Linux – Dual-Boot – Fixing the EFI FAT32 UUID..

Although I had successfully achieved a dual-boot uEFI Fedora27/Windows7 system, the expanded EFI partition issue was still unresolved..   I had successfully expanded the partition size, but the expansion of the FAT32 filesystem on it did not work, as gparted was unable to handle it.   After more research, I came to the conclusion that the only reliable solution was to back-up the entire EFI partition contents, and re-create the FAT32 filesystem in the already-expanded partition, and restore the contents..

This worked, but I had to remember that current Fedora systems default to UUIDs in fstab, and – of course – the FAT32 partition UUID had changed with the filesystem re-creation..     Personally, I still prefer the old /dev/sdX format in fstab, but others may prefer to just change the UUID to the ‘new’ one, except that in this dual-boot scenario, that would not work..

The real problem came on rebooting into Win7, when it threw an ”error: no such device <oldUUID>.” error..   but then – after a while – went ahead and booted OK..    I needed to fix this, and restore the ‘original’ UUID..

It seems that changing the ‘UUID’ on FAT32 systems is relatively convoluted, and some of the suggestions I found simply did not work..   I used a spare USB stick with a FAT32 partition for testing..

Eventually I found a rather complex solution here:  https://superuser.com/questions/1247972/change-uuid-of-vfat-partition , and thanks to Tommy for the info..     I tested this on the USB stick first, and then on the actual boot disk, and it worked..   If you are going to try this yourself, I would recommend – carefully – cutting/pasting the ‘complex’ command, taking care to substitute the correct drive/partition info..

Robert Gadsdon.   March 26, 2018.


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