Posting in this forum because people here might also be working cross-platform between OS X and Linux. I have an external USB drive (USB 2) that was formatted on a CentOS Linux system (ext4 filesystem) and was used as an rsync-based backup for that system. Im now trying to access this on a Mac (Mavericks) using FUSE for OS X. Ive done this in the past (way past) successfully with other drives, but not this time. When I turn the drive on OS X thinks about it for a while and then pops up a window with The disk you inserted was not readable by this computer. Assuming this is an OS X vrs. etc4 issue, I click Ignore and look in the Disk Utility. Things look OK there at first glance showing the drive name in the left-side panel with partition information below it, although the latter (disk3s1) is greyed out. It also shows the partition map scheme to be Master Boot Record (which sounds odd to me). The drive is not, however, mounted. Cannot see it anywhere in the GUI (in Finder, for example) and a df s command in the Terminal shows no sign of it. Also, it cannot be ejected/dismounted through the Disk Utility. Looking in the ever-helpful logs I find an entry in the system log: kernel: USBMSC Identifier (non-unique): DAA877039488 0x152d 0x2336 0x100, 2 The ID shown (DAA877...) is the same as that shown in the Disk Utility information for the drive. After some googling on this helpful error message I learn little of use. Taking the drive and putting on a second Linux system there are no problems at all. Put it back on OS X, problems. Replace the USB cable, same problem. Any ideas as to whats going on, or how to remedy it? I dont think its even getting to the point where FUSE would kick in.