Freeze VM?

[glockmane]

Hey guys,

 

I want to create a Windows 10 VM for executing untrusted executables, therefore I want it to be clean on every boot.. Is this possible?

 

Best Regards

Stefan

[JorgeB]

Yes but not automatically, you use a script though, make a copy of the vdisk when the VM is shutdown in the state you want, then just copy back overwriting existing one before VM start, if using btrfs you can do this with reflinks so copy takes a couple of seconds and also it will use much less space, only the differences between them.

[glockmane]

So basically I install OS and everything I want, make a copy of the vdisk once and copy back this backup everytime before vm starts?

 

Maybe I should consider using btrfs, but I'm a bit unsure if there are drawbacks..

[JorgeB]

9 minutes ago, glockmane said:

So basically I install OS and everything I want, make a copy of the vdisk once and copy back this backup everytime before vm starts?

Yep.

 

Btrfs can be more finicky, especially with hardware issues, xfs is supposed to support reflinking in the near future, maybe it already does, not sure since I don't keep up with xfs development.

[glockmane]

51 minutes ago, johnnie.black said:

[...] if using btrfs you can do this with reflinks so copy takes a couple of seconds and also it will use much less space, only the differences between them.

Does this mean I have to do something else to use the reflink feature? If I understand correctly filesystem does everything by itself, so if I copy a file reflink will automatically be used and if it gets modified only changed blocks will be written?

 

According to this thread (second last post) reflinking is enabled with xfs by default with the newer Unraid releases.. So I guess I should stay with xfs for the moment..

 

https://forums.unraid.net/bug-reports/prereleases/unable-to-format-new-drives-system-locks-up-rc5-r732/page/2/

 

(you also replied there ;))

[JorgeB]

I know they were doing the work for xfs to support reflinking, not sure if it's already working, easy to try though, just copy a large file/vdisk, if the copy is instantaneous and no extra space is used it's already working.

 

cp --reflink=always /path/to/souce /path/to/dest

 

Note: filesystem needs to have been recently created, with Unraid 6.8.x