I build custom ISO Ubuntu 20 according to this article.
After the custom ISO is ready, I install the OS from it, and at first, the error appears:
Check finished errors found in 1 files.
Could you tell me how to find this error and fix it?
I already checked md5sum, I read about it.
It is mentioned in this bug report that "Windows write System Volume Information on any filesystem it can understand (EFI boot partition in this case) which causes the checksum to fail.". This matches my experience, where the error was reported, repeatably, if the USB stick is inserted into a live Windows system between the time it was created and when it is booted.
Looking closer, a folder
System Volume Information is added to the small
EFI (Fat-12/16/32) partition.
Advice: Avoid inserting live USB while Windows is running.
Based on what I can discover from looking at this bug report and discussion (Check error with 20.04-desktop ISO) it appears this is just a built-in limitation of the file checking where the efi.img file is modified when it is loaded and that really means it can't be verified. I would advise go ahead and ignore this error! That is what I have done with my Xubuntu installation and I have had no problems at all (since then I have also noticed this error when installing Ubuntu Mate and I also ignored it in that case as well!)