9

Suddenly a secondary drive with HFS+ partition changed from read-write to read-only. How can I use the mount command to reverse it in mountain lion?

16

Try using mount -u -w:

sudo mount -u -w /Volumes/YourDriveName

-u modifies the status of an already mounted filesystem. -w mounts a filesystem as read-write.

3

The answers in this thread did not work for me, but this did:

  sudo mount -u -o rw /Volumes/VolName
2

Occassionaly when this happens to me I need to use the disk utility included with OSX to verify and repair the disk. Any attempts to use mount -u -w /Volume/NIKON-S9700 will fail with this error:

$ sudo mount -u -w "/Volumes/NIKON-S9700"
mount_msdos: /dev/disk2s1 on /Volumes/NIKON-S9700: Permission denied

You can tell that the disk is mounted read-only like so:

$ mount
/dev/disk1 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk2s1 on /Volumes/NIKON-S9700 (msdos, local, nodev, nosuid, read-only, noowners)

NOTE: Notice the "read-only" in the output above for device /dev/disk2s1.

Once I run a repair disk from Disk Utility the drive when mounted shows up like this:

$ mount
/dev/disk1 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk2s1 on /Volumes/NIKON-S9700 (msdos, local, nodev, nosuid, noowners)

Incidentally the repair disk button might sometimes show up as grayed out. I typically have to unmount and remount the disk with Disk Utility running in order to get this button to show up as clickable.

screenshot of Disk Utility with mounted SD Card

     ss#1

1

This happens sometimes when a drives filesystem is corrupted. Run Disk Utility and check the filesystem and drive for errors.

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