I've come up with a more minimal test that doesn't require the whole
GNS3 infrastructure.
1. Create a one-line 'meta-data' file:
{instance-id: ubuntu, local-hostname: ubuntu}
2. Create the following 'user-data' file:
#cloud-config
hostname: ubuntu
network:
config: disabled
resize_rootfs: noblock
users:
- name: ubuntu
plain_text_passwd: foobar
lock_passwd: false
shell: /bin/bash
sudo: ALL=(ALL) NOPASSWD:ALL
3. Build a CIDATA image acceptable to cloud-init:
genisoimage -input-charset utf-8 -o cloudinit.iso -l -relaxed-filenames
-V cidata -graft-points meta-data user-data
4. With a copy of Ubuntu's cloudimg in the current directory, create a 1
TB thin provisioned disk:
qemu-img create -f qcow2 -b ubuntu-20.04-server-cloudimg-amd64.img
test.qcow2 1T
5. Start qemu with a VNC server on whatever port you'd like (you must be
in group kvm):
qemu-system-x86_64 -enable-kvm -cdrom cloudinit.iso -drive
file=test.qcow2,if=ide,media=disk,discard=on -m 4G -vnc 0.0.0.0:88 -net
none
I can change ide to virtio, but if I change it to scsi it either hangs
during boot (Ubuntu 18 host) or complains "machine type does not support
if=scsi,bus=0,unit=0" (Ubuntu 20 host).
I can do the following to get scsi:
qemu-system-x86_64 -enable-kvm -cdrom cloudinit.iso -device virtio-scsi-
pci,id=scsi -drive file=test.qcow2,id=root-img,if=none,discard=on
-device scsi-hd,drive=root-img -m 4G -vnc 0.0.0.0:88 -net none
For any drive type, you start it running, let it sit there at a boot
prompt, and watch the size of test.qcow2. The bad behavior is that it
grows into the 30-40 GB range.
On a Ubuntu 18 host, I see the bad behavior for drive types ide and
virtio. scsi seems to be OK.
On an Ubuntu 20 host, I only see the bad behavior for drive type ide.
virtio and scsi seem OK.
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https://bugs.launchpad.net/bugs/1974100
Title:
inode lazy init in a VM fills virtual disk with garbage
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