# Booting from grub

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## The Problem

I have a dual system window10/Ubuntu16.04 installed in my laptop. Today I can not access window files from Ubuntu and tried one command line from youtube which seems to mess things up :< The system did not boot like before but entering into the grub prompt instead. It seems that system does not know where/what to boot now and may need a manual configuration.

## The solution

I spent some time googling and found these two posts quite useful for me. Here and Here

First, I changed the booting priority in bios so that linux will boot first. I have an Asus laptop. To enter into BIOS, hold F2 when starting your machine.

### Find the root system

When in grub prompt, type ls to check files in the system. You will see things like (hd0),(hd0,gpt1), … ls each one to find where the root system is (you can omit the gpt label). For me, it is (hd0,gpt9). ls (hd0,9)/ outputs things like:

lost+found/ bin/ ... vmlinuz ... initrd.img ...


If you have many linuxes installed, double check if it is the right system by command cat (hd0,9)/etc/issue.

### Boot the system

Now, it is time let GRUB know the system you want to boot by typing commend:

grub> set root (hd0,9)
grub> Linux /vmlinuz root=/dev/sta5
grub> initrd /initrd.img
grub> boot

• If you do not know where your root device is, you can use UUID for specifying the path. type cat /etc/fstab and check the output. The UUID for the root device is located in the entry where \ is in the <mount on> column. Then you can replace root=/dev/sta5 by root=UUID=[UUID you found].

• If you want to specify the kernel version of your linux, you can check available ones by typing ls (hd0,9)/boot/. To suppress the output, you can do set pager=1. Now you can boot the system you want by

grub> set root (hd0,9)
grub> Linux /boot/vmlinuz-[version] root=/dev/sta5
grub> initrd /boot/initrd.img-[version]
grub> boot


The version has to be the same in the second and thrid command line or you will get a kernel panic.

Hurrah, the system now boots correctly. To fix it permantly, after you boot succesfully. Type these in the shell:

$update-grub$ grub-install /dev/sda


Hopefully, I did not mess up with linux again…

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