units: avoid redundant VT clearing by agetty

TTYVTDisallocate=yes already clears the VT. agetty does not need to do
it again. Run it with --noclear.

Felix Miata found the double clearing confusing in this bugreport:
https://bugzilla.redhat.com/show_bug.cgi?id=828007
Add a comment explaining what clears the VT.

diff --git a/units/getty@.service.m4 b/units/getty@.service.m4
index 6d458360a4e67d2a65e82b800d2f5eb55ee0b009..fcf1de197fb94383e7b5b9cf8e2bbdf995f75037 100644 (file)
--- a/units/getty@.service.m4
+++ b/units/getty@.service.m4
@@ -41,7 +41,8 @@ ConditionPathExists=/dev/tty0
 
 [Service]
 Environment=TERM=linux
-ExecStart=-/sbin/agetty %I 38400
+# the VT is cleared by TTYVTDisallocate
+ExecStart=-/sbin/agetty --noclear %I 38400
 Type=idle
 Restart=always
 RestartSec=0