Ubuntu-image command crashed

snowsky · March 10, 2021, 3:01pm

Hi,

I run ubuntu-image command on ubuntu 20.04. It seems there is some issue with the state machine in ubuntu-image command. Please let me know if you got the same issue. Thanks.

Crash in state machine Traceback (most recent call last): File “/usr/lib/python3/dist-packages/ubuntu_image/main.py”, line 393, in main list(state_machine) File “/usr/lib/python3/dist-packages/ubuntu_image/state.py”, line 82, in next step() File “/usr/lib/python3/dist-packages/ubuntu_image/assertion_builder.py”, line 52, in populate_rootfs_contents for subdir in os.listdir(src): FileNotFoundError: [Errno 2] No such file or directory: ‘/tmp/tmp_qwecr6s/unpack/image’

snowsky · March 10, 2021, 3:09pm

Got more logs with debug:

DEBUG:ubuntu-image:-> [ 4] populate_rootfs_contents
ERROR:ubuntu-image:uncaught exception in state machine step: [4] populate_rootfs_contents
Traceback (most recent call last):
File “/usr/lib/python3/dist-packages/ubuntu_image/state.py”, line 82, in next
step()
File “/usr/lib/python3/dist-packages/ubuntu_image/assertion_builder.py”, line 52, in populate_rootfs_contents
for subdir in os.listdir(src):
FileNotFoundError: [Errno 2] No such file or directory: ‘/tmp/tmph0_0kqsi/unpack/image’
ERROR:ubuntu-image:Crash in state machine
Traceback (most recent call last):
File “/usr/lib/python3/dist-packages/ubuntu_image/main.py”, line 393, in main
list(state_machine)
File “/usr/lib/python3/dist-packages/ubuntu_image/state.py”, line 82, in next
step()
File “/usr/lib/python3/dist-packages/ubuntu_image/assertion_builder.py”, line 52, in populate_rootfs_contents
for subdir in os.listdir(src):
FileNotFoundError: [Errno 2] No such file or directory: ‘/tmp/tmph0_0kqsi/unpack/image’

ijohnson · March 10, 2021, 3:27pm

What is the model assertion you are using with ubuntu-image?

snowsky · March 10, 2021, 3:34pm

Sorry, I replaced some strings in the assertion, something like:

type: model
authority-id: xxx
series: 16
brand-id: xxx
model: xxx
architecture: amd64
base: core18
classic: false
snaps:

default-channel: latest/edge
id: xxx
name: xxx
type: gadget
default-channel: 18/stable
id: pYVQrBcKmBa0mZ4CCN7ExT6jH8rY1hza
name: pc-kernel
type: kernel
default-channel: latest/edge
id: xxx
name: xxx
type: app
default-channel: latest/stable
id: sLCsFAO8PKM5Z0fAKNszUOX0YASjQfeZ
name: docker
type: app
store: xxx
timestamp: 2021-03-09T10:10:10Z
sign-key-sha3-384: xxx

ijohnson · March 10, 2021, 3:36pm

are you trying to build a uc18 or uc20 image?

snowsky · March 10, 2021, 3:42pm

I’m going to build uc18 for now and uc20 in near future

ijohnson · March 10, 2021, 4:02pm

unfortunately the model assertion for uc18 is different than for uc20, see https://ubuntu.com/core/docs/reference/assertions/model for uc18 style model assertions and see the “Model definition” header at https://ubuntu.com/core/docs/uc20/release-notes for uc20

snowsky · March 10, 2021, 4:11pm

oops, it may be a feature to verify if an assertion follow the correct syntax.

snowsky · March 10, 2021, 4:19pm

Thanks @ijohnson, this issue came from the other question here, Build image with OS/snapd/kernel snaps from stable channel. Bringing the same question from there, is it possible to build image with kernel snaps from stable channel but gadget from edge channel if using uc18? Thanks.

ijohnson · March 10, 2021, 4:57pm

For UC18, I am not sure, but that’s precisely why we allowed it for UC20

snowsky · March 10, 2021, 6:02pm

Quick questions, I guess I can use --extra-snaps to use snap files to work around the issue for uc18? Can I use --cloud-init parameter for core20 with ubuntu-image command? The error is:

ubuntu-image: error: base: core20 model assertion detected, the following features are unsupported: --cloud-init

Thanks!

ogra · March 10, 2021, 6:06pm

nope … you can not … i know the cloud.cfg file needs to be somewhere inside your gadget snap now but i do not know the details where exactly it has to be or if there is a specific name required … ian might know though …

snowsky · March 10, 2021, 6:08pm

Got it, great to know before preparing the upgrade to uc20, thanks @ogra!

ijohnson · March 11, 2021, 6:04pm

For cloud-init with UC20, you have the following options:

Put it in the root of your gadget snap as cloud.conf
Put it in the ubuntu-seed partition at <ubuntu-seed>/data/etc/cloud/cloud.cfg.d/ with filenames ending with .cfg
Provide through external filesystems that cloud-init will by default searches, for example the NoCloud datasource will search for drives labeled CIDATA with files in the root labeled meta-data and user-data
Put it in ubuntu-seed, and let snapd filter out unsafe configuration from the config so only certain keys are allowed

Option 1 is always allowed with UC20, regardless of model assertion grade. Option 2 is only allowed with model assertion grade dangerous Option 3 is allowed only with model assertion grade dangerous and signed (so this does not work for secured). Option 4 is currently being worked on and will be allowed for model assertions grade signed and dangerous.

Here’s a table of allowed cloud-init methods vs the model assertion grade

Method	Dangerous	Signed	Secured
Ubuntu-seed
NoCloud CIDATA
Gadget cloud.conf
Ubuntu-seed filtered

snowsky · March 11, 2021, 11:05pm

Amazing, thanks for the details @ijohnson

jamesh · March 29, 2021, 2:47am

I had a go at trying to implement the “cloud.conf in gadget snap” option, and am not having much luck. My model is set to grade: dangerous.

I can see that the cloud.conf from my gadget snap has been copied to /etc/cloud/cloud.cfg.d/80_device_gadget.cfg, but it isn’t obvious that any of the directives have been run (I tried using runcmd and write_files).

On the first boot (after the initial unpack/setup boot), the only reference to “cloud” I see in the journal is:

Mar 29 02:33:04 ubuntu snapd[1880]: devicemgr.go:891: System initialized, cloud-init reported to be in disabled state, disabled permanently

ogra · March 29, 2021, 9:36am

i cant find a referenc for this anymore (probably someone told it to me on IRC) but i happen to remember that the filename needs to be cloud.cfg in the gadget case and that you need a “nocloud” section in it (i could mis-remember or it might be outdated info tough) …

jamesh · March 29, 2021, 9:47am

I’d originally tried with cloud.cfg, which doesn’t work. When I switched to cloud.conf (as documented in @ijohnson’s post), I could see that the config file was being copied out of my gadget snap. And the snapd code is definitely looking for that file name:

github.com

snapcore/snapd/blob/4405f25a553d31876bfe5346948b9b8f0e2b67d4/sysconfig/cloudinit.go#L113-L121


	// next check if there is a gadget cloud.conf to install
	if HasGadgetCloudConf(opts.GadgetDir) {
		// then copy / install the gadget config and return without considering
		// CloudInitSrcDir
		// TODO:UC20: we may eventually want to consider both CloudInitSrcDir
		// and the gadget cloud.conf so returning here may be wrong
		gadgetCloudConf := filepath.Join(opts.GadgetDir, "cloud.conf")
		return installGadgetCloudInitCfg(gadgetCloudConf, WritableDefaultsDir(opts.TargetRootDir))
	}

I’ll have to look more into the nocloud thing. From a brief read of the docs, that seemed to be about feeding cloud-init data into the system from some external source. Here, the config has already been copied to /etc/cloud by snapd.

ijohnson · March 29, 2021, 11:40am

Can you share the cloud.conf you tried using? I think it’s a formatting issue in that it only works if you format the cloud.conf a certain way

jamesh · March 29, 2021, 1:42pm

This is the cloud.conf file I was using:

The write_files stanza is to a location that is made writable in the boot file system. The runcmd command references a script shipped inside one of the snaps required by the model definition.