I have a single 500GB SSD partitioned in two with Fedora 40 installed in one partition. Now, I am thinking of keeping my Fedora installation intact and install Debian 12 in another partition of the same drive. I know I can choose ‘Install Debian alongaide Fedora’ during Debian installation but I don’t want to do it as I want to keep separate ‘/home’ directory for each OS, so that if Debian doesn’t work as expected, I can safely remove it without loosing any data from my Fedora installation. I searched Youtube and the internet quite a bit but looks like everybody thinks that dual booting in Linux with other OS means the peimary OS must be Windows. Nobody thinks that someone can be interested in dual booting two Linux distros!!! Strange thinking!!! So, I am back again asking for help though I thought I would be able to do it without disturbing you people as I have already bombarded you with tons of questions in other threads. But, what can I do if people are not interested on dual booting two Linux distros with manual partitioning? So, please guide me again.
Note: Everything I have written about people’s thinking are with an exception of my extended family here.
I do it all the time, and more than two
I assume you are booting Fedora with grub.
With more than one distro, you hzve to decide which distro is to be in control of grub… lets say you decide Fedora will retain control of grub,
Here are the steps
make sure you have a disk backup.
make partitions for Debian root and Debian home. Use gparted to make these. You might have to shrink the Fedora partitions to get space. Format the new root and home partitions to ext4
you need to know whether you are using uefi boot or legacy boot. you also need to know your partition table type … msdos or gpt
boot from your Debian install flash drive… start the install process
at the partitioning step, choose manual or custom partitioning
do not make any partitions with the installer… you already made them with gparted… but you need to define mount points for ‘/’ and ‘/home’ … and maybe for /boot/efi if you are using uefi boot
let the install run on to the end where it asks where to install grub. Tell it not to install grub.
let the install complete and then reboot into Fedora
In Fedora do ‘update-grub’… i am guessing that Fedora has this command… if not use ‘mkconfig -o /boot/grub.cfg’
Reboot, and this time the grub menu should show both Fedora and Debian
And when applying the change (adding “iommu=soft”), I think it has to be done from Fedora, but for the Debian entry.
I should check how this goes, for that I could install Fedora and then Debian on a VM, but sadly I don’t have the time for it now.
My extended family here is an exception. Original post edited.
I partitioned my 500 GB SSD (477.77 GB in actual) equally in Windows with exFAT file system before I installed Fedora. So, I have 238.88GB free for Debian. I think that would be enough and I want Fedora to control the GRUB.
Though my motherboard supports UEFI and GPT but I would like to go with LEGACY BIOS and MBR because if I use UEFI, Linux may not be able to read my other MBR partitioned NTFS drives and without UEFI, I cannot format the partition in GPT. Am I correct or wrong?
This is the most confusing part where I struggle. It is also the most dreadful part for me. Tell me, if I mess up the Debian installation will it mess up the GRUB bootloader? And though I am not using UEFI, some distros force to create a EFI partition. Without that those distros will never let you to continue the installation process.Hope Debian would not do that.
I don’t know. I have to check.
The rest, I think, I have to see through the process in practical and then I can let you know the result. Let’s see what happens. If something goes wrong, I have to delete all the partitions in this SSD at most and as I always install Linux with other drives disconnected, no harm will be there for my data. So, I think I should give it a try. Thanks for the guidance @nevj.
You can, but you have to make a special partition called a
‘bios-grub partition’… about 1Mb is enough, and leave it unformatted… that is where grub will go if you legacy boot
Alternatively stay with msdos partition table for your legacy boot… it is OK
Yes defining mount points is difficult… hard to give a guide… every installer is different.
The mount point for the root partition is called ‘/’
The mount point for the home partition is called ‘/home’
You will not have an efi partition if you set legacy boot in your bios before you start the install
You just have to struggle with the installer until you master setting mount points.
It will stop you if they are missing.
No. Only if you tell it to install grub. Dont let it do that.
Yes I have encountered that. I think if you have the bios set to legacy boot, it may stop that.
If you have to, make an EFI partition, just to keep it happy. It only needs 512Mb.
Practice is everything.
Dont worry about the second reply yet.
You only need that if you change grub parameters in Debian
Aaaaand I messed up. I used the Debian live USB to boot into and installed Debian from within the live OS and it messed up because in there, Debian doesn’t ask anything about grub installation. So, can I revive my Fedora and make the bootloader giving options to choose the OS to boot?
Skywalker, forgive me for once again repeating my tired old admonition: make sure everything important is backed up!! It’s just as simple as inserting a sufficiently large usb key in the computer and copying the Home folders onto it.
Then, whatever mistakes you make won’t damage anything you care about. I’ve run into grub problems over and over, so I just format the entire drive and start over. I actually have a 1T external hard drive permanently installed into one of the usb ports on the back of my computer and save everything that I might want later to that. After three plus years, it’s not even half full. And I’m multi-booting five distros on two HDDs.
Yes, do what Laszlo says… it will make your Debian controlled grub detect Fedora.
then
if you want you can switch grub control back to Fedora simply by going into Fedora and doing grub-install and update-grub
Firstly, I always disconnect all my data drives and Windows system drive before installing Linux. So, Windows and data are safe. Plus I never put anything important in system drive/partition because if anything goes south, I would be in big problem. I have the backup of Firefox bookmarks and passwords and those are safe in separate data drive. So there is nothing to worry for me. I just trying to save the time of repeat installation of two OS and also want to learn if there is any revival tactics in case of emergency. But many thanks for your concern.
@kovacslt
Thanks, one can also use the Debian grub menu and count down, starting with #0 to the Fedora entry, usually #2, and set th.e GRUB_DEFAULT=2 and Fedora will boot first
Probably a good practice, but may I ask why you keep Windows? I have it on a separate computer so it can’t pollute Linux. I don’t use it for anything but games.
So, please guide me again.
)
