I have a pc which was running Windows 10 and I wanted to create another partition and dual boot Pop-OS. I followed instructions to create a bootable USB drive and use Gparted to make a new partition. Installed Pop-OS and everything seemed good. Linux now running on my machine. However, I noticed that there was no option after POST to select which os I wanted to run. I found a command (11 year old post) to hold SHIFT down while booting and it showed me the blue Grub screen with operating systems on it and only the Pop GNU/Linux option was listed. Another post (dated 2018) suggested running 'gnome-disks' to see what is there and it showed the two partitions for Windows and the two for Linux. Only the Linux was mounted, so I mounted all of them and rebooted, but to no avail. I ran 'ntfsfix /dev/sda2' where sda2 is my ntfs partition for Windows, and got this error: 'Refusing to operate on read-write mounted device /dev/sda2.' I am still learning the system, but have learned so much already because of this problem. I need some help please.
1 Answer
there is 2 ways to dual boot
at the bios/efi level, if the motherboard supports it, use its boot manager, and select between disks to boot. This obviously only works if you are using multiple disks, and not different operating systems on one disk.
with linux using grub2, the grub2 boot menu. Your bios/efi boots your disk, either the one and only disk or a selected disk of many, and grub (grand unified boot loader) launches and has a menu listing where one of many listings will boot by default unless interrupted and a different one chosen. The menu entries can point to anything, typically the one linux operating system your using with past kernel versions listed as you've done updates over time. But it is here you configure grub2 to have menu entries pointing to other operating systems (i.e. windows) which may be on the same disk as your pop-os linux or could be on a different disk the physical location is trivial.
in /etc/default/grub place
GRUB_DISABLE_OS_PROBER=false
it is typically not present, and grub2 will or should search automatically all connected disks for other operating systems by default and place the menu entry for you; but to be sure enter this to be explicit (i know how RHEL/CentOS operate, can't speak for all linux versions)
then do a
grub2-mkconfig -o <location of grub.cfg>
# typically </boot/efi/EFI/redhat/grub.cfg> for me, with redhat or centos
and then that rebuild of grub2 will have menu entries you can select to boot the various operating systems that are present; you may need to alter the <grub.cfg location> depending on your setup.
sudo apt install os-prober; sudo os-prober; sudo update-grub. I'm not adding this as an answer because I haven't worked with Pop OS. Feel free to add an answer if the approach works for you.