tmpfiles: make "f" lines behaviour match what the documentation says
CHANGE OF BEHAVIOUR — with this commit "f" line's behaviour is altered
to match what the documentation says: if an "argument" string is
specified it is written to the file only when the file didn't exist
before. Previously, it would be appended to the file each time
systemd-tmpfiles was invoked — which is not a particularly useful
behaviour as the tool is not idempotent then and the indicated files
grow without bounds each time the tool is invoked.
I did some spelunking whether this change in behaviour would break
things, but afaics nothing relies on the previous O_APPEND behaviour of
this line type, hence I think it's relatively safe to make "f" lines
work the way the docs say, rather than adding a new modifier for it or
so.
Triggered by:
https://lists.freedesktop.org/archives/systemd-devel/2018-January/040171.html
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index 4d8c368..38cbb73 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -1189,7 +1189,7 @@
assert(i);
assert(path);
- flags = i->type == CREATE_FILE ? O_CREAT|O_APPEND|O_NOFOLLOW :
+ flags = i->type == CREATE_FILE ? O_CREAT|O_EXCL|O_NOFOLLOW :
i->type == TRUNCATE_FILE ? O_CREAT|O_TRUNC|O_NOFOLLOW : 0;
RUN_WITH_UMASK(0000) {
@@ -1200,9 +1200,13 @@
if (fd < 0) {
if (i->type == WRITE_FILE && errno == ENOENT) {
- log_debug_errno(errno, "Not writing \"%s\": %m", path);
+ log_debug_errno(errno, "Not writing missing file \"%s\": %m", path);
return 0;
}
+ if (i->type == CREATE_FILE && errno == EEXIST) {
+ log_debug_errno(errno, "Not writing to pre-existing file \"%s\": %m", path);
+ goto done;
+ }
r = -errno;
if (!i->argument && errno == EROFS && stat(path, &st) == 0 &&
@@ -1223,6 +1227,7 @@
fd = safe_close(fd);
+done:
if (stat(path, &st) < 0)
return log_error_errno(errno, "stat(%s) failed: %m", path);