I have a 1 TB hard drive in a Macbook Pro 6,2 (mid-2010) partitioned with 900 GB for Mac OS X and 100 GB for Ubuntu 14.04. I wanted to make the HFS+ partition (with OS X installed as a boot drive) readable from Ubuntu. I followed another user's answer and did this:

sudo mkdir -R /media/username/MacOS
sudo chown --recursive username:username /media/username
sudo mount -t hfsplus -o uid=USERUID,gid=USERGID /dev/sdx /media/username/MacOS

The chown step seems to go through every file on the HFS+ partition (mounted at /media/username/MacOS) and changes ownership to the user indicated by username. After each change, the process says "Read-only file system". When I access the MacOS partition using sudo nautilus, the files are also read-only.

Based on my research, this is good; HFS+ is supposed to be read-only for Ubuntu unless journaling is turned off, so it seems to be operating as it should. My question, then, is what is chown actually changing? Is it changing the permissions of the files on the HFS+ partition itself, or is it just changing whether Ubuntu gives access to those (read-only) files to my user? In other words, is chown actually making any changes to my Mac OS X files/permissions? Can chown make changes to permissions on a drive that is read-only?


chown cannot make changes to read-only filesystems.

  • So, when I execute chown on a mounted HFS+ parition (for example, my OS X boot drive with my files) and I then have access to read from Ubuntu, it's not modifying the mac files? I know it might be a stupid question, but I'm not sure why it works given that the drive is read-only. – bzodonnell May 7 '15 at 16:50

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