Howto: Removing a disk from a VM - howto identy the right disk?

From time to time, we need to remove disks from a VM. If there's only two or three disks attached to the VM, it's typically not a problem figuring out which one to remove e.g. if the disks have different sizes. But if you have seven or eight disks and they are the same size, then it's a bit more tricky - let's say if you're asked to remove the 'E-drive'. Under 'Edit Settings' for the VM, the disks only have a number which does not necessarily correspond with anything within the VM.

So how to identify exactly which disk that corresponds with a given volume within Windows?

The match can be made by looking at the SCSI target ID for the disk - this can be identified both in WIndows and under 'Edit settings' for the VM (A VM can have four SCSI controllers with up to 15 disks on each controller, so a maximum of 60 disks per VM).

To identify SCSI target ID within the VM:

Go to Computer Management -> Disk Management

Right click a disk and choose Properties

On the General tab you will see the Bus number (SCSI controller) and the Target ID (SCSI target ID), note the number - in this case below the ID is 4.

To identify SCSI target ID from the VI client:

Now go to 'Edit Settings' for the VM under and locate the disk with the corresponding target ID (see Virtual Device Node for the disk). Make sure the that the controller number and SCSI ID is the same. In this case it is Hard Disk 5 that have SCSI ID 4.

Shut down the VM to remove the disk.

Resetting the root password on ESXi 5 (and ESXi 4)

Yesterday, we had a fairly nasty situation at work where a standalone ESXi 4.1 host had to be rebooted. After reboot it did not automatically reconnect to vCenter and so a manual reconnect was done which prompted for root password. Unfortunately, we did not have the root password (don't ask). The host was joined to a domain but it could not be added to vCenter by using domain credentials and ssh to host with domain credentials did not work either. So, having 19 VMs down and no way to power them back on, I was basically screwed (all VMs were residing on DAS).

According to this VMware KB article there is no supported way to reset the root password on an ESXi v4 or v5 other than to reinstall it (or do a repair). I contacted VMware support and they sent me a guide for doing it in an unsupported way.

Finally, I mounted the ESXi 4.1 install ISO and did a repair. This resets most host configurations such a root password, network configuration, ntp settings, domain etc. After this I could set the pas

sword, reconnect to vCenter and then I had to reconfigure the host. Fortunately, the VMs were not completely gone from vCenter but were presented as greyed out orphaned VMs. So I could still see which LUNs the VMs were residing on. That way, the .vmx files could be located (except for one VM that had been renamed in vCenter without svMotioning or migrating it to another LUN afterwards...), the orphaned VM could be removed and the VM could be readded. It was quite a boring process but a least it worked.

Today, I wanted to recreate the password reset method in my home lab to see if I had actually done it in the correct way. I can confirm that, at least, on a virtual ESXi 5 it works and it is possible to reset the password to blank.

These are the steps
Download a Linux live bootable ISO. I used KNOPPIX. Mount the ISO and boot the host.

Once booted into KNOPPIX, open a shell.


Run the following set of commands:

# fdisk -l
# mkdir /mnt/disk
# mount /dev/sda5 /mnt/disk

(Mounting the correct device is the tricky part. To me, it was rather confusing which one to choose. For both the Fujitsu server that I dealt with and for the virtual ESXi, though, it was in sda5 that the state.tgz file was located.
VMware suggested using the following command for HP servers:
# mount /dev/cciss/c0d0p5 /mnt/disk - c0d0p5 is controller 0, disk 0, partition 5)

# cd /mnt/disk
# ls -al
# cp state.tgz state.tgz.bak
# cd /ramdisk
# mkdir temp
# cd temp
# tar zxf /mnt/disk/state.tgz
# ls -al
# tar zxf local.tgz
# cd etc
# nano shadow


Blank out the encrypted password. For example change root:$1$ywxtUqvn$9e1iXjGVd45T5IAgRxAuV.:13358:0:99999:7:::
to root::13358:0:99999:7:::

See below screendumps for before and after:

Save the shadow file.

Run the following commands to repackage everything:

# cd ..
# rm -rf local.tgz
# tar zcf local.tgz *
# chmod 755 local.tgz
# rm -rf /mnt/disk/state.tgz
# tar zcf /mnt/disk/state.tgz local.tgz
# ls -al /mnt/disk/
# umount /mnt/disk
# shutdown -r now

Disabling cores in BIOS for BL460c Gen8

Due mainly to licensing rules imposed by Oracle and Microsoft, there is an increasing demand for either locking VMs to specific hosts (like with VM-host-affinity rules) or for decreasing the number of physical CPUs or logical cores in the ESX hosts.

For HP hardware it is possible to order Blade servers with 2, 4, 6, or 8 cores - at least for BL460c Gen8. But in my company, we like to keep things as standard as possible, not having too many different hardware models.

As per Gen8, it is possible to disable a given number of cores in the BIOS. It has to be increased/decreased in pairs from 1 to 8. So as a minimum you can have 1 core enabled on each CPU. It is not possible to deactivate one of the physical CPUs.

Downloading VMware tools seperately from VMware site

The other day I had to extract the VMware tools ISO for a customer. One way to do it is to log on to a VM that has not updated VMware tools to latest version, choose to upgrade VMware tools manually and then copy all of the files on the mounted ISO and make a new ISO.

However, the different versions of VMware tools can also be downloaded directly from VMware's website on http://packages.vmware.com/tools. There are also tools version for Windows servers.

I found some more info on it on this site

Why Are There Two VMX Files?

Have you noticed that for a powered on virtual machine in vSphere 5.1, there is now an additional VMX file that ends with an ~ (tilde) found within the virtual machine's configuration directory?

This was an observation that was made by a few folks and some thought it might be related to a virtual machine's lock file which is created when a virtual machine is powered on. After a bit of research, it turns out this extra VMX file is not a lock file but actually an "edit file". This edit file is a copy of the original VMX file and when changes are required, they are applied to the edit file first. Once the changes are complete, the edit file is then atomically swapped with the original VMX file which helps prevent potential VMX file corruption. In the worst case event where the original VMX file is somehow corrupted, the virtual machine can be restored using the edit file.

This is another reason why you should not be manually editing a virtual machine's VMX file, especially when it is still powered on. For any VMX configuration changes, you should be automating using the vSphere API through the use of either PowerCLI or the vSphere SDK for Perl.