This chapter is from the book
This chapter is from the book
This chapter is from the book
Getting Help
SUSE Linux provides literally thousands of possible commands that can be used to perform various tasks on a server. Having firsthand knowledge of each utility and all parameters that utility may take is a very challenging task! Thankfully, through the use of utility manuals and application documentation, help is never too far away.
Console-Based Help
Working on the command line is the most common method of interacting with SLES. Providing easy access to application and utility usage information from this environment is essential to effectively working on the command line. Thankfully, a help system has been designed around just this need. This system consists of three distinct types of documentation: manual or man pages; info pages; and system and third-party documentation.
man Pages
man pages on Linux are syntax-level documentation of utilities and applications, stored in an easily retrievable, command-line-friendly format. man pages are physically stored in the /usr/share/man directory and divided into the nine sections shown in Table 3.17.
Table 3.17 man Page Sections
|
man Section |
Section Purpose |
|
1 |
Executable programs and commands all users can access |
|
2 |
System calls |
|
3 |
Functions and library routines |
|
4 |
Special device files (/dev/*) |
|
5 |
Configuration file formats and conventions |
|
6 |
Games |
|
7 |
Macro commands and packages |
|
8 |
System administration programs and commands used by the root user |
|
9 |
Kernel routines |
All programs utilizing the man system should store their man pages within the correct section. In order to view man pages for a specific command, the following basic syntax must be used:
man [section] command
Upon entering the man command, you are presented with syntax-level documentation for the specified command or utility. The pages presented typically contain information divided into the following sections:
Name—This is a one-line summary of the application in question. This field is displayed individually when using the whatis command.
Synopsis—This section contains a summary of the command line for the application in question. Optional parameters are enclosed in square brackets [], and required parameters are listed normally.
Description—This section documents the possible parameters the application in question can receive. Some man pages also include specific usage examples in this section.
Author—The author’s name and contact information are typically noted in this section.
Reporting Bugs—Information on where to report bugs for the specific utility is normally noted in this section.
Copyright—The utility’s copyright information is normally displayed in this section.
See Also—This section identifies additional locations for information on the utility in question. Quite often this section will identify related utilities, man pages, and info pages for the specific utility. Checking all specified resources is recommended for advanced usage techniques including troubleshooting of the utility.
Most man pages are only a few pages in length, but some man pages can be quite detailed with many, many pages of information. (See man bash for one such example!) Navigation through larger man pages can be greatly simplified with details on a few valid keystrokes. Table 3.18 lists a small number of important navigation commands within man.
Table 3.18 Internal man Keystrokes
|
Keystroke |
Description |
|
PageDown |
Scroll down one page at a time. |
|
PageUp |
Scroll up one page at a time. |
|
Enter |
Scroll down a single line at a time. |
|
Space |
Scroll down one full window at a time. |
|
/pattern |
Invokes the search dialog for the specified pattern. When you press Enter, the next instance of the desired term will be located. Navigating to the next hit is done by pressing "n". Moving to the previous instance of the search term is done using "N". |
|
?pattern |
Invokes the search-backward dialog for the specified pattern. When you press Enter, the first instance (in the backward direction) of the desired term will be located. You can navigate to the previous hit by pressing "n". You can move to the next instance of the search term using "N". |
|
q |
Quit the man page system. |
It is also common to want to search through man pages for a specific type of utility. Although searching through the contents of all man pages is possible, it is more likely that you just need to locate a command that performs a specific action. Searching just the "Name" section of all man pages is the best way to accomplish this. The apropos or man -k commands can be used for this purpose. For example, to find all commands related to cron, you would use the following command:
The output of this man command would be a listing of all commands containing the word "cron" anywhere in the Name field. After the utility has been identified, the man page for the desired command can then be directly accessed for more information.
info Pages
In addition to the man system, information regarding programs and commands can also be found using the info system. Due to the syntax-documentation-only focus of man pages, background information, tutorials, and detailed information on using the program in question are sometimes lacking in man pages. The info system was created to directly resolve that issue.
info pages are detailed usage instructions and program or command guides. This documentation is accessed via an emacs-type interface that supports hypertext links, and advanced navigation features not found in the man system. The following command is an example of using the info system to locate documentation on the Concurrent Versions System (CVS):
Within the info system, multiple individual pages of information make up the entire set of info pages for each specific application. These pages of information are referred to as nodes. You can page through nodes one at a time, or you can jump to specific pages through the use of hypertext links. For new users, this navigation can be challenging.
To help node navigation, info pages all display a header across the top of the page. This header includes information such as the current node, next and previous nodes, and information regarding the parent node. Although this helps to visualize your location in the info system, you still need to know basic navigation commands before you’ll feel entirely at home. Table 3.19 describes some of these important navigation keys.
Table 3.19 Internal info Keystrokes
|
Keystroke |
Description |
|
n |
Next node. |
|
p |
Previous node. |
|
u |
Parent node. |
|
Space |
Scroll down one page at a time. |
|
Del |
Scroll up one page at a time. |
|
b |
Return to the beginning of the current node. |
|
Tab |
Select next hypertext link. |
|
m <link text> |
Performs a direct jump to the specified subnode. Pressing Tab displays all available subnodes. When entering a subnode name, enter enough characters to ensure the subnode name is not ambiguous. |
|
Enter |
Follow current hypertext link. Hypertext links are designated by an asterisk (*) at the beginning of the link, and a double colon (::) at the end of the link. |
|
q |
Quit the info system. |
System and Third-Party Documentation
The final common forms of documentation found on SLES are system- and application-specific documentation. This documentation can be in HTML, PDF, plain text, or many other formats. All application-specific documentation can be found in application-specific directories beneath /usr/share/doc/ packages. SLES-specific documentation, release notes, and a collection of HOWTO guides can also be found beneath specific directories in /usr/share/doc.
Graphical Help Systems
KDE and GNOME both have an integrated help system. This makes accessing help from a graphical environment a much simpler task than from the command line. The graphical help systems normally provide help for the graphical environments, but they also provide access to the existing man and info pages as well.
KDE Help
In KDE, the KDE Help Center is the interface into the SUSE help system. To access the SUSE help system, single-click on the "SUSE Help Center" icon (the image of a gecko in the middle of a life preserver) from the KDE Kicker. When you’re in the Help Center, SUSE documentation and application-specific documentation can easily be accessed.
Using KDE, info pages and man pages can also be easily viewed. To access these systems, launch Konqueror and enter a specific URL for man or info pages. The syntax for accessing man pages is man:<desired_pages>. For example, man:ls would be used to view the man pages for the ls command from within Konqueror. To access info pages, substitute info: for man:, for example, info:cvs to view the info pages for CVS.
GNOME Help
As with KDE, GNOME also provides a graphical help system. This help system is based on the yelp utility.
From within GNOME, the help system is accessed from the Applications program menu. Within this menu, click on the Help icon (life preserver) to launch yelp at the home page for GNOME help. If complete GNOME documentation is installed, links to GNOME-specific help will be displayed on the yelp home page. (SLES does not provide GNOME Desktop documentation.) Links to additional documentation (man and info pages) are also displayed on the yelp home page.