Macbook won’t allow write to any external HD’s

[GalacticStreamLord]

I own a Macbook that now does not allow me to write to any of the external drives that I own!!!

I have an 8TB SEAGATE HDD MacOS Extended (Case-Sensitive Journaled)

500GB Samsung 860 Evo MacOS extended

A 2TB Toshiba (Passport?) MacOS extended

Permissions are all Read&Write on these drives


Also.. I literally took that Samsung 860 EVO SSD right out of the box.. tried to format on the macbook and it wouldn’t mount

Then I plugged it into my iMac and it formatted & mounted just fine

Now it mounts to the Macbook but it won’t write. Oh! I can read/transfer data from all of these drives to the Macbook.. so this makes literally no sense to me at all

Can someone come up with an explanation for this?!?!

 

[GalacticStreamLord]

It’s really killing me guys.. LUL

 

[Fishrrman]

Can you write to USB flash drives that are plugged into the MB ?

 

[Brian33]

I know you said all permissions are Read&Write, but I would turn on "Ignore ownership on this volume." Now can you write to it? If that enabled writing to the drive, it's a good indication that it is a permissions (unix-style) issue.

Right-click any external drive on your desktop or in the Finder sidebar and select "Get Info." At the very bottom of the resulting window is a checkbox to toggle this setting.

 

[GalacticStreamLord]

I already tried “Ignore permissions” and my flashdrives do the exact same thing

 

[Fishrrman]

OP:

Are you logged into a "standard" (non-administrative) account?
Or... are you logged in as an administrator...?

 

[Brian33]

I think the volumes are being mounted read-only (for some unknown reason). You can test this idea by opening Terminal.app and entering the following command: mount (Any user may issue this command.)

The output will show all mounted filesystems, one per line, each followed by a bunch of attributes within parenthesis. Many of them will be hidden from normal view (indicated by 'nobrowse'). Find the line with your external drive, and see if it is marked 'read-only'. I re-mounted one of mine as read-only and here's the output now:

brian@imac:~(0)$ mount
/dev/disk1s1 on / (apfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
/dev/disk1s4 on /private/var/vm (apfs, local, noexec, journaled, noatime, nobrowse)
/dev/disk0s3 on /Volumes/BOOTCAMP (ntfs, local, read-only, noowners)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk3s2 on /Volumes/Backup of imac-boot (hfs, local, nodev, nosuid, journaled)
/dev/disk3s4 on /Volumes/imac-other (hfs, local, nodev, nosuid, journaled)
/dev/disk5 on /Volumes/imac-TM-backup (hfs, local, nodev, nosuid, journaled)
/dev/disk2s2 on /Volumes/imac-hdd (hfs, local, nodev, nosuid, journaled)
/dev/disk3s3 on /Volumes/Backup of imac-hdd (hfs, local, nodev, nosuid, read-only)

If any of yours are marked 'read-only' like mine mounted as '/Volumes/Backup of imac-hdd' above, then that's the problem -- even the super-user won't be able to write to them, no matter what permissions are set. However, an Admin user can re-mount it as read-write using the 'mount' command:

sudo mount -uw <mount-point>

...where you replace <mount-point> with something like "Volumes/my-external-drive". If you have spaces in your mount-point name you will need to use quotes or else precede each space with a backslash character: \

I don't know why they'd be mounted read-only, and they may revert to being mounted read-only again after a reboot until it's figured out. I think there's a file or some way to tell macOS to mount certain filesystems read-only at boot time, but at the moment I don't remember how.