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Linux partition shows as EFI System (FAT)

Problem: I used rEFIt and its “Partitioning Tool” to install Linux, but now the Linux partition is marked as “EFI System Partition (FAT)”.

Solution: Update to rEFIt 0.9 or newer, and re-run the “Partitioning Tool” in the rEFIt menu.

This is caused by a bug in GNU parted. When you use parted to edit a GPT disk, and you mark a partition with the “boot”/“active” flag in parted, its GPT type is set to “EFI System Partition”, no matter what file system it contains. The “Partitioning Tool” in rEFIt 0.8 and older copied that type information into the MBR table without verifying it. Starting in version 0.9, there is a workaround in place that will detect this situation, detect the file system actually present in the partition, and assign an appropriate MBR partition type.

Another solution is to re-run parted, remove the “boot”/“active” flag from the Linux partition (it is meaningless for GPT), and later re-run the “Partitioning Tool” in rEFIt. That will change the type in both partition tables.

If you only care about the MBR partition type, you can use Linux fdisk to change that directly.