I have Linux (Mint) as my main desktop and Macbook (Mac OS X) as my mobile computer. To backup these machines, I have an external disk which I formatted using HFS+ format. Following instructions, I disabled journaling for this disk.
This morning I tried to copy files from my Linux machine to the external disk. It won't allow me, saying that the disk is read-only. Hmmm... I checked and double checked that the format is correct and that journaling is tuned off. I tried to create a folder and it failed also. Obviously.
Then, I decided to open a terminal session and create a simple file on the external disk; "touch junk". It worked! So, the disk is already mounted read and write. I tried to copy files again and it still didn't work. Puzzled.
What if the problem is with my file manager? I am using Nemo. I installed Nautilus file manager just for the heck out of it. Copying files with Nautilus worked! Strange ... but at least I have a solution for my backup purposes. I still don't know why, though. I'll investigate later, I need to do some backups now.