Can't Write to Partition on External Drive
August 20, 2019 8:02 AM   Subscribe

My USB external drive has two partitions (partition 1 is "Mac OS Extended", partition 2 is "Mac OS Extended - Journaled"). I've had this set-up for years with no problems. Suddenly Partition 1 won't let me write. Its "Get Info" says "You can only read", even though permissions grant me read/write privilege. Here's "Get Info" for both partitions. Help?
posted by Quisp Lover to Computers & Internet (6 answers total)
 
Have you tried running Disk Utility and performing "First Aid" on the drive or the partition?
posted by SansPoint at 8:07 AM on August 20, 2019


Response by poster: Yes but seems to be a permissions issue.
posted by Quisp Lover at 8:13 AM on August 20, 2019


Maybe you could try to ignore permissions? How to do this described here.
posted by bluecore at 10:29 AM on August 20, 2019


Response by poster: Thanks, but [er the screenshot I posted, that option is already checked, unfortunately.
posted by Quisp Lover at 11:39 AM on August 20, 2019


Best answer: Oh that is strange and disconcerting. It would help to know what version of the system you are running, and if either of those partitions contains a bootable system install.

I’m wondering if because the first partition was not formatted as journaled (an odd choice for most users) it is exposing a bug in newer versions of the system since APFS was added. Searching online shows an increase in people reporting similar problems after MacOS 10.13 came out (which is when APFS really started to be used on the Mac), but no clear solution.

I’d make sure i had good backups of anything i cared about (including on the other partition) before mucking about with anything that changes permissions, etc. (I suspect changing permissions is barking up the wrong tree in this case.)

I saw a couple of places that said a restart fixed similar problems. I’d go further and do a shut down (not restart), turn off the drive if it has a physical power switch, and (to be a bit superstitious) unplug the drive from the computer. Plug back in and turn everything back on.
posted by D.C. at 2:09 PM on August 20, 2019


Response by poster: Partition 2 is a bootable clone. I'm running MacOS 10.14.5. Since I've been using Partition 1 as recently as a week ago, I doubt this is a bug exposed by OS upgrades.

I just did a shutdown and a cycle off/on of the drive, and it did clear the problem.

Oddly, both drives are now showing "You have custom access" (whereas, per my screenshot above, only Partition 2 said that before, while Partition 1 said "You can only read").
posted by Quisp Lover at 3:18 PM on August 20, 2019


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