Realm Linux install with VMXNET driver support

From NCSUTechstaffDocs

Jump to: navigation, search

Within VMware ESX /ESXi there are usually, but not always, three different NIC card choices available when you create or edit a virtual guest. You either get "E1000" and "Enhanced vmxnet" or "Flexible" and "Enhanced vmxnet". You will never see "Flexible" and "E1000." "Enhanced vmxnet" is really a VMXNET 2 adapter in ESX /ESXi. In newer ESX versions VMXNET 3 is also a choice of network adapter. Whether you see "Flexible" or "E1000" or "Enhanced vmxnet" or VMxnet 3 depends on what OS you have chosen in the creation wizard and also what version of VMware ESX you are running...

What do these choices mean? To understand this a little better we will discuss briefly the various network adapters available to our guest OS within ESX / ESXi. This is what VMware says about their various emulated NIC cards:

  • Vlance - An emulated version of the AMD 79C970 PCnet32 LANCE NIC, an older 10 Mbps NIC with drivers available in most 32bit guest operating systems except Windows Vista and later. A virtual machine configured with this network adapter can use its network immediately.
  • VMXNET - The VMXNET virtual network adapter has no physical counterpart. VMXNET is optimized for performance in a virtual machine. Because operating system vendors do not provide built-in drivers for this card, you must install VMware Tools to have a driver for the VMXNET network adapter available.
  • Flexible - The Flexible network adapter identifies itself as a Vlance adapter when a virtual machine boots, but initializes itself and functions as either a Vlance or a VMXNET adapter, depending on which driver initializes it. With VMware Tools installed, the VMXNET driver changes the Vlance adapter to the higher performance VMXNET adapter.
  • E1000 — An emulated version of the Intel 82545EM Gigabit Ethernet NIC, with drivers available in most newer guest operating systems, including Windows XP and later and Linux versions 2.4.19 and later.
  • VMXNET 2 (Enhanced) - The VMXNET 2 adapter is based on the VMXNET adapter but provides some high-performance features commonly used on modern networks, such as jumbo frames and hardware offloads. This virtual network adapter is available only for some guest operating systems on ESX/ESXi 3.5 and later. VMXNET 2 is supported only for a limited set of guest operating systems. Operating system vendors, including Red Hat, do not provide built-in drivers for this card in RHEL 5. In RHEL 6 the driver is provided because it is in the upstream kernel by this point.
  • VMXNET 3 - The VMXNET 3 adapter is the next generation of a paravirtualized NIC designed for performance, and is not related to VMXNET or VMXNET 2. It offers all the features available in VMXNET 2, and adds several new features like multiqueue support (also known as Receive Side Scaling in Windows), IPv6 offloads, and MSI/MSI-X interrupt delivery. VMXNET 3 is supported only for virtual machines version 7 and later, with a limited set of guest operating systems. Operating system vendors, including Red Hat, do not provide built-in drivers for this card in RHEL 5. In RHEL 6 the driver is provided again because it is in the Upstream kernel by this point.

ITECS is currently using a new enough ESX cluster to use VMXNET 2/3 network cards. ( cluster)

There is a problem with doing Realm Linux installs using only a VMXNET 2/3 NIC since the network is required for the install process.

The vmxnet 2 and 3 "enhanced" virtual network adapter has no physical counterpart. One way to make Realm Linux install is to modify the various boot iso files so that they contain the vmxnet 2 and 3 NIC driver. Anaconda, which is the Red Hat Linux installer, must also be able to recognize the adapter as a NIC and to select it for the source of the install and the second stage. It turns out that it is possible to modify Realm Linux boot CDs such that they will work with this enhanced vmxnet 2/3 NIC. It is also possible to modify PXE boot so that it will work also. This requires little extra work if you are already making boot.iso's.



A VM with the vmxnet 2 and 3 NIC installed and VMware tools configured. You will need this so that you can grab the kernel drivers. The version of the kernel is extremely important. For Red Hat 5.5 this is version 2.6.18-128.el5 of the Linux kernel.

Red Hat Enterprise Linux ISOs

First, we need to grab the Red Hat Enterprise Linux ISOs that go with the version we are trying to fix. They can be downloaded from:

For example, the current "spin" of Realm Linux 5 is based on Red Hat Enterprise Linux 5.5 so we need the 5.5 iso files. Download these ISOs.

Install a virtual machine with a flavor of Red Hat. Lets start with server 5.5 x86_64. Install a virtual machine with this set of iso files:

  • rhel-server-5.5-x86_64-disc1.iso
  • rhel-server-5.5-x86_64-disc2.iso
  • rhel-server-5.5-x86_64-disc3.iso
  • rhel-server-5.5-x86_64-disc4.iso
  • rhel-server-5.5-x86_64-disc5.iso

Once you have the OS installed, install VMware tools somehow. Make sure that you have the right NIC configured.("Enhanced vmxnet" for VMXNET 2 card) Make sure you do not register the machine in Red Hat network and do not upgrade the machine with yum. You must be running the same exact kernel as the 5.5 install time kernel which is 2.6.18-194.el5. You must have the virtual machine powered down to effect changes in the virtual network card. It seems it is not possible to change a NIC from "Flexible" type to "Enhanced vmxnet" type in ESX so I power down the guest, remove the "Flexible" NIC, then add a "Enhanced vmxnet" NIC. Once the vmxnet 2 and 3 NICs are configured as the guest eth0 and eth1 NICs and the system has powered on to runlevel 3 type this command:

/usr/bin/ -default

Verify that your network is working, waiting for DNS updates if required. Make sure that you got a lease for an IP address via DHCP and that you can connect / ping to NCSU IP addresses, etc...

Once you run "" a driver module will be created in /lib/modules/2.6.18-194.el5/misc/ called vmxnet.ko. If you have a vmxnet 3 NIC installed you will also have a vmxnet3.ko file here.

This vmxnet.ko file and the vmxnet3.ko file are the drivers that must be added to the Realm Linux install CD for server 5.5 x86_64. There are many steps to this process...

Realm Linux ISOs

We need to grab the Realm Linux ISOs that go with the version we are trying to fix. They can be downloaded from:

In this example we will use server-5.5-x86_64-webks.iso. You will need to repeat for each type. (Server 5 x86, server 5 x86_64, client 5 x86, client 5 x86_64.)

You should now have the Realm Linux boot.iso:

  • server-5.5-x86_64-webks.iso

Next we need to mount this iso file.

Type these commands:

mkdir /mnt/server55
mount -o loop /tmp/server-5.5-x86-webks.iso /mnt/server55

Next, we need to copy the contents of the iso to a temporary work area...

mkdir /tmp/EL5server55
cp -a /mnt/server55/* /tmp/EL5server55/

Since we are done with the original iso now we can unmount it...

umount /mnt/server55
rmdir /mnt/server55

Creating a temporary work area

At this point, lets also create a temporary work area...

mkdir /tmp/work
cd /tmp/work

Next, we need to copy the init RAM disk to this work area...

cp /tmp/EL5server55/isolinux/initrd.img .

Next we need to unpack the init RAM disk. With a 2.6 kernel its a gzipped cpio archive....

mkdir initrd
cd initrd
zcat ../initrd.img | cpio -id

This will explode the contents of the initrd.img disk into the current working directory (initrd) so that we can modify things.

Gathering information

At this point you will need to gather some information for use later, so on your reference VM system perform the following:



Now that we know what PCI card we are looking for, we actually need some hex numbers, which you can get by typing:

lspci -n


Modifying modules.cgz

We now need to explode the modules cpio archive from within the initrd subdirectory

mkdir /tmp/work/modules
cd /tmp/work/modules
zcat ../initrd/modules/modules.cgz  | cpio -id

Our initrd.img modules.cgz file contains x86_64 2.6.18-194.el5 modules.

We want to now copy in the modules from your reference VM system. On the virtual machine the module is located in




The vmxnet.ko and vmxnet3.ko module will only be in place if you have the VMware Tools rpm installed on your reference VM and you have run the script on that same virtual machine.

cd /tmp/work/modules/2.6.18-194.el5/x86_64
cp /lib/modules/2.6.18-194.el5/misc/vmxnet*.ko .
chmod 744 vmxnet*

Time to pack the modules back up again...

cd /tmp/work/modules
find . | cpio -o -H crc | gzip -9 > /tmp/work/initrd/modules/modules.cgz

This will create a new cpio archive and replace the modules.cgz from the original initrd.img with our own modified modules.cgz file. Notice in this case the cpio format type is crc.

Making Anaconda find the driver

Now we need to modify a few more files to get this to work.

cd /tmp/work/initrd/modules

Using your favorite text editor, edit the pci.ids file.

You will have to search for VMware, and as you do you will notice there is a "15ad" number which came from the first part of the pair of hex codes you were supposed to remember.

It looks like this in the file:

15ad  VMware Inc
	0405  Abstract SVGA II Adapter
	0710  Abstract SVGA Adapter

Now you can put the folowing lines in:

0720  VMware Adapter
07b0  VMware Adapter

Where 0720 and 07b0 is replaced by whatever hex codes you saw. So for our ESX cluster the file looks like this:

15ad  VMware Inc
        0405  Abstract SVGA II Adapter
        0710  Abstract SVGA Adapter
        0720  VMware Adapter
        07b0  VMware Adapter

Next you will need to add the following lines to the file module-info:

        "VMware vmxnet ethernet driver"
        "VMware vmxnet3 ethernet driver"

The file should contain tab characters and not spaces before the second and third and 5th/6th lines...

Next you will need to get the vmxnet entries for the modules.alias file. On the reference VM system, it was in the /lib/modules/2.6.18-194.el5/modules.alias file.

cd /lib/modules/2.6.18-194.el5/
grep vmxnet modules.alias  >> /tmp/work/initrd/modules/modules.alias

The contents we were looking for:

alias pci:v000015ADd00000720sv*sd*bc*sc*i* vmxnet
alias pci:v00001022d00002000sv*sd*bc*sc*i* vmxnet
alias pci:v000015ADd000007B0sv*sd*bc*sc*i* vmxnet3

Package our custom initrd.img

Ok, now that the hard work is over its time to package the initrd.img back up...

cd /tmp/work/initrd
find . | cpio -o -H newc | gzip -9 > /tmp/work/initrd.img.vmxnet

Notice in this case the cpio format type is newc.

Now copy that new custom initrd into your temporary iso work environment blowing away the old file:

cp /tmp/work/initrd.img.vmxnet /tmp/EL5server55/isolinux/initrd.img

The initrd.img must also be preserved for CLS to use on the PXE-all server.

cp /tmp/work/initrd.img.vmxnet /tmp/initrd.img.vmxnet.server5.5.x86_64

Give each initrd a descriptive name so that OIT can know which initrd is which.

Create our custom iso file

Now as a last step we need to create the new iso file. We'll call it server-5.5-x86_64-webks.iso and write it to /tmp. We can do that with this command:

mkisofs -R -T -J -V "server55x86_64" -b isolinux/isolinux.bin \
-c isolinux/ -o /tmp/server-5.5-x86_64-webks.iso -no-emul-boot \
-boot-load-size 4 -boot-info-table /tmp/EL5server55

Now you need to copy the custom iso file you just created to your VMware ESX or ESXi storage area for install isos. At this point you should be able to install Realm Linux x86_64 server 5.5 virtual machines with a vmxnet 2/3 NIC. You need to repeat this process for each CD type for Realm Linux. So you need a x86 server and a x86 and x86_64 client CD before you are finished. The descriptively named init ramdisks mentioned above will also need to be set aside for each type to be copied to the campus PXE server to be used with the PXE-all dhcp template in QIP.

ITECS created ISOs in AFS

ITECS created a set of Realm Linux 5 install ISOs and they are available in an AFS locker if this would be useful to other groups on campus. The ISOs can be copied from:


The ISOs were built with the vendor provided VMware Tools version: VMwareTools-8195-261974.

Realm Linux post install

If you use these ISOs or PXE boot and you set up a Realm Linux 5/6 box with a VMXNET 2/3 NIC you need to plan for what to do post install.

  • Use the open VMware tools provided by VMware by adding the line:
    use oit-vm/use/open-vm-tools

    in the web kickstart config file. This is the method ITECS uses for all new vms.

Hopefully this guide will explain all the details of how to create the required boot media for RHEL 5. Thankfully these tricks are not needed for RHEL 6 as it supports vmxnet 2 and vmxnet 3 adapters "out of the box." So this method will only be required as long as we use RHEL 5.

Special thanks to Dave Rose posting these instructions on his blog. [1] We mirrored these here in the techies wiki so that NCSU systems administrators could learn how we added support for VMXNET drivers within the install media in case it needs to be done again for a future RHEL 5 point release.

Personal tools