2015 IMAC Won't Reset in Recovery Mode

Question

2015 IMAC Won't Reset in Recovery Mode

I can’t get my 2015 iMac to start in Recovery Mode. (Core i5" 2.8 21.5”) My ultimate goal is connecting it to my 2019 IMAC to use as a second monitor. (I purchased the thunderbolt 2 -3 adapter plus thunderbolt 2 cable.). I assumed that I would need to have 2015 IMAC with updated software (I don’t know what software it’s running). Rarely used. Kids don’t know personal login or admin login information. I used Guest account for login but I could not update the software without admin login info. I tried to start IMAC in recovery mode several times by restarting computer and pressing Cmm R until Apple logo comes on screen. It did nothing. Same intro screen.

I read the following from MacWorld:

Title: Reset your password using Recovery Assistant and your Apple ID

When you start up your Mac and select the user you wish to log in as you should see a ? beside the Enter Password field. Click on the ? and you might see a password hint. Below the password hint you should see the option to “Restart and show password reset options”. If you click on this your Mac will restart with Recovery Assistant open.

If you don’t see the ? this could be because you haven’t started up your Mac from off–so switch the Mac off and turn it on again.

If you still don’t see the ? and Recovery Assistant option at start up move to the next step.

If you didn’t see the option to “restart and show password reset options” detailed above, you can still enter the Recovery mode and use the Recovery Assistant to change your password.

The process will depend on whether you have a Mac powered by an Intel processor or one that uses one of Apple’s M-series chips, such as the M1 or M2.

On an Intel Mac: Restart the Mac and press and hold Command and R until the Apple logo appears

(End)

There was no option to “restart“. I tried Cmm R several times. I read somewhere to hold Cmm Option R. I did that and got a big question mark in middle of screen that gave -5101 F error.

In Apple Community, I found posts on -5101F error. Someone had success getting rid of error by reinstalling earlier OS by pressing Shift+Option+Command+R and then Start button. I pressed those keys. I’m now looking at a box labeled OS X Utilities with 4 options: Restore from Time Machine Backup, Reinstall OS X, Get Help Online, Disk Utility.

Not sure what path to take? There’s no information on my IMAC that needs saved, and I don’t have backups, so a complete erase of contents is OK.

That leaves 2 options: reinstall or disk utility. Both may not be viable without admin login information? And I’m not familiar with Disk Utility. If they are workable, do they help my situation? Again, I am trying to access Recovery Mode so I can reset admin and login information; then I can update software. Once updated, I can connect it to my 2019 IMAC to use as second monitor.

Perhaps the computer does not need updated to use as a second monitor? Even if that’s the case, I would like to reset the admin and login information. Appreciate any guidance.

Earlier Mac models

Posted on Mar 31, 2024 9:08 AM

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Answer 1

Top-ranking reply

den.thed

Level 10

97,736 points

Mar 31, 2024 10:17 AM in response to ryanfromseven hills

ryanfromseven hills wrote:

I can’t get my 2015 iMac to start in Recovery Mode. (Core i5" 2.8 21.5”) My ultimate goal is connecting it to my 2019 IMAC to use as a second monitor. (I purchased the thunderbolt 2 -3 adapter plus thunderbolt 2 cable.). I assumed that I would need to have 2015 IMAC with updated software (I don’t know what software it’s running). Rarely used. Kids don’t know personal login or admin login information. I used Guest account for login but I could not update the software without admin login info. I tried to start IMAC in recovery mode several times by restarting computer and pressing Cmm R until Apple logo comes on screen. It did nothing. Same intro screen.

Neither of those Mac's support Target Display Mode, so you can throw that idea out the window.

carefully read > Use your iMac as a display with target display mode - Apple Support

I read the following from MacWorld:

Title: Reset your password using Recovery Assistant and your Apple ID

When you start up your Mac and select the user you wish to log in as you should see a ? beside the Enter Password field. Click on the ? and you might see a password hint. Below the password hint you should see the option to “Restart and show password reset options”. If you click on this your Mac will restart with Recovery Assistant open.

If you don’t see the ? this could be because you haven’t started up your Mac from off–so switch the Mac off and turn it on again.

If you still don’t see the ? and Recovery Assistant option at start up move to the next step.

If you didn’t see the option to “restart and show password reset options” detailed above, you can still enter the Recovery mode and use the Recovery Assistant to change your password.

The process will depend on whether you have a Mac powered by an Intel processor or one that uses one of Apple’s M-series chips, such as the M1 or M2.

On an Intel Mac: Restart the Mac and press and hold Command and R until the Apple logo appears

(End)

There was no option to “restart“. I tried Cmm R several times. I read somewhere to hold Cmm Option R. I did that and got a big question mark in middle of screen that gave -5101 F error.

In Apple Community, I found posts on -5101F error. Someone had success getting rid of error by reinstalling earlier OS by pressing Shift+Option+Command+R and then Start button. I pressed those keys. I’m now looking at a box labeled OS X Utilities with 4 options: Restore from Time Machine Backup, Reinstall OS X, Get Help Online, Disk Utility.

Not sure what path to take? There’s no information on my IMAC that needs saved, and I don’t have backups, so a complete erase of contents is OK.

That leaves 2 options: reinstall or disk utility. Both may not be viable without admin login information? And I’m not familiar with Disk Utility. If they are workable, do they help my situation? Again, I am trying to access Recovery Mode so I can reset admin and login information; then I can update software. Once updated, I can connect it to my 2019 IMAC to use as second monitor.

Perhaps the computer does not need updated to use as a second monitor? Even if that’s the case, I would like to reset the admin and login information. Appreciate any guidance.

To reset the Admin. Password, see > If you forgot your Mac login password - Apple Support

To completely reset the 2015 iMac. Follow the Erase and Reinstall directions in the lower half,

of > What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

Then setup using the same Apple ID, if you are keeping it for other family members to use.

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Answer 2

Apr 1, 2024 3:39 AM in response to rkaufmann87

My biggest regret is not posting my issue earlier. Thank you Old Toad, den.thed, and rkaufmann87. You saved me a lot of aggravation and a trip to the Apple Store. Sadly, as you pointed out, I’m staring at a beautiful iMac 2015 in mint condition that’s not usable. I’m pondering if I can use it for storage. My next biggest regret is posting the issue. My apologies to the 3 of you for wasting your time. Had I searched 2015 iMAC external monitor, I would have seen the countless postings on this issue. In my pathetic defense, I did my research on reseting iMac, Recovery Mode, etc. But the assumption that the 2015 iMAC could be used as an external monitor was, in fact, false never crossed my mind. I had never heard of Target Display Mode or anything related. I believe what I learned is that it’s a computer, not a monitor.

I sincerely appreciate Old Toad, den.thed, and rkaufmann87 for responding. I was successful in resetting the login and admin passwords. I’m returning the adapter and thunderbolt 2 cable, which costs $80, and searching for an inexpensive monitor. In the meantime I connected my 2019 iMAC to a LG HDMI 47” 1920 x 1080p TV. I'm trying to figure out the resolution -- it looks barely decent.

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Answer 3

rkaufmann87

Level 10

149,496 points

Mar 31, 2024 10:20 AM in response to ryanfromseven hills

You are wasting your time, Target Display Mode has been dead for many many years. No iMac made after 2011 or so will work. Please carefully review Target Display Mode , and you will see both Macs are too new. If you need an external display, please just buy one. You can find them starting at about $87 and up to about $1500.

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Answer 4

Old Toad

Level 10

218,260 points

Mar 31, 2024 11:48 AM in response to ryanfromseven hills

NOTE : if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe or Recovery mode. This makes it act as a wired keyboard as will insure a successful boot into Safe or Recovery mode.

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