Implement masking and overriding of generators

Sometimes it is necessary to stop a generator from running. Either
because of a bug, or for testing, or some other reason. The only way
to do that would be to rename or chmod the generator binary, which is
inconvenient and does not survive upgrades. Allow masking and
overriding generators similarly to units and other configuration
files.

For the systemd instance, masking would be more common, rather than
overriding generators. For the user instances, it may also be useful
for users to have generators in $XDG_CONFIG_HOME to augment or
override system-wide generators.

Directories are searched according to the usual scheme (/usr/lib,
/usr/local/lib, /run, /etc), and files with the same name in higher
priority directories override files with the same name in lower
priority directories. Empty files and links to /dev/null mask a given
name.

https://bugs.freedesktop.org/show_bug.cgi?id=87230

1 files changed, 3 insertions, 2 deletions

diff --git a/src/sleep/sleep.c b/src/sleep/sleep.c
index 2fb5f0c8e0..cc1ffa63f1 100644
--- a/src/sleep/sleep.c
+++ b/src/sleep/sleep.c
@@ -92,6 +92,7 @@ static int execute(char **modes, char **states) {
                 arg_verb,
                 NULL
         };
+        static const char* const dirs[] = {SYSTEM_SLEEP_PATH, NULL};
 
         int r;
         _cleanup_fclose_ FILE *f = NULL;
@@ -107,7 +108,7 @@ static int execute(char **modes, char **states) {
         if (r < 0)
                 return r;
 
-        execute_directory(SYSTEM_SLEEP_PATH, DEFAULT_TIMEOUT_USEC, arguments);
+        execute_directories(dirs, DEFAULT_TIMEOUT_USEC, arguments);
 
         log_struct(LOG_INFO,
                    LOG_MESSAGE_ID(SD_MESSAGE_SLEEP_START),
@@ -126,7 +127,7 @@ static int execute(char **modes, char **states) {
                    NULL);
 
         arguments[1] = (char*) "post";
-        execute_directory(SYSTEM_SLEEP_PATH, DEFAULT_TIMEOUT_USEC, arguments);
+        execute_directories(dirs, DEFAULT_TIMEOUT_USEC, arguments);
 
         return r;
 }