Incorrect behavior with create() after destroy()

[ach5948]

Required information

• Distribution: Debian
• Distribution version: Stretch
• python version: 3.5.3
• The output of
  • lxc-start --version: 2.0.7
  • uname -a: Linux 4.9.0-3-amd64 lxc/lxc#1 SMP Debian 4.9.30-2+deb9u2 (2017-06-26) x86_64 GNU/Linux

Issue description

After instantiating, creating, and destroying a linux container, calling create without re-instantiating returns false rather than recreating the container

Steps to reproduce

1. test = lxc.Container("test")
2. test.create(template="debian")
3. test.destroy()
4. test.create(template="debian")

the second call simply returns false

[anirudh-goyal]

Hello, could me and my classmates work on this issue please?

Was originally planning to work on issue https://github.com/lxc/python3-lxc/issues/15 but it turns out someone already opened a PR for it.

[anirudh-goyal]

Hey @stgraber, just wanted to check in again if it would be okay for me to work on this issue? Thanks!

[stgraber]

Absolutely!

[stgraber]

Assigned it to you now!

[anirudh-goyal]

Thanks for assigning it @stgraber!

I've been a little lost trying to think of the solution.

• The create and destroy functions in the lxc.c file in this python repo are eventually making a call to functions in lxc/lxccontainer.h

• I'm guessing that the fix is actually in the lxc/lxc repo in lxccontainer.c .

• Moreover, I'm having a hard time trying to set up things to run. I had a file structure as follows:

• lxc -- lxc -- python3-lxc

However, when I go to python3-lxc and run python3 setup.py build, I get an error saying that lxc.c:27:10: fatal error: 'lxc/lxccontainer.h' file not found

Could you please give me some direction here? Or do you think this issue is more involved than we think it is and would require a lot of context?

[stgraber]

Ok, so the issue here is that create() creates a rootfs for a container while destroy() deletes the container itself including its path. It's that step which is preventing it be re-created as the object still has its old config, causing it to prevent a new create() run.

To fix this in python3-lxc, I think we need to changes:

• create() needs to call save_config() if the container isn't defined (self.defined)
• destroy() needs to call clear_config() on success, this needs a new python3 wrapper for destroy to handle that

As this is not going to be touching the C part of this, you can just install python3-lxc on an Ubuntu system and then use this in a python3 shell to reproduce the issue:

import lxc
test = lxc.Container("test")
test.destroy()
test.create("busybox")
test.destroy()
test.create("busybox")

This should output True every time when this issue is fixed.

You can directly mess with the python3 binding live by editing /usr/lib/python3/dist-packages/lxc/__init__.py on such a system.

[anirudh-goyal]

Thanks a lot for the explanation, that makes sense. I was able to set things up on an Ubuntu system and edit the binding as you suggested for testing it.

I'm a little confused by one thing though. Even before I made any changes, all my create() calls are returning False. Do you know what might be the issue here?

Going off of the Steps to Reproduce in the issue description, this is what I'm getting:

test = lxc.Container("test") -> test.create(template="debian") False test.destroy() False test.create(template="debian") False

I did, however, open a PR #23 that does the changes you suggested.

[stgraber]

Yeah, test with busybox not debian, we don't ship the debian template by default.