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Re: [LUG] Linux Training


On 13/02/17 21:20, M. J. Everitt via list wrote:

> What's your experience of Docker like - I'm using KVM in a couple of
> places without issue, friends using Xen, but for my Gentoo tasks, I was
> thinking of knocking up a couple of Containers with a stage3 for testing ...

You beat me to it actually! Virtualization has charged ahead so rapidly
there's a bewildering amount of choice now and the field is constantly
changing as well. KVM tends to be the non-dedicated workstation/server
RPM flavoured version favoured by RedHat and SUSE particularly although
it will work perfectly well on any Linux (and Solaris descendants and
sort-of BSD), usually in a combination version *with* Qemu. Qemu itself
is almost like full virtualization - including even running different
hardware platforms like MIPS or RISC on x64 - from before normal
virtualization existed outside of mainframe land. It's still very much
alive and going strong, including on Windows:


Xen also runs on pretty much any Linux but is normally segregated off
into "proper big boy tools" land, particularly in the guise of XenServer
which is usually positioned as the FLOSS equivalent of VMWares ESX
product line. Normally a Xen box is a dedicated, powerful VM-host only
system, often in a cluster as opposed to a workstation where you just
want to spin something up for testing.

ESX is by far the most mature and powerful non-mainframe virtualization
platform but ouch, those licensing fees! XenServer will do 95% of it for
a fraction of the cost but if the beancounters are prepared to seriously
cough up for business infrastructure that's where most of the serious VM
stuff has been happening for a decade and counting now... until
Microsoft had to stick their oar in of course. Their homegrown virt
platform Hyper-V was the laughing stock of the industry until they did
their usual thing of throwing money and resources at it (fun fact:
Microsoft is one of the largest contributors of code to the Linux
kernel, mostly due to their Hyper-V extensions) and suddenly at some
point it stopped being crap, to everyone's surprise. Now it's no longer
a case of Microsoft being the thing you want to virtualize on a proper
(Linux) host but can legitimately now serve as the platform you
virtualize Linux on. Weird, but a life saver for MS-centric shops who
can't afford ESX and don't want to figure out how to admin Linux based
hypervisors. Even comes standard as an optional install on all >home
editions of Windows 10 where I can only describe it as annoyingly

This is mostly in reply to your other post, but specifically as regards
to Docker which is of course the latest "thing" in virtualization, I'd
hugely encourage you to have a play with it despite your better
reservations. I pretty much groaned and tried to dismiss it for a good
while ("oh great, someone has reinvented the chroot/jail/zone concept
AGAIN - wake me up when it doesn't suck") until inevitably clients got
brave and wanted to try it... It's genuinely a bit of a game changer to
be honest. Whilst it IS remarkably familiar territory to those who
remember chroots/jails/zones/LXC/OpenVZ/etc it works more as a sort of
virtualization lite mixed with filesystem overlays type of thing. I got
into it accidentally at a client behest because they'd caught the
fashionable DevOps bug and a large part of that is of course continuous
integration via Jenkins and related stuff: a devil to get running
sweetly but once it is alive, you wonder how the hell you did without it.

Docker absolutely rocks for quickly testing and then deploying light
weight virtualization layers (as they call them, "containers") on
systems with way less overhead than for conventional full VMs. Like the
pi-hole docker example I gave the other day for example: someone else
builds and (hopefully) tests a working setup for a particular task (DNS
proxy with blocking) and once it's ok, it gets shoved into a repository
and then you can grab and deploy it to anything else running Docker
knowing that it will come up and work *exactly the same*.

From your other post of a few days ago about shipping statically linked
binaries - which had so many interesting points in I had to abandon an
epically overlong reply to halfway through!) from universal repos, you
should technically LOVE Docker. It does also integrate very well with
systemd via systemd-nspawn if you like that sort of thing but be warned,
because Docker is so beloved of the new wave of damn kids/silicon valley
maniacs as the hippest of hip technologies you're going to be neck-deep
in cutting edge tools and confusing jargon almost immediately: this was
certainly one of the main things putting me off it to start with. But
you're a Gentoo guy, so it's not going to be anything you can't handle :]

All of the most cutting edge and sophisticated stuff in this area is
squarely in the hands of a few major players - Docker themselves of
course, Google (who run most of their worldwide presence on vast
virtualized container farms via Kubernetes) and perhaps surprisingly
Intel, who are well, well ahead of everyone else's Linux game on this
with the biggest Linux flavour most people have probably never heard of:

Be warned though, Docker is a slippery slope down into madness - you
could probably already spend an entire career in there and once you
start exploring beyond a few test containers on a local workstation and
get into DevOps, continuous integration, OpenStack/Kubernetes enterprise
scale and beyond container farms it gets serious, very quickly indeed.
That's not a bad thing, but containerisation is the first
"revolutionary" tech in many years I've stumbled into and not just hit
the ground running after 10 minutes on Google - I've barely even begun
to wrap my head around it and think I'm going to have to actually buy
some books and so some good old fashioned homework for once. Containers
certainly are the future! (For now, until someone uses them to invent
the replacement of course.)


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