Lab 2a: System documentation

Task 1: Using and configuring man pages

Description

First, we start a separate terminal,

su to root and run the following command in the background (with the “&”). We will need it later on, but it might take a while to run depending on your system.

mandb -cqs &

From another terminal, run the following 2 commands:

man 1 passwd

man 5 passwd

Command

# mandb -cqs &

Screenshot

What is the difference between the two man 1 passwd & man 5 passwd?

man 1 passwd

PASSWD(1)

User utilities

The passwd utility is used to update user's authentication token(s).

man 5 passwd

PASSWD(5)

Linux Programmer's Manual

NAME

passwd - password file

DESCRIPTION

The /etc/passwd file is a text file that describes user login accounts for the system. It should have read permission allowed for all users (many utilities, like ls(1) use it to map user IDs to usernames), but write access only for the superuser.

Now run the command:

man passwd

Which one is shown (section 1 or section 5)?

Section 1 is shown

We look in the file /etc/man_db.conf. Look for the SECTION entry in the file to verify the above behaviour.

While we are in the file, we also look at the MANDATORY_MANPATH section, to see in which directories the man command will look for man pages by default.

mandatory_manpath section

Now we run the following two commands and compare them (you might like to run them in two separate terminals):

man grep

info grep

Comparing the info page to the man page (in general terms) we can see that they are quite different.

man grep

man grep #provides general commands manual for grep, egrep, fgrep

info grep

This manual is for version 3.1 of GNU Grep.

This manual is for ‘grep’, a pattern matching engine.

whatis passwd vs apropos passwd

Next we try the commands whatis passwd & apropos passwd:

Which one returns more results? Why?

whatis passwd returns less result comparing to apropos passwd. Becasues:

whatis
searches the manual page names and displays the manual page description of any name matched.

apropos
searches the descriptions for instances of keyword. keyword is usually a regular expression, as if (-r) was used, or may contain wildcards (-w), or match the exact keyword (-e). Using these options, it may be necessary to quote the keyword or escape (\) the special characters to stop the shell from interpreting them.

whatis passwd

apropos passwd

Task 2: Finding installed package documentation

Installed package documentation is in the directory /usr/share/doc/sed*/.

Task 3: Finding documentation on the Internet

www.tldp.org (The Linux Documentation Project) is a good place to start for up to date Linux documentation.

HOWTO document about the Linux Clock - https://tldp.org/HOWTO/Clock-2.html

The main Linux FAQ - https://tldp.org/FAQ/pdf/Linux-FAQ.pdf

Linux System Administrator’s Guide (or SAG for short) - https://tldp.org/LDP/sag/html/index.html

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