Does EFI partition's disk position really matter?

Question

Level 1

16 points

Does EFI partition's disk position really matter?

NOTE: This post supersedes https://discussions.apple.com/thread/253541997

I needed to resize partitions on the 1.0 TB SSD in my 2013-2019 Mac Pro running High Sierra. Disk Utility would not allow this without first creating a new partition, which I didn't want to do, so I booted from an external clone and used iPartition. I shrank two of the three partitions, including the macOS partition, and enlarged one partition. There seemed to be no problems.

I rebooted from the internal SSD and ran the Partition Map test in TechTool Pro, which found problems with the partition map layout of the drive. I ran TTPro's Partition Repair, which was unable to perform a repair.

I then ran First Aid in Disk Utility, which said:

Checking for an EFI system partition

Problems were found with the partition map which might prevent booting

A repair attempt in diskutil in the Terminal failed with "Error: -69767: This disk doesn't contain an EFI system partition...."

However, "diskutil list" produced the following (I've redacted my name here):

[REDACTED]-Mac-Pro:~ [REDACTED]$ diskutil list disk0

/dev/disk0 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk0

1: Apple_HFS HDD 344.3 GB disk0s1

2: Apple_HFS Documents SSD 332.9 GB disk0s2

3: Apple_HFS macOS SSD 290.8 GB disk0s3

4: Apple_HFS eDrive 31.9 GB disk0s4

5: EFI EFI 209.7 MB disk0s5

(The partition named "HDD" is just named that way because it contains files I transferred from an HDD in my old "cheesegrater" Mac Pro. It's really just a partition on the SSD.)

I've had no problems booting up this happened, and the Mac works normally. Running Recovery (via Internet) finds no problems. EtrecheckPro and the Mac's system report also identify the EFI as disk0s5.

Ideally, the EFI should be disk0s1. Perhaps this is why Disk Utility reports the "disk doesn't contain an EFI system partition...."

Since I'm able to boot up okay, does it really matter that the EFI is at position disk0s5 rather than disk0s1? If not, I'd rather not go through erasing the SSD and recreating everything.

Posted on Jan 9, 2022 10:07 AM

Reply

Answer 1

BDAqua

Level 10

250,619 points

Jan 9, 2022 12:57 PM in response to scott01

I don't think position matters, but reformat is the only way to repair many APFS faults, heres terminal for all my bootable attached drives...

diskutil list

/dev/disk0 (internal):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme 28.0 GB disk0

1: EFI EFI 314.6 MB disk0s1

2: Apple_APFS Container disk4 27.6 GB disk0s2

/dev/disk1 (external):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme 1.9 TB disk1

1: EFI EFI 314.6 MB disk1s1

2: Apple_HFS SSD2 1.9 TB disk1s2

/dev/disk2 (external):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme 1.9 TB disk2

1: EFI 209.7 MB disk2s1

2: Apple_APFS Container disk5 1.9 TB disk2s2

/dev/disk3 (internal, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *1.0 TB disk3

1: EFI EFI 209.7 MB disk3s1

2: Apple_APFS Container disk4 1000.0 GB disk3s2

/dev/disk4 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1.0 TB disk4

Physical Stores disk0s2, disk3s2

1: APFS Volume Macintosh HD 11.3 GB disk4s1

2: APFS Volume Macintosh HD - Data 654.7 GB disk4s2

3: APFS Volume Preboot 84.5 MB disk4s3

4: APFS Volume Recovery 529.0 MB disk4s4

5: APFS Volume VM 2.1 GB disk4s5

/dev/disk5 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1.9 TB disk5

Physical Store disk2s2

1: APFS Volume SSD3 - Data 719.3 GB disk5s1

2: APFS Volume Preboot 375.3 MB disk5s2

3: APFS Volume Recovery 626.3 MB disk5s3

4: APFS Volume VM 17.2 GB disk5s4

5: APFS Volume 15.3 GB disk5s5

6: APFS Volume Update 1.6 MB disk5s6

/dev/disk6 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *8.0 TB disk6

1: EFI EFI 209.7 MB disk6s1

2: Apple_APFS Container disk9 1.6 TB disk6s2

3: Apple_HFS 1013** 1.6 TB disk6s3

4: Apple_APFS Container disk7 1.6 TB disk6s4

5: Apple_HFS 1014** 3.2 TB disk6s5

/dev/disk7 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1.6 TB disk7

Physical Store disk6s4

1: APFS Volume 1016** - Data 1.1 TB disk7s1

2: APFS Volume 14.9 GB disk7s2

3: APFS Volume Preboot 280.5 MB disk7s3

4: APFS Volume Recovery 658.7 MB disk7s4

5: APFS Volume Update 45.1 KB disk7s5

/dev/disk8 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *4.0 TB disk8

1: EFI EFI 209.7 MB disk8s1

2: Apple_HFS 4TB 4.0 TB disk8s2

3: Apple_Boot Recovery HD 650.0 MB disk8s3

/dev/disk9 (synthesized):

#: TYPE NAME SIZE IDENTIFIER

0: APFS Container Scheme - +1.6 TB disk9

Physical Store disk6s2

1: APFS Volume 1015** - Data 654.1 GB disk9s1

2: APFS Volume 1015** 11.3 GB disk9s2

3: APFS Volume Preboot 79.3 MB disk9s3

4: APFS Volume Recovery 542.2 MB disk9s4

Reply

Answer 2

scott01 Author

Level 1

16 points

Jan 10, 2022 10:48 AM in response to BDAqua

Thanks again, BDAqua. I looked at DiskWarrior's features, and it appears to be mainly for rebuilding volume structures and for data recovery. TechTool Pro can already do that, and there are no problems with my volume structures, according to both TTPro and Disk Utility. I doubt if DW could do anything about the EFI partition being in the "wrong place" on the disk. Ultimately, as I said, I guess I'll have to erase with Disk Utility, create new partitions and copy everything back into them from external clones (with SuperDuper). A few hours.

Reply

Answer 3

BDAqua

Level 10

250,619 points

Jan 9, 2022 4:11 PM in response to scott01

Well DiskWarrior can fix most HFS+ problems, expensive some say, but worth it\s weight in Latinum!

http://www.alsoft.com/DiskWarrior/

Reply

Answer 4

BDAqua

Level 10

250,619 points

Jan 10, 2022 11:50 AM in response to scott01

Yes, seems Reformat is needed.

Reply

Answer 5

scott01 Author

Level 1

16 points

Jan 9, 2022 3:59 PM in response to BDAqua

Thanks, BDAqua. I'm not using APFS, sticking with HFS+, but I do know I'll have to reformat eventually to repair any other partition map problems that arise. Alas.

Reply

Does EFI partition's disk position really matter?

Similar questions