[Libguestfs] Which ISO format/layout does virt-builder expect?

[Scott Gorton]

I'm running into a bit of trouble using virt-builder and I'm hoping that someone might be able to point in the right direction.

My build process creates a custom ISO image which is subsequently used to kickstart an Oracle X4-2 server using PXE.  The ISO is a minimal install and contains a suite of packages and customization scripts to properly configure our box during first boot.  The process works great for kickstarting baremetal machines as well as VMs created with virt-manager or vsphere.

I'd like to be able to use virt-builder to build virtual images automatically (i.e., take our .ISO and generate a qcow2 of a properly installed system).  Unfortunately, virt-builder doesn't seem to like the format of my ISO image.  The tool dies during the "Setting passwords" step because it's attempting to create a temp file in /etc and my ISO doesn't have an /etc directory at this point.

Here's a snippet that shows the error message:

[  16.0] Setting passwords
libguestfs: trace: mktemp "/etc/shadow.guestfsXXXXXX"
libguestfs: trace: mktemp = NULL (error)
virt-builder: error: libguestfs error: mktemp: /etc/shadow.guestfsyU5Zwo:
No such file or directory

Is there a particular ISO format that virt-builder expects?

As a test, I used virt-builder to successfully create a centos-6 image.  I looked in my .cache/virt-builder directory, unxz'd the image and then mounted the partitions.  It appears that the sanitized centos-6 image is fully complete (i.e., contains a typical filesystem, has an /etc, an /etc/passwd...etc.) whereas mine seems more like a linux image that is in a ready-to-be-installed state.

virt-inspector on my ISO shows:

<?xml version="1.0"?>
<operatingsystems>
  <operatingsystem>
    <root>/dev/sda</root>
    <name>linux</name>
    <arch>x86_64</arch>
    <distro>oraclelinux</distro>
    <major_version>6</major_version>
    <minor_version>0</minor_version>
    <package_format>rpm</package_format>
    <package_management>yum</package_management>
    <format>installer</format>
    <mountpoints>
      <mountpoint dev="/dev/sda">/</mountpoint>
    </mountpoints>
    <filesystems>
      <filesystem dev="/dev/sda">
        <type>iso9660</type>
        <label>iDVA 4.95.0 x86_64</label>
        <uuid>2015-11-20-19-50-52-00</uuid>
      </filesystem>
    </filesystems>
    <applications/>
  </operatingsystem>
</operatingsystems>

Likewise, if I mount my ISO I have a filesystem that looks like:

drwxrwxr-x  3 test test      4096 Nov 19 18:03 images
drwxrwxr-x 11 test test      4096 Nov 19 18:05 iqcustom
-rw-rw-r--  1 test test 966785078 Nov 19 18:08 iqcustom.tar.gz
drwxrwxr-x  2 test test      4096 Nov 19 18:03 isolinux
-rw-rw-r--  1 test test      2368 Nov 19 18:03 ks-dell.cfg
-rw-rw-r--  1 test test     15158 Nov 19 18:03 ks-oracle.cfg
-rw-rw-r--  1 test test     15985 Nov 19 18:03 ks-pxe.cfg
-rw-rw-r--  1 test test      3061 Nov 19 18:03 ks-pxe-oracle-vm.cfg
-rw-rw-r--  1 test test      2176 Nov 19 18:03 ks-vm.cfg
drwxrwxr-x  2 test test     36864 Nov 19 18:04 Packages
drwxrwxr-x  2 test test      4096 Nov 19 18:04 repodata
-r--r--r--  1 test test      3106 Nov 19 18:05 TRANS.TBL
drwxrwxr-x  3 test test      4096 Nov 19 18:05

In contrast, mounting one of the partitions in the centos-6 image shows:

dr-xr-xr-x.  2 root root  4096 Oct 31  2014 bin
drwxr-xr-x.  2 root root  4096 Oct 31  2014 boot
drwxr-xr-x.  2 root root  4096 Oct 31  2014 dev
drwxr-xr-x. 73 root root  4096 Dec  9 16:26 etc
drwxr-xr-x.  2 root root  4096 Sep 23  2011 home
dr-xr-xr-x. 10 root root  4096 Oct 31  2014 lib
dr-xr-xr-x.  9 root root 12288 Oct 31  2014 lib64
drwx------.  2 root root 16384 Oct 31  2014 lost+found
drwxr-xr-x.  2 root root  4096 Sep 23  2011 media
drwxr-xr-x.  2 root root  4096 Sep 23  2011 mnt
drwxr-xr-x.  3 root root  4096 Oct 31  2014 opt
drwxr-xr-x.  2 root root  4096 Oct 31  2014 proc
dr-xr-x---.  2 root root  4096 Oct 31  2014 root
dr-xr-xr-x.  2 root root 12288 Oct 31  2014 sbin
drwxr-xr-x.  2 root root  4096 Oct 31  2014 selinux
drwxr-xr-x.  2 root root  4096 Sep 23  2011 srv
drwxr-xr-x.  2 root root  4096 Oct 31  2014 sys
drwxrwxrwt.  2 root root  4096 Oct 31  2014 tmp
drwxr-xr-x. 13 root root  4096 Oct 31  2014 usr
drwxr-xr-x. 19 root root  4096 Oct 31  2014 var


Note: we build our ISO using mkisofs.  Is there some other tool/process that we should use to generate ISOs that satisfy virt-builder?  Should I be starting from a Live CD format?

Cheers!


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