Red Hat System Administration II

Objectives

After completing this section, you should be able to:

Creating a Kickstart Profile

You can automate the installation of Red Hat Enterprise Linux using a feature called Kickstart. Using Kickstart, you specify everything Anaconda needs to complete an installation, including disk partitioning, network interface configuration, package selection, and other parameters, in a Kickstart text file. By referencing the text file, Anaconda performs the installation without further user interaction.

Kickstart files begin with a list of commands that define how to install the target machine. Lines starting with # characters are comments to be ignored by the installer. Additional sections begin with a directive, recognized by a % first character, and end on a line with the %end directive.

The %packages section specifies the software to be installed on the target system. Specify individual packages by name (without versions). Package groups, specified by name or ID, are recognized by beginning them with an @ character. Environment groups (groups of package groups) are recognized by beginning them with the @^ characters. Specify modules, streams, and profiles with @module:stream/profile syntax.

Groups have mandatory, default, and optional components. Normally, Kickstart installs mandatory and default components. To exclude a package or package group from installation, precede it with a - character. However, excluded packages or package groups may still install if they are mandatory dependencies of other requested packages.

A Kickstart configuration commonly uses two additional sections, %pre and %post, which contain shell scripting commands that further configure the system. The %pre script is executed before any disk partitioning is done. Typically, this section is used only if actions are required to recognize or initialize a device before disk partitioning. The %post script is executed after the installation is otherwise completed.

You must specify the primary Kickstart commands before the %pre, %post, and %packages sections, but otherwise, you can place these sections in any order in the file.

Kickstart File Commands

Installation Commands

Define the installation source and how to perform the installation. Each is followed by an example.

Partitioning Commands

Define the devices and partitioning scheme to be used.

Network Commands

Define the network features used by the host.

Location and Security Commands

Configure settings related to security, language, and regions.

Miscellaneous Commands

Configure miscellaneous items related to logging during the installation and the host power state at completion.

Example Kickstart File

The first part of the file consists of the installation commands, such as disk partitioning and installation source.

#version=RHEL8
ignoredisk --only-use=vda
# System bootloader configuration
bootloader --append="console=ttyS0 console=ttyS0,115200n8 no_timer_check net.ifnames=0  crashkernel=auto" --location=mbr --timeout=1 --boot-drive=vda
# Clear the Master Boot Record
zerombr
# Partition clearing information
clearpart --all --initlabel
# Use text mode install
text
repo --name="appstream" --baseurl=http://classroom.example.com/content/rhel8.2/x86_64/dvd/AppStream/
# Use network installation
url --url="http://classroom.example.com/content/rhel8.2/x86_64/dvd/"
# Keyboard layouts
# old format: keyboard us
# new format:
keyboard --vckeymap=us --xlayouts=''
# System language
lang en_US.UTF-8
# Root password
rootpw --plaintext redhat
# System authorization information
auth --enableshadow --passalgo=sha512
# SELinux configuration
selinux --enforcing
firstboot --disable
# Do not configure the X Window System
skipx
# System services
services --disabled="kdump,rhsmcertd" --enabled="sshd,rngd,chronyd"
# System timezone
timezone America/New_York --isUtc
# Disk partitioning information
part / --fstype="xfs" --ondisk=vda --size=10000

The second part contains the %packages section, detailing which packages and package groups should be installed, and which packages should not be installed.

%packages
@core
chrony
cloud-init
dracut-config-generic
dracut-norescue
firewalld
grub2
kernel
rsync
tar
-plymouth

%end

The last part contains any %pre and %post installation scripts.

%post --erroronfail

# For cloud images, 'eth0' _is_ the predictable device name, since
# we don't want to be tied to specific virtual (!) hardware
rm -f /etc/udev/rules.d/70*
ln -s /dev/null /etc/udev/rules.d/80-net-name-slot.rules

# simple eth0 config, again not hard-coded to the build hardware
cat > /etc/sysconfig/network-scripts/ifcfg-eth0 << EOF
DEVICE="eth0"
BOOTPROTO="dhcp"
ONBOOT="yes"
TYPE="Ethernet"
USERCTL="yes"
PEERDNS="yes"
IPV6INIT="no"
EOF

%end

Kickstart Installation Steps

To successfully automate installation of Red Hat Enterprise Linux, follow these steps:

Creating a Kickstart File

Use either of these methods to create a Kickstart file:

The Kickstart Generator website at https://access.redhat.com/labs/kickstartconfig/ presents dialog boxes for user inputs, and creates a Kickstart directives text file with the user's choices. Each dialog box corresponds to the configurable items in the Anaconda installer.

Figure 12.3: Basic Configuration with Kickstart Generator

Creating a Kickstart file from scratch is typically too complex, but editing an existing Kickstart file is common and useful. Every installation creates a /root/anaconda-ks.cfg file containing the Kickstart directives used in the installation. This file makes a good starting point when creating Kickstart file manually.

ksvalidator is a utility that checks for syntax errors in a Kickstart file. It ensures that keywords and options are properly used, but it does not validate that URL paths, individual packages, or groups, nor any part of %post or %pre scripts will succeed. For instance, if the firewall --disabled directive is misspelled, ksvalidator could produce one of the following errors:

[user@host ~]$ ksvalidator /tmp/anaconda-ks.cfg
The following problem occurred on line 10 of the kickstart file:

Unknown command: frewall

[user@host ~]$ ksvalidator /tmp/anaconda-ks.cfg
The following problem occurred on line 10 of the kickstart file:

no such option: --dsabled

The pykickstart package provides ksvalidator.

Publish the Kickstart File to Anaconda

Make the Kickstart file available to the installer by placing it in one of these locations:

The installer must access the Kickstart file to begin an automated installation. The most common automation method uses a network server such as an FTP, web, or NFS server. Network servers facilitate Kickstart file maintenance because changes can be made once, and then immediately used for multiple future installations.

Providing Kickstart files on USB or CD-ROM is also convenient. The Kickstart file can be embedded on the boot media used to start the installation. However, when the Kickstart file is changed, you must generate new installation media.

Providing the Kickstart file on a local disk allows you to quickly rebuild a system.

Boot Anaconda and Point it to the Kickstart File

Once a Kickstart method is chosen, the installer is told where to locate the Kickstart file by passing the inst.ks=LOCATION parameter to the installation kernel. Some examples:

Figure 12.4: Specifying the Kickstart file location during installation

For virtual machine installations using the Virtual Machine Manager or virt-manager, the Kickstart URL can be specified in a box under URL Options. When installing physical machines, boot using installation media and press the Tab key to interrupt the boot process. Add an inst.ks=LOCATION parameter to the installation kernel.