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From the Library of Outcast Outcast Red Hat® RHCSA™/RHCE® Cert Guide: Red Hat Enterprise Linux (EX200 and EX300) Sander van Vugt 800 East 96th Street Indianapolis, Indiana 46240 USA From the Library of Outcast Outcast Red Hat RHCSA/RHCE Cert Guide: Red Hat Enterprise Linux (EX200 and EX300) Publisher Paul Boger Sander van Vugt Associate Publisher David Dusthimer Copyright© 2016 Pearson Certification Published by: Pearson IT Certification 800 East 96th Street Indianapolis, IN 46240 USA All rights reserved No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher, except for the inclusion of brief quotations in a review Printed in the United States of America First Printing August 2015 Library of Congress Control Number: 2015942167 ISBN-13: 978-0-7897-5405-9 ISBN-10: 0-7897-5405-3 Warning and Disclaimer This book is designed to provide information about Red Hat RHCSA and Red Hat RHCE certification Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied Trademarks All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized Pearson IT Certification cannot attest to the accuracy of this information Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark Warning and Disclaimer Every effort has been made to make this book as complete and as accurate as possible, but no warranty or fitness is implied The information provided is on an “as is” basis The author and the publisher shall have neither liability nor responsibility to any person or entity with respect to any loss or damages arising from the information contained in this book or from the use of the companion website, DVD, or programs accompanying it Acquisitions Editor Denise Lincoln Production Manager Sandra Schroeder Development Editor Ellie Bru Project Editor Mandie Frank Copy Editor Keith Cline Technical Editors Frederik Vos Ross Brunson William “Bo” Rothwell Publishing Coordinator Vanessa Evans Designer Alan Clements Composition Nonie Ratcliff Senior Indexer Cheryl Lenser Proofreader The Wordsmithery LLC Special Sales For information about buying this title in bulk quantities, or for special sales opportunities (which may include electronic versions; custom cover designs; and content particular to your business, training goals, marketing focus, or branding interests), please contact our corporate sales department at or (800) 382-3419 For government sales inquiries, please contact For questions about sales outside the U.S., please contact From the Library of Outcast Outcast About the Author Sander van Vugt is an independent Linux trainer, author, and consultant living in the Netherlands Sander is the author of the best-selling Red Hat Certified System Administrator (RHCSA) Complete Video Course and also of the Red Hat Certified Engineer (RHCE) Complete Video Course He has also written numerous books about different Linux-related topics, and many articles for Linux publications around the world Sander has been teaching Red Hat, SUSE, and LPI Linux classes since 1994 As a consultant, he specializes in Linux high-availability solutions and performance optimization You can find more information about Sander on his website at For more information about RHAT certification and additional resources, visit the author’s Red Hat Certification page at From the Library of Outcast Outcast About the Technical Reviewers Frederik Vos is a senior technical trainer in Linux training and also in several virtualization solutions, such as VMware vSphere, XenServer, and KVM For the past years Frederik has working for XTG in Gouda, a training center specializing in virtualization solutions and Linux, as a teacher and Linux evangelist, responsible for the Linux portfolio at XTG He has specialized in data center infrastructures (several Linux distributions), hypervisors, networking, and storage solutions and cloud computing (Cloudstack, Cloudplatform, and OpenStack) He has a lot of knowledge as a teacher and also real-world experience as a system engineer and as a long-time (1997) Linux user Ross Brunson has more than 20 years of experience as a Linux and open source trainer, training manager, and technologist and is author of the popular LPIC-1 Exam Cram (Que Publishing), as well as the Pearson LPIC-1 Certification Guide Ross recently spent almost years as the director of member services for the Linux Professional Institute, building the member program, conducting dozens of Trainthe-Trainer sessions, and providing support for the worldwide Master Affiliate network spanning 100+ countries Ross holds a number of key IT certifications and is also author of several successful technical books, dozens of technical courses for major organizations (including the first LPI Certification Bootcamp) He is also skilled at both contributing to and building community around IT products He lives in Paradise Valley, Montana, with his family and enjoys traveling far and wide, winter sports, and photography William “Bo” Rothwell, at the impressionable age of 14, crossed paths with a TRS-80 Micro Computer System (affectionately known as a Trash 80) Soon after, the adults responsible for Bo made the mistake of leaving him alone with the TSR-80 He immediately dismantled it and held his first computer class, showing his friends what made this “computer thing” work Since this experience, Bo’s passion for understanding how computers work and sharing this knowledge with others has resulted in a rewarding career in IT training His experience includes Linux, UNIX, and programming languages such as Perl, Python, Tcl, and Bash Bo owns several IT certifications, including earning his original RHCE in 2003 He is a former RHCI (Red Hat Certified Instructor) and the founder and president of One Course Source, an IT training organization From the Library of Outcast Outcast Dedication This book is dedicated to my family: Florence, Franck, and Alex Together we’ve made great accomplishments over the past year Acknowledgments This book could not have been written without the help of all the people who contributed to it To start, I want to thank the people at Pearson, Denise Lincoln and Ellie Bru in particular We’ve worked a lot together over the past year, and this book is another milestone on our road to success! Next I want to thank my technical proofreaders What has made this book special is that the first round of technical proofreading was completely done by volunteers We started with 10 volunteers, but just made it all the way to the end Many thanks to Giles, the man behind the great and very useful website, the only one who reviewed all the chapters I also want to thank Jaques Weewer, Rob Mokkink, and all the other volunteer technical reviewers You made many suggestions without which the book would not have the high quality that it has right now From the Library of Outcast Outcast We Want to Hear from You! As the reader of this book, you are our most important critic and commentator We value your opinion and want to know what we’re doing right, what we could better, what areas you’d like to see us publish in, and any other words of wisdom you’re willing to pass our way We welcome your comments You can email or write to let us know what you did or didn’t like about this book[md]as well as what we can to make our books better Please note that we cannot help you with technical problems related to the topic of this book When you write, please be sure to include this book’s title and author as well as your name and email address We will carefully review your comments and share them with the author and editors who worked on the book Email: Mail: Pearson IT Certification ATTN: Reader Feedback 800 East 96th Street Indianapolis, IN 46240 USA Reader Services Visit our website and register this book at for convenient access to any updates, downloads, or errata that might be available for this book From the Library of Outcast Outcast Contents at a Glance Introduction xxxix Part 1: RHCSA CHAPTER Installing Red Hat Enterprise Linux Server CHAPTER Using Essential Tools CHAPTER Essential File Management Tools CHAPTER Working with Text Files CHAPTER Connecting to Red Hat Enterprise Linux CHAPTER User and Group Management CHAPTER Configuring Permissions CHAPTER Configuring Networking CHAPTER Managing Processes CHAPTER 10 Working with Virtual Machines CHAPTER 11 Managing Software CHAPTER 12 Scheduling Tasks CHAPTER 13 Configuring Logging 295 CHAPTER 14 Managing Partitions 319 CHAPTER 15 Managing LVM Logical Volumes CHAPTER 16 Basic Kernel Management CHAPTER 17 Configuring a Basic Apache Server CHAPTER 18 Managing and Understanding the Boot Procedure CHAPTER 19 Troubleshooting the Boot Procedure CHAPTER 20 Using Kickstart CHAPTER 21 Managing SELinux CHAPTER 22 Configuring a Firewall CHAPTER 23 Configuring Remote Mounts and FTP CHAPTER 24 Configuring Time Services 33 57 85 103 123 151 177 205 225 249 281 349 369 389 405 429 451 473 499 515 539 From the Library of Outcast Outcast viii Red Hat RHCSA/RHCE Cert Guide Part 2: RHCE 555 CHAPTER 25 Configuring External Authentication and Authorization CHAPTER 26 Configuring an iSCSI SAN CHAPTER 27 System Performance Reporting CHAPTER 28 System Optimization Basics CHAPTER 29 Configuring Advanced Log Features CHAPTER 30 Configuring Routing and Advanced Networking CHAPTER 31 An Introduction to Bash Shell Scripting CHAPTER 32 Advanced Firewall Configuration CHAPTER 33 Managing Advanced Apache Services CHAPTER 34 Configuring DNS CHAPTER 35 Configuring a MariaDB Database CHAPTER 36 Configuring NFS 781 CHAPTER 37 Configuring Samba File Services CHAPTER 38 Setting Up an SMTP Server CHAPTER 39 Configuring SSH CHAPTER 40 Managing Time Synchronization CHAPTER 41 Final Preparation 875 CHAPTER 42 Theoretical Pre-Assessment Exams 557 577 607 627 641 655 683 701 719 741 759 801 825 845 859 881 RHCSA Practice Exam A 887 RHCSA Practice Exam B 891 RHCE Practice Exam A 895 RHCE Practice Exam B 899 Index 902 Elements on DVD and Companion Website APPENDIX A Answers to the “Do I Know This Already” Quizzes and “Review Questions” APPENDIX B Memory Tables APPENDIX C Memory Tables Answer Key APPENDIX D Setting Up Identity Management APPENDIX E Study Planner Glossary From the Library of Outcast Outcast Contents Introduction xxxix Part 1: RHCSA Chapter Installing Red Hat Enterprise Linux Server “Do I Know This Already?” Quiz 7 Foundation Topics 11 Preparing to Install Red Hat Enterprise Linux 11 What Is Red Hat Enterprise Linux Server? Getting the Software 11 12 Using CentOS 12 Other Distributions 13 Understanding Access to Repositories 13 Understanding Red Hat Enterprise Linux Server Variants and Add-Ons 14 Setup Requirements 15 Course Environment Description 16 Performing a Manual Installation Summary 17 29 Exam Preparation Tasks 29 Review All Key Topics 29 Define Key Terms 30 Review Questions 30 End-of-Chapter Labs 30 Lab 1.1 Chapter 31 Using Essential Tools 33 “Do I Know This Already?” Quiz 33 Foundation Topics 36 Basic Shell Skills 36 Executing Commands 36 I/O Redirection 37 Using Pipes 39 History 40 Bash Completion 42 From the Library of Outcast Outcast Glossary 17 Message user agent The part of an email solution that is used by the user to access and receive messages Module A piece of snap-in code Modules are used by several systems on Linux such as the kernel, GRUB 2, rsyslog, and more Via modules, Linux components can be extended easily, and adding functionality does not require a total rewrite of the software Mount To access files on specific storage devices, the storage device needs to be mounted on a directory This sets up the specified directory as the access point to files on the storage device Mounts are typically organized by the systems administrator and are not visible to end users Mount map file In automount, the file that defines the file systems that need to be mounted and maps them to the mount points MTA See message transfer agent MUA See message user agent Multipath In SAN environment, it is important that redundancy is provided to access storage devices The result is that the same storage device may be seen twice, which makes it unclear to the client which storage device it needs to connect to To fix this problem, a multipath driver can be used This driver will present one uniform multipath device, and from this device access to the specific backing device is regulated Multipliers In regular expressions, a character that indicates that multiple of the previous character are referred to N Name server In DNS, the name server is the server that is configured with a database that contains resource records that are used to answer to the DNS queries NAT Also referred to as masquerading, see masquerading for more details Netfilter The part of the Linux kernel that implements firewalling Netmask See subnet mask Network Address Translation See masquerading Network File System The Network File System (NFS) is a common UNIX solution to export physical file systems to other hosts on the network The other hosts can mount the exported NFS directory in their local file system Network Information System A legacy system that was used to provide centralized databases on Linux to store information about users, groups, hosts, and more From the Library of Outcast Outcast 18 Red Hat RHCSA/RHCE Cert Guide Network time Time that is provided on the network Network Time Protocol A standard that is used to provide reliable time to servers in a network NTP on RHEL is implemented by the chronyd service NFS See Network File System nice A method to change the priority of Linux processes A negative nice value will make the process more aggressive, giving it a higher priority (which is expressed by a lower priority number!); a positive nice value will make a process less eager so that it gives priority to other processes NIS See Network Information System nslcd The legacy backend service that is used on an LDAP client NTP See Network Time Protocol Null client In email, refers to a mail client where an SMTP service such as Postfix is running but is configured only to allow the client to send outgoing messages For receiving incoming messages additional services are needed O Octal A numbering scheme that uses the numbers through only Used when working with Linux permissions using the umask or the chmod commands OpenStack An open source cloud solution that is rapidly becoming the de facto standard in cloud computing and offers infrastructure as a service OR A logical operation where the second command is only executed if the first command was not able to execute Output module In rsyslog, a module that is used to send log messages to a specific destination Output modules make rsyslogd flexible and allow for the usage of log destinations that are not native to rsyslog Ownership In file system permissions, the effective permissions that a user has are based on ownership Every file has a user owner and a group owner assigned to it P Package A bundle that is used to distribute software A package typically contains a compressed archive of files and metadata that includes instructions on how to install those files Package group A group of packages that can be installed as such using the yum groups install command From the Library of Outcast Outcast Glossary 19 Package groups In yum, a group of software packages that can be installed with one single command Pager A program that can be used to browse page by page through a text file The less utility provides one of the most common Linux pagers Parent shell The environment from which a shell script or program is started Processes or child scripts will inherit settings from the parent shell Partition A subdivision of a hard disk on which a file system can be created to mount it into the directory structure Password A token that is used in authentication The password is a secret word that can be set by individual users and will be stored in an encrypted way Passphrase Basically a password, but it is supposed to be longer and more secure than a password Path The complete reference to the location of a file Permissions Attributes that can be set on files or directories to allow users or groups access to these files or directories Permissive A mode in SELinux where nothing is blocked, but everything is logged in the audit log This mode is typically used for troubleshooting SELinux issues Physical backup A backup where the files containing the actual data are written to the backup Physical backups are more difficult to create than logical backups, but at the same time are more reliable Physical extent The physical building block that is used when creating LVM physical volumes Typically, they have the size of multiple megabytes Physical volume The foundation building block of an LVM configuration The physical volume typically corresponds to a partition or a complete disk device PID See process identification number Pipe A structure that can be used to forward the output of one command to be used as input for another command Policy See SELinux policy Port A number that is used by a process to offer access to the process through a network connection Portable Operating System Interface A standard that was created to maintain compatibility between operating systems The standard mainly applies to UNIX and guarantees that different flavors of Linux and UNIX are compatible to one another From the Library of Outcast Outcast 20 Red Hat RHCSA/RHCE Cert Guide Port forwarding A firewalling technique where traffic that is coming in on a specific port is forwarded to another port which may be on the same host and on a different host Portmap The portmapper is a remote procedure call service that needs to run on systems that provide RPC services Portmapper uses dynamic ports that not correspond to specific TCP or UDP ports; the service will pick a UDP or TCP port that will be used as long as the process is active When restarted, chances are that different ports are used They need to be mapped to fixed UDP and TCP ports in order to make it possible to open the firewall for these ports Portmapper is still used by components of the NFS service Portal In iSCSI, a portal is the IP address and ports on which iSCSI target services are available POSIX See Portable Operating System Interface Primary In DNS, the primary name server that is responsible for the resource records in the DNS database Primary group Every Linux user is a member of a primary group When you are creating files, the primary group is assigned as the group owner of the file Primary partition In MBR, one of a maximum of four partitions that can be created in the Master Boot Record See also extended partition Principal In Kerberos, refers to the entity that can be identified and verified using Kerberos credentials Priority In rsyslog, used to specify the severity of a logged event Based on the severity, specific actions can be taken Priority In process handling, specifies the importance of a process Process priority is expressed with a number (which can be modified using nice) Processes with a lower priority number will be serviced before processes with a higher priority number Private key In public/private key encryption, the key that is used to generate encrypted data Privileged user See root Proc A kernel interface that provides access to kernel information and kernel tunables This interface is available through the /proc file system From the Library of Outcast Outcast Glossary 21 Process A task that is running on a Linux machine Roughly, a process corresponds to a program, although one program can start multiple processes Process identification number A unique number that is used to identify a process running on a Linux system Protocol A set of rules that is used in computing, for instance in computer networking to establish communications between two computers Pseudo Root File System In NFSv4, refers to a solution where multiple shares are exported by an NFS server Instead of mounting each individual share, the NFS client mounts the root file system on the NFS server, which gives access to all shares he is entitled to Pseudo root mount In NFSv4, a mount of the root directory system or another high-level directory that hasn’t been specifically exported by the NFS server, but which gives access to all exported file systems where the client has access to Public key In cryptography, the key that is typically sent by a server to a client so that the client can send back encrypted data PV See physical volume Q Queue In process management, the queue is used for processes to be waiting before they can be executed R Realm An authentication domain in Kerberos Real Time Clock The hardware clock that is installed on the computer motherboard Reboot The procedure of stopping the computer and starting it again Record In relation databases, a record is a collection of fields that together are used to store data about one object in the database Recursion In DNS, recursion happens when one name server is not capable of resolving DNS requests and needs to forward the request to another name server In file systems, recursion refers to including the contents of a subdirectory, as in ls -R Red Hat Enterprise Linux The name for the software that Red Hat sells subscriptions for It is available in a server and a desktop edition From the Library of Outcast Outcast 22 Red Hat RHCSA/RHCE Cert Guide Red Hat Network The platform that Red Hat offers to provide patches for customers that have an active subscription To provide these patches and updates, Red Hat Network is providing the repositories that are needed for this purpose Red Hat Package Manager The name for the package format that is used on RHEL for software packages and for the Package Management software RPM has become the standard for package management on many other Linux distributions as well Redirect Method where something is sent somewhere else Used mainly in DNS Reference clock A clock that is used as a time source in an NTP time configuration Typically, a reference clock is a highly reliable clock on the Internet, but it can be an internal clock on the computers motherboard as well Regular expression A search pattern that allows users to search text patterns in a flexible way Not to be confused with shell metacharacters Relative file name directory A file name that is relative to a directory that is not the root Relay host In email traffic, a relay host is a host that messages are forwarded to Relay hosts are used to prevent all clients from having to send out messages for themselves The advantage of using relay hosts is that it is much easier to secure them because security efforts can be focused on one or a limited amount of hosts Remote Procedure Calls A method for interprocess communication that allows a program to execute code in another address space Remote Procedure Calls is an old protocol and as such is still used in the Network File System Repository An installation source that contains installable packages and an index that contains information about the installable packages so that the installation program yum can compare the version of packages that are currently installed with the version of packages that is available in the repository Resident memory Memory pages that are in use by a program Resolver The DNS client part that contains a list of DNS servers to contact to resolve DNS queries Resource record An entry in the DNS database Multiple types of resource records exist, of which the Address (A) resource record takes care of translating names to IP addresses RHEL RHN See Red Hat Enterprise Linux See Red Hat Network From the Library of Outcast Outcast Glossary 23 Rich rules Rules in firewalld that allow the usage of a more complicated syntax so that more complex rules can be defined Root The privileged user account that is used for system administration tasks User root has access to all capabilities, which means that permissions not apply to the user root, which means that the root user account is virtually unlimited Root directory The starting point of the file system hierarchy, noted as / RPC See Remote Procedure Calls RPM See Red Hat Package Manager RTC See Real Time Clock Runner In network teaming, refers to the protocol that is used to send packets over the different interfaces in the network team configuration Runners The protocol specifications that are to be used for setting up teamed aggregated network interfaces rsyslogd The generic daemon that logs messages S Samba The name for the Linux service that implements the SMB protocol SAN Storage-area network, a solution where disk devices are shared at a block level over the network As such, they can be used in the same way as local disk devices on a Linux system iSCSI and Fiber Channel are the common SAN protocols Scheduler The part of the Linux kernel that monitors the queue of runnable processes and allocates CPU time to these processes Scientific Linux A Linux distribution that is based on the Red Hat packages from which the Red Hat logo has been removed A very good choice for people that are looking for a freely available alternative to Red Hat Enterprise Linux Secondary group A group that a user is a member of but which membership is not defined in the /etc/passwd file When creating new files, the secondary group will not automatically become the owner of those files Secure Shell A solution that allows users to open a shell on a remote server where security is implemented by using public/private key cryptography Secure Sockets Layer See Transport Layer Security SELinux A Linux kernel security module that provides a mechanism for supporting access control security policies From the Library of Outcast Outcast 24 Red Hat RHCSA/RHCE Cert Guide Server Message Blocks An application level protocol that is used to provide shared access to files, printers, and serial ports, which on Linux is implemented in the Samba server ServerRoot In Apache, refers to the location where server configuration files are expected to be found Services In systemd: processes that need to be started to provide specific functionality In firewalld: a configuration of firewall settings that is used to allow access to specific processes Share A directory to which remote access is configured using a remote file system protocol such as NFS or CIFS Shebang Used in a script to indicate which shell should be used for executing the code in the shell script If no shebang is used, the script code will be interpreted by the parent shell, which may lead to errors in some cases A shebang starts with a #, which is followed by a ! and the complete pathname of the shell, such as #!/bin/bash Shell The environment from which commands can be executed Bash is the default shell on Linux, but other shells exist as well Shell metacharacters Characters such as *, ?, and [a-z] that allow users to refer to characters in file names in a flexible way Signal An instruction that can be sent to a process Common signals exist, such as SIGTERM and SIGKILL, but the Linux kernel allows a total of 32 different signals to be used To send a signal to a process, the kill command enables you SMB See Server Message Blocks Snapshot A “photo” of the actual state of a file system Software time See system time Source context In SELinux, a context is a label that identifies allowed operations Everything in an SELinux environment has a context The source context is the context of the processes or users that initiate an action SQL See Structure Query Language SSH See Secure Shell SSH tunneling A technique where a secure connection is created using SSH, which can be used to send data in a secured way SSL See Secure Sockets Layer From the Library of Outcast Outcast Glossary 25 sssd The modern backend service that is used by remote logins through different types of protocols, such as LDAP, Kerberos, Active Directory, and more Standard error The default location where a program sends error messages to Standard input The default location where a program gets its input from Standard output The default location where a program sends its regular output to Static route A route that is defined manually by a network administrator STDERR See standard error STDIN See standard input STDOUT See standard output Storage backend In iSCSI, a storage backend is the storage device that is used on the iSCSI target behind the LUN that provides access to the shared block devices to iSCSI initiators Stratum In time synchronization, stratum is used to indicate the distance between a server and an authoritative Internet time source Structured Query Language request data from databases The language that is used as a generic interface to Subdomain In DNS, a subdomain is a subdivision of any domain In the domain, example is a subdomain of the top-level domain com Subnet mask A logical subdivision of an IP network Subshell A shell that is started from another shell Typically, by running a shell script a subshell is started Swappiness The willingness of the Linux kernel to move memory pages from physical RAM to swap Swappiness is set as a parameter in the /proc/sys/vm directory, which can be modified to tune the swap behavior Symbolic link A special type of file that contains a reference to another file or directory in the form of an absolute or relative path Sysctl A service that is used on system startup to allow kernel tunables to be set automatically or to set kernel tunables manually and to display the parameters that are currently in use sysctl The service that can be used to load Linux kernel tunables Sysfs The kernel interface that is mounted on the /sys directory and which is used to provide access to parameters that can be used for managing hardware settings From the Library of Outcast Outcast 26 Red Hat RHCSA/RHCE Cert Guide Systemd The service manager on RHEL Systemd is the very first process that starts after the kernel has loaded, and it takes care of starting all other processes and services on a Linux system System time The time that is maintained by the operating system When a Linux system boots, system time is set to the current hardware time, and while the operating system is running, it is often synchronized using the Network Time Protocol T Table In relational databases, a set of data that can serve as an independent entity and can be related to other tables Tainted kernel A kernel in which unsupported kernel modules have been loaded tar The Tape Archiver; the default Linux utility that is used to create and extract backups Target (in iSCSI) See iSCSI target Target (in systemd) A collection of unit files that can be managed together Target context The SELinux context that is set to a target object, such as a port, file, or directory Teaming In networking, refers to a technique that allows multiple network interfaces to be joined in a trunked network interface Network teaming is used for increased performance, and increased redundancy Terminal Originally, the screen that was used by a user to type commands on On modern Linux systems, pseudo terminals can be used as a replacement A pseudo terminal offers a shell window from which users enter the commands that need to be executed TFTP See Trivial File Transfer Protocol TGT See Ticket Granting Ticket Thread A thread can be used as a subdivision of a process Many processes are single threaded, which means that it is basically one entity that needs to be serviced On a multicore or multi-CPU computer system it makes sense working with multithreaded processes If that is the case, the different cores can be used to handle the different threads, which allows a process to benefit from multi core or multi threaded environments Ticket Granting Ticket In a Kerberos environment, a Ticket Granting Ticket is a small encrypted identification file that a kerberos user or service may use to get access to services in a Kerberized environment From the Library of Outcast Outcast Glossary 27 Time stamp An identifier that can be used on files, database records and other types of data to identify when the last modification has been applied Many services rely on time stamps To ensure that time stamped based systems work properly, time synchronization needs to be configured Time synchronization A system that ensures that multiple servers are using the exact same time To accomplish time synchronization, it is common to use an external time server, as defined in the Network Time Protocol (NTP) Time To Live In IP traffic, the Time To Live defines how long a packet must stay alive until it is discarded Time To Live is expressed as the number of routers that can be passed as a maximum In DNS, Time To Live refers to the maximum amount of time that DNS information is allowed to be kept in cache before it needs to be requested again TLS See Transport Layer Security Top Level Domain In Domain Name System, the top-level domain identifies the highest level of DNS domain names Originally, there was a limited number of toplevel domains available (such as com, org, and net), but this number has recently been extended Transport Layer Security A cryptographic protocol that is created to ensure secured communications over a computer network In TLS, public and private keys are used, and certificates authenticate the counterparty Trivial File Transfer Protocol A service that is used on installation servers and in other environments The server that needs to be installed will boot from the network card using PXE boot The DHCP server is the first to answer to this PXE boot by providing an IP address Then, the DHCP server redirects the request to the TFTP server which will provide a boot image TTL See Time To Live TTY A program that provides a virtual terminal on Linux Every terminal still has a TTY name, which is either tty1-6 for virtual TTYs or /dev/pts/0-nn for pseudo terminals U udev A service that works together with the Linux kernel to initialize hardware UEFI See Extensible Firmware Interface umask An octal value that defines the default permissions as a shell property umount The command that is used to decouple a file system from the directory where it is mounted on From the Library of Outcast Outcast 28 Red Hat RHCSA/RHCE Cert Guide Unbound The name of the DNS service on RHEL which can be used as a caching-only DNS name server Unit In systemd, refers to an item that is managed by systemd Different types of units exist, including service, path, mount, and target units Universal time coordinated A time standard that is globally the same, no matter which specific time zone a user is in Universal Time Coordinate roughly corresponds to Greenwich mean time Universal Unique ID An identification number that consists of a long random hexadecimal number and which is globally unique Umount The process that needs to be performed to decouple a storage device from the directory it is mounted on Unprivileged user A regular non-root user account to which access restrictions as applied by permissions apply Upstart The system that was used in RHEL to start services during system initialization User An entity that is used on Linux to provide access to specific system resources Users can be used to represent people, but many services also have a dedicated user account, which allows the service to run with the specific permissions that are needed for that service Userspace The area of memory that is accessible by application software that has been started with nonroot privileges UTC See Universal time coordinated UUID See Universal unique ID V Value The data that is assigned to a specific property, variable, or record Variable A label that contains a specific value that can be changed dynamically In scripting, variables are frequently used to allow the script to be flexible Vfat The Linux kernel driver that is used to access FAT-based file systems FAT is a commonly used file system in Windows environments The Linux Vfat driver allows usage of this file system VG See volume group virbr See virtual bridge From the Library of Outcast Outcast Glossary 29 Virsh A shell interface that allows for management of KVM virtual machines and their environment Virtual bridge A software bridge (which is like a network switch) that is used mostly in virtual environments to allow multiple hosts to access the same network interface Virtual host In the Apache web server, a virtual host is a collection of configuration settings that is used to address a web server What makes it a virtual host is that one installation of the Apache web server can be configured with multiple virtual hosts, which allows administrators to run multiple websites on one Apache server Virtual memory The total amount of addressable memory Virtual memory is called virtual memory because it does not refer to memory that really exists Its only purpose is to make sure that Linux programs can set an address pointer that is unique and not in use by other programs Volume group The abstraction layer that in logical volume manager is used to represent all available storage presented by physical volumes from which logical volumes can be created W Want An indication for a systemd unit file that it is supposed to be started from a specific systemd target Wants target A definition of the systemd units that are required in a specific systemd Web Server Gateway Interface A specification for a uniform interface between web servers and web server applications or framework for the Python programming language Wildcard The * character, which in a shell environment refers to an unlimited amount of any characters WSGI See Web Server Gateway Interface X From the Library of Outcast Outcast 30 Red Hat RHCSA/RHCE Cert Guide XFS A high-performance 64-bit file system that was created in 1993 by SGI and which in RHEL is used as the default file system Xinetd The Internet Superservice This is a service that listens for incoming connections on other managed services These managed services will be started by xinetd when their service is needed, and they will be shut down when they are needed no longer Y Yellowdog Update Manager The meta package handler that on RHEL is used to install packages from yum repositories Yum See Yellowdog Update Manager Z Zone In firewalld, a zone is a collection of one or more network interfaces that specific firewalld rules are associated with From the Library of Outcast Outcast Where are the Companion Content Files? Register this digital version of Red Hat RHCSA/RHCE Cert Guide to access important downloads The print version of this title comes with a disc of companion content As an eBook reader, you have access to these files by following the steps below: Go to register and log in or create a new account Enter the ISBN: 9780789754059 (NOTE: Please enter the print book ISBN provided to register the eBook you purchased.) Please note that many of our companion content files can be very large, especially image and video files If you are unable to locate the files for this title by following the steps at left, please visit contact and select the “Site Problems/ Comments” option Our customer service representatives will assist you Answer the challenge question as proof of purchase Click on the “Access Bonus Content” link in the Registered Products section of your account page to be taken to the page where your downloadable content is available The Professional and Personal Technology Brands of Pearson From the Library of Outcast Outcast ... Theoretical Pre-Assessment Exams 5 57 577 6 07 6 27 641 655 683 70 1 71 9 74 1 75 9 801 825 845 859 881 RHCSA Practice Exam A 8 87 RHCSA Practice Exam B 891 RHCE Practice Exam A 895 RHCE Practice Exam B 899 Index... Number: 20159421 67 ISBN-13: 978 -0 -78 97- 5405-9 ISBN-10: 0 -78 97- 5405-3 Warning and Disclaimer This book is designed to provide information about Red Hat RHCSA and Red Hat RHCE certification Every... repoquery 275 Summary 276 Exam Preparation Tasks 276 Review All Key Topics 276 Complete Tables and Lists from Memory 277 Define Key Terms 277 From the Library of Outcast Outcast xviii Red Hat RHCSA/ RHCE
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