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

[JP Vossen <jp@jpsdomain.org>]

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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