Re: [PLUG] Video link: "Virtualizing Bare-Metal Systems with QEMU" and meeting bookmarks

["Keith C. Perry" <kperry@daotechnologies.com>]

Definitely...

Rich actually mentioned nspawn to me before but I haven't had a chance to practice my systemd-fu.

Systemd is complex enough to have talks on smaller components.  So I would +1 for nspawn.

---
KP-

On Oct 12, 2015 5:02 PM, JP Vossen <jp@jpsdomain.org> wrote:
>
> Jumping *way* back to the bind mount stuff, I use them mostly for 
> getting grub to install right, but I was just reading 
> http://www.linux.it/~ema/2015/10/07/systemd-is-your-friend/ today and it 
> has some good systemd stuff on `journalctl` and and `systemd-nspawn` for 
> containers that do all the bind mounts for you. 
>
> We probably need some more presos on systemd; I know I do... 
>
>
> On 10/12/2015 03:45 PM, Keith C. Perry wrote: 
> > Agreed.  QEMU used to have an internal CIFS (samba) type of connectivity 
> > but I seem to recall it when away. 
> > 
> > However, it looks like there is now something called VirtFS 
> > 
> > http://wiki.qemu.org/Documentation/9psetup 
> > 
> > Kinda cool to see Plan 9 mentioned in a production context  :D 
> > 
> > 
> > ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 
> > Keith C. Perry, MS E.E. 
> > Owner, DAO Technologies LLC 
> > (O) +1.215.525.4165 x2033 
> > (M) +1.215.432.5167 
> > www.daotechnologies.com <http://www.daotechnologies.com/> 
> > 
> > ------------------------------------------------------------------------ 
> > *From: *"Rich Mingin (PLUG)" <plug@frags.us> 
> > *To: *"Philadelphia Linux User's Group Discussion List" 
> > <plug@lists.phillylinux.org> 
> > *Sent: *Monday, October 12, 2015 1:21:15 PM 
> > *Subject: *Re: [PLUG] Video link: "Virtualizing Bare-Metal Systems with 
> > QEMU" and meeting bookmarks 
> > 
> > Right, the biggest problem with two systems directly accessing a single 
> > filesystem is concurrency. If you can safeguard against that, it's 
> > sorta-mostly-kinda-safe, but still strongly advised against. 
> > I'm still transitioning to a more strongly FOSS virtualization stack, 
> > but VMware uses a special pseudo-networking mode to share FSes between 
> > hosts and guests. It looks like a network filesystem to guests, so 
> > they're aware of changes, but behind the curtain it acts more like raw 
> > disk access. If Qemu/KVM doesn't have something similar, that might be 
> > worth putting together a gofundme to raise a bounty to get something 
> > like it implemented. 
> > 
> > On Mon, Oct 12, 2015 at 1:17 PM, Keith C. Perry 
> > <kperry@daotechnologies.com <mailto:kperry@daotechnologies.com>> wrote: 
> > 
> >     Yep, that's might I made mention of "raw" disk images.  :) 
> > 
> >     Since I usually keep the system volume separate for my vm (or at 
> >     least when I am building them) I can loop mount the partition then 
> >     do whatever bulk data moves are needed (e.g. move source code for 
> >     later compiling) and then convert back to qcow2. 
> > 
> >     Steve if you're talking about having an on going live share between 
> >     and disk then sshfs or any other networking is the safest but slowest. 
> > 
> >     As previously mentioned, using the virtio devices are generally the 
> >     most efficient as well. 
> > 
> >     Fun fact... sharing a raw disk image between a VM host and guest 
> >     does seem to work (I did that a when I was building some FOSScon usb 
> >     multiboot keys) but I'm not sure its "safe".  You would have to take 
> >     care to make sure you are not making changes to the same files at 
> >     the same time. YMMV 
> > 
> >     --- 
> >     KP- 
> > 
> >     On Oct 12, 2015 12:52 PM, Rich Freeman <r-plug@thefreemanclan.net 
> >     <mailto:r-plug@thefreemanclan.net>> wrote: 
> >     > 
> >     > On Mon, Oct 12, 2015 at 12:09 PM, Steve Litt 
> >     <slitt@troubleshooters.com <mailto:slitt@troubleshooters.com>> wrote: 
> >     > > On Mon, 12 Oct 2015 10:40:56 -0400 (EDT) 
> >     > > "Keith C. Perry" <kperry@daotechnologies.com 
> >     <mailto:kperry@daotechnologies.com>> wrote: 
> >     > > 
> >     > > 
> >     > >> I'm not sure how many people are familiar with how to use "mount 
> >     > >> --bind".  It's one of the things I mentioned that was needed 
> >     for one 
> >     > >> the approaches to virtualizing a system (i.e. reinstalling boot 
> >     > >> information) but was out of scope for the talk. 
> >     > > 
> >     > > Hi Keith, 
> >     > > 
> >     > > If you know of a way to bind mount a Qemu host directory within 
> >     a Qemu 
> >     > > guest, I'd really love to hear it. Right now I'm doing a sshfs to 
> >     > > 10.0.2.2, but as you can imagine, it's slow as molassas. 
> >     > 
> >     > That was what I was getting at with my question around bind mounts. 
> >     > There are ways of mounting filesystems through qemu, but while they 
> >     > might behave like bind mounts, they aren't actually bind mounts. 
> >     > Within the guest you could certainly use bind mounts. 
> >     > 
> >     > Bind-mounting from a host into a container isn't a problem since they 
> >     > share the same kernel.  A VM does not use the same kernel as the host 
> >     > (granted, with paravirtualization it gets a bit more fuzzy but the 
> >     > same principles apply). 
> >     > 
> >     > -- 
> >     > Rich 
>
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