cephadm: add option to install systemd unit only

Cephadm is responsible for installing systemd units on the system. If
for some reasons the units are missing, this newly added option cephadm
    unit-install will install them (and do nothing else).

This is useful in some cases where going through the others means of
creating such unit are not possible, or do extra unwanted things.

Signed-off-by: Cyril Duval <[email protected]>

Author: fayak

src/cephadm/cephadm.py

@@ -5493,6 +5493,24 @@ def command_ceph_volume(ctx):
 ##################################
 
 
+def command_unit_install(ctx):
+    # type: (CephadmContext) -> int
+    if not ctx.fsid:
+        raise Error('must pass --fsid to specify cluster')
+
+    fsid = ctx.fsid
+    install_base_units(ctx, fsid)
+    unit = get_unit_file(ctx, fsid)
+    unit_file = 'ceph-%[email protected]' % (fsid)
+    with open(ctx.unit_dir + '/' + unit_file + '.new', 'w') as f:
+        f.write(unit)
+        os.rename(ctx.unit_dir + '/' + unit_file + '.new',
+                  ctx.unit_dir + '/' + unit_file)
+    call_throws(ctx, ['systemctl', 'daemon-reload'])
+
+    return 0
+
+
 @infer_fsid
 def command_unit(ctx):
     # type: (CephadmContext) -> int
@@ -7223,6 +7241,10 @@ def _get_parser():
         required=True,
         help='daemon name (type.id)')
 
+    parser_unit_install = subparsers.add_parser(
+        'unit-install', help="Install the daemon's systemd unit")
+    parser_unit_install.set_defaults(func=command_unit_install)
+
     parser_logs = subparsers.add_parser(
         'logs', help='print journald logs for a daemon container')
     parser_logs.set_defaults(func=command_logs)