Dom0 max RAM - Low memory Qubes OS installations

Honestly I haven’t seen dom0 use more than 1.5GB so far. So 2-2.5GB seems
more reasonable to me.

2GB appears to cause a lot of dom0 memory swapping when one starts a lot of VMs. 3GB appears to be more stable.

Ironically pulseaudio’s memory grows linearly in dom0 with the number of started VMs.

How do you track this? Just by looking at the output of something like top?

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Not my experience.

How can we apply this to an EFI boot.

In my current install I have no file at /etc/default/grub
But I have in /boot/efi/EFI/qubes/xen.cfg that seems to be the correct file to modify.

Do I edit the file directly or there is a similar procedure with grub2-mkconfig ?

Thanks for your help on that matter,

So based on that link, I applied below procedure :slight_smile:

  1. duplicate folder /boot/efi/EFI/qubes into one named qubes2
    cp -avr -- /boot/efi/EFI/qubes /boot/efi/EFI/qubes2

  2. edit file xen.cfg in qubes2 folder to adapt options parameter dom0_mem=max:8192M and save

  3. identify your boot partition disk with df /boot/efi or lsblk command

  4. check the actual boot configuration with efibootmgr -v

  5. add new boot and makes it first priority with command below to adapt to your hdd partition (-d and -p) and .efi correct path (-l) and desired name (-L)
    efibootmgr -v -c -u -L Qubes2 -l /EFI/qubes2/xen.efi -d /dev/sda -p 1

  6. reboot and check BIOS to make sure you boot on the correct one

It did boot correctly but when arriving at login it seems my usb doesn’t respond nor for mouse or keyboard or yubikey, at luks it did works tho.

How can I update xen configuration to apply RAM value of 8192M ?

Am I really the only one here who cares to have more RAM, or is the EFI thing that is not common ?

Why does standard Qubes OS installation doesn’t pick the max to fit the max available RAM ?

I know quite a lot of users who would have switch to qubesOS but the lack of RAM stopped them to do so, well if the standard install doesn’t even pick your hardware to fit it is surely a miss here…

original post deleted

Hi, everyone, I also have a question on this topic. Memory usage for each Qube is always maxed out at 4000MB, although I think some may need more and I have 32GB of RAM. When I watch videos in a Qube or have many browser tabs open, the video stutters and the websites sometimes crash. Can I increase the memory for the Qube or set it to increase automatically?

Thanks in advance!

The maximum of 4000 MB can be changed in the qube settings. If you switch on the tick below, the memory management will adjust RAM on the fly up to this value. Depending on your resources bottleneck, increasing the max memory might help with the video shutter.

OK thanks! If I increase the RAM capacity, the Qube always uses exactly as much memory as the maximum indicates, is the RAM then also in use or is it only theoretically available? And I have another question, which doesn’t fit the topic of RAM, but maybe it’s still possible, what are the pre-installed Qubes for, such as Personal, Work and so on, because I can’t install any additional software in the AppVMs anyway?

AFAIK this memory is available for other qubes when needed.

It’s better to create new topics for different questions, otherwise other users won’t find the answer.

Of course you can install software in AppVMs (via templates).

See also:

OK thank you!!

»My« dom0 doesn’t accept reducing memory via

sudo nano etc/default/grub
GRUB_CMDLINE_XEN_DEFAULT="... dom0_mem=max:2048M ..."
grub2-mkconfig -o /boot/grub2/grub.cfg

What am I missing here?

Thanks in advance!

Mine does.

To give more info. “My computer behaves strangely” diagnoses do not help.
How do you know dom0 doesn’t accept it?

xl list in dom0 terminal and Open Qube Manager in panel are showing the default 4000+ RAM/memory after reboot with new grub.cfg. No error messages during generating grub config file. found theme, found linux image, found initrd image.

Qubes 4.1
dom0 5.10.104-3.fc32.qubes.x86_64

Could you paste (not re-type but paste from dom0), if not whole grub, but at least whole XEN_DEFAULT line
Did you update dom0 recently?
Did you try to regenerate initramfs?
Maybe you should try kernel-latest. I’m using it for months, without issues.
Did you track journalctl -f while recreating grub?
Did you grep it or dmesg after reboot?
I’m not saying any of these would help, but something you could try until someone else comes up with a better tip.


According to the widget on the top right corner of my desktop Dom0 is using around 3200MB all time.
Is this supposed to happen?


- me.

In the default, yes.
Max_mem for dom0 is 4G

So then: if I assigned 8GB of max RAM to Dom0 it would use 8GB?

Because according to that variable name 4GB is the max RAM that Dom0 could use. And for me it uses around 3000MB all time.

I don’t really know how could I lower the max RAM if it’s already using almost 4GB all time. Am I missing something regarding how RAM works in XEN?

Best regards,

- me.

Setting dom0 RAM higher will lower the available RAM for your VMs. Most people don’t want that.