Q: How to change permissions on external FW800 Time Machine backup drive.
I started a related discussion here, but replies dried up for reasons unknown, hence my zeal to start this new thread. Hopefully this new topic will garner the attention it deserves.
As I stated in that other discussion, I have an external FW800 hard disk that I used with my old 2009 iMac (running El Capitan) to make Time Machine backups. I recently purchased a 5K iMac and am trying to continue using it without reformatting it, so as to retain the older backups I have on it. But when I use ENTER TIME MACHINE, I find I cannot go back in time to see older backups, even though I can see them by digging down into the drive in the Finder. I believe the problem pertains to the fact that I see many folders with the round, red bar icon (which means "no access"). My computer name has changed, but my login name and password is the same on this new iMac. Even so, I am barred from accessing many folders.
How do I change permissions on my external drive so I have full access to every file and folder on it?
Thank you.
Posted on Nov 26, 2015 5:14 PM
Thank you for your suggestion and for your 2 kind replies here, but please understand I prefer NOT to pay for Apple Support (what you referred me to), which is why I posted here in the Support Communities.
I have found the solution myself, and for the sake of others who find this thread, following in my footsteps, I will share all the steps I took to discover that solution, as follows...
It seems that the tilde "~" character means "home directory" in UNIX, which is clearly something I do NOT want to use, so I ran the following line in the Terminal:
sudo chown -R `id -un`:`id -gn` /Volumes/2TB\ Backup
I let it run about 15 minutes and many files on my TM backup drive scrolled across the screen. But after each line it said, "Operation not permitted." So a change of Ownership via the Terminal on an external TM Backup drive does NOT work. I used CNTRL-C to cancel.
I then used the following Terminal command to check the permissions on that drive:
ls -led /Volumes/2TB\ Backup
Terminal replied:
drwxrwxrwt 8 root admin 680 Nov 30 15:55 /Volumes/2TB Backup
I then opened the 2TB Backup drive and checked inside my User folders. But the red circle with bar which prevents access remains visible.
— — — — — — — — — —
I then tried Pondini's TM support page suggestion (which he says is a "last resort") in the Terminal to remove all access controls:
sudo chmod -RN /Volumes/2TB\ Backup
After a few seconds, Terminal replied:
chmod: Failed to clear ACL on file Desktop PN: Operation not permitted
Terminal then sat there, with a gray block text cursor sitting beneath the above line, rather than give me the normal "[MacName:~ HomeFolder$" prompt. But after about 5 minutes, Terminal replied:
chmod: Failed to clear ACL on file coreservicesd_3216FE5A-C240-5B0B-BBBF-A771A3B135CA_CrashHistory.plist: Operation not permitted
chmod: Failed to clear ACL on file mdworker_3216FE5A-C240-5B0B-BBBF-A771A3B135CA_CrashHistory.plist: Operation not permitted
So I just left the Terminal to finish the job until I could see the regular prompt. Terminal continued to report certain files in the same manner ("chmod: Failed to clear ACL on file... Operation not permitted"). I let it run for a couple days, but then grew weary of it so I cancelled within the Terminal. When I checked my FW800 drive in the Finder, the red circle and bar preventing access was still there. And using Enter Time Machine still does not allow me to go back in Time to access old Backups on that drive.
— — — — — — — — — —
I then fired up my old G4 Cube running OS 10.4, with my fingers crossed. Why? Because Time Machine was introduced in Leopard, and I have Tiger (one OS X version prior) on my G4 Cube. It was my hope that I might get lucky with permissions tweaks. To my delight, OS X Tiger allowed me to use the Finder Get Info box to change permissions on my external FW800 TM drive to Read/Write, even for "Everyone," although it was only on folders I selected inside my User folder of each backup. It took me a few hours of manual labor to tweak permissions that way, but I persevered and accomplished the task.
I had tried to use Terminal commands on my G4 Cube and let it run over a weekend, but permissions were NOT changed. Not sure if it is a bug in Tiger or just Tiger's lack of knowledge about Time Machine, but I was able to exploit it to my advantage insofar as the Finder Get Info box works under Tiger. Once again, I manually opened my "user" folder inside each backup, selected all the folders inside, then used Get Info to change the permissions to READ/WRITE for system, wheel, everyone (all listed). I then moved that FW800 drive back to my iMac and checked. I can now use the ENTER TIME MACHINE command, I can restore files just fine (going back several years), AND I can continue making Time Machine backups too. HURRAH! PROBLEM SOLVED.
So for those of you following in my footsteps, using an old Mac running OS 10.4 (or possibly earlier) is the old fix I could find.
I must admit that it's sad I even need to go through this though. These are MY files. I should NEVER, EVER be barred access from them, regardless of whether I change to a new Mac or not. It's not right. And no, I shouldn't be forced to erase my TM HDD and start over either. That should be MY CHOICE. Thankfully I found a solution. I can access old backups AND continue making new backups with my new iMac to my external FW800 HDD. I am greatly relieved.
Posted on Dec 7, 2015 4:13 PM

