Create a minimal, automated Btrfs Fedora guest template with Oz

I needed to create an automated Btrfs guest for a test. A trivial virt-install based automated script couldn’t complete the guest install (on a Fedora Rawhide host) — it hung perpetually once it tries to retrieve .treeinfo, vmlinuz, initrd.img. On my cursory investigation with guestfish, I couldn’t pin-point the root cause. Filed a bug here

[Edit, 31JAN2014: The above is fixed by adding –console=pty to virt-install command-line; refer the above bug for discussion.]

In case someone wants to reproduce with versions I noted in the above bug:

  $ wget http://kashyapc.fedorapeople.org/virt/create-guest-qcow2-btrfs.bash
  $ chmod +x create-guest-qcow2-btrfs.bash
  $ ./create-guest-qcow2-btrfs.bash fed-btrfs2 f20

Oz
So, I resorted to Oz – a utility to create automated installs of various Linux distributions. I previously wrote about it here

Below I describe a way to use it to create a minimal, automated Btrfs Fedora 20 guest template.

Install it:

 $ yum install oz -y 

A minimal Kickstart file with Btrfs partitioning:

$ cat Fedora20-btrfs.auto
install
text
keyboard us
lang en_US.UTF-8
network --device eth0 --bootproto dhcp
rootpw fedora
firewall --enabled ssh
selinux --enforcing
timezone --utc America/New_York
bootloader --location=mbr --append="console=tty0 console=ttyS0,115200"
zerombr
clearpart --all --drives=vda
autopart --type=btrfs
reboot

%packages
@core
%end

A TDL (Template Description Language) file that Oz needs as input:

$ cat f20.tdl
<template>
  <name>f20btrfs</name>
  <os>
    <name>Fedora</name>
    <version>20</version>
    <arch>x86_64</arch>
    <install type='url'>
      <url>http://dl.fedoraproject.org/pub/fedora/linux/releases/20/Fedora/x86_64/os/</url>
    </install>
    <rootpw>fedora</rootpw>
  </os>
  <description>Fedora 20</description>
</template>

Invoke oz-install (supply the Kickstart & TDL files, turn on debugging to level 4 — all details):

$ oz-install -a Fedora20-btrfs.auto -d 4 f20.tdl 
[. . .]
INFO:oz.Guest.FedoraGuest:Cleaning up after install
Libvirt XML was written to f20btrfsJan_29_2014-11:38:44

Define the above Libvirt guest XML, start it over a serial console:

$  virsh define f20btrfsJan_29_2014-11:38:44
Domain f20btrfs defined from f20btrfsJan_29_2014-11:38:44

$ virsh start f20btrfs --console
[. . .]
Connected to domain f20btrfs
Escape character is ^]

Fedora release 20 (Heisenbug)
Kernel 3.11.10-301.fc20.x86_64 on an x86_64 (ttyS0)

localhost login: 

It’s automated, fine, but still slightly more tedious (TDL file looks redundant at this point) to create custom guest image templates.

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Unattended F19 guest creation with Oz

Oz has been in development for a couple of years, which lets you install various guest operating systems with minimal user-input.

A simple wrapper script is here

Usage:
$ yum install oz -y
$  ./oz-jeos.bash guest-name distro
      'distro': f19, f18
       Examples: oz-jeos.bash f19-jeos f19  # create f19
                 oz-jeos.bash f18-jeos f18  # create f18

If you prefer to invoke manually…

Create a TDL (Template Description Language) file:

$ cat << EOF > f19.tdl
<template>
  <name>$NAME</name>
  <os>
    <name>Fedora</name>
    <version>19</version>
    <arch>x86_64</arch>
    <install type='url'>
      <url>http://dl.fedoraproject.org/pub/fedora/linux/releases/19/Fedora/x86_64/os/</url>
    </install>
    <rootpw>fedora</rootpw>
  </os>
  <description>Fedora 19</description>
  <disk>
    <size>25</size>
  </disk>
</template>

NOTE: From the above TDL file, you can elide the disk attribute if you don’t need 25G of disk. The default disk size is 10G.

Invoke Oz:

$ oz-install -d 4 f19.tdl 2>&1 \
  | tee /var/tmp/f19-oz-log.txt