Category Archives: VirtualBox and VMware
How to Save Time by Using Snapshots in VirtualBox
Snapshots are a massive time saver when you are testing settings and configuration for your test labs. Read on to see how you can take advantage of them while following along with our articles.
The basic idea of a snapshot is that you setup your virtual machine exactly how you want it, take a snapshot, and then you can make any changes you want. You could even install something awful, because it doesn’t matter – all you have to do is roll back the snapshot, and your virtual machine will be exactly how it was before.
It’s the perfect way to do a bunch of testing and figure things out, without breaking your setup. Plus, it’s a virtual machine, so you could always reload it anyway.
Taking a Snapshot
Taking a snapshot in VirtualBox is actually very easy, and when done can save massive amounts of time. To get started open up your Virtual Machine and click on the Machine menu item, then select Take Snapshot…
Since we will be snapshotting a clean install you will need to give your snapshot an intuitive name and description to remember this.
The virtual machine will then dim out periodically while a point in time snapshot is taken.
Reverting To a Snapshot
The purpose of reverting to a snapshot is so that you can go back in time to a particular state, in our case a clean state just after we installed the OS. Since we can only do this when the virtual machine is not on, go ahead and shut it down.
Then select your virtual machine from the list and switch over to the snapshots view. Here you will see a list of the various snapshots you may have taken. To restore to a snapshot simply right click on it and choose Restore Snapshot From the Context Menu.
For most situations you are going to want to uncheck the option to create a snapshot of the virtual machine current state. The reason being is that you will normally want to restore when you have broken something, there’s no point in taking a snapshot of a broken configuration.
You will then see that the “Current State” will become the same as the snapshot you selected to restore to.
Now when you power on the virtual machine you will see the virtual machine quickly reverting itself.
Always remember that without snapshots, recording the Geek School would be nearly impossible, so remember to use them and save yourself countless hours. That’s all there is to it.
Getting started with GNS3 (Installation and configuration)
Up & Running With GNS3 1.X
How to Setup GNS3
Adding your own PC to GNS3 with MS Loopback
MicroNugget: GNS3 and Windows 8
MicroNugget: How to Tune GNS3 to Avoid a 100% CPU Utilization?
MicroNugget: Connecting Virtual Box Hosts to GNS3 Networks
MicroNugget: Virtual PC Simulators & GNS3
MicroNugget: Using Wireshark with GNS3
MicroNugget: Connecting GNS3 to the Internet
MicroNugget: The ASA in GNS3
How To Install GNS3 1.0 on Windows 8.1
GNS3 1.0 was released to the world on October 21st, 2014. I have been using previous versions of GNS3 for some time now to simulate networks and to practice for my Cisco certifications. For those of you who aren’t familiar with GNS3, it is an application that allows you to build networks for free. The caveat there is you need to supply the images for your equipment. GNS3 supports Cisco, Juniper, HP, Arista, Citrix, and Brocade (as specified on their site, gns3.com. You build out a virtual lab which means there is no need to purchase physical hardware.
Before getting started, you’ll need to sign up on GNS3‘s website. Once you have an account. You can download GNS3. Click on the Windows download button to begin.
Once you open the installation file, click through the standard setup screen and agreement until you get to the Choose Components section.
Select all the components you will need – almost everything. SolarWinds is a new application packaged with GNS3. If you already have some of the components installed, such as Wireshark, you can uncheck it.
After completing installation, Start GNS3.
Upon opening GNS3, you will be prompted to save your new project locally or in the cloud. For the purposes of setting up GNS3 I will skip this.
Click on Edit and then Preferences.
Expand Dynamips and select IOS routers.
This is where you must supply your IOS image. I cannot supply these images for you. Click on New to add your image.
Enter the name of the Image and its platform.
Set the amount of RAM to be allocated to IOS.
Select the default adapters you want installed for each new instance of this device.
After you finish, the router will be displayed with its settings.
Click on the General tab to view your settings. Make any changes as you see fit.
The Console applications tab is where you can configure what application is to be used to console into your devices within GNS3.
The Packet capture tab displays your settings for capturing traffic on links between your devices within GNS3. Notice the capture analyzer command using SolarWindows Response Time Viewer.
Click OK to close the Preferences window.
The big window in the middle of GNS3 is your topology view. This is wear you drag and drop devices from the left menu item.
To add a device, click on one of the symbols on the left and drag and drop the IOS image you’ve uploaded to GNS3.
The Topology Summary window will display a list of all your devices. A red orb signifies a device that is off. A green orb means the device is on.
Right click on your device and click on Start to turn on your device. Right click again and select Console to bring up Putty to manage your device.
Happy labbing!
GNS3 1.2.1 installation on Ubuntu 14.04
As mentioned in an earlier post GNS3 is moving ahead fast. Currently at version 1.2.1 the GNS3 is looking great. Compared with the version 1.0 Beta 1 which I had installed, the 1.2.1 is not only more stable, but it has the Menu more clean and compact. For example now there is only one Preferences menu where you can adjust all your settings.
During the installation of 1.0 Beta 1 I made some notes in Evernote and it prove to be very useful as the installation was pretty messy. With 1.2.1 I did the same thing, but the installation was very smooth. Still, I said that if I made those notes maybe I should share them for those interested in a quick installation. A more complete guide can be found on GNS3 Community.
1. Download GNS3 1.2.1
Head over to http://www.gns3.com/, create and account and download the bundle archive for Linux.
If you for some reason you don’t want to create an account, you may download each package individually from https://github.com/GNS3
The following lines will assume that you have the bundle archive.
2. Install Ubuntu 14.04 dependencies
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$ sudo apt-get install libpcap-dev uuid-dev libelf-dev cmake
$ sudo apt-get install python3-setuptools python3-pyqt4 python3-ws4py python3-netifaces python3-zmq python3-tornado
$ sudo apt-get install unzip
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3. Unzip the bundle archive
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$ unzip GNS3-1.2.1.source.zip
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You should see 5 packages in GNS3-1.2.1 folder:
dynamips-0.2.14.zip
gns3-server-1.2.1.zip
gns3-gui-1.2.1.zip
iouyap-0.95.zip
vpcs-0.6.zip
4. Install Dynamips
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$ unzip dynamips-0.2.14.zip
$ cd dynamips-0.2.14
$ mkdir build
$ cd build
$ cmake ..
$ make
$ sudo make install
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To check if the correct version is install:
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$ dynamips | grep version
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You should see in the output 0.2.14
5. Install GNS3 Server
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$ unzip gns3-server-1.2.1.zip
$ cd gns3-server-1.2.1
$ sudo python3 setup.py install
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To check if the GNS3 Server is installed correctly:
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$ gns3server
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If you see some output other than an error, than you’re fine.
6. Install GNS3 GUI
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$ unzip gns3-gui-1.2.1.zip
$ cd gns3-gui-1.2.1
$ sudo python3 setup.py install
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To test if the installation is working:
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$ gns3
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You should see a graphical interface of GNS3 launched.
At this moment you have a working GNS3 environment if you want only want to test Cisco hardware emulators. I strongly recommend to continue and install also the rest of the components. Who knows when you’ll need them
7. Install IOUyap (Optional, if you will use IOU images)
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$ unzip iouyap-0.95.zip
$ cd iouyap-0.95.zip
$ make
$ sudo make install
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To test the installation:
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$ iouyap -h
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8. Install VPCS (Optional, if you want to use VirtualPC)
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$ unzip vpcs-0.6.zip
$ cd vpcs-0.6/src
$ mk.sh 64
$ cp vpcs /usr/bin/
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For the third line, the 64 represent 64bit, as my Ubuntu 14.04 is build on 64bit.
The values can be:
– 32 or i386 for 32bit OS
– 64 or amd64 for 64bit OS
Please be sure to use the correct one for your OS.
To test the VPCS:
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$ vpcs
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You should see a Virtual PC being launched. Leave the console with letter q.
9. Install VirtualBox (Optional, if you want to launch VMs)
Download the correct version for your system from https://www.virtualbox.org/wiki/Linux_Downloads. The following lines will assume an Ubuntu 14.04 64bit OS.
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$ apt-get install dkms
$ dpkg -i virtualbox-4.3_4.3.20-96996~Ubuntu~raring_amd64.deb
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You can also use the instructions at https://www.virtualbox.org/wiki/Linux_Downloads and go for an APT installation.The choice is yours.
10. Install Qemu (Optional, if you want to use qemu images)
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$ sudo apt-get install qemu
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11. Install IOU (Optional, if you want to use IOU images)
I’m not a legal matter expert, and the usage of IOU is sort of grey area. Because of this, I’m not going to cover this chapter.
You’re ready to go. Start the GNS3 GUI:
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$ gns3
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Some things to check before going live:
- check in the menu Edit > Preferences to set your desired Paths (in General sections) and to check the paths for the binaries (dynamips, vpcs, iou, virtualbox…)
- add the IOS, virtualbox vm, iou images
- in case of Cisco hardware emulators don’t forget to find the IdlePC value (when you add the IOS image or later with the start of your first router with a certain image) otherwise your CPUs will cry.
If something does not work as described or you need help please let me know in Comments.
[Update 1]
If you get the following error during installation of iouyap:
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GNS3-1.2.2.source/iouyap-0.95 $ make
gcc -g -DDEBUG -Wall -c -o iouyap.o iouyap.c
iouyap.c:40:23: fatal error: iniparser.h: No such file or directory
#include
^
compilation terminated.
make: *** [iouyap.o] Error 1
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Try to install the iniparser as follows:
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sudo apt-get install flex bison
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then
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cd /tmp
curl -L https://github.com/ndevilla/iniparser/archive/master.tar.gz | tar -xz
cd iniparser*
make
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and finally iouyap
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cd /tmp
curl -L https://github.com/GNS3/iouyap/archive/master.tar.gz | tar -xz
cd iouyap*
bison -ydv netmap_parse.y
flex netmap_scan.l
gcc -Wall *.c -I /tmp/iniparser*/src -L /tmp/iniparser* -o iouyap -liniparser -lpthread
strip –strip-unneeded iouyap
sudo mv iouyap /usr/local/bin
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How to Connect Cisco IOU to GNS3-1.1 and Emulate Cisco Switch in GNS3-1.1
Well, what’s up? Today I’m going to discuss an interesting GNS3 Cisco simulator tutorial on how to connect Cisco IOU to GNS3-1.1. This is an alternate way of emulating Cisco switches in GNS3.
So I hope this article will answer how to get a working layer 2 switch in GNS3-1.1
By the way what is a Cisco IOU device? Cisco IOS on UNIX (IOU) is a fully working version of IOS that runs as a user mode UNIX/LINUX platform. IOU is built as an image and runs just like any other program. Layer 2 and layer 3 IOU images are available for switching and routing respectively. Cisco IOS on UNIX is aimed for internal uses only (Cisco employees). Distribution of IOU images to customers or external persons is strictly prohibited.
The new version of GNS3 (1.1) supports IOS on UNIX, thereby providing fantastic Cisco switch simulator to the users. Usually people who are preparing for CCIE Routing and Switching will be using IOS on UNIX facility.
The process to connect Cisco IOU to GNS3-1.1 is a little bit hassle though, but I’m gonna give you simple explanation with step by step procedures.
Tools Required
- GNS3-1.1: Download from here
- Oracle VirtualBox: Download from here
- GNS3 IOU VM.ova: Is the Virtual Unix platform to run IOU image. It is a virtual box OVA file: Download from here
- IOU image: IOU image is intended to use only for Cisco employees, distribution of IOU is strictly prohibited. Please don’t ask me! Google is your friend always.
- iourc.txt file: Is the license of Cisco IOU image. I have no privilege to provide it publicly, but I found adiscussion related to it. It may help you.
Now we are ready to go…
Step 1: GNS3 IOU VM.ova Setup
Double click ‘GNS3 IOU VM.ova’ , it will open up in VirtualBox (if you have installed VMware please right click on the GNS3 IOU VM.ova file and change the ‘open with’ to Oracle VM VirtualBox).
Click Import button, it will be imported to VirtualBox VM list.
Go to Settings → Network → Adapter 1
Make sure it is attached to Host-only Adapter with name VirtualBox Host-Only Ethernet Adapter. Then click OK.
Start the GNS3 IOU VM, then login with following credentials.
User name: root
Password: cisco
Step 2: Upload IOU Image to Unix (GNS3 IOU VM)
Check the IP address of the GNS3 IOU VM by ifconfig command and note down the IP (my case 192.168.56.102).
Now come to the host machine and open any browser (I’m a Chrome fan). Enter the following link in the address bar http://192.168.56.102:8000/upload.
Choose your IOU image and click Upload button.
[Note: the location of the file being copied (/home/gns3/GNS3/images/XXXXXXXXXXXXXXXXXXX)]
Now our IOU device is ready to run….!
[Troubleshoot: Please allow 192.168.56.XX network in the firewall, Disable proxy if you are using. In local PC (host machine) be sure that your VirtualBox Host-Only Ethernet Adapter is set to accept DHCP]
Step 3: GNS3 Server Configuration
By default GNS3 host binding is 127.0.0.0:8000 (local host loopback) address, we have to change the server to 192.168.56.XX:8000.
Go to Edit → Preferences → GNS3 Server → Local Server
Drop down the Host Binding section and choose 192.168.56.XX, local VirtualBox Host-Only Adapter IP (mine 192.168.56.101) and click Apply.
Again Edit → Preferences → GNS3 Server → Remote Server
Add a host by entering UNIX GNS3 IOU VM IP address that we noted in Step 2 (mine 192.168.56.101) and 8000 as port.
Step 4: Connect Cisco IOU to GNS3-1.1
Go to Edit → Preferences → IOS on UNIX → General Settings
The set the path of iourc.txt (iourc.txt can be stored on any directory of your local PC, eg: Desktop), browse and select it.
Now go to IOU Devices, click New button and select server type as Remote. Your remote server will be listed there → Next
You will receive a message “You have chosen to use a remote server, please provide the path to IOU image located on the server!”, just click OK.
Now type a Name for the IOU image and set IOU image path that you noted already in Step 2.
Type should be L2 for switch IOU.
Click Finish button. That’s that!
You have success fully configured Layer 2 Switch in GNS3-1.1…! Go to GNS3 GUI and drag the switch in to work space.
Now explore your new GNS3 Switch!
Hope I explained each steps to get a working IOU in GNS3-1.1
How to convert .img files to .vdi for Virtualbox
VBoxManage convertdd file.img file.vdiVBoxManage convertdd ChromeOS-Cherry.img ChromeOS-Cherry.vdiTo do this is Windows (I haven’t tested it but it should work), open cmd.exe (Start > Run, enter: cmd.exe), navigate to “C:\Program Files\innotek VirtualBox” (using the “cd” command), then run this (after placing the .img file inside the “C:\Program Files\innotek VirtualBox” folder):
VBoxManage.exe convertdd file.img file.vdiPlease let us know if you have tried this in Windows and rather or not it worked.
To use it in VirtualBox, create a new Virtual Machine, select “Use existing hard disk” and browse for the recetly converted .vdi file:
Install Android 4.4 Kitkat on your PC using Virtual Box
Here’s the most expected tutorial from Learn2Crack, and today we are going to show how to install Android KitKat 4.4 on your PC. To install the latest Android Kitkat on Pc Visit this link.
Features of Android 4.4:
1) Support for Restricted Profiles
2) OpenGL ES 3.0 for High-Performance Graphics
3) Bluetooth Smart Ready support
4) Notification Access
Download:
1. Oracle VM VirtualBox
Download the latest version of VirtualBox from https://www.virtualbox.org/wiki/Downloads
2. Android x86 4.4 Image
Download the Android 4.4 image from
http://sourceforge.net/projects/android-x86/files/Release%204.4/android-x86-4.4-RC1.iso/download
Instructions:
1.Install VirtualBox on your PC
2.Open VirtualBox and select New. In the dialog box enter the name as your wish and
select i)Type : Linux
ii)Version : Other Linux
and select Next
3.In the next dialog box enter the memory size as your wish
Note : Minimum 1 GB required for KitKat
and select Next.
4.In the next dialog box select create a virtual hard drive now. Then select VDI and select fixed or dynamically allocated as your wish and create the virtual drive
Note : Mininimum 1 GB required for installation
5.Select Virtual device and select settings, a dialog box appears. In the dialog box select
i)Storage->Storage Tree->Empty
ii)In the attributes section select the Android 4.4 iso file you downloaded and check Live Cd/Dvd, then click Ok
6.Then start the virtual device. In the screen select Install Android-x86 to hard disk.
10.After installing remove live iso from VirtualBox and reboot. Now you can boot into Android 4.4 .
You are done.
Cheers, enjoy….
Some Screenshots
UBUNTU TOUCH EMULATOR: INSTALLATION AND USAGE IN UBUNTU 14.04
A while back, Canonical released an experimental Ubuntu Touch emulator running Unity 8 and Mir. Back then, there were a few bugs, including a nasty one on 64bit that could break the system and since they were fixed, I though I’d write an article on how to properly install and use the Ubuntu Touch Emulator in Ubuntu 14.04, 13.10 and 12.04.
(ARM instance; direct video link)
(x86 instance; direct video link)
sudo add-apt-repository ppa:phablet-team/tools
sudo apt-get update
sudo apt-get install ubuntu-emulatorIf you’ve installed an older version of Ubuntu Emulator, also run an upgrade:
sudo apt-get upgradeCreating and running instances
1. The first thing you need to do is create a new instance – we’ll call it “UbuntuTouch” in the commands below:
Create an ARM instance:
sudo ubuntu-emulator create UbuntuTouch --channel=ubuntu-touch/utopic-proposedTo create an Ubuntu Touch Emulator x86 instance, use the following command:
sudo ubuntu-emulator create UbuntuTouch –arch=i386 –channel=ubuntu-touch/utopic-proposed
The current “stable” image doesn’t seem to work, that’s why I’ve added the Utopic proposed channel for the image in the commands above.
On Ubuntu 12.04, you may get the following error:
Error while converting ~/.local/share/ubuntu-emulator/UbuntuTouch/system.img: Unknown option 'compat'
qemu-img: Invalid options for file format 'qcow2'.2. Then, run the new instance by using the following command:
ubuntu-emulator run UbuntuTouchThe first time you run the emulator, the boot process will take quite a while. When it finishes booting, a shell with Ubuntu Touch will start, asking you to enter the username and password:
3. Optional: change the Ubuntu Touch Emulator size:
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| Ubuntu Touch Emulator with a 0.7 scale on my 1920×1080 monitor. |
ubuntu-emulator run --scale 0.5 UbuntuTouch- the downloaded images are stored under ~/.cache/ubuntuimages
- the images are stored under ~/.local/share/ubuntu-emulator
Deleting instances
To delete an Ubuntu Touch Emulator instance, use the following command:
sudo ubuntu-emulator destroy UbuntuTouchubuntu-emulator listCreating / restoring snapshots
ubuntu-emulator snapshot --create=SNAPSHOT1 UbuntuTouchThen, when you wish to restore this snapshot, use:
ubuntu-emulator snapshot --revert=SNAPSHOT1 UbuntuTouchYou can also use “–revert-pristine” to revert to the originally created snapshot.
vSphere 5.5 – How to install and configure VMware ESXi 5.5
Realtek network cards and VMware ESXi 5.5
Yesterday I decided to upgrade my two ESXi servers from ESXi 5.1 to ESXi 5.5 since the update came out some time ago.
The upgrade from ESXi 5.0 to ESXi 5.1 went great, without any problems. But this time, that is not the case.
My two ESXi servers are white boxes made of the following hardware:
- Motherboard: MSI Z87-G43 (http://www.msi.com/product/mb/Z87-G43.html)
- CPU: i5-4670K (http://ark.intel.com/products/75048/)
- RAM: Kingston HyperX DDR3 1600MHz, 8Gb * 2(16GB total) (http://www.newegg.com/Product/Product.aspx?Item=N82E16820104173)
The problem was the motherboard that ships with an onboard Realtek 8111E network adapter.
This problem has been verified to be the same with Realtek 8168 and Realtek 8169.
The reason for this, is that VMware removed the drivers from the new ESXi 5.5 iso.
In this post I will show you how to get ESXi 5.5 working with the Realtek network adapters.
Some people don’t like to use “not supported” hardware this way, and others had connection problems on the VM’s after doing this. I did not have any problems, and have been running with this solution since I wrote this post (21 days ago now). So i think it is pretty stable.
If you don’t want to use the method below, you can always buy a Intel Pro 1000 network card and put it in a PCI-e slot.
I highly recommend the Intel pro 1000 series, they are fast, reliable and works on any OS out of the box (including ESXi), but they are a little pricy. You can get them here, with free shipping:
Intel Pro 1000 Dual port
Intel Pro 1000 single port
There are two ways to make the upgrade work on your motherboard:
- Using a supported network adapter in a PCI-E slot (See above, regarding the Intel Pro 1000 network adapters)
- Creating a custom ESXi 5.5 iso with the drivers from ESXi 5.1
Putting in a extra network adapter was not an option for me, so I went for option two, and here is how I did it:
Creating a custom ESXi 5.5 iso including the Realtek network drivers
What you need
You just need a Windows XP or higher computer, and the software below.
Getting the needed software
First you need to get the needed software.
The following is what you need to download:
- The original VMware ESXi 5.5 iso (https://my.vmware.com/web/vmware/evalcenter?p=free-esxi5&lp=default)
- ESXi-Customizer (http://www.v-front.de/p/esxi-customizer.html#download)
- The drivers from the old ESXi 5.1 iso (save file and unzip), you only need one of the below depending on what model your network adapter is.
Injecting the drivers and create a new iso file
There is not a lot of steps to this, actually just a couple and it will not take long.
Open the “Esxi-customizer”
First run the .exe for ESXi-customizer to extract it.
When extracted, run the program so you get the following window:
Fill out fields
Simply fill out all 3 fields.
First one: Choose the original VMware ESXi 5.5 iso you downloaded from VMware
Second one: Choose the .VIB file for you Realtek network adapter that you downloaded earlier.
Third one: Choose what folder to use for working folder. A log and the finished new .iso file will be saved here. just create a new folder on your C:\ drive and use it.
If your motherboard support UEFI boot, you can tick the “Create UEFI bootable ISO” if not, then untick this. If you are unsure about this, then untick it!
Tick the auto update check to make sure you always have the latest version of this software.
Do it!
Let’s do it! Press “Run!”
The program will run some commands in the command promt behind it, and that’s it.
It does not take long. Once done, you can close the program.
Upgrade your VMware ESXi server
Now, burn your newly created ISO image of VMware ESXi 5.5 with your Realtek network adapter drivers injected that was created in the folder you choose to be the working folder for the program.
You can also “Burn” it to a usb stick, if your server does not have a optical drive installed. I do not have a guide for this yet.
Boot up your server on the cd/usb and choose to upgrade the system like you would with the original iso.
Note that the custom .iso does not work trough VMware Update Manager.
Feel free to leave a comment below, and rate the post at the top if this helped you!
Difference between vSphere, ESXi and vCenter
VMware Inc. is a software company that develops many suite of software products specially for providing various virtualization solutions. There are many cloud products, datacenter products, desktop products and so on.
vSphere is a software suite that comes under data center product. vSphere is like Microsoft Office suite which has many software like MS Office, MS Excel, MS Access and so on. Like Microsoft Office, vSphere is also a software suite that has many software components like vCenter, ESXi, vSphere client and so on. So, the combination of all these software components is vSphere. vSphere is not a particular software that you can install and use, “it is just a package name which has other sub components”.
ESXi, vSphere client and vCenter are components of vSphere. ESXi server is the most important part of vSphere. ESXi is the virtualization server. It is type 1 hypervisor. All the virtual machines or Guest OS are installed on ESXi server. To install, manage and access those virtual servers which sit above of ESXi server, you will need other part of vSphere suit called vSphere client or vCenter. Now, vSphere client allows administrators to connect to ESXi servers and access or manage virtual machines. vSphere client is installed on the client machine (e.g. Administrator’s laptop). The vSphere client is used from client machine to connect to ESXi server and do management tasks. So now what is vCenter? Why we need it? Try cloning existing virtual machine using just a vSphere client without vCenter server.
vCenter server is similar to vSphere client but it’s a server with more power. vCenter server is installed on Windows Server or Linux Server. VMware vCenter server is a centralized management application that lets you manage virtual machines and ESXi hosts centrally. vSphere client is used to access vCenter Server and ultimately manage ESXi servers. vCenter server is compulsory for enterprises to have enterprise features like vMotion, VMware High Availability, VMware Update Manager and VMware Distributed Resource Scheduler (DRS). For example, you can easily clone existing virtual machine in vCenter server. So vCenter is another important part of vSphere package. You have to buy vCenter license separately.
The diagram above shows vSphere suite in a more descriptive way. vSphere is a product suite, ESXi is a hypervisor installed on a physical machine. vSphere Client is installed on laptop or desktop PC and is used to access ESXi Server to install and manage virtual machines on ESXi server. vCenter server is installed as virtual machine on top of ESXi server. vCenter server is a vSphere component which is mostly used in large environment where there are many ESXi server and dozens of virtual machines. The vCenter server is also accessed by vSphere client for management purpose. So, vSphere client is used to access ESXi server directly in small environment. In larger environment, vSphere client is used again to access vCenter server which ultimately manages ESXi server.
