I have Arch Linux and Linux Mint installed. I chose “Grub” as a boot loader in the installer.
After the installation grub only contained an entry for EOS, and none for the other two.
You need to enable os-prober in /etc/default/grub
Then run sudo grub-mkconfig -o /boot/grub/grub.cfg
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Yes. I know.
My suggestion is to add this to the iso installer by default. These are sane defaults that every other distro ships with (Ubuntu, Manjaro, Linux Mint).
That is no longer the default in grub and we deliberately keep it disabled due to people frequently having issues with os-prober. If someone wants to enable they have that option.
It can be noted that os-prober was disabled also in part because it was noted to be a security issue. This is because it mounts all partitions on the disk as root using the grub-mount command to check if they contain other OSes. As a result, this can be exploited and used to gain root privileges. For this reason, os-prober is disabled in some distros. From my understanding.
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This really seems like a serious security issue. Can you share more about this? (CVE link or relevant articles?)
Shouldn’t grub-mount be strictly mounting in read-only mode?
This is all new for me. All distros I know automatically detect all possible OS’s. Thinking of distros concerned with security like Ubuntu and Fedora. That’s why I’m surprised to hear about this.
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This was a decision made upstream by the grub team quite sometime ago and had some controversy. Then other grub changes caused major issues which is one of the reason’s why the default is now systemd-boot and grub has to be selected in the installer if the user wants to use grub on EndeavourOS. I still use grub and a lot of distro’s have os-prober either enabled or not. That’s their choice and i think there was some back and forth on this issue. The installer on EndeavourOS is set up to automatically detect Windows and add the entry in grub hence why os-prober is disabled as the default. This is my understanding and interpretation based only on what i know. I may not be entirely correct in my assumptions or view either. This is why you see the message or something similar.
Warning: os-prober will not be executed to detect other bootable partitions. Systems on them will not be added to the GRUB boot configuration. Check GRUB_DISABLE_OS_PROBER documentation entry
If you are concerned with the security implications of having os-prober enabled as mentioned above, you might want to look into creating a grub boot entry for your Archlinux via a custom.cfg in /boot/grub.