Stacked disks
Hello,
I would like to set up stacked disk images as follows:
1) Base-image of Ubuntu, with ubuntu-minimal installed.
2) Multiple other images all based on the single image above, with various single-purpose packages installed; eg Apache, Exim, etc.
Now, comes the hard part:
Q2: What happens if I change the underlying ubuntu-minimal image (For a good example, to apply security updates), while several of the other "upper" images (Apache Exim, etc) are running?
Q1: Easier: If everything is down, can I change the underlying image and will the changes be properly reflected in the "upper" (dependent) images?
I see problems with simply a file-based algorithm which looks first in the upper image, and then in the base image..
It's really a reconciliation problem..
FYI: I was a KVM forum attendee; I'm building a hosting infrastructure based on KVM, and so clearly saving / consolidating space & updates such as in the example above is of keen interest to me.
And Thanks again to the Qumranet team for an informative and successful conference!
Thanks,
Joe
-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/
Quoted 9 lines
Hello,
I would like to set up stacked disk images as follows:
1) Base-image of Ubuntu, with ubuntu-minimal installed.
2) Multiple other images all based on the single image above, with various single-purpose packages installed; eg Apache, Exim, etc.
Quoted 7 lines
Now, comes the hard part:
Q2: What happens if I change the underlying ubuntu-minimal image (For a good example, to apply security updates), while several of the other "upper" images (Apache Exim, etc) are running?
Q1: Easier: If everything is down, can I change the underlying image
and
Quoted 8 lines
will the changes be properly reflected in the "upper" (dependent) images?
I see problems with simply a file-based algorithm which looks first in the upper image, and then in the base image..
It's really a reconciliation problem..
The quick answer:
You can't do that (both 1, 2).
This disks are block devices that represent a physical disk. Doing something
to a block in the base image can erase information that the next image relays on.
Actually it is good practice to chmod a-w BASE_IMG if there are children.
So you shouldn't mess with the base image, you can replicate it and update all of them.
A better answer:
There is unionFS that might help here: All VMs will mount ro the base image while
having another drive for their private applications. UnionFs work in the file level
above and do the merge between the base and private images so basically you can
update the base image once in a while (when unionFS is down/inactive).
Quoted 4 lines
FYI: I was a KVM forum attendee; I'm building a hosting infrastructure based on KVM, and so clearly saving / consolidating space & updates
such
Quoted 8 lines
as in the example above is of keen interest to me.
And Thanks again to the Qumranet team for an informative and successful conference!
Thanks,
Joe
Thanks for the participation and for choosing KVM. We enjoyed the forum too.
-Dor
-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/
Thanks, Dor, we'll plan accordingly, and make the base images read-only.
Cheers,
joe
Quoted 58 lines · Dor Laor
Quoted 9 lines
Hello,
I would like to set up stacked disk images as follows:
1) Base-image of Ubuntu, with ubuntu-minimal installed.
2) Multiple other images all based on the single image above, with various single-purpose packages installed; eg Apache, Exim, etc.
Quoted 7 lines
Now, comes the hard part:
Q2: What happens if I change the underlying ubuntu-minimal image (For a good example, to apply security updates), while several of the other "upper" images (Apache Exim, etc) are running?
Q1: Easier: If everything is down, can I change the underlying image
and
Quoted 8 lines
will the changes be properly reflected in the "upper" (dependent) images?
I see problems with simply a file-based algorithm which looks first in the upper image, and then in the base image..
It's really a reconciliation problem..
The quick answer:
You can't do that (both 1, 2).
This disks are block devices that represent a physical disk. Doing something
to a block in the base image can erase information that the next image relays on.
Actually it is good practice to chmod a-wBASE_IMGif there are children.So you shouldn't mess with the base image, you can replicate it and update all of them.
A better answer:
There is unionFS that might help here: All VMs will mount ro the base image while
having another drive for their private applications. UnionFs work in the file level
above and do the merge between the base and private images so basically you can
update the base image once in a while (when unionFS is down/inactive).Quoted 3 lines
FYI: I was a KVM forum attendee; I'm building a hosting infrastructure based on KVM, and so clearly saving / consolidating space & updates
such
Quoted 6 lines
as in the example above is of keen interest to me.
And Thanks again to the Qumranet team for an informative and successful conference!
Quoted 6 lines
Quoted 2 lines
Thanks,
JoeThanks for the participation and for choosing KVM. We enjoyed the forum too.
-Dor
-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/