<p dir="ltr">Did not mean to take it offline. </p>
<div class="gmail_quote">On Jan 31, 2015 11:21 AM, "Michael B. Trausch" <<a href="mailto:mike@trausch.us">mike@trausch.us</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div>On 01/31/2015 09:38 AM, Jim Kinney
wrote:<br>
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<p dir="ltr">Containers as in docker/containers or something else?</p>
<div class="gmail_quote">On Jan 31, 2015 9:37 AM, "Michael
Trausch" <<a href="mailto:mike@trausch.us" target="_blank">mike@trausch.us</a>> wrote:<br type="attribution">
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<div>I just use QCOW2 containers. When things get borked,
it's very easy and efficient to restore. :)</div>
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<br>
(BTW - did you mean to take this off-list?)<br>
<br>
QCOW2 is a container file format for virtual block devices, allowing
snapshots, etc.<br>
<br>
A couple months back I had to do a complex staged install of a
system that I didn't have good accessibility for. So I used QEMU to
install the OS, staged on two QCOW2 HDDs and then I took the QCOW2
images and wrote a small statically-linked utility to write them
from a special-purpose initramfs.<br>
<br>
It turns out, QCOW2 makes for a <b>VERY</b> convenient format for
block image backup in its own right, without the use of VM
software. Added bonus is that it can be dumped straignt into a VM
in order to do testing/debugging on it.<br>
<br>
Restoration from a saved QCOW2 image is very simple: load the L1
table, load the L2 tables, walk them to find the actual used
clusters, and read the stored clusters and write them to the correct
location on the target device. Going the other way is pretty
simple, too: Read clusters from HDD, if they aren't all-zeroes,
write them to the QCOW2 image.<br>
<br>
It's also a great, simple format for using to work around Windows
brain-deadness. For example: working with common Rπ SD images from
Windows when actually on an SD card? Impossible. (Well, not
completely. Just impossible in the default configuration of a
Windows system.)<br>
<br>
So I'm talking about a very low-level use of QCOW2, for a purpose
other than its intended, albeit one for which it serves quite
nicely.<br>
<br>
— Mike<br>
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