make an external drive non-bootable

[alyousha]

Hi,
Short request-i need to make an external drive non-bootable on a macbook pro running 10.10.4.

long story:

I have an external 2tb drive that i used to use as an internal macbook pro boot drive, i replaced it with an ssd then installed caddy to make a second internal hdd in my laptop. however it will not work, the macbook would display the sign indicating it can't find operating system...tried pressing option during startup and it gives me the ssd as startup but then it wont work i tried other drives in the caddy and the macbook works perfect, tried switching drives around inside and as soon as the 2tb is inside it does not work-other drives work-and the 2bt works fine as external drive and i ran diagnostics on it-nothing wrong. i figured it's because its a bootable drive...how do i make it non-bootable, tried the unbless command but it doesn't seem to work. many thanks for any tips...
ps i'm a complete newbie to terminal but i can copy and paste

 

[gsahli]

So far, none of the symptoms you list suggest that there's a problem with the 2 TB drive. Possibly with the SSD or with a cable.
I'd try repartitioning the SSD, making sure it has GUID partition scheme. Then reinstalling OS X.

 

[cradom]

Have you tried going into System Preferences and selecting a Startup Disk?

 

[alyousha]

So far, none of the symptoms you list suggest that there's a problem with the 2 TB drive. Possibly with the SSD or with a cable.
I'd try repartitioning the SSD, making sure it has GUID partition scheme. Then reinstalling OS X.

---------------
hi, thank you for the reply. it is GUID. also the ssd works fine as external and internal drive, i suspected the cable and i received and installed a new one yesterday...did not make a difference, it definitely has nothing to do with hardware placement as i tried putting 2 different drives in the macbook and they work fine. tried many combinations with that ssd and without...everything works till i put that 2tb drive in as a second drive instead of a smaller one which work ok with the ssd being the osx. the 2b works fine as external drive but not when its internal. i was thinking of just interning the command to make it non bootable (deleted all the osx folders and files) also worth noting i had refit but i uninstalled it). formatting partitioning are not an option...really struggling with data management at the moment. partly having it as internal drive is to make data management easier.

 

[alyousha]

hi. yes i have. thats when it indicates theres no osx. when i remove the 2tb as a second internal drive the macbook boots just fine from the ssd. if i add a diffrent drive as a second internal hard drive (caddy) the macbook works fine and i have 2 internal drives...for some reason the macbook does not not like that 2tb. so i'm thinking the only reason is it used to be a boot drive. thx

 

[harryb2448]

Why do you want it 'non-bootable'? The only reason I could imagine was to run Time Machine on it, and to do that I suggest you do go the formatting way, ensuring the Partition Map is set to GUID. What odel MBP and are you referring to placing the 2TB drive in the optical drive slot, if it has one?

Some earlier models, 2001, have a SATA III 6Gb/ps hard drive speed, however they have a SATA II 3Gb/ps optical drive speed.

 

[MightyGem]

Do you need the information that's on this drive? As harry says, just reformat it.

 

[alyousha]

Why do you want it 'non-bootable'? The only reason I could imagine was to run Time Machine on it, and to do that I suggest you do go the formatting way, ensuring the Partition Map is set to GUID. What odel MBP and are you referring to placing the 2TB drive in the optical drive slot, if it has one?

Some earlier models, 2001, have a SATA III 6Gb/ps hard drive speed, however they have a SATA II 3Gb/ps optical drive speed.

its a late 2011 15 inch i7 2.2gh.
the caddy (the enclosure that replaces the optical dive to allow a second hard drive)
i can't format it or partition it at the moment, its almost full along with a few other 5tb drives.
does it have to be GUID to be internal drive even thou i don't need it to be the boot drive?
why i want to make it non-bootable is because i swaped around internal drives and the caddy works perfect as the enclosure for the boot drive or as the second drive...no problems with any other drives than this 2TB. and because the problem seems to manifest in the OS starting up so its a guess it has to do with it being bootable....maybe I'm wrong, is it hard to reverse the bootable commands?
thx for the reply.

 

[gsahli]

Your conclusion that being bootable causes this trouble is what we find unreasonable. My mini has an SSD and the original 500 GB drive. I'm able to select which drive I want to boot from in system prefs.
For some simple troubleshooting, run this command and compare:
greg$ diskutil list
/dev/disk0 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *120.0 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_HFS MacSSD 119.2 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3

/dev/disk1 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *500.1 GB disk1
1: EFI EFI 209.7 MB disk1s1
2: Apple_HFS Macintosh HD 499.2 GB disk1s2
3: Apple_Boot Recovery HD 650.0 MB disk1s3

 

[gsahli]

I should have said run that command (diskutil list) in the Terminal.

 

[ferrarr]

Put the 2TB drive in an external enclosure, then erase it.

Or hold option at startup, does it list all startup drive options?

 

[alyousha]

Thank you all for the replies. can't format it as i don't have space anywhere else left. in a few weeks i will try and report back.
thank you.