无法在 WSL 2 Ubuntu20.04 上通过 Ansible 启动服务

Question

I am trying to run Ansible playbook on WSL 2 with Ubuntu20.04. Majority of tasks work properly, however all tasks which manage the services (eg start nginx) fails.

Ansible code:

  - name: NGINX - enable and start nginx service
    systemd:
      name: nginx
      enabled: yes
      state: started

I get the following error in command line:

TASK [ansible-role-nginx : NGINX - enable and start nginx service]
fatal: [webapp]: FAILED! => {"changed": false, "msg": "Service is in unknown state", "status": {}}

Info about WSL 2 system:
uname -a:

Linux CPX-TRWO066I0YQ 5.4.72-microsoft-standard-WSL2 #1 SMP Wed Oct 28 23:40:43 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a:

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.2 LTS
Release:        20.04
Codename:       focal

ansible --version:

ansible 2.9.16
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/ubuntu/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python3.8/dist-packages/ansible
  executable location = /usr/local/bin/ansible
  python version = 3.8.5 (default, May 27 2021, 13:30:53) [GCC 9.3.0]

systemd --version:

systemd 245 (245.4-4ubuntu3.6)
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid

When I start service by command: sudo service nginx start - it works properly.

Please, let me know if you have any suggestions or solutions for this case.

Answer 1

There are actually two problems you are running into. First, it looks like you are specifically using the Ansible systemd module . That's not going to work, since WSL doesn't support systemd without extensive effort.

Since the WSL Ubuntu 20.04 distribution, as you've noticed, does provide a fallback to the service command, you should be able to simply swap that out with the Ansible service module . Eg:

- name: NGINX - enable and start nginx service
    service:
      name: nginx
      enabled: yes
      state: started

But then you are going to run into the second issue -- WSL doesn't provide any sort of "startup script" support. As we've already mentioned, systemd isn't supported, but neither is the older SysVInit. WSL uses it's own init system as PID 1 to bootstrap the interoperability between the native Windows services and WSL/Linux.

So the "enabled" flag just isn't going to do anything.

The question is really when do you want to start the service:

• When Windows boots?
• When the user logs in?
• When the WSL instance is started for the first time manually (through, say, a Windows Terminal invocation)?

The first two should be possible with a Windows Task Manager script that runs something like wsl -u root service nginx start . The "logs in" is definitely an easier use-case. I've noticed some issues with Windows terminating the WSL instance if it isn't started inside a user session. If you run into that, there's a possible workaround, but I'd suggest a separate question/answer to cover it.

Starting nginx on first WSL invocation would involve:

• Setting up sudoers (through visudo , of course) to allow your user to run sudo service nginx start without a password.
• Editing your startup files (eg .bash_profile ) to include something like service nginx status || sudo service nginx start service nginx status || sudo service nginx start .