A free 8GB USB key given to me shows up in Snow Leopard as read-only.

$ mount
/dev/disk1 on /Volumes/USB DISK (ntfs, local, nodev, nosuid, read-only, noowners)

How can I mount it read-write? According to the provider of the USB key:

"The USB needs to be unlocked. Right click USB-properties-security-select everyone-edit-permissions for everyone-Allow full control"

But I think these must be instructions for a different OS.

I'd be fine with reformatting it - there's nothing valuable on it.

Attempting to force the issue with mount doesn't seem to work:

$ sudo mount -w -t ntfs /dev/disk1 "/tmp/USB"
$ touch /tmp/USB/foo
-bash: foo: Read-only file system

It's read-only because it's formatted with NTFS (the Windows filesystem), which OS X can only read without the help of third party software. If reformatting isn't a problem, then that's likely the easiest way to go. If you need to transfer between OS X and Windows with the stick, use the FAT filesystem. If you're just using it with Macs, the defaults will work fine.

  • 2
    apple.stackexchange.com/questions/58721/… lists several products that provide read/write access to NTFS filesystems. I've been using Tuxera since Snow Leopard and had no issues so far. – jaume Oct 30 '13 at 7:24
  • Thanks. Discovered today that formatting it with "the defaults" indeed wasn't readable by Windows. – Steve Bennett Oct 31 '13 at 6:27

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