[one-users] putting OS images in the image repository

[Carlos Martín Sánchez]

Hi Steven,

This is an interesting use-case. When we designed the image repository, we
had to make a compromise between "expectable behaviour" and "advanced
customization usage". I guess this falls into the advanced usage, but
OpenNebula is flexible enough to take this challenge.


To automatically save all VM disks that use a certain Image, you can use
hooks.

I would add a new flag to all the relevant images in your system, either
having them in the image template, or adding them afterwards [1]:
oneimage addattr <image_id> AUTO_SAVE YES

This will add the flag to the template:

$ oneimage show 1
IMAGE  INFORMATION

[...]

IMAGE TEMPLATE

*AUTO_SAVE=YES*
DEV_PREFIX=hd
NAME=test_image
PATH=/home/cmartin/trabajo/scratch/steven/disk.img
TYPE=OS

To add a new hook to the system, edit $ONE_LOCATION/etc/oned.conf [2] and
add something similar to the following:

VM_HOOK = [
    name      = "auto_save",
    on        = "CREATE",
    command   = "auto_save.rb",
    arguments = "$VMID" ]

This will execute a new script, placed in
$ONE_LOCATION/share/hooks/auto_save.rb, every time a new VM is created.
I suggest you to use ruby, because the ruby OCA API [3] will make it easier.

This script will have to:
1) Get the complete information for VM <vm_id> from OpenNebula.
2) For each disk, check if it is using an Image.
2.1) Get that image's information, and look for the AUTO_SAVE=YES attribute.
If it's present, then issue a onevm saveas operation over that <vm-id> and
<disk-id>.

To be able to identify the disks later, you could include in the new image
name the  <vm-id>_<disk-id> string.


This way, files will be all managed by OpenNebula in the repository. If you
are doing this for back-up purposes, and you won't actually instantiate a VM
using this saved images, you can always move that files away from the
repository and then delete the images.


This is the easiest and "elegant" way I see to do this, but any
other opinions are welcome.

I'd also like to ask the community if more people feel this should be
supported out of the box by OpenNebula. If so, we could start a discussion
to determine the specific features or requirements this would imply.


Best regards,
Carlos.

[1] http://opennebula.org/doc/2.0/cli/oneimage.html
[2] http://opennebula.org/documentation:rel2.0:oned_conf#hook_system
[3] http://opennebula.org/documentation:rel2.0:ruby

Carlos Martín, Cloud Technology Engineer/Researcher
DSA Research Group: web http://dsa-research.org and blog
http://blog.dsa-research.org
OpenNebula Open Source Toolkit for Cloud Computing:
http://www.OpenNebula.org


On 30 November 2010 21:56, Steven Timm <timm at fnal.gov> wrote:

>
> In
> http://www.opennebula.org/documentation:rel2.0:img_guide
>
> it says
>
> "When images are published they are always cloned, and persistent images
> are never cloned. Therefore, an image cannot be public and persistent at the
> same time. To manage a public image that won't be cloned, unpublish it first
> and make it persistent. "
>
> I have stored a 10GB OS image in the repository
> and made it public
>
> -bash-3.2$ oneimage show 8
> IMAGE  INFORMATION
> ID             : 8
> NAME           : new-2.6.18-194.26.1.img
> TYPE           : OS
> REGISTER TIME  : 11/29 14:15:13
> PUBLIC         : Yes
> PERSISTENT     : No
> SOURCE         :
> /var/lib/one/image-repo/920301ec2fcc29f9c621c3ebe2a8f5ac6b27fca6
> STATE          : used
> RUNNING_VMS    : 2
>
> IMAGE TEMPLATE
> DEV_PREFIX=vd
> NAME=new-2.6.18-194.26.1.img
> -bash-3.2$
>
>
> I would like to have this available as a template image for
> many users to be able to use.
> I have successfully been able to have 2 users
> use it as part of a VM with the following syntax
>
> DISK   = [ image = "new-2.6.18-194.26.1.img" ]
>
>
> However, I find that this automatically implies a
> SAVE=NO once the VM is launched, with no way to override it.
> From output of onevm show:
>
> DISK=[
>  CLONE=YES,
>  DISK_ID=0,
>  IMAGE=new-2.6.18-194.26.1.img,
>  IMAGE_ID=8,
>  READONLY=NO,
>  SAVE=NO,
>  SOURCE=/var/lib/one/image-repo/920301ec2fcc29f9c621c3ebe2a8f5ac6b27fca6,
>  TARGET=vda,
>  TYPE=DISK ]
>
>
> -----------------------------------------
>
> So is there any way to do the following:
>
> 1) have the VM registered in the repository for all to see
> 2) be launched public and cloned on launch so it can be used
>   in multiple VM's at once
> 3) have the result be saved in an image-specific file when
>   each VM is shut down, and not back to the repository?
>
> ***I know that if I execute the onevm saveas command I can
> get this done on a machine-by-machine basis but would
> prefer a way to make it automatic.
> ---------------------------------------------------------
>
> The second question is closely related, namely:
> Once a public image is declared in the database, is there any way
> to actually update the content of that image, such that for instance
> Name = "latest kernel template image"
>
> could be periodically updated with the latest kernel
> and all new VM's would pick it up?
>
>
> Thanks
>
> Steve Timm
>
> ------------------------------------------------------------------
> Steven C. Timm, Ph.D  (630) 840-8525
> timm at fnal.gov  http://home.fnal.gov/~timm/
> Fermilab Computing Division, Scientific Computing Facilities,
> Grid Facilities Department, FermiGrid Services Group, Assistant Group
> Leader.
> _______________________________________________
> Users mailing list
> Users at lists.opennebula.org
> http://lists.opennebula.org/listinfo.cgi/users-opennebula.org
>
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