Dom0 max RAM - Low memory Qubes OS installations

[unman]

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

Not my experience.

[Guillaume]

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,
Guillaume

[Guillaume]

So based on that link, I applied below procedure

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…

[Guillaume]

original post deleted

[personal]

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!

[fsflover]

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.

[personal]

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?

[fsflover]

@personal

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?

AFAIK this memory is available for other qubes when needed.

@personal

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?

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:

What’s the first things you should do when getting qubes

My suggested super-short introduction: When you boot into Qubes OS for the first time, you will have the following virtual machines for your service. Sys-net contains drivers for your WiFi card and connects to the network, so it’s untrusted by default (don’t run Firefox there!). Sys-firewall protects you from DMA attacks and allows to use the “Firewall rules” in the Settings of other qubes. Sys-whonix provides Tor connection to anon-whonix (in which you should run Tor browser). All connected u…

[personal]

OK thank you!!

[anon81475885]

»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!

[enmus]

Mine does.

@anon81475885

What am I missing here?

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

[anon81475885]

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

[enmus]

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?
kernel-5.10.109-1.fc32.qubes.x86_64
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.

[1c9567f8]

Hi,

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

Thanks,

- me.

[unman]

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

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

Qubes memory manager (qmemman)

[1c9567f8]

@unman

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.

[tripleh]

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

[1c9567f8]

I know, but I was asking that in order to understand how does RAM allocation works. The idea is I (if possible) reduce the amount of RAM allocated to Dom0.

[augsch]

Dom0, as a linux instance, will try to use the most of your RAM to provide cache for the disk. In fact, it doesn’t really need that much RAM to run. If you didn’t install anything manually in dom0, and has not that many VMs running concurrently (less than 10, I assume), it’s safe to reduce the max_mem to 1536M.

[1c9567f8]

Okey, thanks for the explanation.
Having thta little extra RAM is going to be a great improvement for me. Also, I use i3 as my VM so I suppose that it’s even lighter than running a full DE.

I’m going to reduce it now.

Thanks again. c: