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Cobbler for Bare Metal Provisioning
by Steve O'Neill
Before you begin:
This should really be behind some kind of router. I am going to use an EdgeRouter X with no ports forwarded. The EdgeRouter will provide DHCP and DNS to its internal network of 10.0.0.0/24.
First, create a new CentOS VM. I created mine on a CentOS host using KVM and cockpit-machines for GUI management. Making a snapshot does not appear to be supported at the time of this writing, but it can be done by command line.
It should have bridged networking and be able to access the network. A second physical NIC on the host should be directly attached so the VM can act as a PXE server for its own internal network.
On the VM, run these commands:
**dnf install epel-release
dnf module enable cobbler
dnf install cobbler
dnf install cobbler-web**
I didn’t install cobbler-web at first and was confused a little bit because checking https://host_ip/cobbler-web wasn’t showing anything. Restarting apache resolved it:
apachectl restart
Cobbler uses a self-signed SSL certificate. Creds are “cobbler” and “cobbler”.
We need a few more pre-requisites:
dnf install yum-utils dnf-plugins-core debmirror pykickstart syslinux xinetd
Interestingly, the guides I followed didn’t make it clear that you must install and configure DHCP-Server (dhcpd) beforehand. I caught this by trying to “cobbler sync” but it was also shown during “cobbler check”. It will also complain that “named” (Bind) isn’t installed, but we will be ignoring that.
- Set a static IP for the 2nd [physical] NIC that you associated with the VM. We are going to give it a private IP, 172.168.10.1. Use the nmtui command to do so:
- Install DHCP server:
dnf install dhcp-server
Don’t bother editing /etc/dhcp/dhcpd.conf. That file is dynamically updated by Cobbler. If we were to open that, it would remind us that DHCP server settings are now controlled by Cobbler anyhow:
# ******************************************************************
# Cobbler managed dhcpd.conf file
# generated from cobbler dhcp.conf template (Sun Dec 26 20:16:44 2021)
# Do NOT make changes to /etc/dhcpd.conf. Instead, make your changes
# in /etc/cobbler/dhcp.template, as /etc/dhcpd.conf will be
# overwritten.
# ******************************************************************
To actually make changes to the DHCP settings, edit /etc/cobbler/dhcp.template:
subnet 172.24.10.0 netmask 255.255.255.0 {
option routers 172.24.10.1;
option domain-name-servers 10.0.0.1;
option subnet-mask 255.255.255.0;
range dynamic-bootp 172.24.10.80 172.24.10.140;
default-lease-time 21600;
max-lease-time 43200;
next-server $next_server;
class "pxeclients" {
match if substring (option vendor-class-identifier, 0, 9) = "PXEClient";
This file is where I am defining the internal network that our PXE server will provide. It will be 172.24.10.0/24, a subnet I chose at random. Make sure you choose a subnet in the RFC1918 private range.
Notice that we are letting the EdgeRouter, 10.0.0.1, do DNS for now. It’s not necessary to install Bind on the VM or the host.
Restart cobbler (systemctl cobblerd restart) and run cobbler sync again
Configure Cobbler
Download an ISO. We will start with Ubuntu Server.
wget -P /mnt/iso http://mirror.math.princeton.edu/pub/ubuntu-iso/focal/ubuntu-20.04.3-live-server-amd64.iso
mkdir /mnt/iso
mount -o loop ubuntu-20.04.3-live-server-amd64.iso /mnt/iso/
cobbler import --arch=x86_64 --path=/mnt/iso --name=Ubuntu_Server_Live
Verify that it came down from the command line or the web console:
[root@pxe-server iso]# cobbler distro list
Ubuntu_Server_Live-casper-x86_64
You can also get a report with “cobbler distro report”
[root@pxe-server iso]# cobbler distro report
Name : Ubuntu_Server_Live-casper-x86_64
Architecture : x86_64
Automatic Installation Template Metadata : {'tree': 'http://@@http_server@@/cblr/links/Ubuntu_Server_Live-casper-x86_64'}
TFTP Boot Files : {}
Boot loader : grub
Breed : ubuntu
Comment :
Fetchable Files : {}
Initrd : /var/www/cobbler/distro_mirror/Ubuntu_Server_Live-x86_64/casper/initrd
Kernel : /var/www/cobbler/distro_mirror/Ubuntu_Server_Live-x86_64/casper/vmlinuz
Kernel Options : {}
Kernel Options (Post Install) : {}
Management Classes : []
OS Version : focal
Owners : ['admin']
Redhat Management Key :
Remote Boot Initrd : ~
Remote Boot Kernel : ~
Template Files : {}
Things are going well. However, this comes up during Cobbler Check:
some network boot-loaders are missing from /var/lib/cobbler/loaders. If you only want to handle x86/x86_64 netbooting, you may ensure that you have installed a recent version of the syslinux package installed and can ignore this message entirely. Files in this directory, should you want to support all architectures, should include pxelinux.0, menu.c32, and yaboot.
Solution:
dnf install -y grub2-efi-x64-modules efibootmgr
yum install -y grub2-efi-x64 shim-x64
/usr/share/cobbler/bin/mkgrub.sh
This doesn’t make the error message go away because it doesn’t copy over yaboot to /var/lib/cobbler/loaders. But it does enable EFI booting.
These are the fundamentals of setting up Cobbler in an example context.
tags: linux