Mount hfs+ partion

Question

I want to mount a hfs+ partion on an external drive. I have installed hfsprogs and created a folder to mount at /media/hfs. Nevertheless this

# sudo mount -t hfsplus /dev/sdb2 /media/hfs

mount: wrong fs type, bad option, bad superblock on /dev/sdb2,
missing codepage or helper program, or other error

fails.

# dmesg | tail
[ 1778.517677] hfs: write access to a journaled filesystem is not supported, use the 
force option at your own risk, mounting read-only.
[ 1778.550769] hfs: invalid extent max_key_len 15237
[ 1778.550797] hfs: failed to load extents file
[ 1892.776860] hfs: write access to a journaled filesystem is not supported, use the 
force option at your own risk, mounting read-only.
[ 1892.777288] hfs: invalid extent max_key_len 15237
[ 1892.777297] hfs: failed to load extents file

I am certain that /dev/sdb2 is correct because I checked it with gparted. Any ideas?

Solution

It seems the partition is either not formatted, formatted from a recent OSX version with options currently unknown to the hfs+ driver, or needing a repair.

In the case of an unformatted partition, gparted will see it correctly as HFS+ because it's just a flag in the partition table.

In case of needing a repair, just plug the disk into an OSX machine, run Disk Utility and use the repair button (bottom right, after you selected the partition in the side pane).

I'm not aware of any recent HFS+ options not understood by the HFS+ driver, but it has happened in the past. The only solution in this case is to wait.