RHCE Certification Lab

RHCE Certification Lab

Chapter 1. Local and Remote Logins

Chapter 2. File System Navigation

Chapter 3. Users and Groups

Chapter 4. File Permissions

Chapter 5. SELinux Permissions

Chapter 6. Process Management

Chapter 7. Updating Software Packages

Chapter 8. Creating and Mounting File Systems

Chapter 9. Service Management and Boot Troubleshooting

Chapter 10. Network Configuration

Chapter 11. System Logging and NTP

Chapter 12. Logical Volume Management

Chapter 13. Scheduled Processes

Chapter 14. Mounting Network File Systems

Chapter 15. Firewall Configuration

Chapter 16. Virtualization and Kickstart

RHCE Certification Lab - Volume 2)

Chapter 1. Managing IPv6 Networking

Chapter 2. Configuring Link Aggregation and Bridging

Chapter 3. Network Port Security

Chapter 4. Managing DNS for Servers

Chapter 5. Configuring Email Transmission

Chapter 6. Providing Remote Block Storage

Chapter 7. Providing File-based Storage

Chapter 8. Configuring MariaDB Databases

Chapter 9. Providing Apache HTTPD Web Service

Chapter 10. Writing Bash Scripts

Chapter 11. Bash Conditionals and Control Structures

Chapter 12. Configuring the Shell Environment

Chapter 13. Comprehensive Review

Introduction to systemd

I nt rod uction to systemd

System startup and server processes a re managed by the systemd System and Service Manager.

This progra m provides a method for activati ng system resou rces, server daemons, and other

processes, both at boot time and on a running system.

Daemons a re processes that wait or run i n the backg round performing va rious tasks. To l isten for

con nections, a daemon uses a socket. Sockets may be created by daemons o r may be separated

from the daemon and be created by a nother process, such as systemd, which then passes the

socket to the daemon when a connection is esta b l ished by a client.

A service often refers to one or more daemons, but starting or stopping a service may

instead make a one-time change to the state of the system (for exa mple, to confi g u re network

i nterfaces), which does not i nvo lve leaving a daemon process running afterwa rd.

A bit of history

For many years, process ID 1 of Linux and U N I X systems has been the init process. This process

was responsi b l e for activating other services on the system. Frequently used daemons were

started on systems at boot time with System V a n d Linux Sta ndard Base (LSB) init scripts.

Less freq uently used daemons were started on demand by a n other service, such as initd or

xinetd. These systems have severa l l i m itations, which a re addressed with systemd.

I n Red H at E nterprise L i n u x 7, process ID 1 is syst emd, the new i n it system. A few of the new

featu res provided by systemd include:

• Pa ra l l e l ization capa b i l ities, which increase the boot speed of a system.

• On-demand sta rting of daemons without req uiring a sepa rate service.

• Automatic service dependency management prevents long timeouts, such as not sta rting a

network service when the network is not ava i l ab le.

• A method of t racking related processes together using L i n u x control g rou ps.

2

N ote

With systemd, shel l-based service scripts a re used only for a few legacy services.

Therefore, confi g u ration files with shel l va ria b l es, such as those fou n d i n

/etc/sysconfig, a re being replaced. Those sti l l i n use a re i n c l uded as systemd

enviro n m e nt files and read as N A M E=VA L U E pairs. They a re no longer sourced as a

shel l script.