Messages in this thread | | | Date | Wed, 24 Aug 2011 12:33:14 +0300 | From | Avi Kivity <> | Subject | Re: linux next: Native Linux KVM tool inclusion request |
| |
On 08/24/2011 12:19 PM, Pekka Enberg wrote: > On 8/24/11 11:31 AM, Avi Kivity wrote: >> On 08/23/2011 08:08 AM, Pekka Enberg wrote: >>> As for changes, we've implemented rootfs over 9p with "kvm run" >>> booting to host filesystem "/bin/sh" by default. >> >> Isn't this dangerous? Users expect virtualization to land them in >> sandbox, but here an rm -rf / in the guest will happily junk the host >> filesystem. > > Not really because I never run the tool as root. However, you're right > that > we should not default to /bin/sh if you're root.
Well, just trashing /home/penberg would be bad too, no? (my recent experience indicates it's not that catastrophic - anything important sits on a server somewhere and the local data is just a cache).
>> >> Still dangerous (but just to the guest), since it's not a true >> snapshot. If the host filesystem changes underneath the guest, it >> will see partial and incoherent updates. Copy-on-write only works if >> the host filesystem doesn't change. > > That's a generic problem with overlayfs based solutions, isn't it? > We're planning > to use copy-on-write only on files that aren't supposed to change that > often - > like /usr and /lib.
So the guest won't see bad data that often?
Overlay works fine if the host tree is readonly. So if you have a separate tree for guests, you can share it with any number of them. Just don't share the host root.
Note this probably isn't a problem booting to /bin/bash, just booting a full-featured guest with package management and other database-like apps that expect exclusive control over their data.
> I suppose we should force shared files to be read-only in > the guest. >
Yes, that's safer.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
| |