I recently installed Windows 7 on my hard drive, losing access to Manjaro.
Willing to recover access to it, I found a tutorial in Manjaro wiki of how to restore GRUB Bootloader (https://wiki.manjaro.org/index.php/Restore_the_GRUB_Bootloader).
In a live session, I followed every step of the guide, correctly mounted the partition where Manjaro is installed (sda7) to /mnt and afterwards run update-grub (I haven't an additional partition for boot) and this is what Terminal outputs:
[manjaro /]# update-grub Generating grub configuration file ... Found theme: /usr/share/grub/themes/manjaro/theme.txt Found linux image: /boot/vmlinuz-4.19-x86_64 Found initrd image: /boot/intel-ucode.img /boot/initramfs-4.19-x86_64.img Found initrd fallback image: /boot/initramfs-4.19-x86_64-fallback.img Found Windows 7 on /dev/sda1 Found memtest86+ image: /boot/memtest86+/memtest.bin done
It looks like it detects the files that Manjaro needs in order to boot but it doesn't add an entry for it, however it correctly adds the Windows entry.
Related to the Troubleshooting section in the guide, which says:
If Arch Linux wasn't recognized after an update-grub then probably your Arch installation is missing the package lsb-release.
I found all the files that the lsb-release package installs to the file-system so I don't think that would be the problem.
sda1 is the System Reserved partition of Windows 7, which is installed on sda2.
Manjaro is installed inside an extended partition which contains two partitions; linux-swap(sda6) and Manjaro(sda7).