Why is my exFAT external HDD read-only?


My 1.5Tb Toshiba external HDD has become read-only.
I think it was working normally on MATE 21.04 but i'm not sure anymore. I upgraded to 20.10 quite quickly. Maybe i hadn't tried writing to it yet.

I am using a dual-boot setup and it still works as usual (read/write) on Windows.

It is formatted exFAT and after some searching i installed exFAT fuse and exFAT utils, but still i can't write to it and Permissions are still apparently undeterminable.

Can anyone help me out with this?


The disk is mounted as '/media/JD2' instead as '/media/username/JD2'
This means:

  1. root owns the disk
  2. you do not own the disk as user
  3. you can not write to it because you don't own the disk.

Try to write something as superuser:
echo testing123 |sudo tee /media/JD2/testing456

read it back:
sudo cat /media/JD2/testing456

check your mount options while it's mounted
mount |grep sdc

This should get you something like:
/dev/sdc1 on /media/username/JD2 type fuseblk (rw,nosuid,nodev,relatime,user,default_permissions,blksize=4096,uhelper=udisks2)

Make sure it contains 'rw' and 'user'.

This is what the 'man' file has to say (man mount):

   Non-superuser mounts
   Normally, only the superuser  can  mount  filesystems.   However,  when
   fstab  contains the user option on a line, anybody can mount the corre‐
   sponding filesystem.

   Thus, given a line

          /dev/cdrom  /cd  iso9660  ro,user,noauto,unhide

   any user can mount the iso9660 filesystem found on  an  inserted  CDROM
   using the command:
          mount /cd

   Note that mount is very strict about non-root users and all paths spec‐
   ified on command line are verified before fstab is parsed or  a  helper
   program  is  executed.  It's strongly recommended to use a valid mount‐
   point to specify filesystem, otherwise mount may fail. For example it's
   bad idea to use NFS or CIFS source on command line.

   For  more details, see fstab(5).  Only the user that mounted a filesys‐
   tem can unmount it again.  If any user should be able  to  unmount  it,
   then  use users instead of user in the fstab line.  The owner option is
   similar to the user option, with the restriction that the user must  be
   the  owner of the special file.  This may be useful e.g. for /dev/fd if
   a login script makes the console user owner of this device.  The  group
   option is similar, with the restriction that the user must be member of
   the group of the special file.

So, back to your attached picture, if you click on the 'gears' icon and then select 'mount options' you should see the mount options in the 4th input-field. Make sure it contains 'rw' and 'user' and all should be fine.


Thanks again for the info.

Turns out it was as simple as toggling on 'User Session Defaults' after clicking the cogs.

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