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#1 2013-02-06 22:15:43

spareproject
Member
Registered: 2013-02-02
Posts: 4

multiple arch boot

I've had arch installed for a while now and love it but really interested in playing around with different kernels and generally breaking things till I found out how it works.
Ive currently got full disk encryption and lvm setup on my laptop and looking to make a multi arch boot system but due to total lack of research before investing in a mac book air
I have to go through macs internet recovery and wipe the disk before being able to boot from usb after a arch install : /

So to hopefully save me a night of endless reinstalls I was wondering if anyone knows how i should go about this. I know i need a EFI partion mounted in /boot
but confused as to how many boot partions & efi partions i would need. Is it possible to install say 3 different /root partions with the same /boot and /boot/efi mounted on them?

Or will I need a seperate /boot and /efi for each. Probably a bit of a noobish question but currently only been able to find information on arch installs along side
windows, mac or ubuntu. First time having to do anything other than a copy and paste job to install grub aswell ^_^.

Any advise or a point in the right direction is most appreciated

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#2 2013-02-07 00:31:20

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 5,661

Re: multiple arch boot

As far as I know, you can have only one EFI partition. I think you could have multiple /boot partitions. You wouldn't normally need them but if you are looking to install multiple "versions" of Arch, perhaps you might want them. (I'm thinking you could keep one completely standard which you'd always then be able to boot from.) Also, since Arch doesn't name its kernels etc. with version numbers, this might be safest. (Otherwise, if you upgrade one system, you might not be able to boot the other system because the kernel it expects has disappeared.) Not sure about any of this, though. (Except the 1 EFI partition.)


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#3 2013-02-07 00:58:54

nomorewindows
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Registered: 2010-04-03
Posts: 2,978

Re: multiple arch boot

You can save your package files on another drive that you have already downloaded from the internet.


I may have to CONSOLE you about your usage of ridiculously easy graphical interfaces...
Look ma, no mouse.

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#4 2013-02-07 05:27:48

WonderWoofy
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From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: multiple arch boot

cfr wrote:

As far as I know, you can have only one EFI partition. I think you could have multiple /boot partitions. You wouldn't normally need them but if you are looking to install multiple "versions" of Arch, perhaps you might want them. (I'm thinking you could keep one completely standard which you'd always then be able to boot from.) Also, since Arch doesn't name its kernels etc. with version numbers, this might be safest. (Otherwise, if you upgrade one system, you might not be able to boot the other system because the kernel it expects has disappeared.) Not sure about any of this, though. (Except the 1 EFI partition.)

You can actually have as many evidence system partitions as you want. I used to keep a spare one on a separate disk, but about a month ago I extracted the archiso onto it as my "backup" (it was just super quick that way).

You can certainly share a /boot or efi partition amongst several installations, but like VCR mentioned, if you have two arch installs using the official kernel and you update one but not the other, you are likely going to run into issues until you update the other as well.

Edit: You know that if you use refind, it can actually read certain filesystems, so you could potentially just not use a /boot at all and just have every kernel/initramfs kept with its respective rootfs.

Last edited by WonderWoofy (2013-02-07 05:30:16)

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#5 2013-02-07 21:59:46

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 5,661

Re: multiple arch boot

I see on a separate disk but if you have multiple EFI partitions on the same disk, how does the firmware know which one to boot from? I thought you could only have one on a disk active at one time for that reason (but now I'm curious about what's possible).


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#6 2013-02-08 01:19:44

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: multiple arch boot

You can have as many as you please.  When you enter the UEFI Shell, it differentiates them by marking them as fs0, fs1, fs2, etc.  I believe that when you make an entry (whether with efibootmgr or the tool in the shell), you specify the disk and partition of the efi application you are setting up, so it uses the UUID to determine where that *.efi is on your disk.  Though I am not 100% sure that it uses the UUID, I can see no other plausible way. This is especially since the prevalence of UUIDs really came about as EFI was.

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#7 2013-02-08 01:24:36

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 5,661

Re: multiple arch boot

So what would it do if you had multiple EFI partitions with efi apps in the default locations? Would it just be arbitrary which it booted?


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#8 2013-02-08 03:04:16

WonderWoofy
Member
From: Los Gatos, CA
Registered: 2012-05-19
Posts: 8,412

Re: multiple arch boot

I am not sure what you are asking there?  What default location are you referring to?

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#9 2013-02-08 22:34:58

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 5,661

Re: multiple arch boot

All I meant is that if I don't have any custom EFI menu entries but I have a valid application EFI/boot/bootx64.efi and I choose to boot from the HDD in the bios or from the device menu, then the machine will boot using that .efi application. If I had several EFI partitions, would it simply be arbitrary which one it looked in for the  EFI/boot/bootx64.efi? That is, in the case where the partitions are on different drives, there's no issue but if I have multiple EFI partitions on the same drive then in case I am booting from that device (rather than from a configured custom menu entry), will the firmware look to the first EFI partition on the disk? Or will it find one of them randomly? Or something else?


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Arch Linux | x86_64 | GPT | EFI boot | grub2 | systemd | LVM2 on LUKS
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