how to use an overlay filesystem?

[Buday Gergely]

Hi there,

my scenario is the following: I have a classroom with two dozens of Windows 7 machines.

I would like to create a read-only virtual disk that is placed on a network drive. That disk would contain a standard install of Fedora 20.

Now I would like to have an overlay filesystem that is based on the virtual disk above, and, per user we would have the difference. Since I would not encourage the installation of large packages, that overlay filesystems would contain only configuration modifications mostly. I would share these diffs through Samba to have password protection.

Is this doable with Virtualbox? How? Would it make acceptable speeds for running basic services like httpd and mysqld?

Cheers

- Gergely

[Geoff Nordli]

On 14-09-15 06:44 AM, Buday Gergely wrote:
>
> Hi there,
>
> my scenario is the following: I have a classroom with two dozens of
> Windows 7 machines.
>
> I would like to create a read-only virtual disk that is placed on a
> network drive. That disk would contain a standard install of Fedora 20.
>
> Now I would like to have an overlay filesystem that is based on the
> virtual disk above, and, per user we would have the difference. Since
> I would not encourage the installation of large packages, that overlay
> filesystems would contain only configuration modifications mostly. I
> would share these diffs through Samba to have password protection.
>
> Is this doable with Virtualbox? How? Would it make acceptable speeds
> for running basic services like httpd and mysqld?
>
> Cheers
>
> - Gergely
>
>
HI Gergely.

Not sure if this is really the best way to go about it.

Why not run the VMs from the local Windows 7 classroom machines?

Geoff

[Buday Gergely]

HI Gergely.

Not sure if this is really the best way to go about it.

Why not run the VMs from the local Windows 7 classroom machines?

Geoff

---

Geoff,

I do want to run the virtual machines on the Windows machines.

The problem lies at that students do not necessarily take seat at the same machine from class to class.

So I want to serve their virtual disks from the network.

- Gergely

[Jason Crawford]

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[Geoff Nordli]

On 14-09-19 12:55 AM, Buday Gergely wrote:
> HI Gergely.
>
> Not sure if this is really the best way to go about it.
>
> Why not run the VMs from the local Windows 7 classroom machines?
>
> Geoff
>
> ---
>
> Geoff,
>
> I do want to run the virtual machines on the Windows machines.
>
> The problem lies at that students do not necessarily take seat at the same machine from class to class.
>
> So I want to serve their virtual disks from the network.
>
> - Gergely
>

I see, that makes sense.

You mentioned all of the disks are going to be the same except for some
configuration changes. How are you planning on deploying these
changes? Why do those changes need to be different?

Are students going to snapshot the disk at any point?

As Jason was pointing out, I think the solution is more around content
synchronization than running stuff from the server.

Maybe you use the main image as a "base" and then you create snapshots
from that for each individual student. The base image would already be
on every student computer. Therefore when they sit down you only need
to copy in the "snapshot" portion of each student.

If you do this will may want to put swap and temp on a different disks
to keep change set small; discarding those changes at the end of the
session.

Their changes would be on their home directory. When they login, they
run a script that copies all of that data from their home to the local
machine.

When they are finished, run the script that saves their data to the server.

If you do it this way, they can also do snapshots, since all of that
data would get synced to their home dir.

Geoff

[Alex Smith (K4RNT)]

Yeah, why not set up their home directories on a file server, and mount
them on the VMs using NFS? Then you could set the disks for the base system
as non-persistent and then on any reboot it would revert any changes
automatically.

Would that accomplish your needs?

" 'With the first link, the chain is forged. The first speech censured, the
first thought forbidden, the first freedom denied, chains us all
irrevocably.' Those words were uttered by Judge Aaron Satie as wisdom and
warning... The first time any man's freedom is trodden on, we’re all
damaged." - Jean-Luc Picard, quoting Judge Aaron Satie, Star Trek: TNG
episode "The Drumhead"
- Alex Smith
- Huntsville, Alabama metropolitan area USA

On Fri, Sep 19, 2014 at 8:35 AM, Geoff Nordli <geoffn-***@public.gmane.org> wrote:

> On 14-09-19 12:55 AM, Buday Gergely wrote:
> > HI Gergely.
> >
> > Not sure if this is really the best way to go about it.
> >
> > Why not run the VMs from the local Windows 7 classroom machines?
> >
> > Geoff
> >
> > ---
> >
> > Geoff,
> >
> > I do want to run the virtual machines on the Windows machines.
> >
> > The problem lies at that students do not necessarily take seat at the
> same machine from class to class.
> >
> > So I want to serve their virtual disks from the network.
> >
> > - Gergely
> >
>
> I see, that makes sense.
>
> You mentioned all of the disks are going to be the same except for some
> configuration changes. How are you planning on deploying these
> changes? Why do those changes need to be different?
>
> Are students going to snapshot the disk at any point?
>
> As Jason was pointing out, I think the solution is more around content
> synchronization than running stuff from the server.
>
> Maybe you use the main image as a "base" and then you create snapshots
> from that for each individual student. The base image would already be
> on every student computer. Therefore when they sit down you only need
> to copy in the "snapshot" portion of each student.
>
> If you do this will may want to put swap and temp on a different disks
> to keep change set small; discarding those changes at the end of the
> session.
>
> Their changes would be on their home directory. When they login, they
> run a script that copies all of that data from their home to the local
> machine.
>
> When they are finished, run the script that saves their data to the server.
>
> If you do it this way, they can also do snapshots, since all of that
> data would get synced to their home dir.
>
> Geoff
>
>
>
> ------------------------------------------------------------------------------
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>
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[Peter Ondruška]

OK, if you had ZFS (Solaris, and others) you could use ZFS snapshot for
this purpose. Search the Internet, Oracle definitely have whitepaper on
this use and VirtualBox.

On Monday, 15 September 2014, Buday Gergely <gbuday-8YGdQ0kaVPyfeM/lT+***@public.gmane.org> wrote:

> Hi there,
>
>
>
> my scenario is the following: I have a classroom with two dozens of
> Windows 7 machines.
>
>
>
> I would like to create a read-only virtual disk that is placed on a
> network drive. That disk would contain a standard install of Fedora 20.
>
>
>
> Now I would like to have an overlay filesystem that is based on the
> virtual disk above, and, per user we would have the difference. Since I
> would not encourage the installation of large packages, that overlay
> filesystems would contain only configuration modifications mostly. I would
> share these diffs through Samba to have password protection.
>
>
>
> Is this doable with Virtualbox? How? Would it make acceptable speeds for
> running basic services like httpd and mysqld?
>
>
>
> Cheers
>
>
>
> - Gergely
>
>
>
>
>

[Geoff Nordli]

On 14-09-19 07:46 AM, Peter Ondruška wrote:
> OK, if you had ZFS (Solaris, and others) you could use ZFS snapshot
> for this purpose. Search the Internet, Oracle definitely have
> whitepaper on this use and VirtualBox.
>
> On Monday, 15 September 2014, Buday Gergely <gbuday-8YGdQ0kaVPyfeM/lT+***@public.gmane.org
> <mailto:gbuday-8YGdQ0kaVPyfeM/lT+***@public.gmane.org>> wrote:
>
> Hi there,
>
> my scenario is the following: I have a classroom with two dozens
> of Windows 7 machines.
>
> I would like to create a read-only virtual disk that is placed on
> a network drive. That disk would contain a standard install of
> Fedora 20.
>
> Now I would like to have an overlay filesystem that is based on
> the virtual disk above, and, per user we would have the
> difference. Since I would not encourage the installation of large
> packages, that overlay filesystems would contain only
> configuration modifications mostly. I would share these diffs
> through Samba to have password protection.
>
> Is this doable with Virtualbox? How? Would it make acceptable
> speeds for running basic services like httpd and mysqld?
>
> Cheers
>
> - Gergely
>
>
Peter, that is exactly how we use it, but we scale to 1000s of VMs.

We use zfs snapshot/clone, expose as an iscsi lun and then use the vbox
built-in iscsi initiator to remotely connect to the LUN on the SAN.

VBox + ZFS + Illumos rocks!!

Geoff