Install and Configure a PXE Boot Server for Kickstart Installation on CentOS 7

I am moving away from Foreman managed PXE functionality to a standalone PXE boot server.

Homelab Update

I’ve been using Katello to manage my homelab for some years now, and it’s done the job well. Upgrades can be painful at times but you learn to read the CHANGELOG.

My main area of interest has shifted in the last twelve months. I’ve been focused on adopting Docker and getting into the world of containers and infrastructure as a code. Due to global pandemic, the Red Hat Summit 2020 was held online as a Virtual Experience, and I was able to attend it for the first time. I was surprised to see so many OpenShift use cases: from Public Health England using OpenShift to support scientific computing to automotive industry building flexible production infrastructures. I will admit that I did not anticipate the scale of it.

Fast forward some months, I changed jobs to work on a Kubernetes project. As a result, my homelab requirements have changed. I fell in love with Kubernetes. I migrated from Puppet to Ansible. I’ve found myself using Katello less and less. Its system requirements have also increased by 50%. When I started with Katello I could get away with 8GB of memory. This has grown to 12GB over time and has become a resource hog.

What I use My PXE Boot Server For

I use KVM to run my virtual machines (it’s enterprise quality and free). When I deploy a new VM, I normally do the following:

$ VM_ID="08"
$ virt-install \
  --connect qemu+ssh://[email protected]/system \
  --name srv${VM_ID} \
  --network bridge=br0,model=virtio,mac=C0:FF:EE:D0:5E:${VM_ID} \
  --disk path=/var/lib/libvirt/images/srv${VM_ID}.qcow2,size=16 \
  --pxe \
  --ram 2048 \
  --vcpus 1 \
  --os-type linux \
  --os-variant centos7.0 \
  --sound none \
  --rng /dev/urandom \
  --virt-type kvm

This uses PXE boot to provision a new CentOS 7 server, issues a static DHCP lease based on my pre-defined list of MAC addresses (that does not change), and creates a dynamic DNS entry. Once the server is up and running, I use Ansible to configure it without having to SSH into the VM manually.

Using this approach I can spin up half a dozen of servers to deploy my multi-master Kubernetes homelab, or re-build the workstations that also run on CentOS 7.

Software

A PXE boot server requires DHCP, TFTP and FTP (or NFS) to function properly, but these services don’t have to be deployed on a single machine. My DHCP server configuration is described here and won’t be covered in this article.

Software used in this article:

1. CentOS 7
2. tftp-server 5.2
3. vsftpd 3.0

SELinux set to enforcing mode and firewalld is enabled.

PXE Boot Server Hardware Requirements

1. 1 CPU
2. 1GB RAM
3. 16GB disk
4. The IP address of the PXE boot server is 10.11.1.20

Install and Configure FTP Server

We use FTP to share OS installation media to PXE boot clients.

Install vsftpd package and ensure that the service is enabled:

$ sudo yum install vsftpd -y
$ sudo systemctl enable vsftpd

Configure /etc/vsftpd/vsftpd.conf:

anonymous_enable=YES
local_enable=NO
write_enable=NO
local_umask=022
dirmessage_enable=YES
xferlog_enable=YES
connect_from_port_20=YES
xferlog_std_format=YES
ftpd_banner=Welcome to homelab FTP service.
listen=YES
listen_ipv6=NO
listen_port=21
pam_service_name=vsftpd
userlist_enable=YES
tcp_wrappers=YES
pasv_enable=YES
pasv_address=10.11.1.20
pasv_min_port=60000
pasv_max_port=60029

Configure firewall rules including passive port range:

$ sudo firewall-cmd --permanent --add-service=ftp
$ sudo firewall-cmd --permanent --add-port=60000-60029/tcp
$ sudo firewall-cmd --reload

Start the service:

$ sudo systemctl start vsftpd

Install TFTP Server

Install tftp-server package and ensure that the service is enabled:

$ sudo yum install tftp-server -y
$ sudo systemctl enable tftp && sudo systemctl start tftp

Configure firewall rules:

$ sudo firewall-cmd --permanent --add-service=tftp
$ sudo firewall-cmd --reload

Download and Create CentOS 7 FTP Installation Media

Download a CentOS 7 ISO image. Make sure to download the full DVD version, e.g.:

$ sudo yum install curl -y
$ curl -# -O http://mirror.ox.ac.uk/sites/mirror.centos.org/7.9.2009/isos/x86_64/CentOS-7-x86_64-DVD-2009.iso

Mount the image and copy its content to the FTP location:

$ sudo mkdir -p /mnt/iso /var/ftp/pub/pxe/CentOS7
$ sudo mount CentOS-7-x86_64-DVD-2009.iso /mnt/iso
$ sudo cp -prv /mnt/iso/* /var/ftp/pub/pxe/CentOS7/
$ sudo umount /mnt/iso

Verify:

$ curl ftp://10.11.1.20/pub/pxe/CentOS7/
-rw-r--r--    1 0        0              14 Oct 29 21:14 CentOS_BuildTag
drwxr-xr-x    3 0        0              35 Oct 26 16:25 EFI
-rw-rw-r--    1 0        0             227 Aug 30  2017 EULA
-rw-rw-r--    1 0        0           18009 Dec 09  2015 GPL
drwxr-xr-x    2 0        0              43 Oct 26 16:25 LiveOS
drwxr-xr-x    2 0        0          225280 Nov 04 11:30 Packages
-rw-rw-r--    1 0        0            1690 Dec 09  2015 RPM-GPG-KEY-CentOS-7
-rw-rw-r--    1 0        0            1690 Dec 09  2015 RPM-GPG-KEY-CentOS-Testing-7
-r--r--r--    1 0        0            2883 Nov 04 11:36 TRANS.TBL
drwxr-xr-x    3 0        0              57 Oct 26 16:26 images
drwxr-xr-x    2 0        0             198 Nov 02 16:17 isolinux
drwxr-xr-x    2 0        0            4096 Nov 04 11:35 repodata

Create Kickstart File

Kickstart files contain answers to all questions normally asked by CentOS installation program. By providing a prepared kickstart file when the installation begins we can perform deployments automatically.

This is the kickstart file /var/ftp/pub/pxe/centos7-ks.cfg that I use for my CentOS 7 servers (a 16GB disk required).

#version=CentOS7
# Install OS instead of upgrade
install
# System authorisation information
auth --enableshadow --passalgo=sha512
# Use network installation
url --url="ftp://10.11.1.20/pub/pxe/CentOS7"
# Use graphical install
graphical
# Keyboard layouts
keyboard --vckeymap=gb --xlayouts='gb'
# System language
lang en_GB.UTF-8
# SELinux configuration
selinux --enforcing
# Firewall configuration
firewall --enabled --ssh
firstboot --disable

# Network information
network  --bootproto=dhcp --device=eth0 --nameserver=10.11.1.2,10.11.1.3 --noipv6 --activate
# Reboot after installation
reboot
ignoredisk --only-use=vda

# Root password
rootpw --iscrypted $6$7YZ0gnLkLPrl6rRO$NTjTQx1nesw5JLjtiAVdn3UBSbahUBGDFSiGGfrMNfGBum5aFs.TQcNX1SEuoWX/TmQ/ZMfiMnyHDs9uu9VH9.
# System services
services --enabled="chronyd"
# System timezone
timezone Europe/London --isUtc
# System bootloader configuration
bootloader --location=mbr --timeout=1 --boot-drive=vda
# Clear the Master Boot Record
zerombr
# Partition clearing information
clearpart --all --initlabel

# Disk partitioning information
part /boot --fstype="xfs" --ondisk=vda --size=1024 --label=boot --asprimary
part pv.01 --fstype="lvmpv" --ondisk=vda --size=15359
volgroup vg_os pv.01
logvol /tmp  --fstype="xfs" --size=1024 --label="lv_tmp" --name=lv_tmp --vgname=vg_os
logvol /  --fstype="xfs" --size=14331 --label="lv_root" --name=lv_root --vgname=vg_os

%packages
@^minimal
@core
chrony

%end

%addon com_redhat_kdump --disable --reserve-mb='auto'

%end

%anaconda
pwpolicy root --minlen=6 --minquality=1 --notstrict --nochanges --notempty
pwpolicy user --minlen=6 --minquality=1 --notstrict --nochanges --emptyok
pwpolicy luks --minlen=6 --minquality=1 --notstrict --nochanges --notempty
%end

Copy the content and save it as /var/ftp/pub/pxe/centos7-ks.cfg.

Install Syslinux and Configure PXE Boot Menu

The Syslinux project covers lightweight bootloaders for network booting (PXELINUX) and more.

Install syslinux package:

$ sudo yum install syslinux -y

Copy syslinux boot loaders to the tftp server’s boot directory:

$ sudo cp -prv /usr/share/syslinux/* /var/lib/tftpboot/

Copy initrd.img and vmlinuz from the CentOS 7 installation media to /var/lib/tftpboot/networkboot/CentOS7/:

$ sudo mkdir -p /var/lib/tftpboot/networkboot/CentOS7
$ sudo cp -pv /var/ftp/pub/pxe/CentOS7/images/pxeboot/{initrd.img,vmlinuz} /var/lib/tftpboot/networkboot/CentOS7/

Create the PXE configuration directory:

$ sudo mkdir -p /var/lib/tftpboot/pxelinux.cfg

Create the PXE boot configuration file /var/lib/tftpboot/pxelinux.cfg/default with the following content:

default menu.c32
prompt 0
timeout 30
menu title Homelab PXE Menu
label Install CentOS 7 Server
  kernel /networkboot/CentOS7/vmlinuz
  append initrd=/networkboot/CentOS7/initrd.img inst.repo=ftp://10.11.1.20/pub/pxe/CentOS7 ks=ftp://10.11.1.20/pub/pxe/centos7-ks.cfg

A Note About DHCP next-server

DHCP server has to be configured to use 10.11.1.20 as the next-server, e.g.:

allow booting;
allow bootp;
next-server 10.11.1.20; # TFTP
filename "pxelinux.0";

For DHCP server configuration, see here.

Perform a Network Boot

Create a VM that uses Network Boot (PXE). Start the VM and observe the automated process.