Linux All-in-One For Dummies, 5th Edition (2014)

Book VIII. Linux Certification

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Contents at a Glance

Chapter 1: Studying for the Linux Essentials Certification Exam

Chapter 2: Studying for the CompTIA Linux+ Powered by LPI Certification Exams

Chapter 3: Other Linux Certifications

Chapter 1. Studying for the Linux Essentials Certification Exam

In This Chapter

Getting an overview of the Linux Essentials Exam

Looking at the details of each domain

Just as there are many levels of degree attainment you can achieve through an educational institution (associate’s degree, bachelor’s, master’s, doctorate), there are multiple levels of Linux certification available. This book is written primarily for the Linux+ certification from CompTIA and the LPI LX0-101 and LX0-102 exams. As such, it covers everything you need to know to study and pass LPI’s lower-level certification, known as Linux Essentials.

The following sections provide an overall look at the exam, and then explore the topics beneath each of the domains.

Overview of Linux Essentials

The Linux Essentials Certificate of Achievement was created by the Linux Professional Institute (LPI) to appeal to the academic sector. Students taking classes in Linux may not get through all the topics necessary to pass the two exams (LX0-101 and LX0-102) to gain the Level 1 certification, but LPI still wanted to recognize and authenticate their knowledge. This program was created through international collaboration with a classroom focus in mind. As of this writing, the program is live in Europe, the Middle East, and Africa, with plans to roll out to other regions in the near future.

Linux Essentials is a certificate of achievement, intended to be a much lower-level (subset) certification than the Level 1 certification. Although Linux Essentials is recommended, it’s not required for any of the LPIC professional certifications.

There are five domains (called Topics) on the exam; Table 1-1 shows them, along with the weighting for each.

Table 1-1 Domains on the Linux Essentials Exam

The sections that follow look at each of these topics in more detail.

The Linux Community and a Career in Open Source

Table 1-2 shows the subtopics, weight, description, and key knowledge areas for this topic.

To adequately address these topics, focus on these files, terms, and utilities: Android; Apache; Audacity; Blender; BSD; C; CentOS; Creative Commons; Debian; DHCP; DNS; Firefox; FLOSS; FOSS; Gimp; GPR; ImageMagick; LibreOffice; MySQL; NFS; OpenLDAP; OpenOffice.org; Password issues; Perl; PHP; Python; Postfix; PostgreSQL; Privacy issues and tools; Samba; Shell; Terminal and Console; and Thunderbird.

In addition, focus on these topics: Use of common open source applications in presentations and projects; using a browser; privacy concerns; configuration options; searching the web; and saving content.

Here are the top ten items to know as you study for this domain:

1. Linux is the best-known example of open source software so far developed (and still in development).

2. The shell is the command interpreter that resides between the user and the operating system. While a number of shells are available, the most common today is the bash shell.

3. A plethora of applications and tools is available for use with the various Linux distributions. Many of these tools are also open source.

4. The Apache Software Foundation distributes open source software under the Apache license that is Free and Open Source (FOSS).

5. The Free Software Foundation (FSF) supports the free (open source) software movement and copyleft under the GNU General Public License. Copyleft makes it possible for modifications to be made to software while preserving the same rights in the produced derivatives.

6. The Open Source Initiative (OSI) also supports the open source software movement, as does the GNOME Foundation, Ubuntu Foundation, and many other organizations.

7. OpenOffice.org was a popular suite of open source office productivity software. LibreOffice is a fork of OpenOffice that has eclipsed it in popularity.

8. Samba makes it possible for Linux systems to share files with Windows-based systems.

9. Thunderbird is a popular mail and news client originally created by the Mozilla Foundation.

10. A number of web browsers are available for Linux. The most popular currently is Firefox.

Using the Command Line to Get Help

Table 1-3 shows the subtopics, weight, description, and key knowledge areas for this topic.

To adequately address these topics, focus on these files, terms, and utilities: &&; . and ..; /usr/share/doc; ||; apropos; cd; common options for ls; cp; echo; history; Home and ~; info; locate; man; man pages; mkdir; mv; PATH env variable; recursive listings;rm; rmdir; substitutions; touch; whatis; whereis; and which.

Here are the top ten items to know as you study for this domain:

1. Regular expressions – often referred to as globbing – can be used with the shells available in Linux to match wildcard characters. Among the possible wildcards, the asterisk (*) will match any number of characters; the question mark (?) will match only one character.

2. Linux is a case-sensitive operating system.

3. Files can be “hidden” by preceding their names with a single period (.). In pathnames, however, a single period (.) specifies this directory and two periods (..) signifies the parent directory.

4. Absolute paths give the full path to a resource, while relative paths give directions from where you are currently working. An example of an absolute path would be /tmp/eadulaney/file whereas a relative link would be ../file.

5. Files can be copied using cp or moved using mv. Files can be deleted with rm and directories (which are created with mkdir) can be removed with rmdir. Recursive deletion can be done with rm –r.

6. To change directories, use the cd command. When used without parameters, this will move you to your home directory. To see what directory you are presently working in, us the pwd (present working directory) command.

7. The ls command has a plethora of options to allow you to list files. The –a option will list all (including hidden) files.

8. Help is available through the manual pages (accessed with the man command) and info (which shows help files stored beneath /user/info).

9. The whatis command shows what manual pages are available for an entry while whereis shows the location of the file and all related files (including any manual pages).

10. Many standard utilities allow you to enter the name of the executable followed by "--help" to obtain help only on the syntax.

The Power of the Command Line

Table 1-4 shows the subtopics, weight, description, and key knowledge areas for this topic.

To adequately address these topics, focus on the following files, terms, and utilities: /bin/sh; arguments; bash; bzip2; case; common tar options; cut; exit status; extracting individual files from archives; find; for loops; grep; gzip; head; if; less; nano; Partial POSIX Basic Regular Expressions ([^],^,$); Partial POSIX Extended Regular Expressions (+,(),|); pico; read; sort; tail; tar; test; unzip; variables; vi; wc; while; xargs; and zip.

Here are the top ten items to know as you study for this domain:

1. Standard input (stdin) is traditionally the keyboard and standard output (stdout) is traditionally the monitor. Both can be redirected, as can standard error (stderr) using the symbols >, >>, <, and |.

2. Commands can be joined on the command line by the semicolon (;) and each command will run independent of each other. You can also use the pipe (|) to send the output of one command as the input of another command.

3. The cut command can pull fields from a file and they can be combined using either paste or join. The latter offers more features than the former and can be used with conditions.

4. The wc command can count the number of lines, words, and characters in a file.

5. The grep utility (and its counterparts egrep and fgrep) can be used to find matches for strings within files.

6. The find command can be used to search the system for files/directories that meet any number of criteria. When these entities are found, the xargs command can be used to look deeper within them for other values (such as in conjunction with grep).

7. You can use the tar command (which can combine multiple files into a single archive) to do backups.

8. In addition to archiving, you can also compress files with the gzip or pack commands. To uncompress files, use uncompress, gunzip, or unpack.

9. Variables can be given at the command line and referenced as $1, $2, and so on, or entered into the executing file with the read command.

10. Logic can be added to scripts by testing conditions with test or [. Commands can execute using if-then-fi deviations or through looping (while, until, or for). You can use the exit command to leave a script or use break to leave a loop.

The Linux Operating System

Table 1-5 shows the subtopics, weight, description, and key knowledge areas for this topic.

To adequately address these topics, focus on the following files, terms, and utilities: desktop configuration (GUI versus command line); dig; display types; drivers; free; hard drives and partitions; ifconfig; IPv4; IPv6; libraries; maintenance cycles (beta and stable); memory addresses; motherboards; netstat; optical drives; peripherals; ping; power supplies; processes and process tables; processors; system messaging and logging; programs; packages and package databases; ps; resolv.conf; route; ssh; system configuration; and top.

Here are the top ten items to know as you study for this domain:

1. When run, every command spans at least one process; processes can be viewed with ps or top (which updates the display dynamically).

2. Jobs can run in the foreground or background and be moved between the two. Jobs running in the foreground can be suspended by pressing Ctrl+Z.

3. IPv4 uses 32-bit addresses, each divided into four octets. The first octet identifies the class of address (A, B, C). The address can be public or private.

4. The ifconfig utility can be used to see the current IP configuration of the network cards.

5. The ping utility is an all-purpose tool for testing connectivity. It sends echo messages to a specified host to see whether that host can be reached. You can use ping with the loopback address (127.0.0.1) to test internal configuration.

6. The route utility displays the routing table and allows you to configure it.

7. The netstat utility shows the current status of ports – those that are open, listening, and so on.

8. The system log is /var/log/messages and this is where the majority of events are written to by the system log daemon (syslogd). Messages routed there can be viewed with the dmesg command.

9. The logrotate command can be used to automatically archive log files and perform maintenance as configured in /etc/syslog.conf.

10. You can manually write entries to log files using the logger command.

Security and File Permissions

Table 1-6 shows the subtopics, weight, description, and key knowledge areas for this topic.

To adequately address these topics, focus on the following files, terms, and utilities: /etc; /etc/group; /etc/passwd; /etc/shadow; /tmp; /var; /var/tmp; chgrp; chmod; chown; groupadd; groupdel; groupmod; hard links; id; last; ls –d; ls –l; ls –s;passwd; setgid; setuid; sticky bit; su; sudo; useradd; userdel; usermod; w; and who.

Here are the top ten items to know as you study for this domain:

1. File and directory permissions can be changed with the chmod command (which accepts numeric and symbolic values).

2. Adding 1000 to standard permissions turns on the “sticky bit”; adding 2000 turns on the SGID permission. Adding 4000 turns on the SUID permission.

3. Links are created with the ln command. A “hard” link is nothing more than an alias to a file (sharing the same inode). The ln –s command creates a symbolic link that is an actual file with its own inode. The symbolic link contains a pointer to the original file and can span across file systems; the hard link cannot.

4. User accounts can be added by manually editing the configuration files or by using the useradd command; they can be removed with userdel.

5. The groupadd utility can be used to create groups and groupdel can be used to remove groups. Groups can be modified with groupmod and users can change from one group to another with the newgrp command.

6. Passwords are changed with the passwd command. Older systems stored passwords in /etc/passwd; now passwords are stored in /etc/shadow, where they are more secure.

7. To see who logged on most recently and may currently still be on the network, you can use the last command.

8. The su command allows you to become another user (returning with exit). If no other username is specified, then the root user is implied, hence the su for superuser.

9. Use sudo instead of su when you want to run a command as another user (usually root) without becoming that user.

10. The who command shows who is logged on; the w command shows information combining who with uptime.