Changes to make dcron more Docker friendly

Dockerfile

@@ -0,0 +1,29 @@
+# Build dcron
+FROM alpine AS builder
+COPY . /src
+RUN apk add --no-cache gcc make musl-dev \
+	&& cd /src \
+	&& make \
+	&& make install
+
+# Build image
+FROM alpine
+
+# Alpine includes a copy of dcron as part of busybox.
+# Delete the /var/spool/cron dir and then recreate it.
+RUN rm -rf /var/spool/cron \
+# These are copied from the Makefiles
+	&& install -o root -d -m0755 -g root /var/spool/cron \
+	&& install -o root -d -m0755 -g root /etc/cron.d
+
+# Copy crond and crontab
+COPY --from=builder /usr/local/sbin/crond /usr/local/sbin/crond
+COPY --from=builder /usr/local/bin/crontab /usr/local/bin/crontab
+
+# Start dcron
+ENTRYPOINT ["/usr/local/sbin/crond", "-C", "-f", "-L", "-"]
+CMD []
+
+# Mark /var/spool/cron as a volume so cron settings are persisted there
+VOLUME /var/spool/cron
+

README

@@ -71,7 +71,7 @@ wanting to edit defs.h directly, try editing the DEFS line in the Makefile inste
 	make PREFIX=/usr CRONTAB_GROUP=users
 
 (3) If you're using the git version, you might also want to `make man`,
-to be sure the manpages are updated. This requires 
+to be sure the manpages are updated. This requires
 [pandoc](http://johnmacfarlane.net/pandoc/).
 
 
@@ -117,6 +117,30 @@ Here is the superuser's crontab, created using `sudo crontab -e`:
 
 	-rw-------  0 root   root      513 Jan  6 18:58 /var/spool/cron/crontabs/root
 
+DOCKER
+------
+
+Using `dcron` with docker is rather straight forward.
+
+To build the base image use:
+
+	docker build -t dcron dcron-source-dir
+
+To add on any additional scripts:
+
+	cd your-project-dir
+	echo dcron.dockerfile <<DOCKERFILE
+	FROM dcron
+	COPY jobs /etc/crond.d/
+	COPY mailer /usr/local/bin/mailer
+	CMD ["-M", "/usr/local/bin/mailer"]
+	DOCKERFILE
+	docker build -t mycron -f dcron.dockerfile .
+
+To run the resulting docker image:
+
+	docker run -d -v cron_data:/var/spool/cron mycron
+
 TESTING
 -------
 

database.c

@@ -265,11 +265,12 @@ ReadTimestamps(const char *user)
 							}
 							sec = (time_t)-1;
 							ptr = strptime(ptr, CRONSTAMP_FMT, &tm);
-							if (ptr && (*ptr == 0 || *ptr == '\n'))
+							if (ptr && (*ptr == 0 || *ptr == '\n')) {
 								/* strptime uses current seconds when seconds not specified? anyway, we don't get round minutes */
 								tm.tm_sec = 0;
 								tm.tm_isdst = -1;
 								sec = mktime(&tm);
+							}
 							if (sec == (time_t)-1) {
 								printlogf(LOG_ERR, "unable to parse timestamp (user %s job %s)\n", file->cf_UserName, line->cl_JobName);
 								/* we continue checking other timestamps in this CronFile */

defs.h

@@ -117,7 +117,7 @@
 #define LOCALE_LOGHEADER "%c %%s " LOG_IDENT ": "
 
 /* Limits */
-#define MAXOPEN			256		/* close fds < this limit */ 
+#define MAXOPEN			256		/* close fds < this limit */
 #define MAXLINES		256		/* max lines in non-root crontabs */
 #define SMALL_BUFFER	256
 #define RW_BUFFER		1024
@@ -169,5 +169,7 @@ typedef struct CronNotifier {
 	struct	CronWaiter *cn_Waiter;
 } CronNotifier;
 
+extern short Quit;
+
 #include "protos.h"
 

main.c

@@ -28,12 +28,14 @@ Prototype const char *Mailto;
 Prototype char *TempDir;
 Prototype char *TempFileFmt;
 
+short Quit = 0;
 short DebugOpt = 0;
 short LogLevel = LOG_LEVEL;
 short ForegroundOpt = 0;
 short SyslogOpt = 1;
-const char  *CDir = CRONTABS;
-const char  *SCDir = SCRONTABS;
+short CreateCronDirsOpt = 0;
+const char *CDir = CRONTABS;
+const char *SCDir = SCRONTABS;
 const char *TSDir = CRONSTAMPS;
 const char *LogFile = NULL; 	/* opened with mode 0600 */
 const char *LogHeader = LOGHEADER;
@@ -72,7 +74,7 @@ main(int ac, char **av)
 
 	opterr = 0;
 
-	while ((i = getopt(ac,av,"dl:L:fbSc:s:m:M:t:")) != -1) {
+	while ((i = getopt(ac,av,"dl:L:fbSc:s:m:M:t:C")) != -1) {
 		switch (i) {
 			case 'l':
 				{
@@ -159,25 +161,53 @@ main(int ac, char **av)
 				if (*optarg != 0) SendMail = optarg;
 				break;
 			case 'm':
-				if (*optarg != 0) Mailto = optarg;
+				if (*optarg == 0) break;
+
+				for (const char *c = optarg; *c != 0; ++c) {
+					if (*c == '@') {
+						Mailto = optarg;
+						break;
+					}
+				}
+
+				if (Mailto == NULL && *optarg == '/') {
+					char *buffer = malloc(256);
+					FILE* file = fopen(optarg, "r");
+					if (file) {
+						size_t s = fread(buffer, 1, 256, file);
+						if (s < 1) {
+							free(buffer);
+						} else {
+							buffer[s] = 0;
+							Mailto = buffer;
+						}
+						fclose(file);
+					}
+				}
+				break;
+			case 'C':
+				CreateCronDirsOpt = 1;
 				break;
+
 			default:
 				/*
 				 * check for parse error
 				 */
 				printf("dillon's cron daemon " VERSION "\n");
-				printf("crond [-s dir] [-c dir] [-t dir] [-m user@host] [-M mailer] [-S|-L [file]] [-l level] [-b|-f|-d]\n");
-				printf("-s            directory of system crontabs (defaults to %s)\n", SCRONTABS);
-				printf("-c            directory of per-user crontabs (defaults to %s)\n", CRONTABS);
-				printf("-t            directory of timestamps (defaults to %s)\n", CRONSTAMPS);
-				printf("-m user@host  where should cron output be directed? (defaults to local user)\n");
-				printf("-M mailer     (defaults to %s)\n", SENDMAIL);
-				printf("-S            log to syslog using identity '%s' (default)\n", LOG_IDENT);
-				printf("-L file       log to specified file instead of syslog\n");
-				printf("-l loglevel   log events <= this level (defaults to %s (level %d))\n", LevelAry[LOG_LEVEL], LOG_LEVEL);
-				printf("-b            run in background (default)\n");
-				printf("-f            run in foreground\n");
-				printf("-d            run in debugging mode\n");
+				printf("crond [-s dir] [-c dir] [-t dir] [-m user@host|file] [-M mailer] [-S|-L [file]] [-l level] [-b|-f|-d]\n");
+				printf("-s                 directory of system crontabs (defaults to %s)\n", SCRONTABS);
+				printf("-c                 directory of per-user crontabs (defaults to %s)\n", CRONTABS);
+				printf("-t                 directory of timestamps (defaults to %s)\n", CRONSTAMPS);
+				printf("-C                 create per-user crontabs and timestamps directories, if they do not exists\n");
+				printf("-m user@host|file  where should cron output be directed? (defaults to local user)\n");
+				printf("                   if you specify a file, the email address will be read from the file.\n");
+				printf("-M mailer          (defaults to %s)\n", SENDMAIL);
+				printf("-S                 log to syslog using identity '%s' (default)\n", LOG_IDENT);
+				printf("-L file            log to specified file instead of syslog\n");
+				printf("-l loglevel        log events <= this level (defaults to %s (level %d))\n", LevelAry[LOG_LEVEL], LOG_LEVEL);
+				printf("-b                 run in background (default)\n");
+				printf("-f                 run in foreground\n");
+				printf("-d                 run in debugging mode\n");
 				exit(2);
 		}
 	}
@@ -215,6 +245,19 @@ main(int ac, char **av)
 		exit(1);
 	}
 
+	if (CreateCronDirsOpt) {
+		if (mkdir(CDir, 0755) == -1 && errno != EEXIST) {
+			fdprintf(2, "failed to create %s", CDir);
+			perror(": ");
+			exit(1);
+		}
+		if (mkdir(TSDir, 0755) == -1 && errno != EEXIST) {
+			fdprintf(2, "failed to create %s", TSDir);
+			perror(": ");
+			exit(1);
+		}
+	}
+
 	if (ForegroundOpt == 0) {
 
 		int fd;
@@ -269,11 +312,12 @@ main(int ac, char **av)
 		/* daemon in foreground */
 
 		/* stay in existing session, but start a new process group */
-		if (setpgid(0,0)) {
-			perror("setpgid");
-			exit(1);
+		if (getsid(0) != getpid()) {
+			if (setpgid(0,0)) {
+				perror("setpgid");
+				exit(1);
+			}
 		}
-
 		/* stderr stays open, start SIGHUP ignoring, SIGCHLD handling */
 		initsignals();
 	}
@@ -305,6 +349,11 @@ main(int ac, char **av)
 		for (;;) {
 			sleep((stime + 1) - (short)(time(NULL) % stime));
 
+			if (Quit) {
+				fdprintf(2, "\n"); // print new line in case of Ctrl-C
+				break;
+			}
+
 			t2 = time(NULL);
 			dt = t2 - t1;
 
@@ -338,7 +387,7 @@ main(int ac, char **av)
 					SynchronizeDir(SCDir, "root", 0);
 					ReadTimestamps(NULL);
 				}
-			} 
+			}
 			if (rescan < 60) {
 				CheckUpdates(CDir, NULL, t1, t2);
 				CheckUpdates(SCDir, "root", t1, t2);
@@ -360,6 +409,5 @@ main(int ac, char **av)
 			}
 		}
 	}
-	/* not reached */
 }
 

subs.c

@@ -138,6 +138,10 @@ void waitmailjob(int sig) {
 	/* if all children still running, child == 0 */
 }
 
+void quit(int sig) {
+	Quit = 1;
+}
+
 void
 initsignals (void) {
 	struct sigaction sa;
@@ -157,6 +161,7 @@ initsignals (void) {
 		fdprintf(2, "failed to start SIGHUP handling, reason: %s", strerror(errno));
 		exit(n);
 	}
+
 	sa.sa_flags = SA_RESTART;
 	sa.sa_handler = waitmailjob;
 	if (sigaction (SIGCHLD, &sa, NULL) != 0) {
@@ -165,5 +170,27 @@ initsignals (void) {
 		exit(n);
 	}
 
-}
+	sa.sa_flags = SA_RESTART;
+	sa.sa_handler = quit;
+	if (sigaction (SIGINT, &sa, NULL) != 0) {
+		n = errno;
+		fdprintf(2, "failed to start SIGINT handling, reason: %s", strerror(errno));
+		exit(n);
+	}
+
+	sa.sa_flags = SA_RESTART;
+	sa.sa_handler = quit;
+	if (sigaction (SIGTERM, &sa, NULL) != 0) {
+		n = errno;
+		fdprintf(2, "failed to start SIGTERM handling, reason: %s", strerror(errno));
+		exit(n);
+	}
 
+	sa.sa_flags = SA_RESTART;
+	sa.sa_handler = quit;
+	if (sigaction (SIGQUIT, &sa, NULL) != 0) {
+		n = errno;
+		fdprintf(2, "failed to start SIGQUIT handling, reason: %s", strerror(errno));
+		exit(n);
+	}
+}