Automatic Configuration? Especially bootloader

Hi, I'm a newb and I have a question. I already looked at Forum FAQ and the wiki.

Does Manjaro automatically configure (write to configuration files)? I am especially concerned with the bootloader. I write my own bootloader and I don't want Manjaro to overwrite my bootloader for whatever reason (update etc.) Actually I switched from my favorite distro to Manjaro because my old distro DID exactly that.

Thanks for any info
Peter

Welcome!

If you are using grub, Manjaro will update the grub configuration based on the preferences set in /etc/default/grub. If you aren't using grub, that won't happen.

If you don't want grub, you may have to use manjaro-architect to do the install.

It you want a more detailed answer, it would help to have some more specific information about what you are trying to accomplish.

Any manjaro version, not just manjaro architect, at calamares installer will allow users not to install bootloader, if they choose to.

Furthermore, if bios-legacy installations, will let user install grub to its partition. On any uefi installation, default boot can be easily reset with efibootmgr.

I see no issue in your question. Carry on.

However, please be aware that booting up manjaro from other os bootloader will require some manual modifications to its configuration.
Search intel-ucode in this forum for further explanation. Others can explain.

Explain "I write my own bootloader."

Thanks for both answers. And thanks for the info about intel-ucode.

Well, I like tinkering with bootloaders, kernels and operating systems and I did the following (on a PC without EFI):
First I installed Manjaro (I think with bootloader into Master Boot Record). From Manjaro I installed my self-written MBR-bootsector into the MBR and grub to sda1 partition bootsector. But I used grub-install not a Manjaro tool. The whole thing boots fine. MY MBR boots grub from sda1 which loads the rest of grub.

Writing a MBR bootsector is not as difficult as it seems on the first glance.
After some small additions to my code I want to write the rest of the bootloader (A bootsector alone doesn't do much...)

Now my problem is that Manjaro might silently overwrite my MBR code because it "thinks" there is grub. I used xubuntu and had a custom grub menu, and xubuntu "suddenly" overwrote it taking away an important boot menu entry.

How can I avoid that Manjaro does that?

By default, the way pacman/ALPM works for upgrades it will not overwrite modified files.
It will create a .pacnew for you to inspect and merge.

As said, at bootloader install location, select, "Install to System". That's the Manjaro term for 'Installing to Partition'. But note I always install using 'Manual' (Manjaro term) or 'Advanced' (in other distro terms). Not sure if option to install grub to partition is available in other install options, (like er.. default, whole drive, automatic, alongside...). This way, it will never override the default grub unless you do 'grub-install /dev/sda'. To create a core.img if the first sector gets destroyed, use the --no-bootsector option.
That's creating the core.img. This command will make a core.img without installing grub.

grub-install --no-bootsector

But you'll still need to make a grub.cfg, right? In your case, I imagine that will be manually made.
This is how I made my own grub.

Note also at any grub OS (including grub-legacy), after installation, we can always reset its grub to its own partition. Therefore you can install whatever distro (with grub) and then set it to its own partition later.

More actual info:

$ grep -r grub /usr/share/libalpm/hooks/*
/usr/share/libalpm/hooks/99-grub.hook:Exec = /usr/bin/update-grub

$ cat /usr/share/libalpm/hooks/99-grub.hook
[Trigger]
Type = File
Operation = Install
Operation = Upgrade
Operation = Remove
Target = boot/vmlinuz-*

[Action]
Description = Updating Grub-Bootmenu
When = PostTransaction
Exec = /usr/bin/update-grub

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