Re: Access to GPT and partitions within a VND image

[mlelstv%serpens.de@localhost (Michael van Elst)]

mp%petermann-it.de@localhost (Matthias Petermann) writes:

>I am using file-backed vnds as storage for my Xen domains. In each of 
>the vnds there is a GPT with the corresponding partitions.
>Is there an easy way to access the GPT and the partitions from outside, 

If they are vnds these are already existing on the outside and create
wedges (dk devices) on attachment. In a user domain, they appear as
e.g. xbd devices.

If you write the GPT from a DomU, the host doesn't know about it
immediately. You can use dkctl makewedges to trigger autodiscovery,
re-attach the vnd devices or reboot.


>i.e. preferably from the host to the image file? I would like to 
>implement a kind of thin-provisioning, where I copy a base image as a 
>sparse file over and over again, and then change a few small things in 
>it before the first start of the domain - like the fixed IP address.

Not exactly sparse, each domain has its own image.

N.B. there are caveats when the backing store uses and exposes
large sectors (not the common 512e case).

-- 
-- 
                                Michael van Elst
Internet: mlelstv%serpens.de@localhost
                                "A potential Snark may lurk in every tree."