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Access High Sierra partition from El Capitan

I'm still using an early 2011, 15" MacBook Pro. I've installed an SSD, and I made a new partition on it a few years ago. The original part is on El Capitan 10.11.6, and the new one is updated to the newest OS possible for this mac--High Sierra 10.13.6. I'm able to access the El Capitan partition when it's booted up on the High Sierra partition. It just shows up as a connected drive on the desktop. For some reason, when it's booted up on the El Capitan partition, I am not able to access the High Sierra partition. When I open Disk Utility, it shows that there's another partition on the drive called "untitled" (even though it is titled), but it doesn't appear in the drop-down menu. I haven't been able to find a solution online to make it visible. Any help would be appreciated!

MacBook Pro 15″, macOS 10.13

Posted on Jun 3, 2021 8:31 AM

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Posted on Jun 3, 2021 7:04 PM

macOS 10.13+ uses the new APFS file system. macOS 10.11 and earlier doesn't understand the new APFS file system since APFS did not exist when macOS 10.11 was released. If you want to share files, then you must either store the files on the older HFS+ partition or store them on an external HFS+ formatted drive. Another option would be to store them a NAS which can be accessed over the local network.

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Jun 3, 2021 7:04 PM in response to JellyBellJar

macOS 10.13+ uses the new APFS file system. macOS 10.11 and earlier doesn't understand the new APFS file system since APFS did not exist when macOS 10.11 was released. If you want to share files, then you must either store the files on the older HFS+ partition or store them on an external HFS+ formatted drive. Another option would be to store them a NAS which can be accessed over the local network.

Jun 4, 2021 1:21 AM in response to JellyBellJar

As noted the El Capitan drive cannot see the High Sierra drive because it cannot see APFS formatted drives.

If you want to switch from El Capitan to High Sierra restart your mac while pressing and holding the option/ alt key

this will show the Startup Manager where you will be able to select the High Sierra drive, press return and you will

be able to switch to the High Sierra drive.

Jun 4, 2021 8:47 AM in response to HWTech

Good to know, thank you!

I am also curious what the best way to use Time Machine to backup my drive would be? I can start a new thread for this question if that’s better, but if I use the High Sierra partition to do my TM backups, I believe that backs up the entire drive, including both partitions? That is what I’ve been doing, but unfortunately I have had a lot of trouble lately getting my backups on High Sierra to complete. Looking online, it seems that this is a common problem. If I backup on the El Capitan partition, there’s no problem, but it doesn’t back up the HS partition. Any info you have would be appreciated.

Jun 4, 2021 9:18 PM in response to JellyBellJar

I don't use TM so I cannot say, but I would expect that TM will only backup the system (i.e. partition/volume) you are booted into unless you can add other volumes/drives to the backup. It would probably be best to start a new thread about your TM questions so you may attract contributors with knowledge of TM to advise you on the best options for backing up a dual booting system.

Access High Sierra partition from El Capitan

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