I've seen a lot of questions in regards to installing Solus alongside other Linux distributions in UEFI mode, particularly in regards to installing the bootloader in the correct place. Currently, the Solus installer doesn't present multiple ESP (EFI System Partition) partitions to install the bootloader to, which means it may overwrite existing entries. So... Let's take care of that.

When you choose to install Solus alongside another system, you'll need to edit your partitions manually in GParted, which means you'll be creating another set of partitions on your disk for Solus. This includes a new FAT32 formatted partition which will be your ESP. To prevent the installer from latching on to an existing ESP from another OS installed on disk, we're going to remove the "boot" and "esp" flags from the respective ESP.

Open GParted, right click on the existing ESP, and select "Manage Flags"

Then, uncheck the "boot" and/or "esp" options. (Typically deselecting one will also deselect the other.)

From there, we can create the new partitions for Solus as we normally would. Create a new FAT32 formatted partition of around 500MB and enable the "boot" and "esp" flags. Once you've created the partitions you want to use for the new Solus installation, you can continue as normal.

While disabling the "boot" and "esp" flags on other systems' ESPs should not prevent them from being recognized by your UEFI, or being manipulated by its respective OS, you may want to re-enable these flags on those partitions once you have completed the installation.

    Much appreciated.
    Perhaps you can write a tutorial on how to boot windows and other distro uefi grub OS from Solus bootloader? (without going through the bios firmware boot). Thanks.

      kyrios Anything in particular I'm supposed to be looking at or is it just a link drop and silence?

          @Schyken
          You would then have another linux OS with grub, I presume.
          If this is the case, what is the 'usual' (as in normal use, not testing or checking things out) bootloader that you use?
          The other linux grub or solus ...er......clr-boot-manager?
          Or do you 'toggle' at bios bootsetup to select the boot?

          If you 'normally' use the other OS grub to boot Solus, you will need to 'update-grub at that OS whenever there's a new Solus kernel, right?
          And have you found a way to boot the other linux (or windows) from Solus bootloader?

          Thanks for sharing.

            Schyken Anything in particular I'm supposed to be looking at or is it just a link drop and silence?

            The 2nd. I drop the link there for people who may find this topic when struggling with UEFI install.

            gohlip Nope.

                  Nope? To which question?

                  I asked @Schyken to share with us how he did it if he did it.
                  For me, the question is 'yes' to all and I am already doing all these.
                  In fact I have in a uefi system grub, refind and systemd-boot and they all boot all OS's in any bootloader or no bootloader OS's. And I have 4 $esp's in a single disk.
                  I was just asking @Schyken to share his method.

                    a month later

                    gohlip Ah, so I use my UEFI boot menu rather than a boot manager from the OS. So, when I install Solus to its own ESP, I can boot into it (if it's not default already) by selecting its entry from the UEFI boot menu. If I install another distro alongside it with GRUB or rEFInd or whatever, by default that OS is the primary entry, so I don't have to worry about whether Solus shows up in their GRUB or vice versa. I choose which OS I want to boot into beforehand and entirely ignore the OS-specific boot manager.

                    (I hope this properly answers your question. I may have misunderstood, and if so I do apologize in advance!)

                        @Schyken
                        You answered exactly to my question and I understood your reply. Thanks.
                        @sgvd
                        Your workaround involves having 2 $esp for Solus. I also understand what you're doing.

                        My method is as follows. (To boot non systemd-boot OS from systemd-boot bootloader)
                        First make Solus totally systemd-boot and treat it as such.
                        To boot non systemd-boot OS, copy their core.efi file into systemd-boot $esp
                        Make entries in /boot/loader/entries
                        and in their entry.conf just one line will boot that non-systemd-boot OS.
                        For example...

                        title   Kubu    Aug sda 8
linux   /kubu.efi

                        Note I've renamed this kubuntu's core.efi file to kubu.efi so it can be differentiated from other OS's core.efi file.

                        As a side note, grub 2 (uefi) can boot OS's with any bootloader or no bootloader or with different $esp's whether or not their $esp is /boot or /boot/efi.
                        Refind can pick up all efi files anywhere and boot them (or set a manual entry to boot specific kernels).
                        Systemd-boot must have the kernels/efi_files in the same $esp to boot.
                        Naturally, and I have many OS's, my normal bootloader is grub 2.

                        2 years later

                        If you mean $esp should be flagged, linux do not require flags, but windows need to. If you have windows, then the windows $esp needed to be flagged, if sharing with linux, then yes, the $esp needs to be flagged. Otherwise no. But no harm if it is flagged in linux even if not necessary.

                        But if you mean if it needed to be in fstab, yes it needed to be specified in /etc/fstab. But installation should automatically take care of that.

                        a year later