Install XCP-ng 7.4.1 without lossing VMs on local disk

Recently, my xenserver (v7.0) dom0 had been experiencing ballooning of the memory used and pFsense, which handles routing, runs in the virutal environment, my local networking stopped and so did access to Internet. I have also been following the XCP-ng project and waiting for their release. The XCP-ng 7.4.0 was the first release (out 31 March 2018) but as being the very first one, I had decided to wait.

With the recent memory issue rearing its head multiple times in the last month, I checked the XCP-ng project for update and was pleasently surprised to see that version 7.4.1 was out. I downloaded the iso and dumped it on a usb stick using:

dd if=XCP-ng_7.4.1.iso of=/dev/sdX bs=8M status=progress oflag=direct

At this stage the installer disk was ready. I wanted to do a clean install, but did not want to loose my VMs which were on a separate SSD in the VM host server. I searched the web and found an article which matched what I wanted. Link: https://support.citrix.com/article/CTX136342

Read warning in  step 3 in the above article. My case was upgrading from 7.0 from pre-6.5 partioning scheme of xenserver. So, in my case it would have destroyed my local storage repository (SR) but the local SR was on a seprate data disk and it was safe. Next important thing to note is to not choose any disk for Virtual Machine storage (step 4). Rest was smooth sailing for the install.

Post-install, I skipped step 9 as my local SR was not on the OS disk. Followed the rest of the steps without any issue except that the xe pbd-plug (step 15) failed:

[root@xen1 ~]# xe pbd-plug uuid=73b3a9f5-998e-bd19-3d0e-b1085cd114fc      
Error code: SR_BACKEND_FAILURE_47
Error parameters: , The SR is not available [opterr=no such volume group: VG_XenStorage-627ed824-d806-7533-aa72-044f31b918a6],

It took some time to search on the web but the problem came out to be something quite simple: step 11 command for xe sr-introduce should have contained the option "type=ext" instead of "type=lvm":

# xe sr-introduce uuid=39baf126-a535-549f-58d6-feeda55f7801 type=ext name-label=”Local storage” content-type=user
I performed the remaining steps to plug the PBD and then used the instructions to restore the metadata. The VMs were there as earlier (check with xe vm-list)

Now the system is running the free version of xenserver, XCP-ng with all features. Next on the list is to get XCP-ng Center working. For now it crashes upon start when run on a Windows 7 machine.