How to edit grub from under LinuxLive?

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it-noob2016-01-12 15:24:37

linux

it-noob, 2016-01-12 15:24:37

I welcome everyone.
I asked a slightly incorrect question in the form, so I am writing in detail.
Windows 8.1 was installed on the laptop (60% that I put it on UEFI, although maybe not - I don’t remember - I have a GPT disk), after that I installed Linux Mint as a second axis. On purpose, I left about 40 GB as free space, not as a partition, so that Mint itself would choose the sizes for the partitions and put it there. Rebooted, the laptop could not find the boot sector. In Linux Mint, nothing could be done with grub, editing the file did not help, installing programs did not help either. Since there was nothing important on the laptop, I decided not to bother, formatted it, removed the security settings (Secure mode UEFI) in the BIOS and installed Windows 10, installed Linux Mint, but the laptop still loads Win10 - my basic knowledge is lame.
Suspicion of the incompatibility of the laptop and my crooked hands. Previously, Linux Mint or CentOS 7 was installed as a second axis on a laptop with mbr without UEFI.
I apologize for the abstract questions:
1. What could happen that grub was not loaded when the laptop was started (first case)?
2. How can I put the OS boot manager into the original Linux Mint assembly, or what can I run from under LinuxLive to edit grub?
On the second question, an addition: the fact is that when executing commands under root, it gave an error about the lack of opportunity (not right!) In the /cow directory - there is a suspicion that this is due to LinuxLive, as well as the fact that applications were not installed on it .

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2 answer(s)

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sixhundredsixtyfive, 2016-01-13
@sixhundredsixtyfive

You need to restore grub. To do this, boot into live and open the root terminal. Next, you need to make a boot record at the beginning of the disk from which the boot should be loaded, for example grub-install /dev/sda (exactly sda and not sda1). A boot entry will be created that starts grub, which Windows has erased with its installation. It would also be nice to update grub so that it sees Windows, for this there is the update-grub /dev/sda command.

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it-noob, 2016-01-13
@it-noob

The system defeated me, I completely installed Mint on the disk and even so the bootloader did not find the laptop. I converted the disk to mbr - now I'm installing Win10, but the solution was so close. Hope dies last....