[clug] I need help with KVM vitualization [SOLVED]

Brenton Ross rossb at fwi.net.au
Tue Jul 21 04:38:53 UTC 2020 

When shutting down the host I usually manually shut down the VMs first.
This ensures that things get shut down in the correct order, servers
after their clients.

I have observed that shutting down the host will automatically shut
down to VMs. However, it can cause a rather long pause in the shut down
process, so I try to avoid that.

As for a crash out - I think it is pretty much the same for all VMs and
the host - they might be able to recover, or not.

On the subject of suspend/hibernate:
My system uses a lot of NFS between the VMs and I discovered that
simply freezing the VMs was a bad idea as they would have the wrong
time when they restarted and communications would fail.

However, I inadvertently hit suspend on the Ubuntu host one day. On
resuming I was surprised to find that my NFS server and a client both
resumed OK. Sadly the client I was using most at the time did not fair
so well. At that point I was not very confident about the state of
things so I rebooted all the VMs. 

Brenton 

On Mon, 2020-07-20 at 14:38 +1000, Eyal Lebedinsky via linux wrote:
> On 2020-07-19 21:48, Eyal Lebedinsky via linux wrote:
> > On 2020-07-19 21:07, Michael Still via linux wrote:
> > > https://moozing.wordpress.com/2015/06/24/converting-a-physical-machine-to-a-virtual-machine/
> > > 
> > > This looks like a reasonable guide to me.
> > 
> > Yes, it reads well.
> 
> Good progress was made.
> 
> Booting fedora live iso works, and I then can mount my system and see
> it is OK.
> 
> Booting my image hangs after a short time. No messages seen in
> /var/log.
> I rebuilt initramfs with added virtio_blk and it continued further
> but not enough.
> 
> At this point I wanted to capture the console log. I created a second
> serial device with
> a device type 'file'. Now the system booted all the way! Turns out
> the kernel argument
> 'serial=tty0' needed to change to 'console=tty1'. Go figure.
> 
> All in all, it was a straight forward process.
> 
> I removed more kernel boot command line options that were required
> for the old mobo.
> Also needed to adjust some permissions on the host (exports, ssh and
> such) to allow
> the bridge. I will probably find more, hiding in some dark corners.
> 
> Finally I learnt the hard way how to leave full screen view.
> 
> I found out that hibernate does not work (or maybe it is VERY slow,
> it said 20% and went
> quiet for at least 10 minutes). Should I use a qemu feature (I see
> 'pause' and 'shutdown/save')?
> I think 'save' is the persistent equivalent to linux 'hibernate'.
> 
> What do people do to ensure that when the host shuts down the guests
> are safe?
> How resilient is libvirt after a cold crash?
> 
> cheers,
> 	Eyal
> 
> > Initially I think that I need to create a storage pool on a large
> > partition,
> > there is not enough room on /. I may actually modify 'default' to
> > the new location.
> > 
> > BTW, I have stray items left from the first failure, like
> > 
> > $ sudo virsh pool-list
> >   Name      State    Autostart
> > -------------------------------
> >   default   active   yes
> >   eyal      active   yes
> > 
> > and 'eyal' is actually my home directory.
> > 
> > If I do
> >      $ sudo virsh pool-destroy eyal
> > will the pool be gone but the data remain untouched? The man page
> > says so.
> > 
> > I also see
> > 
> > $ sudo virsh list --all
> >   Id   Name       State
> > ---------------------------
> >   -    fedora32   shut off
> > 
> > But there is no image file anywhere. All I can find is
> > 
> > $ sudo ls -l `sudo find /var/lib/libvirt/ -name '*fedora32*'`
> > /var/lib/libvirt/qemu/channel/target/domain-3-fedora32:
> > total 0
> > srwxrwxr-x 1 qemu qemu 0 Jul 18 23:38 org.qemu.guest_agent.0
> > 
> > /var/lib/libvirt/qemu/domain-3-fedora32:
> > total 8
> > -rw------- 1 qemu qemu 32 Jul 18 23:38 master-key.aes
> > srwxrwxr-x 1 root root  0 Jul 18 23:38 monitor.sock
> > 
> > I expect I can safely 'delete' it in virt-manager? This is the only
> > vm listed there.
> > 
> > I can see related files under /etc/libvirt/ describing the above
> > resources.
> > 
> > > Michael
> > 
> > Thanks,
> >      Eyal
> > 
> > > On Sun, 19 Jul 2020, 8:02 pm Eyal Lebedinsky via linux, <
> > > linux at lists.samba.org> wrote:
> > > 
> > > > On 2020-07-19 19:29, Michael Still via linux wrote:
> > > > > KVM is a totally cromulent tool to do this sort of thing, but
> > > > > you'd have
> > > > 
> > > > a
> > > > > better experience if you were using libvirt or a libvirt
> > > > > wrapper
> > > > > (virt-manager, a hobby project from a burnt out cloud
> > > > > engineer, that sort
> > > > > of thing).
> > > > 
> > > > I am not even clear about how kvm, qemu and libvirt relate to
> > > > each other.
> > > > Hence my search for a good doco.
> > > > 
> > > > > What you describe should just work.
> > > > 
> > > > "should"...
> > > > 
> > > > I did use virt-manager in this case. I pointed it at the vdi
> > > > file and let
> > > > it boot.
> > > > It then failed etc.
> > > > 
> > > > My plan now is this:
> > > > - start virt-manager, tell it the disk size I want, memory,
> > > > CPUS... boot a
> > > > clonezilla iso.
> > > > then:
> > > > - clone from the original machine to this empty disk.
> > > > or:
> > > > - create an ext4 partition. Mount it.
> > > > - rsync the content of the original machine into this partition
> > > > - probably fix fstab and install grub
> > > > 
> > > > > Michael
> > > > > 
> > > > > On Sun, 19 Jul 2020, 4:51 pm Eyal Lebedinsky via linux, <
> > > > > linux at lists.samba.org> wrote:
> > > > > 
> > > > > > The first thing I need is a pointer at a good doco that
> > > > > > explains what
> > > > > > linux kvm is and how to import
> > > > > > a physical machine into the virtual domain.
> > > > > > 
> > > > > > I dd'ed the root disk (/dev/sda) to a file on a local disk
> > > > > > of the
> > > > 
> > > > machine
> > > > > > that will be the VM host.
> > > > > > I searched for instructions and found most are missing what
> > > > > > I consider
> > > > > > essential detail, like where
> > > > > > exactly I should run each step etc. Others have a more
> > > > > > complicated setup
> > > > > > (lvm and what not).
> > > > > > 
> > > > > > My main worry is that I tried it once, used the GUI tool
> > > > > > (virt-manager)
> > > > > > and pointed it at a disk
> > > > > > image (from a VirtualBox I had lying around). It started
> > > > > > booting
> > > > 
> > > > (offered
> > > > > > the grub selection)
> > > > > > then showed a screen with three dots and gone quiet. After
> > > > > > a few
> > > > 
> > > > minutes I
> > > > > > got an error message
> > > > > > and a dracut prompt.
> > > > > > 
> > > > > > Not knowing how to proceed I decided to just abandon this
> > > > > > vm. I issued
> > > > > > 'halt' inside the small
> > > > > > console window and it did it.
> > > > > > It also shut down the host machine (and probably every
> > > > > > other linux
> > > > 
> > > > machine
> > > > > > in Australia - I
> > > > > > could not tell).
> > > > > > 
> > > > > > I was surprised that a virtual tool can do this to the
> > > > > > host, having used
> > > > > > Vmware and VirtualBox
> > > > > > where there is a clear fence around the VM world.
> > > > > > 
> > > > > > So much fun, but I probably need to educate myself better
> > > > > > about what KVM
> > > > > > really is.
> > > > > > 
> > > > > > My need is simple:
> > > > > >      - I have an image (dd) of the disk from a physical
> > > > > > machine. I want
> > > > 
> > > > to
> > > > > > run it as a virtual
> > > > > >        machine on another host. How do I import the image?
> > > > > >      - Is kvm the correct tool for this? Should I go back
> > > > > > to using
> > > > > > VirtualBox?
> > > > > > 
> > > > > > TIA
> > > > > > 
> > > > > > -- 
> > > > > > Eyal at Home (eyal at eyal.emu.id.au)
> > > > > > 
> > > > > > -- 
> > > > > > linux mailing list
> > > > > > linux at lists.samba.org
> > > > > > https://lists.samba.org/mailman/listinfo/linux
> > > > > > 
> > > > 
> > > > 
> > > > -- 
> > > > Eyal at Home (eyal at eyal.emu.id.au)
> > > > 
> > > > -- 
> > > > linux mailing list
> > > > linux at lists.samba.org
> > > > https://lists.samba.org/mailman/listinfo/linux
> > > > 
> > 
> > 
> 
> 
> -- 
> Eyal at Home (eyal at eyal.emu.id.au)
>

More information about the linux mailing list