Have an external hard disk with hfsplus or hfs+ partition on it? This is how you can mount it under linux (specifically, Debian) :
in os x :
- disable journaling in the partition/external hdd in disk utility or use run the command “diskutil disableJournal /dev/disk1s1″ in terminal.
in linux :
- apt-get install hfs*
- mount -t hfsplus -o rw /dev/sdb1 /mnt/extdisk