Arch Linux

DaveBullet

Member

Registered: 2023-03-14

Posts: 9

[SOLVED] Dual boot 2 arch installations - separate kernel files

Hello,

I'd like to install arch twice on the same machine.  One version is my debug/ compile, lots of stuff on it.  the other is my "production" which will only have runtime / bare minimum packages.

I can get both installed in separate partitions...my problem occurs when pacstrapping the 2nd installation... wanting to overwrite the 1st installation's kernel in /boot.

I can rename the kernels and repoint GRUB to boot the correct one... my concern is when it comes time to apply system upgrades (pacman -S linux?)

I might want to test this on the "Debug" install.. but may accidentally overwrite the "prod" installs kernel.

Is there a way to permanently point the target kernel filename to a different directory on boot, or different filename in the same directory? such that upgrades to the kernel apply to the right location?

Last edited by DaveBullet (2023-03-17 22:02:01)

Head_on_a_Stick

Member

From: The Wirral

Registered: 2014-02-20

Posts: 8,489

Website

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

my problem occurs when pacstrapping the 2nd installation... wanting to overwrite the 1st installation's kernel in /boot

Why are you sharing the same /boot partition?

Just use /efi or /boot/efi for the EFI system partition. GRUB doesn't need the ESP mounted under /boot.

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Para todos todo, para nosotros nada

Scimmia

Fellow

Registered: 2012-09-01

Posts: 12,182

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

Mount the ESP to /efi, then bind mount a dir on that to /boot.

DaveBullet

Member

Registered: 2023-03-14

Posts: 9

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

Thanks for the suggestion @scimmia.  I didn't know about bind mounts.

I ended up doing the following that worked.

1. Change both installs to mount the ESP partition as /efi and not /boot
2. Move the kernels for each image into subdirectories on the ESP partition - e.g. /efi/image1 and /efi/image2
3. Add a bind mount to each image's /etc/fstab, such that it would mount the /efi/image1 or /efi/image2 to /boot
4. Update /efi/grub/grub.cfg to load the correct /image1/<kernel> or /image2/<kernel> for each boot option.   (this was after first running grub-mkconfig -o /boot/grub/grub.cfg on the first install to pick up the 2nd install's partition and add it to the config).  NB: Don't forget to pacman -S os-prober and ensure GRUB_DISABLE_OS_PROBER=false in /etc/default/grub to allow grub to detect multiple additional installs.

Here's my /efi tree

[root@arch-pc-debug efi]# tree debug-boot/ prod-boot/ EFI
debug-boot/
├── initramfs-linux-fallback.img
├── initramfs-linux.img
└── vmlinuz-linux
prod-boot/
├── initramfs-linux-fallback.img
├── initramfs-linux.img
└── vmlinuz-linux
EFI
├── BOOT
│   ├── BOOTX64.EFI
│   ├── fbx64.efi
│   └── mmx64.efi
├── Dell
│   └── logs
│       └── diags_current.xml
└── GRUB
    ├── BOOTX64.CSV
    ├── grub.cfg
    ├── grubx64.efi
    ├── mmx64.efi
    └── shimx64.efi

And here is the /etc/fstab for image1 (debug) - this mounts ESP partition to /efi but then binds the /efi/debug-boot as /boot for the booted linux:

UUID=1AD3-F799          /efi            vfat            rw,relatime,fmask=0022,dmask=0022,cod
epage=437,iocharset=ascii,shortname=mixed,utf8,errors=remount-ro        0 2

# Bind mount so that this linux sees the /efi/<instance-boot> as its /boot location for upgra
des to linux etc.. (to not clash with the other installation)
/efi/debug-boot /boot   none    defaults,bind   0       0

Trilby

Inspector Parrot

Registered: 2011-11-29

Posts: 30,330

Website

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

What's the purpose of the bind mount here?  Why not just leave the /boot directory on the root partition of each system?

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"UNIX is simple and coherent" - Dennis Ritchie; "GNU's Not Unix" - Richard Stallman

Scimmia

Fellow

Registered: 2012-09-01

Posts: 12,182

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

Some people just prefer to have /boot on a separate partition. That appears to be what they want, so I gave them a solution that fit with the way they want their system set up.

DaveBullet

Member

Registered: 2023-03-14

Posts: 9

Re: [SOLVED] Dual boot 2 arch installations - separate kernel files

What's the purpose of the bind mount here?  Why not just leave the /boot directory on the root partition of each system?

I was going to just do that and not bother with boot being on the ESP partition. I had assumed - wrongly that GRUB might care about needing the boot kernel on the same partition as ESP (as that was the way I first installed Arch from a USB stick).

I might go back to moving boot onto the root / single partition of each install.