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

Fri Dec 11 17:02:21 UTC 2015

Perhaps an example will clarify.  Let's say that I want to create a virt-builder repository image for CentOS-6.5-x86_64-bin-DVA1.iso image that I downloaded off of a CentOS mirror.

1) First, let's mount the ISO to see what's inside

# mkdir /mnt/centos-6.5
# mount -o loop CentOS-6.5-x86_64-bin-DVD1.iso /mnt/centos-6.5
# cd /mnt/centos-6.5
# ls -l

-r--r--r-- 2 root root     14 Nov 29  2013 CentOS_BuildTag
dr-xr-xr-x 3 root root   2048 Nov 29  2013 EFI
-r--r--r-- 2 root root    212 Nov 27  2013 EULA
-r--r--r-- 2 root root  18009 Nov 27  2013 GPL
dr-xr-xr-x 3 root root   2048 Nov 29  2013 images
dr-xr-xr-x 2 root root   2048 Nov 29  2013 isolinux
dr-xr-xr-x 2 root root 655360 Nov 29  2013 Packages
-r--r--r-- 2 root root   1354 Nov 27  2013 RELEASE-NOTES-en-US.html
dr-xr-xr-x 2 root root   4096 Nov 29  2013 repodata
-r--r--r-- 2 root root   1706 Nov 27  2013 RPM-GPG-KEY-CentOS-6
-r--r--r-- 2 root root   1730 Nov 27  2013 RPM-GPG-KEY-CentOS-Debug-6
-r--r--r-- 2 root root   1730 Nov 27  2013 RPM-GPG-KEY-CentOS-Security-6
-r--r--r-- 2 root root   1734 Nov 27  2013 RPM-GPG-KEY-CentOS-Testing-6
-r--r--r-- 1 root root   3380 Nov 29  2013 TRANS.TBL

(Note: it's an install image like the one I've been trying to use)

2) Now following your instructions (https://rwmj.wordpress.com/2014/09/11/creating-a-local-virt-builder-repository/)
I'll move the iso to my ~/builder directory,  compress it and add an entry in my index file.

# // unmount the iso and move to builder directory
# umount /mnt/centos-6.5
# mv CentOS-6.5-x86_64-bin-DVD1.iso builder
# cd builder

# // get the original size of the iso
# ls -l CentOS-6.5-x86_64-bin-DVD1.iso
-rwxr--r-- 1 root root 4467982336 Dec 11 11:04 CentOS-6.5-x86_64-bin-DVD1.iso

# // compress it using prescribed settings
# xz --best --block-size=16777216 CentOS-6.5-x86_64-bin-DVD1.iso

# // get the size of the compressed image
# ls -l
-rwxr--r-- 1 root root 4287626520 Dec 11 11:04 CentOS-6.5-x86_64-bin-DVD1.iso.xz

# // create a sha512 checksum
# sha512sum CentOS-6.5-x86_64-bin-DVD1.iso.xz
ea57956dc36afc497e2508d8e5bda983b87c11007301d1d11936281ed3eb5fdff46fe125df8941df56a5f22866218d18fd426017a7adf032d90defc8e20b2ace  CentOS-6.5-x86_64-bin-DVD1.iso.xz

# // update the index file (steps omitted)
# // show the contents of the index file
# cat index
[centos-6.5]
name=centos-6.5
arch=x86_64
file=CentOS-6.5-x86_64-bin-DVD1.iso.xz
checksum[sha512]=ea57956dc36afc497e2508d8e5bda983b87c11007301d1d11936281ed3eb5fdff46fe125df8941df56a5f22866218d18fd426017a7adf032d90defc8e20b2ace
format=raw
size=4467982336
compressed_size=4287626520
expand=/dev/sda3
notes=CentOS-6.5

# // see if virt-builder lists the new image
# virt-builder --list|grep centos
gpg: Signature made Sat 05 Dec 2015 06:41:14 PM EST using RSA key ID E1B768A0
gpg: Good signature from "Richard W.M. Jones <rjones at redhat.com>"
gpg:                 aka "Richard W.M. Jones <rich at annexia.org>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: F777 4FB1 AD07 4A7E 8C87  67EA 9173 8F73 E1B7 68A0
centos-6.5               x86_64     centos-6.5
centos-6                 x86_64     CentOS 6.6
centos-7.0               x86_64     CentOS 7.0
centos-7.1               x86_64     CentOS 7.1

3) Notice that centos-6.5 appears in list.  Let's try and create a 6.5 image

# virt-builder --password-crypto sha512 centos-6.5
gpg: Signature made Sat 05 Dec 2015 06:41:14 PM EST using RSA key ID E1B768A0
gpg: Good signature from "Richard W.M. Jones <rjones at redhat.com>"
gpg:                 aka "Richard W.M. Jones <rich at annexia.org>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: F777 4FB1 AD07 4A7E 8C87  67EA 9173 8F73 E1B7 68A0
[   6.0] Downloading: file:///root/builder/CentOS-6.5-x86_64-bin-DVD1.iso.xz
[  19.0] Planning how to build this image
[  19.0] Uncompressing
[  23.0] Opening the new disk
[  25.0] Setting a random seed
virt-builder: warning: random seed could not be set for this type of guest
[  25.0] Setting passwords
virt-builder: error: libguestfs error: mktemp: /etc/shadow.guestfstcTloo:
No such file or directory

If reporting bugs, run virt-builder with debugging enabled and include the
complete output:

  virt-builder -v -x [...]

Notice the " error: libguestfs error: mktemp: /etc/shadow.guestfstcTloo" error.

The issue is that virt-builder expects the ISO image to contain an /etc directory.  This image does not.  It's a stock CentOS-6.5 installer image downloaded from CentOS.

So the question is what do I have to do to create an ISO image that virt-builder can use?  The images that are present in the virt-builder libguestfs.conf file (fetching from http://libguestfs.org/download/builder/index.asc), how are THOSE images built?

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