Migrating (Disk Cloning) from HDD to a smaller SSD with Dual Boot Setup

Okay! This is a post after a long hiatus. Covid-19 pandemic and lockdown provided enough spare time to do some upgrade on my six year old Dell Latitude. It has a dual boot setup with Ubuntu 18.04 and Windows 10 Pro on different partitions.

My existing HDD was a 1TB sata drive harvested from another old laptop that I had upgraded a few years ago. This HDD had  six partitions roughly as follows. None of the partitions were exhausted in space.

1. UEFI Boot - 512M (If you are not using UEFI boot, then this post will not work)
2. ext4 - Ubuntu - 600G
3. Microsoft Reserved (msftres) - 512M
4. Windows Recovery (NTFS) - 1024M
5. NTFS - Main Windows - 300G
6. Unallocated - nnnM

I wanted to migrate to a a new 500G SSD. Obviously, I had to shrink the partitions appropriately to accommodate in the new smaller SSD. I followed the steps mentioned here Ubuntu Howto.

In this post no point of repeating above steps all over again. I will only mention things that didn't work and I had to adjust or redo.

1. Ensure you have Ubuntu Live USB and Windows 10 recovery USB handy
2. Partition #3 and #4 above is not needed and can be deleted altogether
3. Msdos MBR doesn't allow more than four primary partitions. Learnt hard way!!
4. On new SSD (step#7 in the above article link) don't choose Msdos MBR in Diskpart. Use GPT (Guid Partion table). 
1. I had to use gdisk to convert MBR to GPT 
5. Mark first UEFI Partition as bootable in Diskpart
6. Leave at least 1M unallocated space at the end of the new SSD for GPT to write metadata. Learnt it hard way.
7. Fix Grub2- I was unable to boot successfully at first attempt with new SSD. Use Boot-Repair to fix the issue
8. I had to fix boot for windows 10 also. Use windows 10 recovery with diskpart and bootrec to fix windows 10 boot issues.
9. Have plenty of patience and another device with internet connectivity to research issues :-)

That's all. Post questions and comments, if you want to know more

Cheers!