qcow and updates
This question came out of a discussion of nesting (or stringing if you like) disk images using qcow.
If I have an unpatched install image, say CentOS-5.2 (box "A" below). and I make a copy of that with qcow and apply patches to that copy (box "B" below), everything is just fine. But if I should make a working qcow image from the patched version (box "C" below), which works fine initially, what would happen if I applied patches to the "current" version? I assume that would mess up the application version, since it's a physical copy, but I'd like to be sure.
______________
| [A] |
| orig release |
|______________|
||
{qcow copy|
||
____________________
| [B] |
| patched to current |
|____________________|
||
{qcow copy}
||
_________________________
| [C] |
| fully config. app. svr. |
|_________________________|I could play with union filesystem, network mounting of /var and /usr, and other tricks, but I thought I'd check that this really is a problem, and the current version needs a "real" copy to the app server, and then the app server needs to be patched after that.
Signature · 3 lines
Bill Davidsen <[email protected]> "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot
Quoted 23 lines · Bill Davidsen
This question came out of a discussion of nesting (or stringing if you like) disk images using qcow.
If I have an unpatched install image, say CentOS-5.2 (box "A" below). and I make a copy of that with qcow and apply patches to that copy (box "B" below), everything is just fine. But if I should make a working qcow image from the patched version (box "C" below), which works fine initially, what would happen if I applied patches to the "current" version? I assume that would mess up the application version, since it's a physical copy, but I'd like to be sure.
______________ | [A] | | orig release | |______________| || {qcow copy| || ____________________ | [B] | | patched to current | |____________________| || {qcow copy} || _________________________ | [C] | | fully config. app. svr. | |_________________________|
Quoted 2 lines
I could play with union filesystem, network mounting of /var and /usr, and other tricks, but I thought I'd check that this really is a problem, and the current version needs a "real" copy to the app server, and then the app server needs to be patched after that.
Changing anything except the last image in the chain is liable to break. In other words: once you use an image as a base for another image, this first image must never change.
Signature · 1 line
Do not meddle in the internals of kernels, for they are subtle and quick to panic.