LPI exam 102 prep: Linux documentation

Краткие заметки, сделанные при подготовке к сдаче экзамена LPI 117-102 (Junior Level Linux Professional (LPIC-1)).

Local documentation

The primary (and traditional) source of documentation is the manual pages, which
you can access using the man command.

Man pages are displayed using a pager, which is usually the less command on
Linux systems.

The common manual sections, with some example contents
are:
1. User commands (env, ls, echo, mkdir, tty)
2. System calls or kernel functions (link, sethostname, mkdir)
3. Library routines (acosh, asctime, btree, locale, XML::Parser)
4. Device-related information (isdn_audio, mouse, tty, zero)
5. File format descriptions (keymaps, motd, wvdial.conf)
6. Games (note that many games are now graphical and have graphical
help outside the man page system)
7. Miscellaneous (arp, boot, regex, unix utf8)
8. System administration (debugfs, fdisk, fsck, mount, renice, rpm)

In addition to the standard manual pages, the Free Software Foundation has created
a number of info files that are processed with the info program.

your system may also have one or more graphical interfaces to manual
pages, such as xman (from the XFree86 Project) and yelp (the Gnome help
browser).

If you know that a topic occurs in a particular section, you can specify the section.
For example, man 4 tty or man 2 mkdir.

An alternative is to use the -a option to
display all applicable manual sections. If you specify -a, you will be prompted after
quitting the page for each section.

Use man less to find out more about / (search forwards), ? (search backwards), and n (repeat last search), among many other commands.

The info command comes from the makers of emacs, so the searching commands
are more like emacs commands. For example, ctrl-s searches forwards and
ctrl-r searches backwards using an incremental search. You can also move
around with the arrow keys, follow links (indicated with a star) using the Enter key,
and quit using q. Use the --vi-keys option with info if you'd prefer similar key
bindings to those used for man.

The whatis command searches man pages for the name you give and displays the name
information from the appropriate manual pages. The apropos command does a
keyword search of manual pages and lists ones containing your keyword

Manual pages may be in many locations on your system. You can determine the
current search path using the manpath command.

Depending on your system, configuration information for the man system is stored in
/etc/man.config or /etc/manpath.confg. Older systems use /etc/man.conf.

You may have noticed that the apropos and whatis commands ran quickly. This is
because they do not actually search the individual manual pages. Rather, they use a
database created by the makewhatis command. This is usually run by the system
either daily or weekly as a cron job.

If you wish to print the page, specify the -t option to format the page for printing
using the groff or troff program.

In addition to the manual pages and info pages that you have already seen, your
Linux system probably includes a lot more documentation. The customary place to
store this is in /usr/share/doc, or /usr/doc on older systems.

Internet documentation

HOWTOs
are subject-specific help, such as the Linux IPv6 HOWTO.
Guides
are longer, in-depth books, such as Introduction to Linux - A Hands on Guide.
FAQs
are Frequently Asked Questions, such as the Linux Documentation Project
(LDP) FAQ.
man pages
are help on individual commands, as you used in the previous section of this
tutorial.
Linux Gazette
is an online magazine, currently available in English, French, German,
Indonesian, Italian, Portuguese, Russian, and Spanish.

Notifying users

The first two of these, /etc/issue and /etc/issue.net, are displayed on an ASCII
terminal that is connected locally (/etc/issue) or remotely (/etc/issue.net).

Both /etc/issue and /etc/issue.net provide user feedback in the form of a logon
prompt and could also be used to advise users of issues such as impending
outages. However, this is usually done with a message of the day or motd, which is
stored in /etc/motd. The contents of /etc/motd are displayed after a successful login
but just before the login shell is started.