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I know that qcow2 is a file format for disk image files used by QEMU but I found that CentOS provides some cloud images in the qcow2c format (with a c at the end) here.

I assume it's a compressed version of the qcow2 but I didn't find any information related to it on the QEMU documentation or in OpenStack documentation (note that the qcow2c is accepted when uploading an image in OpenStack).

I would like to have some documentation on the qcow2c format and to know how to do a conversion between the qcow2 and the qcow2c formats. The idea is to start from a qcow2 image, do some tweaking on this image using the virt-sysprep utility and then convert it into the qcow2c to save disk space.

Rbsamoht
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1 Answers1

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According to this mailing list thread from 2014:

File: CentOS-7-x86_64-GenericCloud-20141129_01.qcow2c

Desc: This is the same image, run through the qemu qcow2 internal compression setup - while this image is suiteable [sic] for development and play, it comes with non trivial i/o performance penalties and therefore not recommended for production.

This is not any kind of standard format rather a CentOS convention.

The documentation is open source, I believe the downloads page would be the appropriate place to add the documentation as it describes the other downloads to some extent. The wiki is open for everyone to edit!

Community
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qubitrenegade
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