systemctl: verbose message on missing [Install]

People still don't understand what the message implies.
We have to be more verbose (or more intelligent and detect some of the
cases automatically, but that's not so easy).

https://bugzilla.redhat.com/show_bug.cgi?id=884438

1 files changed, 10 insertions, 1 deletions

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index 6d01756ffb..3abd7dc2e1 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -3782,7 +3782,16 @@ static int enable_unit(DBusConnection *bus, char **args) {
         }
 
         if (carries_install_info == 0)
-                log_warning("The unit files have no [Install] section. They are not meant to be enabled using systemctl.");
+                log_warning(
+"The unit files have no [Install] section. They are not meant to be enabled\n"
+"using systemctl.\n"
+"Possible reasons for having this kind of units are:\n"
+"1) A unit may be statically enabled by being symlinked from another unit's\n"
+"   .wants/ or .requires/ directory.\n"
+"2) A unit's purpose may be to act as a helper for some other unit which has\n"
+"   a requirement dependency on it.\n"
+"3) A unit may be started when needed via activation (socket, path, timer,\n"
+"   D-Bus, udev, scripted systemctl call, ...).\n");
 
 finish:
         if (m)