Re: determining root mounting point from GRUB command line prior to boot

[Blue Upsilon]

Hi David,

Ok, thanks for the explanation.

Best,
/Blue Upsilon

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, May 28, 2019 12:28 PM, David Balažic <address@hidden> wrote:

> No. The device names are depending on two things:
>  - the kernel (they enumerate the devices)
>  - the file names in the /dev folder (they can be dynamically created)
>
> You can "ls" the /dev folder, but not more.
>
> With enough knowledge you could correctly guess the name, but I doubt there 
> is a 100% workking solution.
>
> Regards,
> David
>
> On Tue, 28 May 2019 at 00:16, Blue Upsilon via Help-grub <address@hidden> 
> wrote:
>
>> thanks Steve;  but this does not solve my problem.
>> to be more clear this is what i do when i boot:
>> ======
>> grub> set root=(hd0,gpt4)
>> grub> linux /vmlinuz root=/dev/nvme0n1p4
>> grub> initrd /initrd.img
>> grub> boot
>> ======
>>
>> this works;
>> but line #2  can be problematic in some cases.
>> say i'm booting from an external disk backup.
>> then in line 2,    i don't know what to set root equal to.
>> if I do:     ls  /dev    then it does not show the various 
>> sda1,sdb2,nvme0n1p4; etc etc.
>>
>> the only way i see these is:   say i don't set a root=...  argument,   then 
>> the boot FAILS,     and i get to BusyBox  with an initramfs command line.
>> in this command line,  if i do    ls /dev      THEN  i do see the various   
>> /dev/nvme0n1p4,   etc etc....
>> but,  is there a way to see these in GRUB command line?   that way i can 
>> know what to set the root arg equal to.......
>>
>> Cheers,
>> Blue
>>
>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>> On Monday, May 27, 2019 9:28 PM, Steve <address@hidden> wrote:
>>
>>> type
>>> ls
>>> it will list all partitions and drives
>>>
>>> On Mon, 27 May 2019 at 19:26, Blue Upsilon via Help-grub <address@hidden> 
>>> wrote:
>>>
>>>> Hi there,
>>>>
>>>> I use Ubuntu 18.04.
>>>> When I boot from GRUB command line, is there a way to determine what the 
>>>> root mounting point will be, before booting?
>>>>
>>>> i.e., say I know that my partition that has Ubuntu is  (hd0,gpt4).
>>>> so then I do:     set root=(hd0,gpt4)
>>>> and then I happen to know that the correct root mounting point is   
>>>> /dev/nvme0n1p4
>>>> so then I know to do:    linux /vmlinuz root=/dev/nvme0n1p4
>>>> and then i do     initrd /initrd.img     and  boot
>>>>
>>>> but like what if i don't know ahead of time that    /dev/nvme0n1p4   is 
>>>> what I need?
>>>> (this problem comes up when:   say i'm booting from a backup external 
>>>> disk, and i don't know whether it will be /dev/sdb2  or whatever.... etc..)
>>>>
>>>> Thanks,
>>>> Blue Upsilon
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