Is it safe to enlarge EFI partition by shrinking C partition?

Question

I want to enlarge an EFI partition to 600 mb. I am going do it by shrinking sda4 (C:) by 500 mb, then merge it with sda3. Next I will shrink sda3 by 500 mb again and finally merge it to the EFI partition. Is it safe to enlarge the EFI in this way?

Answer 1

Merge? NO! Those partitions are distinct from each other and must remain separate!

If you meant "move" rather than "merge," then technically the answer is still "no" -- no disk operation of this type is 100% safe. A bug, power failure at inopportune time, or other problem can result in catastrophic filesystem damage when you resize or move a partition. That said, such problems are rare, so chances are shrinking /dev/sda4 and then moving the other partitions will work. I STRONGLY recommend doing a complete backup before proceeding, though. Also, I've had limited success when growing FAT partitions. You should back up the ESP and be prepared to re-create the filesystem and restore its contents if you have problems.

One more comment: As I understand it, the Microsoft Reserved partition (your /dev/sda3) is basically just "scratch space" for use by Windows partitioning tools. It holds no vital data. Thus, you might be able to get by with simply deleting it, growing your ESP, and then creating a new Microsoft Reserved partition in the remaining space. This might be safer than shrinking and then moving /dev/sda4; however, I recommend you do some searches to verify this information, because I'm not a Windows expert, so my understanding of the purpose of the Microsoft Reserved partition may be incorrect. Also, it's conceivable that Microsoft expects it to be of a certain size, so shrinking it in this way may reduce its utility.