Enable network.service with systemd

glean is writing out interface scripts to
/etc/sysconfig/network-scripts ; these scripts are run by the LSB/sysv
init script /etc/init.d/network

It is quite possible this isn't enabled in systemd and on a minimal
system (no NetworkManger, cloud-config, systemd-networkd, etc),
nothing may require it, so the upshot is your system boots with no
network.

It can be confusing because the *first* time the system boots, the
glean udev rules are matched on the interface and install the
interface-scripts and then bring it up.

Enable the service when we install the interface config on redhat like
platforms.

Change-Id: Ib2b618dd975ca44e9c6b0a2c9027642ffc46b9b0

glean/cmd.py

@@ -133,6 +133,18 @@ def write_redhat_interfaces(interfaces, sys_interfaces):
     return files_to_write
 
 
+def systemd_enable(service, args):
+    log.debug("Enabling %s via systemctl" % service)
+
+    if args.noop:
+        return
+
+    rc = os.system('systemctl enable %s' % service)
+    if rc != 0:
+        log.error("Error enabling %s" % service)
+        sys.exit(rc)
+
+
 def _exists_debian_interface(name):
     file_to_check = '/etc/network/interfaces.d/{name}.cfg'.format(name=name)
     return os.path.exists(file_to_check)
@@ -273,6 +285,12 @@ def write_static_network_info(
     elif args.distro in ('redhat', 'centos', 'fedora', 'suse', 'opensuse'):
         files_to_write.update(
             write_redhat_interfaces(interfaces, sys_interfaces))
+
+        # glean configures interfaces via
+        # /etc/sysconfig/network-scripts, so we have to ensure that
+        # the LSB init script /etc/init.d/network gets started!
+        systemd_enable('network.service', args)
+
     else:
         return False
 

glean/tests/test_glean.py

@@ -97,6 +97,8 @@ class TestGlean(base.BaseTestCase):
         self.useFixture(fixtures.MonkeyPatch('os.listdir', fake_listdir))
         self.useFixture(fixtures.MonkeyPatch(
             'subprocess.check_output', mock.Mock()))
+        self.useFixture(fixtures.MonkeyPatch('os.system',
+                                             mock.Mock(return_value=0)))
 
         real_path_exists = os.path.exists