of fare—Accessed by clicking the left mouse push button on the desktop, the Work menu provides a menu containing links to commonly used applications such as the Pine editor, Mozilla browser, and other configuration utilities.

Credentials and the X Server

When you're logged into the graphical surround as a normal user, a common operation is to open a terminal and launch graphical Ten customer applications directly from the shell prompt. If your crush credentials are the same every bit your credentials in the graphical environs, these commands can exist executed without issue. However, if you switch identities to that of the root user (or any other user), admission to the 10 server will be denied, and yous will be unable to launch graphical programs.

When starting the X server, your credentials are provided to the X server. For security purposes, SLES configures X to merely permit admission to the local 10 server from trusted sources. Past default, this is only the logged-in user. To let graphical admission while switching users, SLES provides the sux utility.

The sux utility automatically configures the new user's environs to support access to the local X server. The sux utility replaces the functionality of the su utility, which is used to switch identities inside normal shells. The syntax of sux is identical to that of su.

Tunneling X

In add-on to providing graphical access to switched identities, information technology is as well possible to redirect the display of graphical clients running on the SLES server to a remote 10 server running on the local workstation. This is useful when you want to run a graphical plan on the SLES server, simply do not want to start the X server. Running programs in this way is best accomplished by forwarding the X connection through an SSH tunnel.

SSH tunnels can exist established to the SLES server from a Linux workstation using the ssh command. Through the use of the -X startup option, X11 forwarding tin exist enabled via that aforementioned SSH tunnel. When you are connected in this manner, yous can launch graphical programs on the SLES server and display them using the local X server.

Remote Graphical Sessions

Using Virtual Network Calculating (VNC), a graphical desktop session can be started on the local server while physically using a Linux, Windows, or Apple MacOS-based workstation. During the SLES 9 installation, remote administration through VNC can be set to "enabled." Otherwise, remote administration will be disabled and must exist enabled using the YaST – Network Services – Remote Administration module.

When remote assistants has been enabled, VNC connections can exist fabricated to the server using ane of three methods:

• VNC client-based connections—Using a VNC client, a connectedness using the VNC protocol can be fabricated to the server on port 5901. VNC clients include krdc for Linux, and RealVNC for Windows (http://www.realvnc.com). VNC clients are also bachelor for several other platforms.

• VNC connectedness in Konqueror—Using a Linux workstation, the Konqueror browser tin be used to provide a VNC connection to the SLES 9 server. This connection is a true VNC connection and connects to the aforementioned port (5901) that the standalone VNC customer would connect to. The full URL for this type of connection inside Konqueror is vnc://<serverDNSorIP>:5901.

• Brower-based connections—Using a Coffee-capable spider web browser, an HTTP connexion to the server on port 5801 (<serverDNSorIP>:5801) volition invoke the Java-based VNC client.

Although remote administration through VNC is user-friendly, the VNC protocol is not as secure as a full secure shell (SSH) session. For this reason, establishing a full SLES login through VNC is not recommended outside of secure LAN environments.

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