create a shutdown_command method in distro classes (#567)

Under FreeBSD, we want to use "shutdown -p" for poweroff.

Alpine Linux also has some specificities.

We choose to define a method that returns the shutdown command line to
use, rather than a method that actually does the shutdown. This makes it
easier to have the tests in test_handler_power_state do their
verifications.

Two tests are added for the special behaviours that are known so far.

1 files changed, 19 insertions, 0 deletions

diff --git a/cloudinit/distros/__init__.py b/cloudinit/distros/__init__.py
index 2bd9bae8..fac8cf67 100755
--- a/cloudinit/distros/__init__.py
+++ b/cloudinit/distros/__init__.py
@@ -73,6 +73,9 @@ class Distro(metaclass=abc.ABCMeta):
     renderer_configs = {}
     _preferred_ntp_clients = None
     networking_cls = LinuxNetworking
+    # This is used by self.shutdown_command(), and can be overridden in
+    # subclasses
+    shutdown_options_map = {'halt': '-H', 'poweroff': '-P', 'reboot': '-r'}
 
     def __init__(self, name, cfg, paths):
         self._paths = paths
@@ -750,6 +753,22 @@ class Distro(metaclass=abc.ABCMeta):
                 subp.subp(['usermod', '-a', '-G', name, member])
                 LOG.info("Added user '%s' to group '%s'", member, name)
 
+    def shutdown_command(self, *, mode, delay, message):
+        # called from cc_power_state_change.load_power_state
+        command = ["shutdown", self.shutdown_options_map[mode]]
+        try:
+            if delay != "now":
+                delay = "+%d" % int(delay)
+        except ValueError as e:
+            raise TypeError(
+                "power_state[delay] must be 'now' or '+m' (minutes)."
+                " found '%s'." % (delay,)
+            ) from e
+        args = command + [delay]
+        if message:
+            args.append(message)
+        return args
+
 
 def _apply_hostname_transformations_to_url(url: str, transformations: list):
     """