second place in the arms race

Posted by Dick on July 24, 2008

Came across this on my travels last night. 

filters out lusers for no extra charge

filters out lusers for no extra charge

Like your style, girl. Posted without further comment (it might give the game away).

PXE testbed with Cobbler and VMware Fusion

Posted by Dick on July 14, 2008

Something like Puppet could potentially make my life a lot easier.
Puppet can’t do baremetal provisioning; it needs the base OS to be Jumpstart/Kickstarted on first. Fortunately:

  • Cobbler makes running a kickstart server a piece of piss
  • CentOS is a free binary compatible RHEL clone
  • VMWare Fusion takes up a lot less space than a test LAN.

PXE dust

PXE boots require DHCP options that VMware doesn’t enable out of the box.
So I either tweak VMwares dhcpd or use Cobblers DHCP support.

Either choice is fine (they both use ISCs DHCPd anyway);
if you don’t want the overhead of running your cobbler VM all the time,
it probably makes sense to tweak VMwares dhcpd.conf.

Cobbler can add static DHCP entries for systems you define,
(and manage DNS too) so it makes life easier for me
(IRL I’ll have to bribe the DHCP guys to add some options).

install a CentOS 5 VM

  • choose redhat -> RHEL5 as your VM type
  • name it (‘shoemaker’ in my case)
  • 10Gb disk (I just need headless boxes), advanced -> split into 2gb chunks
  • boot your CentoOS 5 iso . Bog standard install takes 4 minutes on my MBP.

install cobbler

EPEL is a collection of decent RPMs (including cobbler and puppet) for RHEL, Fedora and CentOS.
Tell yum about them and install cobbler :

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
yum install -y cobbler

hardcode your IP

(You’ll need to do this if you installed CentOS to use DHCP, which is the easiest way on VMware)

First, find out your IP, gateway and netmask.

ifconfig eth0 | grep 'inet addr'; netstat -rn | grep UG
           inet addr:192.168.21.134  Bcast:192.168.21.255  Mask:255.255.255.0
 0.0.0.0         192.168.21.2    0.0.0.0         UG        0 0          0 eth0

So you need to

echo "GATEWAY=192.169.21.2" >> /etc/sysconfig/network

edit /etc/sysconfig/network-scripts/ifcfg-eth0

# take this out
  BOOTPROTO=dhcp
  # add these
  BOOTPROTO=static
  IPADDR=192.168.21.134
  NETMASK=255.255.255.0

Then /etc/init.d/network restart.

break VMwares DHCP server.

(NB: Other VMs won’t get DHCP responses until cobbler takes over (duh)).

comment out around line 570 of /Library/Application Support/VMware Fusion/boot.sh

569 ######
570 # let shoemaker do this
571 ###   # vmnet-dhcpd puts itself in the background (daemon mode)
572 ###   "$LIBDIR/vmnet-dhcpd" -cf "$LIBDIR/vmnet8/dhcpd.conf" \
573 ###      -lf "$LEASEDIR"/vmnet-dhcpd-vmnet8.leases \
574 ###      -pf /var/run/vmnet-dhcpd-vmnet8.pid vmnet8
575 #####

(Hint: vmnet8 is the NATted subnet, vmnet1 is the host-only one. Edit the right one.)

Then sudo boot.sh –restart.

install cobbler PXE bits

  • xinetd serves up kernels and initrds over TFTP.
  • Apache serves out kickstart files and RPMs.
  • reposync mirrors remote repos (see here )
    yum install -y dhcp reposync
    for i in xinetd cobblerd httpd # we’ll do DHCP later
    do
    chkconfig $i on
    /etc/init.d/$i start
    done

basic cobbler setup

Note: docs refer to ’/var/lib/cobbler/settings’, but my RPM put it at /etc/cobbler/settings

‘cobbler check’ tells you what it needs you to edit. Obey.

Setup Cobblers DHCP management

Put this in settings:

manage_dhcp: 1
next_server: 'ip-of-cobbler-box'
server: 'ip-of-cobbler-box'

Finally, edit /etc/cobbler/dhcp.template
(man dhcpd.conf and/or crib from /Library/Application Support/VMware Fusion/vmnet8/dhcpd.conf) – my effort is here .

cobbler sync builds your DHCP config, /etc/init.d/dhcpd start makes it live.
If dhcpd won’t start, you cocked up the template. Check /var/log/messages, tweak, ‘cobbler sync’, rinse, repeat.

create a kickstart target and boot it

We can use the install ISO to build a distro and boot profile


  mount /dev/cdrom /mnt
  # copies the DVD onto disk
  cobbler import --mirror=/mnt --name=centos5
  cobbler sync

Make a new VM.

  • choose ‘Linux -> Red Hat Enterprise Linux 5’ (or VMware cocks up the disk image)
  • pick a name and disk size
  • untick ‘Start virtual machine and install OS now’

Change any VM settings if you like (defaults are ok).
Power up the VM. You should see it:

  • get an IP (DHCPd)
  • download a kernel and initrd over TFTP (xinetd and TFTPd)
  • present a menu (pxelinux.0),

Choose ‘centos5’ and you’re away.

further reading

I’ll do a followup article soon with a few tricks/gotchas I’ve found so far. In the meantime: