[CentOS-devel] Release for Atomic Host Feb 2015 rolling builds

Gianluca Cecchi

gianluca.cecchi at gmail.com
Tue Mar 10 09:50:09 UTC 2015

On Tue, Mar 10, 2015 at 9:57 AM, Karanbir Singh <mail-lists at karan.org>

> On 09/03/15 19:55, Gianluca Cecchi wrote:
> > the web links of the two images referred above seem not valid any more...
> > Was there any problem with them?
> yes :( those images have a problem with cloud-init. I've since resolved
> the issue and pushed new images, you can find them with sha256's :
> b08bad32dd68553750822ef9b769cd634aac1d0fd65f27c7d32257b47a6596b3
> CentOS-7-x86_64-AtomicHost-20150228_01.qcow2

The new images are quite better, indeed ;-)
I downloads the xz one and then
unxz < CentOS-7-x86_64-AtomicHost.qcow2.xz | dd
of=CentOS-7-x86_64-AtomicHost.qcow2 bs=1024k

>From man page of unxz, it should manage sparse files automatically, but I
noticed with the other image that simply making unxz the uncompressed image
didn't match the sha256sum of the original one given on the web site.

> > Do I have to pass any kernel command line when I start in virt-manager?
> > I also found this "old" link to create the seed image:
> >
> https://rwmj.wordpress.com/2013/12/10/creating-a-cloud-init-config-disk-for-non-cloud-boots/
> Couple of things to keep in mind, the cloud-init iso's volume id needs
> to be 'cidata' and the user-data + meta-data files need to be in the
> root of that iso. This is the geniofs line that I use :
> genisoimage -output configdrive.iso -volid cidata -joliet -rock
> user-data meta-data

OK. The volid suggested matches the one I found in the docs.
And now it works. I see cloud-init phase in console, that I didn't see at
all before, and the hostname of the system is indeed updated.
I can connect without password from my system using the ssh key I generated.
BTW: is it a limitation to use rsa keys or one can use dsa keys too?
To verify that also the password passed through user-data is correctly
gotten, I connect from inside the vm to itself via ssh with the centos user
and using the password it works. And also directly using centos user in
console it works

> then just attach that to the machine instance as a CD drive and it
> should just work from there.
> I've also had problems with instance setup, if I was using an image that
> had already been setup - so I tend to not use the downloaded file, I
> create a qemu snapshot of the qcow2 file and then consume that instead.
> This allows me to go back and refresh my image anytime without needing
> to re-download the image. Something like this should work :
> qemu-img create -f qcow2 -b CentOS-7-x86_64-AtomicHost-20150228_01.qcow2
> myatomic_snap-01.qcow2
> then just use the myatomic_snap-01.qcow2 as your new image ( you can
> check this is a snapshot by qemu-img info myatomic_snap-01.qcow2 )
Thanks for the tip
I also found that for further boots you have to regenerate the iso with a
new instance-id in meta-data.
And I verified it works.
In new iso I put different passowrd for centos user and different hostname
(and differenti instance-id of course).
And after shutdown and connect of new iso, it starts without any problem
with new hostname and password for centos user.
The previous ssh key continues to work (I'm not asked for the key
confirmation, as it is already there inside my known_hosts file.

> > but the virt-builder command is not able to extract kernel and initrd
> > image from the qcow2 image.
> I am not sure if virt-builder can parse an ostree payload, i suspect its
> looking for a generic filesystem inside the image. You might want to
> validate this with the virt-tools list.
I confirm that virt-builder fails with this image too, so I will redirect
question/clarification to virt-tools as you suggested, even if it not
strictly necessary now that the iso method works ok.

Thanks and keep on with the great work!
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