Reasons for using Qemu/VMware/Virtualbox??

linus72 · 03-30-2009, 02:07 PM

Just wondering, but why do members here and Linux users use virtual programs like Qemu,etc?
What things can be accomplished?
I'm sure there are many reasons-please list them...

reptiler · 03-30-2009, 02:12 PM

I use KVM, which build on QEmu.

Why do I use virtualization? Because it makes things easy.

I can easily test another distro/OS without having to leave my main distro. I simply run it in a window.
I can create test-environment which would more hardware than I have available. Like setting up 3 VMs for a cluster.
I can try out stuff without being at risk to mess up my system.
This especially comes in handy as I work on my own distro and thus have a lot of compiling to do, which, if done wrong, could easily mess up my system.

I guess these are the main reasons.

Didier Spaier · 03-30-2009, 02:32 PM

I use VirtualBox in Slackware 12.2 and have two more distributions in it, namely Windows 7 beta and Slackware-current.

For that you need only between 5 and 10 GB space per distribution on your hard disk:

Code:

bash-3.1$ du --max-depth=2 -h /home/didier/.VirtualBox/
15G     /home/didier/.VirtualBox/HardDisks
208K    /home/didier/.VirtualBox/Machines/Slackware
3,1G    /home/didier/.VirtualBox/Machines/Windows7
3,1G    /home/didier/.VirtualBox/Machines
18G     /home/didier/.VirtualBox/
bash-3.1$

This way, I keep a very simple HD layout:

Code:

bash-3.1$ df -h
Sys. de fich.         Tail. Occ. Disp. %Occ. Monté sur
/dev/root              16G  7,9G  7,7G  51% /
/dev/hda2              58G   39G   19G  69% /home
tmpfs                 506M   12K  506M   1% /dev/shm
bash-3.1$

I do not have to change it when I install a new distribution, nor do I have to run lilo in the "real" system.

If you have enough disk space you can have all the distributions in your _near_to_be_released_DVD_ installed in the same box

And you can even have several distributions running at the same time, but don't forget that each needs between 256MB and 1GB of RAM to run.

reptiler · 03-30-2009, 02:39 PM

Quote:

Originally Posted by Didier Spaier

For that you need only between 5 and 10 GB space per distribution on your hard disk:

I usually assign 8. For most things I try that's plenty.

Quote:

Originally Posted by Didier Spaier

And you can even have several distributions running at the same time, but don't forget that each needs between 256MB and 1GB of RAM to run.

In order to run several VMs at a time (each with a GB of RAM) I upgraded to 8GB. And probably later this year I'll go from dual-core to quad-core for even more virtualization fun.

AlucardZero · 03-30-2009, 02:53 PM

Cost. Instead of buying new hardware I can use existing hardware. That hardware may need a RAM/CPU/disk upgrade, but that's still leagues cheaper than new servers.

Crito · 03-30-2009, 03:01 PM

It's cheaper than buying more hardware.

Of course, that assumes your hardware is underutilized. If it's already over-utilized all you're doing is adding another straw to the camel's back. So capacity planning is critically important.

linus72 · 03-30-2009, 03:46 PM

Alright-those are great answers!
Now I have a couple questions-I'll post a different question after somebody answers these...
OK-with Qemu-Puppy and DSL-embedded both distro's can play off CD or USB, without restarting the computer, via Qemu-right?
Now-they both use .sh scripts to do this-but in different ways it seems...?
So, can I make a multi-distro CD/USB that has Qemu, like DSL-embedded/Puppy-Qemu, and is set up so that it will "play" the 4 or 5 distro's on the CD/USB via Qemu, just by inserting the CD/USB and invoking the script?
I would need to make a script that would give me a choice of which distro for Qemu to call up-yes?
How would I go about doing this?

linus72 · 04-01-2009, 01:04 PM

Well-no one really answered my questions above, but I have another one too.
First-how do I setup VirtualBox as Didier has his above?

Second-is the question I asked in the previous post possible-

Code:

Now I have a couple questions-I'll post 

a different question after somebody answers these...
OK-with Qemu-Puppy and DSL-embedded both distro's can play off CD or USB, without restarting the computer, 
via Qemu-right?
Now-they both use .sh scripts to do this-but in different ways it seems...?
So, can I make a multi-distro CD/USB that 
has Qemu, like DSL-embedded/Puppy-Qemu, 
and is set up so that it will "play" the 
4 or 5 distro's on the CD/USB via Qemu, 
just by inserting the CD/USB and invoking the script?
I would need to make a script that would 
give me a choice of which distro for Qemu to call up-yes?
How would I go about doing this?

Third-can a Linux distro-let's say "DSL", be remastered through Qemu, VirtualBox, etc?

Probably not-but could I try remastering through Qemu, etc so if I mess something up no harm done?

Didier Spaier · 04-01-2009, 02:20 PM

In a pinch:

Get VirtualBox here. Follow the last link: all distributions => i386 to download it. At time of writing file's name is VirtualBox-2.1.4-42893-Linux_x86.run

Run or sh the installer as root. It will install in /opt.

Make and install the modules (of course you need the kernel source and headers):

Code:

cd /opt/VirtualBox-2.1.4/src
su
make
make install
Ctrl + d

If I remember well the installer creates itself a symlink /usr/bin/VirtualBox pointing to /opt/VirtualBox/VBox.sh. Otherwise, do it yourself.

You can now run VirtualBox. First time you do so, it will create the ~/.VirtualBox directory

Other way: use the SlackBuilds for VirtualBox-OSE @ http://sackbuilds.org to make yourself the packages and install it. You won't get support for USB in the guests machines in that case, because it is not included in the OSE edition but it works as well.

linus72 · 04-01-2009, 02:26 PM

Ran into an issue in Slackware 12.2 installing Pulseaudio-needed by Virtualbox-
read about Vbox install here-
( http://muhrizky.wordpress.com/2008/1...slackware-122/ )
I built/installed all the dependencies on that page with sbopkg-except when installing pulseaudio it says-

Code:

Building pulseaudio
Building Slackware package for pulseaudio...
  Must have a pulse group to run this script.
    # groupadd pulse
  Or something similar.

What does that mean?

AlucardZero · 04-01-2009, 02:36 PM

It means you must have a group named pulse already. Run

Code:

groupadd pulse

Didier Spaier · 04-01-2009, 02:44 PM

That means that you should do what is written. As root:

Code:

groupadd pulse

To know more: "man groupadd".

There are plenty of guides, how-to and tutorials on the web on that topic, see for instance this one.

linus72 · 04-01-2009, 02:46 PM

Then why am I getting this error?

Code:

******************************************
PACKAGE BUILDING/INSTALLATION SUMMARY LOG
Using SlackBuilds.org 12.2 repository
Using the queuefile

pulseaudio:
Error occurred with build.  Please check the log.

What now?

linus72 · 04-01-2009, 03:29 PM

OK-got pulseaudio installed-downloading Vbox "VirtualBox-2.1.4-42893-Linux_x86.run" now. But can you elaborate on this-
"Make and install the modules (of course you need the kernel source and headers):"
What do you mean by that Didier??

Didier Spaier · 04-01-2009, 03:55 PM

Do this as root:

Code:

chmod +x VirtualBox-2.1.4-42893-Linux_x86.run # make this file executable
./VirtualBox-2.1.4-42893-Linux_x86.run # run the installer
cd /opt/VirtualBox-2.1.4/src
make # make the kernel modules
make install # install it
modprobe vboxnetflt # load the first module
modprobe vboxdrv # load the second module

Note that the "modprobe" commands are only needed once, at next reboot these modules will be automatically loaded.

Please don't mix instructions. IMHO following this link was not needed. For instance I do not have pulseaudio installed and still VirtualBox works here. But don't worry, this won't hurt anyway, so you can keep it

One thing I forgot to tell you: you need to set-up a vboxusers group and make yourself member of it before you run VirtualBox. Do this as root:

Code:

groupadd vboxusers
gpasswd -a  your_user_name vboxusers

Then as a regular user type:

Code:

groups

to check. As hopefully you will see vboxusers in the output, to launch the application type:

Code:

VirtualBox