Docker 为什么JupyterHub内核不与kernel.json对齐？

我正在使用DockerSpawner的SystemUserSpawner（）生成docker容器来运行笔记本

这些容器中的Jupyter是在Python3上运行的，现在我正在尝试向其添加Python2内核

RUN pip3.6 --no-cache install \
    jupyterhub==0.9.0 \
    'notebook>=5.0,<=6.0'
...
RUN python2 -m pip install --upgrade pip
RUN python2 -m pip --no-cache install 'ipython<6'
RUN python2 -m pip --no-cache install ipykernel

看看这个容器中的可用内核，一切似乎都很好：

[zoltan.fedor@7a30bb98f7c0 ~]$ jupyter kernelspec list
Available kernels:
  python2    /usr/share/jupyter/kernels/python2
  python3    /usr/share/jupyter/kernels/python3

但实际内核文件是相同的（标题除外）：

还有Python 3：

vi /usr/share/jupyter/kernels/python3/kernel.json
----
{
 "argv": [
  "python",
  "-m",
  "ipykernel_launcher",
  "-f",
  "{connection_file}"
 ],
 "display_name": "Python 3",
 "language": "python"
}

简单地运行“python”就会出现python 2—它应该：

[zoltan.fedor@7a30bb98f7c0 ~]$ python
Python 2.7.5 (default, Apr 11 2018, 07:36:10) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

那么，为什么这两个内核都在运行Python 3呢？如果有的话，那么我会看到他们都运行Python2，因为他们使用“python”作为“argv”，它应该启动Python2.7.5而不是3.6.5

---

你知道我在这里遗漏了什么吗

事实证明，问题仅仅是我忘了运行以下程序

RUN python2 -m ipykernel install

奇怪的是，python2 kernel.json是在没有它的情况下创建的，它只是没有设置为执行python2。 在此之后，python2内核现在指向：

$ jupyter kernelspec list
Available kernels:
  python2    /usr/local/share/jupyter/kernels/python2
  python3    /usr/share/jupyter/kernels/python3

kernel.json的内容是：

$ vi /usr/local/share/jupyter/kernels/python2/kernel.json
----
{
 "display_name": "Python 2",
 "language": "python",
 "argv": [
  "/usr/bin/python2",
  "-m",
  "ipykernel_launcher",
  "-f",
  "{connection_file}"
 ]
}

现在这真的是一个Python2内核

$ jupyter kernelspec list
Available kernels:
  python2    /usr/local/share/jupyter/kernels/python2
  python3    /usr/share/jupyter/kernels/python3

$ vi /usr/local/share/jupyter/kernels/python2/kernel.json
----
{
 "display_name": "Python 2",
 "language": "python",
 "argv": [
  "/usr/bin/python2",
  "-m",
  "ipykernel_launcher",
  "-f",
  "{connection_file}"
 ]
}