docs: minimum memory requirement for live ISO

[ssoor]

Bug

Host Operating System Version

Microsoft Windows [version 10.0.18362.592]

VM: Hyper-V

Target Operating System Version

fedora-coreos-31.20200210.2.0-live.x86_64.iso

coreos-installer Version

unknown

Expected Behavior
boot to shell

Actual Behavior

2048M memory failed to start, 4192M memory started normally.

Failure message:

[!!!] Failed to isolate default target.

Reproduction Steps

# mem ==2048M 
# /dev/sda == os.vhd(1024G)
# bootiso == fedora-coreos-31.20200210.2.0-live.x86_64.iso

[lucab]

Thanks for the report. It looks like the issue is that the initial VM did not have enough memory. We should better document that requirement for the live ISO. Can you maybe check if 3 GiB are enough?

[ssoor]

Thanks for the report. It looks like the issue is that the initial VM did not have enough memory. We should better document that requirement for the live ISO. Can you maybe check if 3 GiB are enough?

Just tried it and set it to 2200M running normally, 2100M got an error

[ssoor]

@lucab The documentation explains how much memory is needed, but why does a live cd need so much memory?

[jlebon]

@ssoor It's running entirely from RAM. You could e.g. remove the CD after booting. But then you need enough RAM to host both the filesystem and for the OS itself to use. (See somewhat related discussions in #352).

[bgilbert]

2 GB should be enough though. The image is only ~600 MB.

[ssoor]

@jlebon Thanks for the answer, but like @bgilbert said, the image is only ~600MB, and the system does not take up so much memory after booting. and i see that the size of the memory disk is relatively large. Is it caused by it? Can it be reduced appropriately?

memory use:

disk size:

[linquize]

2GB RAM is not OK.
Can boot with 3GB RAM

[dustymabe]

It seems like a lot of people are hitting this. I think we need to:

• document the recommended minimum memory requirement
  • bare-metal: document live ISO memory requirement fedora-coreos-docs#46
• investigate why we need more than 2G
  • investigate why we need > 2G memory for live ISO/PXE boot #407
• consider options for giving a well defined error message to the user when they are hitting this problem

The first two are covered by either a PR or another issue. The last bullet point is something we should consider. Although, if you don't have enough memory, you might not even get to the point where the thing that checks the minimum memory will even run. So it's a tricky problem to solve.