El Capitan can not see an external drive

From the original post I had the same problem with encrypted external HD's not showing after installing El Capitan. I did unmount the disks before installing El Capitan and then plugged drives after but they did not mount and unmountable through disk utilities. However I did find after a full shut down and then plugged back in HD's and boot up that they were available and usual password requirements required to mount. So it appears El Capitan will only recognise encrypted drives after an update from a full reboot. Don't know if this helps anyone.

I have a workaround that has fixed my Seagate Central issue.

The problem is that the NAS box is now trying to connect via SMB instead of by AFP. When I shutdown Samba on my Seagate Central, it now works EXACTLY as it did before I upgraded from Mavericks.

It is really quite easy to do. You just need to know the IP of the server, the admin username and admin password (login and password is same as for a web admin login).

Open a terminal window in El Cap and enter the following commands (making appropriate substitutions):

$ ssh <ADMIN_USERNAME>@<NAS_IP>

Password:

$ sudo su -

# /etc/init.d/samba stop

# exit

$ exit

Everything should be as per pre-El Cap.

I hope this helps!

JK

Hay guys 🙂

I just figured my issue out, my 5TB drive was in process of being encrypted when I updated to El Capitan, and that was the reason why I couldn't use it. I plugged it into my mac running older version of OS and allowed it to finish the encryption. Once that was done I was able to use the drive on El Capitan 🙂

Hey rjp49,

We want to look at the file system or format of the drive first. Remember that FAT32 has a file transfer limit. Anything over a certain amount at one time (for any one file) will not transfer. If the format is NTFS it will not be mountable to the desktop. Usually after a reformat to exFAT or OS X extended journaled will allow it to be recognized.

Sorry Mike, I don't know how to make a post of my own here, however

I had backed up my computer to my Samsung/Segate hard drive just before upgrading to 'El Capitan', now the hard drive is not recognised and no matter what suggestions I try, including downloading from Segate new drivers - n o t h i n g - my hard drive will not be recognised by time machine:((( I've resorted to buying yet another drive from Apple, oh and guess what, that works. I now have a useless £45 hard drive:(( I've also spent well over an hour on the phone to an Apple tech testing out my Mac book Pro - no problems apparently and oh yes, we've had a lot of complaints, try going to Segate and downloading some new drivers!

I'd highly recommend looking into Apple's USB 3.0 interface as the source of any drive issues.

I finally resolved my issue by running Disk Warrior to rebuild directory on external hard drive, and Drive Genius. The drive always worked fine on my MacBook Pro which only has USB 2.0 ports, and continued to work fine on it when it would not work on my Mac Mini which has USB 3.0 ports. After fixing the drive with DW and DG, I have been using the drive without problem for several months now on my Mac Mini with a Belkin USB 2.0 hub which downgrades the 3.0 connection to 2.0. Although (if I'm not mistaken, it's hard to remember after all the ordeal) I was using the drive with the 2.0 hub when I first started having problems. I then plugged it directly into the Mini 3.0 port thinking the hub might be the problem. At any rate, I'm thankful the issue is resolved. But note, I also have a LaCie USB 3.0 external SSD drive plugged directly into the Mac Mini, to which I've had suddenly drop connection twice so far, making Apple USB 3.0 highly suspect.

<Edited by Host>

Angela, does your Mac have USB 3.0 or 2.0 ports? If 3.0 and you have another Mac or access to one that has USB 2.0 ports instead, try plugging your drive into it and see if it's recognized. Or plug a USB 2.0 hub into your 3.0 port and plug your drive into the hub instead of directly into the 3.0 port. If your drive works with USB 2.0 but not 3.0 then your issue is a USB 3.0 one.

HIDarrell

I seem to have 3.0 USB ports. My son has tried it in his Mac which is older and does have El Capitan up to date, nothing, how ever he has the same Samsung hard drive and his works, it is a year old where oa mine is 2yrs.

Open your Disk Utility application (from Utilities folder in Applicatiions); if drive is shown in left hand column, select it and click First Aid button on top, then click Run to repair the drive.

But if your drive isn't recognized (doesn't show up on Desktop), then it probably won't show up in Disk Utility.

Mine didn't, but did show up in Disk Utility in Recovery Mode, which may be worth a try.

Reboot your Mac while holding down Command R keys, then launch Disk Utility from menu bar in Recovery mode.

If drive shows in DU, then run First Aid, Restart your Mac, and see if drive mounts.

That worked for me several times, then quit working. It was a nightmare, and not sure how I finally got drive to consistently mount.

I think I rebuilt the directory with Disk Warrrior, and also rebuilt the drive with Drive Genius, then plugged into my USB 2.0 hub not USB 3.0 port on my Mac.

You said your backup seemed like it was taking forever so you shut it down. If you turned your external drive off without ejecting it, you could have corrupted the drive directory which will cause the drive to be unrecognized and not mount. One brand of software for rebuilding the directory is Disk Warrior. See - http://www.alsoft.com/DiskWarrior/ . Drive Genius can also rebuild the directory, as well as repair the drive and repair permissions (better than Disk Utility), among other useful things. See - https://www.prosofteng.com/drivegenius-defrag-mac-software/ Both are good diagnostic repair tools to have on hand.

I have had this problem with a 3Tb external drive encrypted by Filevault. I tried everything suggested above, plus my copy of Drive Genius and I bought Disk Warrior.

DW would have rescued all the files on the drive which none of the other options could see, but as you can imagine 3Tb (the disk was getting full) of data would have taken days to rescue, if I only had somewhere to put it all.

In the end, I had to go back to Mavericks (which was the OS that I was using when I started the Filevault encryption) and re-install that; try starting up using Mavericks but as soon as I got to a point where it recognised my external drive, I re-named it on the desktop to something completely different. I then re-started in Mavericks again and it worked. The idea was to remove the link between the ext HD name and the Filevault software.

Finally I had my drive working again - and I resolved to never *EVER* use Filevault again on any file or drive, or anything. I feel nervy just typing the name just in case the software tries to destroy 3Tb of data again.

I re-installed El Capitan and the drive works perfectly now it is not encrypted.

No more encryption for me.

I had a sata drive, I took from a previous mac mini, put in a hard enclosure and connected to another mac mini. After functioning perfectly for a short time, suddenly. it was unrecognizable by the mac mini and could not be mounted using disk utility. Finally after reading Darrell's post, I rebuilt the drive with DW. I'm happy and relieved to say Fixing (rebuilding) the disk with DISK WARRIOR, worked for me. I did NOT want to reformat and lose all the data. So this one goes down as a save. Thanks Darrell!!

See - El Capitan constantly resets external USB Hub

Any update to this? I am having the same issue after updating to 10.11.1

I'm positive its the OS. I switched out my old hard drive that has Yosemite on it and my external functioned properly, but when I put my new hard drive in with El Captain my external cannot be read.