How to boot from two external hard drives in a specfic order?











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I have two external hard drives.I want to keep one plugged into a usb port permanently (let us call this one A) and another plugged in every now and then (let us call this one B). Both have Linux operating systems on them.



I want to boot from A if B is not plugged in and from B if it is plugged in.



How can I achieve this? For completeness my current bios look like the following:



enter image description here



It currently seems to be booting simply from the one it last booted from. (If it helps A and B will always be plugged into consistent usb ports and the laptop has no internal hard drive).










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  • If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
    – harrymc
    Nov 25 at 14:39










  • @harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
    – Quantum spaghettification
    Nov 25 at 14:49










  • It's to understand from your picture what is which disk.
    – harrymc
    Nov 25 at 14:50















up vote
1
down vote

favorite












I have two external hard drives.I want to keep one plugged into a usb port permanently (let us call this one A) and another plugged in every now and then (let us call this one B). Both have Linux operating systems on them.



I want to boot from A if B is not plugged in and from B if it is plugged in.



How can I achieve this? For completeness my current bios look like the following:



enter image description here



It currently seems to be booting simply from the one it last booted from. (If it helps A and B will always be plugged into consistent usb ports and the laptop has no internal hard drive).










share|improve this question
























  • If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
    – harrymc
    Nov 25 at 14:39










  • @harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
    – Quantum spaghettification
    Nov 25 at 14:49










  • It's to understand from your picture what is which disk.
    – harrymc
    Nov 25 at 14:50













up vote
1
down vote

favorite









up vote
1
down vote

favorite











I have two external hard drives.I want to keep one plugged into a usb port permanently (let us call this one A) and another plugged in every now and then (let us call this one B). Both have Linux operating systems on them.



I want to boot from A if B is not plugged in and from B if it is plugged in.



How can I achieve this? For completeness my current bios look like the following:



enter image description here



It currently seems to be booting simply from the one it last booted from. (If it helps A and B will always be plugged into consistent usb ports and the laptop has no internal hard drive).










share|improve this question















I have two external hard drives.I want to keep one plugged into a usb port permanently (let us call this one A) and another plugged in every now and then (let us call this one B). Both have Linux operating systems on them.



I want to boot from A if B is not plugged in and from B if it is plugged in.



How can I achieve this? For completeness my current bios look like the following:



enter image description here



It currently seems to be booting simply from the one it last booted from. (If it helps A and B will always be plugged into consistent usb ports and the laptop has no internal hard drive).







hard-drive boot bios external-hard-drive






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share|improve this question













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share|improve this question








edited Nov 25 at 14:23

























asked Nov 25 at 14:10









Quantum spaghettification

1091414




1091414












  • If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
    – harrymc
    Nov 25 at 14:39










  • @harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
    – Quantum spaghettification
    Nov 25 at 14:49










  • It's to understand from your picture what is which disk.
    – harrymc
    Nov 25 at 14:50


















  • If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
    – harrymc
    Nov 25 at 14:39










  • @harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
    – Quantum spaghettification
    Nov 25 at 14:49










  • It's to understand from your picture what is which disk.
    – harrymc
    Nov 25 at 14:50
















If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
– harrymc
Nov 25 at 14:39




If you set B as first in the boot order and A as second, wouldn't that achieve your purpose?
– harrymc
Nov 25 at 14:39












@harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
– Quantum spaghettification
Nov 25 at 14:49




@harrymc That's what I thought, but I don't seem to get a separate option for the two hard drives in my list of boot options.
– Quantum spaghettification
Nov 25 at 14:49












It's to understand from your picture what is which disk.
– harrymc
Nov 25 at 14:50




It's to understand from your picture what is which disk.
– harrymc
Nov 25 at 14:50










1 Answer
1






active

oldest

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up vote
0
down vote













The different USB ports you have will be internally numbered by the USB hub, so one of them will be #0, the next #1, etc. If you activate USB boot, the BIOS or UEFI tries to boot in that sequence.



You can see the assignment numbers in the Windows Device Manager (or a similar program in other OSs) - plug something in each USB port, check in the device manager which internal device number maps to which device, and you will know which of your ports has which number. You might need to dig a bit to find those IDs. There is actually specific software to make it easier, but it is not required; here an example from Windows USB view:
USB view
If you plug your 'A' device in a higher port number than your 'B' device, 'B' will be preferred for booting, and if it is not present, 'A' will be found and used.



I don't know the exact specs for your USB hub; it is possible that it tries to be clever, and assigns the numbers dynamically by usage - first device plugged in becomes #0, next device #1, etc. If this is the case, you cannot easily achieve what you want (because device 'A' would always have the lower ID).






share|improve this answer























  • Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
    – Forward Ed
    Nov 25 at 15:50












  • @ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
    – gronostaj
    Nov 25 at 16:55











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1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
0
down vote













The different USB ports you have will be internally numbered by the USB hub, so one of them will be #0, the next #1, etc. If you activate USB boot, the BIOS or UEFI tries to boot in that sequence.



You can see the assignment numbers in the Windows Device Manager (or a similar program in other OSs) - plug something in each USB port, check in the device manager which internal device number maps to which device, and you will know which of your ports has which number. You might need to dig a bit to find those IDs. There is actually specific software to make it easier, but it is not required; here an example from Windows USB view:
USB view
If you plug your 'A' device in a higher port number than your 'B' device, 'B' will be preferred for booting, and if it is not present, 'A' will be found and used.



I don't know the exact specs for your USB hub; it is possible that it tries to be clever, and assigns the numbers dynamically by usage - first device plugged in becomes #0, next device #1, etc. If this is the case, you cannot easily achieve what you want (because device 'A' would always have the lower ID).






share|improve this answer























  • Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
    – Forward Ed
    Nov 25 at 15:50












  • @ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
    – gronostaj
    Nov 25 at 16:55















up vote
0
down vote













The different USB ports you have will be internally numbered by the USB hub, so one of them will be #0, the next #1, etc. If you activate USB boot, the BIOS or UEFI tries to boot in that sequence.



You can see the assignment numbers in the Windows Device Manager (or a similar program in other OSs) - plug something in each USB port, check in the device manager which internal device number maps to which device, and you will know which of your ports has which number. You might need to dig a bit to find those IDs. There is actually specific software to make it easier, but it is not required; here an example from Windows USB view:
USB view
If you plug your 'A' device in a higher port number than your 'B' device, 'B' will be preferred for booting, and if it is not present, 'A' will be found and used.



I don't know the exact specs for your USB hub; it is possible that it tries to be clever, and assigns the numbers dynamically by usage - first device plugged in becomes #0, next device #1, etc. If this is the case, you cannot easily achieve what you want (because device 'A' would always have the lower ID).






share|improve this answer























  • Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
    – Forward Ed
    Nov 25 at 15:50












  • @ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
    – gronostaj
    Nov 25 at 16:55













up vote
0
down vote










up vote
0
down vote









The different USB ports you have will be internally numbered by the USB hub, so one of them will be #0, the next #1, etc. If you activate USB boot, the BIOS or UEFI tries to boot in that sequence.



You can see the assignment numbers in the Windows Device Manager (or a similar program in other OSs) - plug something in each USB port, check in the device manager which internal device number maps to which device, and you will know which of your ports has which number. You might need to dig a bit to find those IDs. There is actually specific software to make it easier, but it is not required; here an example from Windows USB view:
USB view
If you plug your 'A' device in a higher port number than your 'B' device, 'B' will be preferred for booting, and if it is not present, 'A' will be found and used.



I don't know the exact specs for your USB hub; it is possible that it tries to be clever, and assigns the numbers dynamically by usage - first device plugged in becomes #0, next device #1, etc. If this is the case, you cannot easily achieve what you want (because device 'A' would always have the lower ID).






share|improve this answer














The different USB ports you have will be internally numbered by the USB hub, so one of them will be #0, the next #1, etc. If you activate USB boot, the BIOS or UEFI tries to boot in that sequence.



You can see the assignment numbers in the Windows Device Manager (or a similar program in other OSs) - plug something in each USB port, check in the device manager which internal device number maps to which device, and you will know which of your ports has which number. You might need to dig a bit to find those IDs. There is actually specific software to make it easier, but it is not required; here an example from Windows USB view:
USB view
If you plug your 'A' device in a higher port number than your 'B' device, 'B' will be preferred for booting, and if it is not present, 'A' will be found and used.



I don't know the exact specs for your USB hub; it is possible that it tries to be clever, and assigns the numbers dynamically by usage - first device plugged in becomes #0, next device #1, etc. If this is the case, you cannot easily achieve what you want (because device 'A' would always have the lower ID).







share|improve this answer














share|improve this answer



share|improve this answer








edited Nov 25 at 18:05

























answered Nov 25 at 15:42









Aganju

8,40431335




8,40431335












  • Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
    – Forward Ed
    Nov 25 at 15:50












  • @ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
    – gronostaj
    Nov 25 at 16:55


















  • Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
    – Forward Ed
    Nov 25 at 15:50












  • @ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
    – gronostaj
    Nov 25 at 16:55
















Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
– Forward Ed
Nov 25 at 15:50






Great info as it sort of pertains to something I am doing, but in this case OP did said Linux was the OS, not windows. Does Linux do the same thing as Windows?
– Forward Ed
Nov 25 at 15:50














@ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
– gronostaj
Nov 25 at 16:55




@ForwardEd OS is irrelevant, this is how USB works: ports have predictable order. I don't know if the answer is correct, though. Booting isn't handled by Windows, but by UEFI (which is unaware of what Windows is, it will boot whatever adheres to its spec: be it bootmgr, GRUB2 or Linux kernel)
– gronostaj
Nov 25 at 16:55


















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