Converting a .ovf file to work on an older/different VMWare ESXi (maybe also player) setup

I will be using ESXi because that is what I have; I do not see why it would not work in Player or Workstation.

As you know, the way vmware likes to export/import vm guests is using a ovf format. So, let's say we are supposed to add a guest called strangeguest. We get it as a directory called strangeguest, which contains the disk (strangeguest-disk1.vmdk in our case), the config file strangeguest.ovf and a mysterious file called strangeguest.mf (.mf extension for Mysterious File?). When we try to import it we get an error message that complains we cannot import the OVF. A quick look indicates that strangeguest expects to be of SystemType vmx-12 or better:

admin@fileserver:/export/public/ISOs/strangeguest$ fgrep vmx- strangeguest.ovf         vmx-12
admin@fileserver:/export/public/ISOs/strangeguest$

Thing is our ESXi setup does not support vmx-12 guest in our ESXi as is a bit old and needs to be upgraded (which will be subject of another article). However, right now we need to make this work.

So we cheat.

We know the latest systemtype our ESXi support is vmx-10 by looking at the properties of the guests currently in place. So, how about if we tell strangeguest that it is vmx-10?

admin@fileserver:/export/public/ISOs/strangeguest$ sed -i -e 's/vmx-12/vmx-10/' strangeguest.ovf
admin@fileserver:/export/public/ISOs/strangeguest$ fgrep vmx- strangeguest.ovf         vmx-10
admin@fileserver:/export/public/ISOs/strangeguest$

So we try again and we get a different error (note to myself: get that error message). What did we do wrong? Well, do you remember the mysterious file? Let's see what is inside it:

admin@fileserver:/export/public/ISOs/strangeguest$ cat strangeguest.mf
SHA1(strangeguest.ovf)= 7b11b4aacead791f8aaf76e5ed3c2354349b3b20
SHA1(strangeguest-disk1.vmdk)= 9ccd4817ac2f943f7f29be970b76461850460d18
admin@fileserver:/export/public/ISOs/strangeguest$

So it has the checksum (as SHA1, which is a step about MD5 but still not to be used as it can be lied to, but I digress). Remember we edited strangeguest.ovf!

admin@fileserver:/export/public/ISOs/strangeguest$ sha1sum strangeguest.ovf
f14befc1e790b0043dd5f8e22fd8d601637997bd  strangeguest.ovf
admin@fileserver:/export/public/ISOs/strangeguest$

So, we need to update strangeguest.mf:

sed: -e expression #1, char 83: unterminated `s' command
admin@fileserver:/export/public/ISOs/strangeguest$ sed -i -e \
's/7b11b4aacead791f8aaf76e5ed3c2354349b3b20/f14befc1e790b0043dd5f8e22fd8d601637997bd/' \
strangeguest.mf
admin@fileserver:/export/public/ISOs/strangeguest$ !cat
cat strangeguest.mf
SHA1(strangeguest.ovf)= f14befc1e790b0043dd5f8e22fd8d601637997bd
SHA1(strangeguest-disk1.vmdk)= 9ccd4817ac2f943f7f29be970b76461850460d18
admin@fileserver:/export/public/ISOs/strangeguest$

And we should be rewarded with strangeguest being properly imported.

md5 checksum in powershell

It seems I have been stuck in Windows recently. The main annoyance with that is it loves to fight me and hates to tell me what is going on. As a result, sometimes I need to write my own tools. And, yes, they do tend to emulate what I have used in Linux. Take for example md5sum, an example of a command that just happens to be related to the topic of this article.

Here is how md5sum works in Linux:

raub@desktop:~$ md5sum disallowedcert.sst
6e8bf95470e7f1ca0626012ea21e55f7 disallowedcert.sst
raub@desktop:~$

As the man page tells us, there are other options we can use. But, I do not use most of them. So, how about if we write a quick powershell script to emulate at least the basic usage of md5sum?

Warning

The md5 should not be used for, say, verify integrity of a file if you care about security; the MD5 algorithm can be hacked using collision attacks.

The code

Here is a first shot at the code

# emulate md5sum in powershell
foreach ($file in $args)
{
   $md5 = New-Object -typeName `
          System.Security.Cryptography.MD5CryptoServiceProvider
   $hash = [System.BitConverter]::ToString($md5.ComputeHash([System.IO.File]::ReadAllBytes($file)))
   echo "$hash $file"
}

PS C:\Users\User\test> powershell -executionpolicy bypass -file .\md5.ps1 .\disallowedcert.sst
6E-8B-F9-54-70-E7-F1-CA-06-26-01-2E-A2-1E-55-F7
PS C:\Users\User\test> powershell -executionpolicy bypass -file .\md5.ps1 .\disallowedcert.sst .\e098
cf355c19953274d84772a1cec96dc3356ca.crt
6E-8B-F9-54-70-E7-F1-CA-06-26-01-2E-A2-1E-55-F7
1C-BC-A2-83-77-BA-25-04-3D-6D-42-6E-E2-11-34-55
PS C:\Users\User\test>

Let's improve on it a bit then

# emulate md5sum in powershell
foreach ($file in $args)
{
   $md5 = New-Object -typeName `
          System.Security.Cryptography.MD5CryptoServiceProvider
   $hash = [System.BitConverter]::ToString($md5.ComputeHash([System.IO.File]::ReadAllBytes($file))) `
           -replace "-",""
   echo "$hash $file"
}

Let's try it out

PS C:\Users\User\test> powershell -executionpolicy bypass -file md5.ps1 md5sum.ps1 ntpTime.ps1 
F1930269F287A434993172A362269F8E md5sum.ps1
FC6ED0787947524543D34CFBA3BE641A ntpTime.ps1

PS C:\Users\User\test> 

That's much more like it.

Other versions

If you do not like my script there are a few versions out there you can download and run instead. Pick your poison!