The GRUB bootloader is a small, essential program that manages the boot process for multiple operating systems on your computer.
It can be corrupted or deleted during events like a Windows installation, preventing access to your other operating systems. Fortunately, you can restore the GRUB bootloader using the remaining configuration files located in your Linux root partition.
For Ubuntu installer, click on the Try Ubuntu button.
If no Live CD mode available, press <ctrl> + <alt> + <f2> keys to get to the terminal. For Ubuntu, the default username is ubuntu and the password is empty (just press enter at the password prompt).
$ lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT loop0 7:0 0 1.9G 1 loop /rofs loop1 7:1 0 89.3M 1 loop /snap/core/6673 loop2 7:2 0 53.7M 1 loop /snap/core18/941 sda 8:0 0 20G 0 disk └─sda1 8:1 0 20G 0 part sr0 11:0 1 2G 0 rom /cdrom
$ mkdir tmp
$ sudo mount /dev/sda1 tmp/
$ sudo mount --bind /dev tmp/dev $ sudo mount --bind /proc tmp/proc
$ sudo chroot tmp/ root@ubuntu:/#
root@ubuntu:/# grub-install /dev/sda Installing for i386-pc platform. Unknown device "/dev/sda1": No such device Unknown device "/dev/sda1": No such device Unknown device "/dev/sda1": No such device Unknown device "/dev/sda1": No such device Unknown device "/dev/sda1": No such device Unknown device "/dev/sda1": No such device Installation finished. No error reported.
root@ubuntu:/# exit exit
$ sudo poweroff
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