Re: [gentoo-user] virtualbox in headless configuration broken after update: delayed echo [ RESOLVED, kinda ]

["J. Roeleveld" <joost@antarean.org>]

On 17 June 2020 19:01:54 CEST, Michael <confabulate@kintzios.com> wrote:
>On Wednesday, 17 June 2020 07:32:10 BST J. Roeleveld wrote:
>> On Wednesday, June 17, 2020 7:42:30 AM CEST n952162 wrote:
>> > On 06/17/20 06:48, J. Roeleveld wrote:
>> > > On Tuesday, June 16, 2020 11:08:23 PM CEST n952162 wrote:
>> > >> On 06/16/20 22:36, J. Roeleveld wrote:
>> <snipped>
>> 
>> > > I have not come across MS HyperV outside of small businesses that
>need
>> > > some
>> > > local VMs. These companies tend to put all their infrastructure
>with one
>> > > of
>> > > the big cloud-VM providers (Like AWS, Azure, Googles,...)
>> > > 
>> > > --
>> > > Joost
>> > 
>> > Thank you for this excellent survey/summary.  It tells me that vbox
>is
>> > good for my current usages, but I should start exposing myself to
>Xen as
>> > a possible migration path.
>> 
>> I would actually suggest to read up on both Xen and KVM and try both
>on
>> spare machines.
>> See which best fits your requirements and also see if the existing
>> management tools actually do things in a way that you can work with.
>> 
>> My systems have evolved over the past 25-odd years and I started
>using Xen
>> to reduce the amount of physical systems I had running. At the time,
>VMWare
>> was expensive, KVM didn't exist yet and was missing some important
>features
>> for a few years after it appeared (not sure if this exists yet, not
>found
>> anything about it on KVM):
>> - limit memory footprint of host-VM during boot.
>> - Dedicate CPU-core(s) to the host
>> 
>> Limiting the memory size is important, because there are several
>parts of
>> the kernel (and userspace) that base their memory-settings on this
>amount.
>> This is really noticable when the host thinks it has 384GB available
>when
>> 370GB is passed to VMs.
>> 
>> Dedicating CPU-cores exclusively to the host means the host will
>always have
>> CPU-resources available. This is necessary because all the
>> context-switching is handled by the host and if this stalls, the
>whole
>> environment is impacted.
>> 
>> For a lab-system, I was also missing the ability to save the full
>state of a
>> VM for a snapshot. All the howto's and guides I can find online only
>talk
>> about making a snapshot of the disks. Not of the memory as well.
>Especially
>> when used to Virtualbox, you will notice this issue. When only
>snapshotting
>> the disk, your snapshot is basically the state of when you literally
>pulled
>> the plug of your VM if you want to restore back to this.
>> 
>> For KVM, I have found a few hints that this was planned. But I have
>not
>> found anything about this. Virt-manager does not (last time I looked)
>> support Xen's functionality of storing the memory when creating
>snapshots
>> either. Which is why I don't use that even for my lab/testing-server.
>
>As far as I know QEMU with KVM can take snapshots of the current state
>of RAM, 
>disk(s), CPU - it can take snapshots of images while online.
>
>https://wiki.qemu.org/Features/Snapshots2

Can you point to where in the commands above the memory anf cpu state is actually stored and loaded back when reverting to the snapshot?
From what I see, it is only fhe disk image.
I really need this feature for lab environments where I need the ability to fully roll back to a running instance.


>However, I've only taken snapshots of qcow2 images after I shut down
>the VM.  
>These work as advertised and they are quite handy before major updates/
>upgrades as temporary backups.
>
>
>> As for tips/tricks (below works for Xen, but should also work with
>KVM):
>> 
>> The way I create a new Gentoo-VM is simply to create a new
>block-device
>> (Either LVM or ZFS), do all the initial steps in the chroot from the
>host
>> and when it comes to the first-reboot, umount the filesystems, hook
>it up
>> to a new VM and start that.
>> 
>> Because of this, I can update the host as follows:
>> - create new "partitions" for the host-system.
>> - Install the latest versions, migrate the config across
>> - reboot into the new host.
>> 
>> If all goes fine, I can clean up the "old" partitions and prepare
>them for
>> next time. If there are issues, I have a working "old" version I can
>quickly
>> revert to.
>> 
>> --
>> Joost
>
>I've wanted to migrate a qemu qcow2 image file or two of different OS',
>all 
>currently stored on an ext4 partition on my desktop, to a dedicated
>partition 
>on the disk.  Would this be possible - how?  Would I need to change the
>qcow2 
>to a raw image?

I don't know. One of the reasons I dislike file based images is the lack of transparency and tools. LVM is much simpler for disk based snapshots and management.

--
Joost



-- 
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