Rename hook_status enum.
[dss.git] / dss.c
diff --git a/dss.c b/dss.c
index 4bf01e9..12ad11c 100644 (file)
--- a/dss.c
+++ b/dss.c
@@ -1,3 +1,8 @@
+/*
+ * Copyright (C) 2008 Andre Noll <maan@systemlinux.org>
+ *
+ * Licensed under the GPL v2. For licencing details see COPYING.
+ */
 #include <string.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include "signal.h"
 #include "df.h"
 #include "time.h"
+#include "snap.h"
 
-
-struct gengetopt_args_info conf;
-char *dss_error_txt = NULL;
+/** Command line and config file options. */
+static struct gengetopt_args_info conf;
+/** Non-NULL if we log to a file. */
 static FILE *logfile;
+/** The read end of the signal pipe */
 static int signal_pipe;
-
-/** Process id of current rsync process. */
-static pid_t rsync_pid;
-/** Whether the rsync process is currently stopped */
-static int rsync_stopped;
-/** Process id of current rm process. */
-static pid_t rm_pid;
+/** Process id of current pre-create-hook/rsync/post-create-hook process. */
+static pid_t create_pid;
+/** Whether the pre-create-hook/rsync/post-create-hook is currently stopped. */
+static int create_process_stopped;
+/** Process id of current pre-remove/rm/post-remove process. */
+static pid_t remove_pid;
 /** When the next snapshot is due. */
-struct timeval next_snapshot_time;
-/* Creation time of the snapshot currently being created. */
-int64_t current_snapshot_creation_time;
+static struct timeval next_snapshot_time;
+/** Creation time of the snapshot currently being created. */
+static int64_t current_snapshot_creation_time;
+/** Needed by the post-create hook. */
+static char *path_to_last_complete_snapshot;
+/** \sa \ref snap.h for details. */
+enum hook_status snapshot_creation_status;
+/** \sa \ref snap.h for details. */
+enum hook_status snapshot_removal_status;
 
 
 DEFINE_DSS_ERRLIST;
@@ -55,53 +67,27 @@ DEFINE_DSS_ERRLIST;
        COMMAND(create) \
        COMMAND(prune) \
        COMMAND(run)
-#define COMMAND(x) int com_ ##x(void);
+#define COMMAND(x) static int com_ ##x(void);
 COMMANDS
 #undef COMMAND
 #define COMMAND(x) if (conf.x ##_given) return com_ ##x();
-int call_command_handler(void)
+static int call_command_handler(void)
 {
        COMMANDS
        DSS_EMERG_LOG("BUG: did not find command handler\n");
-       exit(EXIT_FAILURE);
+       return -E_BUG;
 }
 #undef COMMAND
 #undef COMMANDS
 
-/*
- * complete, not being deleted: 1204565370-1204565371.Sun_Mar_02_2008_14_33-Sun_Mar_02_2008_14_43
- * complete, being deleted: 1204565370-1204565371.being_deleted
- * incomplete, not being deleted: 1204565370-incomplete
- * incomplete, being deleted: 1204565370-incomplete.being_deleted
- */
-enum snapshot_status_flags {
-       /** The rsync process terminated successfully. */
-       SS_COMPLETE = 1,
-       /** The rm process is running to remove this snapshot. */
-       SS_BEING_DELETED = 2,
-};
-
-struct snapshot {
-       char *name;
-       int64_t creation_time;
-       int64_t completion_time;
-       enum snapshot_status_flags flags;
-       unsigned interval;
-};
-
-/*
- * An edge snapshot is either the oldest one or the newest one.
+/**
+ * The log function of dss.
+ *
+ * \param ll Loglevel.
+ * \param fml Usual format string.
  *
- * We need to find either of them occasionally: The create code
- * needs to know the newest snapshot because that is the one
- * used as the link destination dir. The pruning code needs to
- * find the oldest one in case disk space becomes low.
+ * All DSS_XXX_LOG() macros use this function.
  */
-struct edge_snapshot_data {
-       int64_t now;
-       struct snapshot snap;
-};
-
 __printf_2_3 void dss_log(int ll, const char* fmt,...)
 {
        va_list argp;
@@ -127,7 +113,7 @@ __printf_2_3 void dss_log(int ll, const char* fmt,...)
 /**
  * Print a message either to stdout or to the log file.
  */
-__printf_1_2 void dss_msg(const char* fmt,...)
+static __printf_1_2 void dss_msg(const char* fmt,...)
 {
        FILE *outfd = conf.daemon_given? logfile : stdout;
        va_list argp;
@@ -136,320 +122,125 @@ __printf_1_2 void dss_msg(const char* fmt,...)
        va_end(argp);
 }
 
-/**
- * Return the desired number of snapshots of an interval.
- */
-unsigned num_snapshots(int interval)
-{
-       unsigned n;
-
-       assert(interval >= 0);
-
-       if (interval >= conf.num_intervals_arg)
-               return 0;
-       n = conf.num_intervals_arg - interval - 1;
-       return 1 << n;
-}
-
-/* return: Whether dirname is a snapshot directory (0: no, 1: yes) */
-int is_snapshot(const char *dirname, int64_t now, struct snapshot *s)
-{
-       int i, ret;
-       char *dash, *dot, *tmp;
-       int64_t num;
-
-       assert(dirname);
-       dash = strchr(dirname, '-');
-       if (!dash || !dash[1] || dash == dirname)
-               return 0;
-       for (i = 0; dirname[i] != '-'; i++)
-               if (!isdigit(dirname[i]))
-                       return 0;
-       tmp = dss_strdup(dirname);
-       tmp[i] = '\0';
-       ret = dss_atoi64(tmp, &num);
-       free(tmp);
-       if (ret < 0) {
-               free(dss_error_txt);
-               return 0;
-       }
-       assert(num >= 0);
-       if (num > now)
-               return 0;
-       s->creation_time = num;
-       //DSS_DEBUG_LOG("%s start time: %lli\n", dirname, (long long)s->creation_time);
-       s->interval = (long long) ((now - s->creation_time)
-               / conf.unit_interval_arg / 24 / 3600);
-       if (!strcmp(dash + 1, "incomplete")) {
-               s->completion_time = -1;
-               s->flags = 0; /* neither complete, nor being deleted */
-               goto success;
-       }
-       if (!strcmp(dash + 1, "incomplete.being_deleted")) {
-               s->completion_time = -1;
-               s->flags = SS_BEING_DELETED; /* mot cpmplete, being deleted */
-               goto success;
-       }
-       tmp = dash + 1;
-       dot = strchr(tmp, '.');
-       if (!dot || !dot[1] || dot == tmp)
-               return 0;
-       for (i = 0; tmp[i] != '.'; i++)
-               if (!isdigit(tmp[i]))
-                       return 0;
-       tmp = dss_strdup(dash + 1);
-       tmp[i] = '\0';
-       ret = dss_atoi64(tmp, &num);
-       free(tmp);
-       if (ret < 0) {
-               free(dss_error_txt);
-               return 0;
-       }
-       if (num > now)
-               return 0;
-       s->completion_time = num;
-       s->flags = SS_COMPLETE;
-       if (!strcmp(dot + 1, "being_deleted"))
-               s->flags |= SS_BEING_DELETED;
-success:
-       s->name = dss_strdup(dirname);
-       return 1;
-}
-
-int64_t get_current_time(void)
-{
-       time_t now;
-       time(&now);
-       DSS_DEBUG_LOG("now: %lli\n", (long long) now);
-       return (int64_t)now;
-}
-
-char *incomplete_name(int64_t start)
-{
-       return make_message("%lli-incomplete", (long long)start);
-}
-
-char *being_deleted_name(struct snapshot *s)
-{
-       if (s->flags & SS_COMPLETE)
-               return make_message("%lli-%lli.being_deleted",
-                       (long long)s->creation_time,
-                       (long long)s->completion_time);
-       return make_message("%lli-incomplete.being_deleted",
-               (long long)s->creation_time);
-}
-
-int complete_name(int64_t start, int64_t end, char **result)
-{
-       struct tm start_tm, end_tm;
-       time_t *start_seconds = (time_t *) (uint64_t *)&start; /* STFU, gcc */
-       time_t *end_seconds = (time_t *) (uint64_t *)&end; /* STFU, gcc */
-       char start_str[200], end_str[200];
-
-       if (!localtime_r(start_seconds, &start_tm)) {
-               make_err_msg("%lli", (long long)start);
-               return -E_LOCALTIME;
-       }
-       if (!localtime_r(end_seconds, &end_tm)) {
-               make_err_msg("%lli", (long long)end);
-               return -E_LOCALTIME;
-       }
-       if (!strftime(start_str, sizeof(start_str), "%a_%b_%d_%Y_%H_%M_%S", &start_tm)) {
-               make_err_msg("%lli", (long long)start);
-               return -E_STRFTIME;
-       }
-       if (!strftime(end_str, sizeof(end_str), "%a_%b_%d_%Y_%H_%M_%S", &end_tm)) {
-               make_err_msg("%lli", (long long)end);
-               return -E_STRFTIME;
-       }
-       *result = make_message("%lli-%lli.%s-%s", (long long) start, (long long) end,
-               start_str, end_str);
-       return 1;
-}
-
-struct snapshot_list {
-       int64_t now;
-       unsigned num_snapshots;
-       unsigned array_size;
-       struct snapshot **snapshots;
-       /**
-        * Array of size num_intervals + 1
-        *
-        * It contains the number of snapshots in each interval. interval_count[num_intervals]
-        * is the number of snapshots which belong to any interval greater than num_intervals.
-        */
-       unsigned *interval_count;
-};
-
-#define FOR_EACH_SNAPSHOT(s, i, sl) \
-       for ((i) = 0; (i) < (sl)->num_snapshots && ((s) = (sl)->snapshots[(i)]); (i)++)
-
-
-
-#define NUM_COMPARE(x, y) ((int)((x) < (y)) - (int)((x) > (y)))
-
-static int compare_snapshots(const void *a, const void *b)
-{
-       struct snapshot *s1 = *(struct snapshot **)a;
-       struct snapshot *s2 = *(struct snapshot **)b;
-       return NUM_COMPARE(s2->creation_time, s1->creation_time);
-}
-
-/** Compute the minimum of \a a and \a b. */
-#define DSS_MIN(a,b) ((a) < (b) ? (a) : (b))
-
-int add_snapshot(const char *dirname, void *private)
-{
-       struct snapshot_list *sl = private;
-       struct snapshot s;
-       int ret = is_snapshot(dirname, sl->now, &s);
-
-       if (!ret)
-               return 1;
-       if (sl->num_snapshots >= sl->array_size) {
-               sl->array_size = 2 * sl->array_size + 1;
-               sl->snapshots = dss_realloc(sl->snapshots,
-                       sl->array_size * sizeof(struct snapshot *));
-       }
-       sl->snapshots[sl->num_snapshots] = dss_malloc(sizeof(struct snapshot));
-       *(sl->snapshots[sl->num_snapshots]) = s;
-       sl->interval_count[DSS_MIN(s.interval, conf.num_intervals_arg)]++;
-       sl->num_snapshots++;
-       return 1;
-}
-
-void get_snapshot_list(struct snapshot_list *sl)
-{
-       sl->now = get_current_time();
-       sl->num_snapshots = 0;
-       sl->array_size = 0;
-       sl->snapshots = NULL;
-       sl->interval_count = dss_calloc((conf.num_intervals_arg + 1) * sizeof(unsigned));
-       for_each_subdir(add_snapshot, sl);
-       qsort(sl->snapshots, sl->num_snapshots, sizeof(struct snapshot *),
-               compare_snapshots);
-}
-
-void free_snapshot_list(struct snapshot_list *sl)
-{
-       int i;
-       struct snapshot *s;
-
-       FOR_EACH_SNAPSHOT(s, i, sl) {
-               free(s->name);
-               free(s);
-       }
-       free(sl->interval_count);
-       free(sl->snapshots);
-}
-
-void stop_rsync_process(void)
+static int disk_space_low(void)
 {
-       if (!rsync_pid || rsync_stopped)
-               return;
-       kill(SIGSTOP, rsync_pid);
-       rsync_stopped = 1;
-}
+       struct disk_space ds;
+       int ret = get_disk_space(".", &ds);
 
-void restart_rsync_process(void)
-{
-       if (!rsync_pid || !rsync_stopped)
-               return;
-       kill (SIGCONT, rsync_pid);
-       rsync_stopped = 0;
+       if (ret < 0)
+               return ret;
+       if (conf.min_free_mb_arg)
+               if (ds.free_mb < conf.min_free_mb_arg)
+                       return 1;
+       if (conf.min_free_percent_arg)
+               if (ds.percent_free < conf.min_free_percent_arg)
+                       return 1;
+       if (conf.min_free_percent_inodes_arg)
+               if (ds.percent_free_inodes < conf.min_free_percent_inodes_arg)
+                       return 1;
+       return 0;
 }
 
-/**
- * Print a log message about the exit status of a child.
- */
-void log_termination_msg(pid_t pid, int status)
+static void dss_get_snapshot_list(struct snapshot_list *sl)
 {
-       if (WIFEXITED(status))
-               DSS_INFO_LOG("child %i exited. Exit status: %i\n", (int)pid,
-                       WEXITSTATUS(status));
-       else if (WIFSIGNALED(status))
-               DSS_NOTICE_LOG("child %i was killed by signal %i\n", (int)pid,
-                       WTERMSIG(status));
-       else
-               DSS_WARNING_LOG("child %i terminated abormally\n", (int)pid);
+       get_snapshot_list(sl, conf.unit_interval_arg, conf.num_intervals_arg);
 }
 
-int wait_for_process(pid_t pid, int *status)
+static void compute_next_snapshot_time(void)
 {
-       int ret;
+       struct timeval now, unit_interval = {.tv_sec = 24 * 3600 * conf.unit_interval_arg},
+               tmp, diff;
+       int64_t x = 0;
+       unsigned wanted = desired_number_of_snapshots(0, conf.num_intervals_arg),
+               num_complete_snapshots = 0;
+       int i, ret;
+       struct snapshot *s = NULL;
+       struct snapshot_list sl;
 
-       DSS_DEBUG_LOG("Waiting for process %d to terminate\n", (int)pid);
-       for (;;) {
-               pause();
-               ret = next_signal();
-               if (ret < 0)
-                       break;
-               if (!ret)
+       assert(snapshot_creation_status == HS_READY);
+       current_snapshot_creation_time = 0;
+       dss_get_snapshot_list(&sl);
+       FOR_EACH_SNAPSHOT(s, i, &sl) {
+               if (!(s->flags & SS_COMPLETE))
                        continue;
-               if (ret == SIGCHLD) {
-                       ret = waitpid(pid, status, 0);
-                       if (ret >= 0)
-                               break;
-                       if (errno != EINTR) { /* error */
-                               ret = -ERRNO_TO_DSS_ERROR(errno);
-                               break;
-                       }
-               }
-               /* SIGINT or SIGTERM */
-               DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
-               kill(pid, SIGTERM);
+               num_complete_snapshots++;
+               x += s->completion_time - s->creation_time;
        }
-       if (ret < 0)
-               make_err_msg("failed to wait for process %d", (int)pid);
-       else
-               log_termination_msg(pid, *status);
-       return ret;
+       assert(x >= 0);
+       if (num_complete_snapshots)
+               x /= num_complete_snapshots; /* avg time to create one snapshot */
+       x *= wanted; /* time to create all snapshots in interval 0 */
+       tmp.tv_sec = x;
+       tmp.tv_usec = 0;
+       ret = tv_diff(&unit_interval, &tmp, &diff); /* total sleep time per unit interval */
+       if (ret < 0 || !s) /* unit_interval < tmp or no snapshot */
+               goto min_sleep;
+       tv_divide(wanted, &diff, &tmp); /* sleep time betweeen two snapshots */
+       diff.tv_sec = s->completion_time; /* completion time of the the latest snaphot */
+       diff.tv_usec = 0;
+       tv_add(&diff, &tmp, &next_snapshot_time);
+       gettimeofday(&now, NULL);
+       if (tv_diff(&now, &next_snapshot_time, NULL) < 0)
+               goto out;
+min_sleep:
+       next_snapshot_time = now;
+       next_snapshot_time.tv_sec += 60;
+out:
+       free_snapshot_list(&sl);
 }
 
-int remove_snapshot(struct snapshot *s)
+
+static int remove_snapshot(struct snapshot *s, char *why)
 {
        int fds[3] = {0, 0, 0};
-       assert(!rm_pid);
+       assert(!remove_pid);
        char *new_name = being_deleted_name(s);
        int ret = dss_rename(s->name, new_name);
        char *argv[] = {"rm", "-rf", new_name, NULL};
 
        if (ret < 0)
                goto out;
-       DSS_NOTICE_LOG("removing %s (interval = %i)\n", s->name, s->interval);
-       stop_rsync_process();
-       ret = dss_exec(&rm_pid, argv[0], argv, fds);
+       DSS_NOTICE_LOG("removing %s snapshot %s (interval = %i)\n",
+               why, s->name, s->interval);
+       ret = dss_exec(&remove_pid, argv[0], argv, fds);
 out:
        free(new_name);
        return ret;
 }
 
+static int snapshot_is_being_created(struct snapshot *s)
+{
+       return s->creation_time == current_snapshot_creation_time;
+}
+
 /*
  * return: 0: no redundant snapshots, 1: rm process started, negative: error
  */
-int remove_redundant_snapshot(struct snapshot_list *sl)
+static int remove_redundant_snapshot(struct snapshot_list *sl)
 {
        int ret, i, interval;
        struct snapshot *s;
        unsigned missing = 0;
 
-       DSS_INFO_LOG("looking for intervals containing too many snapshots\n");
+       DSS_DEBUG_LOG("looking for intervals containing too many snapshots\n");
        for (interval = conf.num_intervals_arg - 1; interval >= 0; interval--) {
-               unsigned keep = num_snapshots(interval);
+               unsigned keep = desired_number_of_snapshots(interval, conf.num_intervals_arg);
                unsigned num = sl->interval_count[interval];
                struct snapshot *victim = NULL, *prev = NULL;
                int64_t score = LONG_MAX;
 
                if (keep >= num)
                        missing += keep - num;
-               DSS_DEBUG_LOG("interval %i: keep: %u, have: %u, missing: %u\n",
-                       interval, keep, num, missing);
+//             DSS_DEBUG_LOG("interval %i: keep: %u, have: %u, missing: %u\n",
+//                     interval, keep, num, missing);
                if (keep + missing >= num)
                        continue;
                /* redundant snapshot in this interval, pick snapshot with lowest score */
                FOR_EACH_SNAPSHOT(s, i, sl) {
                        int64_t this_score;
 
+                       if (snapshot_is_being_created(s))
+                               continue;
                        //DSS_DEBUG_LOG("checking %s\n", s->name);
                        if (s->interval > interval) {
                                prev = s;
@@ -479,20 +270,22 @@ int remove_redundant_snapshot(struct snapshot_list *sl)
                                victim->name, victim->interval);
                        continue;
                }
-               ret = remove_snapshot(victim);
+               ret = remove_snapshot(victim, "redundant");
                return ret < 0? ret : 1;
        }
        return 0;
 }
 
-int remove_outdated_snapshot(struct snapshot_list *sl)
+static int remove_outdated_snapshot(struct snapshot_list *sl)
 {
        int i, ret;
        struct snapshot *s;
 
-       DSS_INFO_LOG("looking for snapshots belonging to intervals greater than %d\n",
+       DSS_DEBUG_LOG("looking for snapshots belonging to intervals greater than %d\n",
                conf.num_intervals_arg);
        FOR_EACH_SNAPSHOT(s, i, sl) {
+               if (snapshot_is_being_created(s))
+                       continue;
                if (s->interval <= conf.num_intervals_arg)
                        continue;
                if (conf.dry_run_given) {
@@ -500,7 +293,7 @@ int remove_outdated_snapshot(struct snapshot_list *sl)
                                s->name, s->interval);
                        continue;
                }
-               ret = remove_snapshot(s);
+               ret = remove_snapshot(s, "outdated");
                if (ret < 0)
                        return ret;
                return 1;
@@ -508,203 +301,405 @@ int remove_outdated_snapshot(struct snapshot_list *sl)
        return 0;
 }
 
-int handle_rm_exit(int status)
+static int remove_oldest_snapshot(struct snapshot_list *sl)
 {
-       int es, ret;
+       struct snapshot *s = get_oldest_snapshot(sl);
 
-       if (!WIFEXITED(status)) {
-               make_err_msg("rm process %d died involuntary", (int)rm_pid);
-               ret = -E_INVOLUNTARY_EXIT;
-               goto out;
-       }
-       es = WEXITSTATUS(status);
-       if (es) {
-               make_err_msg("rm process %d returned %d", (int)rm_pid, es);
-               ret = -E_BAD_EXIT_CODE;
-               goto out;
-       }
-       ret = 1;
-       rm_pid = 0;
-out:
-       return ret;
+       if (!s) /* no snapshot found */
+               return 0;
+       DSS_INFO_LOG("oldest snapshot: %s\n", s->name);
+       if (snapshot_is_being_created(s))
+               return 0;
+       return remove_snapshot(s, "oldest");
 }
 
-int wait_for_rm_process(void)
+static int rename_incomplete_snapshot(int64_t start)
 {
-       int status, ret = wait_for_process(rm_pid, &status);
+       char *old_name;
+       int ret;
 
+       free(path_to_last_complete_snapshot);
+       ret = complete_name(start, get_current_time(),
+               &path_to_last_complete_snapshot);
        if (ret < 0)
                return ret;
-       return handle_rm_exit(status);
+       old_name = incomplete_name(start);
+       ret = dss_rename(old_name, path_to_last_complete_snapshot);
+       if (ret >= 0)
+               DSS_NOTICE_LOG("%s -> %s\n", old_name,
+                       path_to_last_complete_snapshot);
+       free(old_name);
+       return ret;
 }
 
-void kill_process(pid_t pid)
+static int try_to_free_disk_space(int low_disk_space)
 {
-       if (!pid)
-               return;
-       DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
-       kill(pid, SIGTERM);
-}
+       int ret;
+       struct snapshot_list sl;
 
-void handle_sighup()
-{
-       DSS_INFO_LOG("FIXME: no sighup handling yet\n");
+       if (!low_disk_space && conf.keep_redundant_given)
+               return 0;
+       dss_get_snapshot_list(&sl);
+       ret = remove_outdated_snapshot(&sl);
+       if (ret) /* error, or we are removing something */
+               goto out;
+       /* no outdated snapshot */
+       ret = remove_redundant_snapshot(&sl);
+       if (ret)
+               goto out;
+       ret = 0;
+       if (!low_disk_space)
+               goto out;
+       DSS_WARNING_LOG("disk space low and nothing obvious to remove\n");
+       ret = remove_oldest_snapshot(&sl);
+       if (ret)
+               goto out;
+       DSS_CRIT_LOG("uhuhu: not enough disk space for a single snapshot\n");
+       ret = -ERRNO_TO_DSS_ERROR(ENOSPC);
+out:
+       free_snapshot_list(&sl);
+       return ret;
 }
 
-int rename_incomplete_snapshot(int64_t start)
+static int pre_create_hook(void)
 {
-       char *old_name, *new_name;
-       int ret;
+       int ret, fds[3] = {0, 0, 0};
 
-       ret = complete_name(start, get_current_time(), &new_name);
+       if (!conf.pre_create_hook_given) {
+               snapshot_creation_status = HS_PRE_SUCCESS;
+               return 0;
+       }
+       DSS_DEBUG_LOG("executing %s\n", conf.pre_create_hook_arg);
+       ret = dss_exec_cmdline_pid(&create_pid,
+               conf.pre_create_hook_arg, fds);
        if (ret < 0)
                return ret;
-       old_name = incomplete_name(start);
-       ret = dss_rename(old_name, new_name);
-       if (ret >= 0)
-               DSS_NOTICE_LOG("%s -> %s\n", old_name, new_name);
-       free(old_name);
-       free(new_name);
+       snapshot_creation_status = HS_PRE_RUNNING;
        return ret;
 }
 
-int handle_rsync_exit(int status)
+static int post_create_hook(void)
 {
-       int es, ret;
+       int ret, fds[3] = {0, 0, 0};
+       char *cmd;
 
-       if (!WIFEXITED(status)) {
-               make_err_msg("rsync process %d died involuntary", (int)rsync_pid);
-               ret = -E_INVOLUNTARY_EXIT;
-               goto out;
-       }
-       es = WEXITSTATUS(status);
-       if (es != 0 && es != 23 && es != 24) {
-               make_err_msg("rsync process %d returned %d", (int)rsync_pid, es);
-               ret = -E_BAD_EXIT_CODE;
-               goto out;
+       if (!conf.post_create_hook_given) {
+               snapshot_creation_status = HS_READY;
+               compute_next_snapshot_time();
+               return 0;
        }
-       ret = rename_incomplete_snapshot(current_snapshot_creation_time);
-out:
-       rsync_pid = 0;
-       current_snapshot_creation_time = 0;
-       rsync_stopped = 0;
+       cmd = make_message("%s %s/%s", conf.post_create_hook_arg,
+               conf.dest_dir_arg, path_to_last_complete_snapshot);
+       DSS_NOTICE_LOG("executing %s\n", cmd);
+       ret = dss_exec_cmdline_pid(&create_pid, cmd, fds);
+       free(cmd);
+       if (ret < 0)
+               return ret;
+       snapshot_creation_status = HS_POST_RUNNING;
        return ret;
 }
 
-int get_newest_complete(const char *dirname, void *private)
+static void kill_process(pid_t pid)
 {
-       struct edge_snapshot_data *esd = private;
-       struct snapshot s;
-       int ret = is_snapshot(dirname, esd->now, &s);
+       if (!pid)
+               return;
+       DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
+       kill(pid, SIGTERM);
+}
 
-       if (ret <= 0)
-               return 1;
-       if (s.flags != SS_COMPLETE) /* incomplete or being deleted */
-               return 1;
-       if (s.creation_time < esd->snap.creation_time)
-               return 1;
-       free(esd->snap.name);
-       esd->snap = s;
-       return 1;
+static void stop_create_process(void)
+{
+       if (!create_pid || create_process_stopped)
+               return;
+       kill(SIGSTOP, create_pid);
+       create_process_stopped = 1;
 }
 
-__malloc char *name_of_newest_complete_snapshot(void)
+static void restart_create_process(void)
 {
-       struct edge_snapshot_data esd = {
-               .now = get_current_time(),
-               .snap = {.creation_time = -1}
-       };
-       for_each_subdir(get_newest_complete, &esd);
-       return esd.snap.name;
+       if (!create_pid || !create_process_stopped)
+               return;
+       kill (SIGCONT, create_pid);
+       create_process_stopped = 0;
 }
 
-void create_rsync_argv(char ***argv, int64_t *num)
+/**
+ * Print a log message about the exit status of a child.
+ */
+static void log_termination_msg(pid_t pid, int status)
 {
-       char *logname, *newest = name_of_newest_complete_snapshot();
-       int i = 0, j;
+       if (WIFEXITED(status))
+               DSS_INFO_LOG("child %i exited. Exit status: %i\n", (int)pid,
+                       WEXITSTATUS(status));
+       else if (WIFSIGNALED(status))
+               DSS_NOTICE_LOG("child %i was killed by signal %i\n", (int)pid,
+                       WTERMSIG(status));
+       else
+               DSS_WARNING_LOG("child %i terminated abormally\n", (int)pid);
+}
 
-       *argv = dss_malloc((15 + conf.rsync_option_given) * sizeof(char *));
-       (*argv)[i++] = dss_strdup("rsync");
-       (*argv)[i++] = dss_strdup("-aq");
-       (*argv)[i++] = dss_strdup("--delete");
-       for (j = 0; j < conf.rsync_option_given; j++)
-               (*argv)[i++] = dss_strdup(conf.rsync_option_arg[j]);
-       if (newest) {
-               DSS_INFO_LOG("using %s as reference snapshot\n", newest);
-               (*argv)[i++] = make_message("--link-dest=../%s", newest);
-               free(newest);
-       } else
-               DSS_INFO_LOG("no previous snapshot found\n");
-       if (conf.exclude_patterns_given) {
-               (*argv)[i++] = dss_strdup("--exclude-from");
-               (*argv)[i++] = dss_strdup(conf.exclude_patterns_arg);
+static int wait_for_process(pid_t pid, int *status)
+{
+       int ret;
+
+       DSS_DEBUG_LOG("Waiting for process %d to terminate\n", (int)pid);
+       for (;;) {
+               fd_set rfds;
 
+               FD_ZERO(&rfds);
+               FD_SET(signal_pipe, &rfds);
+               ret = dss_select(signal_pipe + 1, &rfds, NULL, NULL);
+               if (ret < 0)
+                       break;
+               ret = next_signal();
+               if (!ret)
+                       continue;
+               if (ret == SIGCHLD) {
+                       ret = waitpid(pid, status, 0);
+                       if (ret >= 0)
+                               break;
+                       if (errno != EINTR) { /* error */
+                               ret = -ERRNO_TO_DSS_ERROR(errno);
+                               break;
+                       }
+               }
+               /* SIGINT or SIGTERM */
+               DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
+               kill(pid, SIGTERM);
        }
-       logname = dss_logname();
-       if (conf.remote_user_given && !strcmp(conf.remote_user_arg, logname))
-               (*argv)[i++] = dss_strdup(conf.source_dir_arg);
+       if (ret < 0)
+               DSS_ERROR_LOG("failed to wait for process %d\n", (int)pid);
        else
-               (*argv)[i++] = make_message("%s@%s:%s/", conf.remote_user_given?
-                       conf.remote_user_arg : logname,
-                       conf.remote_host_arg, conf.source_dir_arg);
-       free(logname);
-       *num = get_current_time();
-       (*argv)[i++] = incomplete_name(*num);
-       (*argv)[i++] = NULL;
-       for (j = 0; j < i; j++)
-               DSS_DEBUG_LOG("argv[%d] = %s\n", j, (*argv)[j]);
+               log_termination_msg(pid, *status);
+       return ret;
 }
 
-void free_rsync_argv(char **argv)
+static int handle_rm_exit(int status)
 {
-       int i;
-       for (i = 0; argv[i]; i++)
-               free(argv[i]);
-       free(argv);
+       remove_pid = 0;
+       if (!WIFEXITED(status))
+               return -E_INVOLUNTARY_EXIT;
+       if (WEXITSTATUS(status))
+               return -E_BAD_EXIT_CODE;
+       return 1;
 }
 
-int create_snapshot(char **argv)
+static int wait_for_rm_process(void)
 {
-       int fds[3] = {0, 0, 0};
-       char *name = incomplete_name(current_snapshot_creation_time);
+       int status, ret = wait_for_process(remove_pid, &status);
 
-       DSS_NOTICE_LOG("creating new snapshot %s\n", name);
-       free(name);
-       return dss_exec(&rsync_pid, argv[0], argv, fds);
+       if (ret < 0)
+               return ret;
+       return handle_rm_exit(status);
 }
 
-void compute_next_snapshot_time(struct snapshot_list *sl)
+static int handle_rsync_exit(int status)
 {
-       struct timeval now, unit_interval = {.tv_sec = 24 * 3600 * conf.unit_interval_arg},
-               tmp, diff;
-       int64_t x = 0;
-       unsigned wanted = num_snapshots(0), num_complete_snapshots = 0;
-       int i, ret;
-       struct snapshot *s;
+       int es, ret;
 
-       gettimeofday(&now, NULL);
-       FOR_EACH_SNAPSHOT(s, i, sl) {
-               if (!(s->flags & SS_COMPLETE))
-                       continue;
-               num_complete_snapshots++;
-               x += s->completion_time - s->creation_time;
+       if (!WIFEXITED(status)) {
+               DSS_ERROR_LOG("rsync process %d died involuntary\n", (int)create_pid);
+               ret = -E_INVOLUNTARY_EXIT;
+               snapshot_creation_status = HS_READY;
+               compute_next_snapshot_time();
+               goto out;
        }
-       assert(x >= 0);
-       if (num_complete_snapshots)
-               x /= num_complete_snapshots; /* avg time to create one snapshot */
-       x *= wanted; /* time to create all snapshots in interval 0 */
-       tmp.tv_sec = x;
-       tmp.tv_usec = 0;
-       ret = tv_diff(&unit_interval, &tmp, &diff); /* time between creation */
-       if (ret < 0) {
-               next_snapshot_time = now;
-               return;
+       es = WEXITSTATUS(status);
+       if (es == 13) { /* Errors with program diagnostics */
+               DSS_WARNING_LOG("rsync process %d returned %d -- restarting\n",
+                       (int)create_pid, es);
+               snapshot_creation_status = HS_NEEDS_RESTART;
+               gettimeofday(&next_snapshot_time, NULL);
+               next_snapshot_time.tv_sec += 60;
+               ret = 1;
+               goto out;
+       }
+       if (es != 0 && es != 23 && es != 24) {
+               DSS_ERROR_LOG("rsync process %d returned %d\n", (int)create_pid, es);
+               ret = -E_BAD_EXIT_CODE;
+               snapshot_creation_status = HS_READY;
+               compute_next_snapshot_time();
+               goto out;
+       }
+       ret = rename_incomplete_snapshot(current_snapshot_creation_time);
+       if (ret < 0)
+               goto out;
+       snapshot_creation_status = HS_SUCCESS;
+out:
+       create_pid = 0;
+       create_process_stopped = 0;
+       return ret;
+}
+
+static int handle_pre_create_hook_exit(int status)
+{
+       int es, ret;
+       static int warn_count;
+
+       if (!WIFEXITED(status)) {
+               snapshot_creation_status = HS_READY;
+               compute_next_snapshot_time();
+               ret = -E_INVOLUNTARY_EXIT;
+               goto out;
+       }
+       es = WEXITSTATUS(status);
+       if (es) {
+               if (!warn_count--) {
+                       DSS_NOTICE_LOG("pre_create_hook %s returned %d\n",
+                               conf.pre_create_hook_arg, es);
+                       DSS_NOTICE_LOG("deferring snapshot creation...\n");
+                       warn_count = 60; /* warn only once per hour */
+               }
+               snapshot_creation_status = HS_READY;
+               compute_next_snapshot_time();
+               ret = 0;
+               goto out;
+       }
+       warn_count = 0;
+       snapshot_creation_status = HS_PRE_SUCCESS;
+       ret = 1;
+out:
+       create_pid = 0;
+       return ret;
+}
+
+static int handle_sigchld(void)
+{
+       pid_t pid;
+       int status, ret = reap_child(&pid, &status);
+
+       if (ret <= 0)
+               return ret;
+
+       if (pid == create_pid) {
+               switch (snapshot_creation_status) {
+               case HS_PRE_RUNNING:
+                       return handle_pre_create_hook_exit(status);
+               case HS_RUNNING:
+                       return handle_rsync_exit(status);
+               case HS_POST_RUNNING:
+                       snapshot_creation_status = HS_READY;
+                       compute_next_snapshot_time();
+                       return 1;
+               default:
+                       DSS_EMERG_LOG("BUG: create can't die in status %d\n",
+                               snapshot_creation_status);
+                       return -E_BUG;
+               }
+       }
+       if (pid == remove_pid)
+               return handle_rm_exit(status);
+       DSS_EMERG_LOG("BUG: unknown process %d died\n", (int)pid);
+       return -E_BUG;
+}
+
+static int check_config(void)
+{
+       if (conf.unit_interval_arg <= 0) {
+               DSS_ERROR_LOG("bad unit interval: %i\n", conf.unit_interval_arg);
+               return -E_INVALID_NUMBER;
+       }
+       DSS_DEBUG_LOG("unit interval: %i day(s)\n", conf.unit_interval_arg);
+       if (conf.num_intervals_arg <= 0) {
+               DSS_ERROR_LOG("bad number of intervals  %i\n", conf.num_intervals_arg);
+               return -E_INVALID_NUMBER;
+       }
+       DSS_DEBUG_LOG("number of intervals: %i\n", conf.num_intervals_arg);
+       return 1;
+}
+
+static int parse_config_file(int override)
+{
+       int ret;
+       char *config_file;
+       struct stat statbuf;
+       char *old_logfile_arg = NULL;
+       int old_daemon_given = 0;
+
+       if (conf.config_file_given)
+               config_file = dss_strdup(conf.config_file_arg);
+       else {
+               char *home = get_homedir();
+               config_file = make_message("%s/.dssrc", home);
+               free(home);
+       }
+       if (override) { /* SIGHUP */
+               if (conf.logfile_given)
+                       old_logfile_arg = dss_strdup(conf.logfile_arg);
+               old_daemon_given = conf.daemon_given;
+       }
+
+       ret = stat(config_file, &statbuf);
+       if (ret && conf.config_file_given) {
+               ret = -ERRNO_TO_DSS_ERROR(errno);
+               DSS_ERROR_LOG("failed to stat config file %s\n", config_file);
+               goto out;
+       }
+       if (!ret) {
+               struct cmdline_parser_params params = {
+                       .override = override,
+                       .initialize = 0,
+                       .check_required = 1,
+                       .check_ambiguity = 0,
+                       .print_errors = 1
+               };
+               if (override) { /* invalidate all rsync options */
+                       int i;
+
+                       for (i = 0; i < conf.rsync_option_given; i++) {
+                               free(conf.rsync_option_arg[i]);
+                               conf.rsync_option_arg[i] = NULL;
+                       }
+                       conf.rsync_option_given = 0;
+               }
+               cmdline_parser_config_file(config_file, &conf, &params);
+       }
+       ret = check_config();
+       if (ret < 0)
+               goto out;
+       if (override) {
+               /* don't change daemon mode on SIGHUP */
+               conf.daemon_given = old_daemon_given;
+               close_log(logfile);
+               logfile = NULL;
+               if (conf.logfile_given)
+                       free(old_logfile_arg);
+               else if (conf.daemon_given) { /* re-use old logfile */
+                       conf.logfile_arg = old_logfile_arg;
+                       conf.logfile_given = 1;
+               }
+       }
+       if (conf.logfile_given) {
+               logfile = open_log(conf.logfile_arg);
+               log_welcome(conf.loglevel_arg);
        }
-       tv_divide(wanted, &diff, &tmp);
-       tv_add(&now, &tmp, &next_snapshot_time);
+       DSS_DEBUG_LOG("loglevel: %d\n", conf.loglevel_arg);
+//     cmdline_parser_dump(logfile? logfile : stdout, &conf);
+out:
+       free(config_file);
+       if (ret < 0)
+               DSS_EMERG_LOG("%s\n", dss_strerror(-ret));
+       return ret;
+}
+
+static int change_to_dest_dir(void)
+{
+       DSS_INFO_LOG("changing cwd to %s\n", conf.dest_dir_arg);
+       return dss_chdir(conf.dest_dir_arg);
 }
 
-void handle_signal(struct snapshot_list *sl)
+static int handle_sighup(void)
+{
+       int ret;
+
+       DSS_NOTICE_LOG("SIGHUP\n");
+       ret = parse_config_file(1);
+       if (ret < 0)
+               return ret;
+       return change_to_dest_dir();
+}
+
+static int handle_signal(void)
 {
        int sig, ret = next_signal();
 
@@ -712,186 +707,218 @@ void handle_signal(struct snapshot_list *sl)
                goto out;
        sig = ret;
        switch (sig) {
-               int status;
-               pid_t pid;
        case SIGINT:
        case SIGTERM:
-               restart_rsync_process();
-               kill_process(rsync_pid);
-               kill_process(rm_pid);
-               exit(EXIT_FAILURE);
+               restart_create_process();
+               kill_process(create_pid);
+               kill_process(remove_pid);
+               ret = -E_SIGNAL;
+               break;
        case SIGHUP:
-               handle_sighup();
+               ret = handle_sighup();
                break;
        case SIGCHLD:
-               ret = reap_child(&pid, &status);
-               if (ret <= 0)
-                       break;
-               assert(pid == rsync_pid || pid == rm_pid);
-               if (pid == rsync_pid)
-                       ret = handle_rsync_exit(status);
-               else
-                       ret = handle_rm_exit(status);
-               free_snapshot_list(sl);
-               get_snapshot_list(sl);
-               compute_next_snapshot_time(sl);
+               ret = handle_sigchld();
+               break;
        }
 out:
        if (ret < 0)
-               log_err_msg(ERROR, -ret);
+               DSS_ERROR_LOG("%s\n", dss_strerror(-ret));
+       return ret;
 }
 
-int get_oldest(const char *dirname, void *private)
+/*
+ * We can not use rsync locally if the local user is different from the remote
+ * user or if the src dir is not on the local host (or both).
+ */
+static int use_rsync_locally(char *logname)
 {
-       struct edge_snapshot_data *esd = private;
-       struct snapshot s;
-       int ret = is_snapshot(dirname, esd->now, &s);
+       char *h = conf.remote_host_arg;
 
-       if (ret <= 0)
-               return 1;
-       if (s.creation_time > esd->snap.creation_time)
-               return 1;
-       free(esd->snap.name);
-       esd->snap = s;
+       if (strcmp(h, "localhost") && strcmp(h, "127.0.0.1"))
+               return 0;
+       if (conf.remote_user_given && strcmp(conf.remote_user_arg, logname))
+               return 0;
        return 1;
 }
 
-int remove_oldest_snapshot()
+static void create_rsync_argv(char ***argv, int64_t *num)
 {
-       int ret;
-       struct edge_snapshot_data esd = {
-               .now = get_current_time(),
-               .snap = {.creation_time = LLONG_MAX}
-       };
-       for_each_subdir(get_oldest, &esd);
-       if (!esd.snap.name) /* no snapshot found */
-               return 0;
-       DSS_INFO_LOG("oldest snapshot: %s\n", esd.snap.name);
-       ret = 0;
-       if (esd.snap.creation_time == current_snapshot_creation_time)
-               goto out; /* do not remove the snapshot currently being created */
-       ret = remove_snapshot(&esd.snap);
-out:
-       free(esd.snap.name);
-       return ret;
+       char *logname, *newest;
+       int i = 0, j;
+       struct snapshot_list sl;
+
+       dss_get_snapshot_list(&sl);
+       newest = name_of_newest_complete_snapshot(&sl);
+       free_snapshot_list(&sl);
+
+       *argv = dss_malloc((15 + conf.rsync_option_given) * sizeof(char *));
+       (*argv)[i++] = dss_strdup("rsync");
+       (*argv)[i++] = dss_strdup("-aq");
+       (*argv)[i++] = dss_strdup("--delete");
+       for (j = 0; j < conf.rsync_option_given; j++)
+               (*argv)[i++] = dss_strdup(conf.rsync_option_arg[j]);
+       if (newest) {
+               DSS_INFO_LOG("using %s as reference snapshot\n", newest);
+               (*argv)[i++] = make_message("--link-dest=../%s", newest);
+               free(newest);
+       } else
+               DSS_INFO_LOG("no previous snapshot found\n");
+       logname = dss_logname();
+       if (use_rsync_locally(logname))
+               (*argv)[i++] = dss_strdup(conf.source_dir_arg);
+       else
+               (*argv)[i++] = make_message("%s@%s:%s/", conf.remote_user_given?
+                       conf.remote_user_arg : logname,
+                       conf.remote_host_arg, conf.source_dir_arg);
+       free(logname);
+       *num = get_current_time();
+       (*argv)[i++] = incomplete_name(*num);
+       (*argv)[i++] = NULL;
+       for (j = 0; j < i; j++)
+               DSS_DEBUG_LOG("argv[%d] = %s\n", j, (*argv)[j]);
 }
 
-/* TODO: Also consider number of inodes. */
-int disk_space_low(void)
+static void free_rsync_argv(char **argv)
 {
-       struct disk_space ds;
-       int ret = get_disk_space(".", &ds);
+       int i;
 
-       if (ret < 0)
-               return ret;
-       if (conf.min_free_mb_arg)
-               if (ds.free_mb < conf.min_free_mb_arg)
-                       return 1;
-       if (conf.min_free_percent_arg)
-               if (ds.percent_free < conf.min_free_percent_arg)
-                       return 1;
-       return 0;
+       if (!argv)
+               return;
+       for (i = 0; argv[i]; i++)
+               free(argv[i]);
+       free(argv);
 }
 
-int try_to_free_disk_space(int low_disk_space, struct snapshot_list *sl)
+static int create_snapshot(char **argv)
 {
-       int ret;
+       int ret, fds[3] = {0, 0, 0};
+       char *name;
 
-       ret = remove_outdated_snapshot(sl);
-       if (ret) /* error, or we are removing something */
-               return ret;
-       /* no outdated snapshot */
-       ret = remove_redundant_snapshot(sl);
-       if (ret)
-               return ret;
-       if (!low_disk_space)
-               return 0;
-       DSS_WARNING_LOG("disk space low and nothing obvious to remove\n");
-       ret = remove_oldest_snapshot();
-       if (ret)
+       name = incomplete_name(current_snapshot_creation_time);
+       DSS_NOTICE_LOG("creating new snapshot %s\n", name);
+       free(name);
+       ret = dss_exec(&create_pid, argv[0], argv, fds);
+       if (ret < 0)
                return ret;
-       make_err_msg("uhuhu: not enough disk space for a single snapshot");
-       return  -ENOSPC;
+       snapshot_creation_status = HS_RUNNING;
+       return ret;
 }
 
-int select_loop(void)
+static int select_loop(void)
 {
        int ret;
-       struct timeval tv = {.tv_sec = 0, .tv_usec = 0};
-       struct snapshot_list sl = {.num_snapshots = 0};
+       /* check every 60 seconds for free disk space */
+       struct timeval tv;
+       char **rsync_argv = NULL;
 
-       get_snapshot_list(&sl);
-       compute_next_snapshot_time(&sl);
        for (;;) {
-               struct timeval now, *tvp = &tv;
                fd_set rfds;
                int low_disk_space;
-               char **rsync_argv;
+               struct timeval now, *tvp;
 
+               if (remove_pid)
+                       tvp = NULL; /* sleep until rm process dies */
+               else { /* sleep one minute */
+                       tv.tv_sec = 60;
+                       tv.tv_usec = 0;
+                       tvp = &tv;
+               }
                FD_ZERO(&rfds);
                FD_SET(signal_pipe, &rfds);
-               if (rsync_pid)
-                       tv.tv_sec = 60;
-               else if (rm_pid)
-                       tvp = NULL;
+               DSS_DEBUG_LOG("tvp: %p, tv_sec : %lu\n", tvp, (long unsigned) tv.tv_sec);
                ret = dss_select(signal_pipe + 1, &rfds, NULL, tvp);
                if (ret < 0)
-                       return ret;
-               if (FD_ISSET(signal_pipe, &rfds))
-                       handle_signal(&sl);
-               if (rm_pid)
+                       goto out;
+               if (FD_ISSET(signal_pipe, &rfds)) {
+                       ret = handle_signal();
+                       if (ret < 0)
+                               goto out;
+               }
+               if (remove_pid)
                        continue;
                ret = disk_space_low();
                if (ret < 0)
-                       break;
+                       goto out;
                low_disk_space = ret;
-               if (low_disk_space)
-                       stop_rsync_process();
-               ret = try_to_free_disk_space(low_disk_space, &sl);
+               ret = try_to_free_disk_space(low_disk_space);
                if (ret < 0)
-                       break;
-               if (rm_pid)
-                       continue;
-               if (rsync_pid) {
-                       restart_rsync_process();
+                       goto out;
+               if (remove_pid) {
+                       stop_create_process();
                        continue;
                }
-               /* neither rsync nor rm are running. Start rsync? */
+               restart_create_process();
                gettimeofday(&now, NULL);
-               if (tv_diff(&next_snapshot_time, &now, &tv) > 0)
+               if (tv_diff(&next_snapshot_time, &now, NULL) > 0)
                        continue;
-               create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
-               ret = create_snapshot(rsync_argv);
-               free_rsync_argv(rsync_argv);
-               if (ret < 0)
-                       break;
+               switch (snapshot_creation_status) {
+               case HS_READY:
+                       ret = pre_create_hook();
+                       if (ret < 0)
+                               goto out;
+                       continue;
+               case HS_PRE_RUNNING:
+                       continue;
+               case HS_NEEDS_RESTART:
+                       ret = create_snapshot(rsync_argv);
+                       if (ret < 0)
+                               goto out;
+                       continue;
+               case HS_PRE_SUCCESS:
+                       free_rsync_argv(rsync_argv);
+                       create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
+                       ret = create_snapshot(rsync_argv);
+                       if (ret < 0)
+                               goto out;
+                       continue;
+               case HS_RUNNING:
+                       continue;
+               case HS_SUCCESS:
+                       ret = post_create_hook();
+                       if (ret < 0)
+                               goto out;
+                       continue;
+               case HS_POST_RUNNING:
+                       continue;
+               }
        }
-       free_snapshot_list(&sl);
+out:
        return ret;
 }
 
-int com_run(void)
+static void exit_hook(int exit_code)
+{
+       int fds[3] = {0, 0, 0};
+       char *argv[] = {conf.exit_hook_arg, dss_strerror(-exit_code), NULL};
+       pid_t pid;
+
+       if (!conf.exit_hook_given)
+               return;
+       DSS_NOTICE_LOG("executing %s %s\n", argv[0], argv[1]);
+       dss_exec(&pid, conf.exit_hook_arg, argv, fds);
+}
+
+static int com_run(void)
 {
        int ret;
 
        if (conf.dry_run_given) {
-               make_err_msg("dry_run not supported by this command");
+               DSS_ERROR_LOG("dry_run not supported by this command\n");
                return -E_SYNTAX;
        }
        ret = install_sighandler(SIGHUP);
        if (ret < 0)
                return ret;
-       return select_loop();
-}
-
-void log_disk_space(struct disk_space *ds)
-{
-       DSS_INFO_LOG("free: %uM/%uM (%u%%), %u%% inodes unused\n",
-               ds->free_mb, ds->total_mb, ds->percent_free,
-               ds->percent_free_inodes);
+       compute_next_snapshot_time();
+       ret = select_loop();
+       if (ret >= 0) /* impossible */
+               ret = -E_BUG;
+       exit_hook(ret);
+       return ret;
 }
 
-int com_prune(void)
+static int com_prune(void)
 {
        int ret;
        struct snapshot_list sl;
@@ -902,7 +929,7 @@ int com_prune(void)
                return ret;
        log_disk_space(&ds);
        for (;;) {
-               get_snapshot_list(&sl);
+               dss_get_snapshot_list(&sl);
                ret = remove_outdated_snapshot(&sl);
                free_snapshot_list(&sl);
                if (ret < 0)
@@ -914,7 +941,7 @@ int com_prune(void)
                        goto out;
        }
        for (;;) {
-               get_snapshot_list(&sl);
+               dss_get_snapshot_list(&sl);
                ret = remove_redundant_snapshot(&sl);
                free_snapshot_list(&sl);
                if (ret < 0)
@@ -930,110 +957,73 @@ out:
        return ret;
 }
 
-int com_create(void)
+static int com_create(void)
 {
        int ret, status;
        char **rsync_argv;
 
-       create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
        if (conf.dry_run_given) {
                int i;
                char *msg = NULL;
+               create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
                for (i = 0; rsync_argv[i]; i++) {
                        char *tmp = msg;
                        msg = make_message("%s%s%s", tmp? tmp : "",
                                tmp? " " : "", rsync_argv[i]);
                        free(tmp);
                }
+               free_rsync_argv(rsync_argv);
                dss_msg("%s\n", msg);
                free(msg);
                return 1;
        }
+       ret = pre_create_hook();
+       if (ret < 0)
+               return ret;
+       if (create_pid) {
+               ret = wait_for_process(create_pid, &status);
+               if (ret < 0)
+                       return ret;
+               ret = handle_pre_create_hook_exit(status);
+               if (ret <= 0) /* error, or pre-create failed */
+                       return ret;
+       }
+       create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
        ret = create_snapshot(rsync_argv);
        if (ret < 0)
                goto out;
-       ret = wait_for_process(rsync_pid, &status);
+       ret = wait_for_process(create_pid, &status);
        if (ret < 0)
                goto out;
        ret = handle_rsync_exit(status);
+       if (ret < 0)
+               goto out;
+       post_create_hook();
+       if (create_pid)
+               ret = wait_for_process(create_pid, &status);
 out:
        free_rsync_argv(rsync_argv);
        return ret;
 }
 
-int com_ls(void)
+static int com_ls(void)
 {
        int i;
        struct snapshot_list sl;
        struct snapshot *s;
-       get_snapshot_list(&sl);
-       FOR_EACH_SNAPSHOT(s, i, &sl)
-               dss_msg("%u\t%s\n", s->interval, s->name);
-       free_snapshot_list(&sl);
-       return 1;
-}
-
-__noreturn void clean_exit(int status)
-{
-       free(dss_error_txt);
-       exit(status);
-}
-
-int read_config_file(void)
-{
-       int ret;
-       char *config_file;
-       struct stat statbuf;
-
-       if (conf.config_file_given)
-               config_file = dss_strdup(conf.config_file_arg);
-       else {
-               char *home = get_homedir();
-               config_file = make_message("%s/.dssrc", home);
-               free(home);
-       }
-       ret = stat(config_file, &statbuf);
-       if (ret && conf.config_file_given) {
-               ret = -ERRNO_TO_DSS_ERROR(errno);
-               make_err_msg("failed to stat config file %s", config_file);
-               goto out;
-       }
-       if (!ret) {
-               struct cmdline_parser_params params = {
-                       .override = 0,
-                       .initialize = 0,
-                       .check_required = 0,
-                       .check_ambiguity = 0
-               };
-               cmdline_parser_config_file(config_file, &conf, &params);
-       }
-       if (!conf.source_dir_given || !conf.dest_dir_given) {
-               ret = -E_SYNTAX;
-               make_err_msg("you need to specify both source_dir and dest_dir");
-               goto out;
-       }
-       ret = 1;
-out:
-       free(config_file);
-       return ret;
-}
 
-int check_config(void)
-{
-       if (conf.unit_interval_arg <= 0) {
-               make_err_msg("bad unit interval: %i", conf.unit_interval_arg);
-               return -E_INVALID_NUMBER;
-       }
-       DSS_DEBUG_LOG("unit interval: %i day(s)\n", conf.unit_interval_arg);
-       if (conf.num_intervals_arg <= 0) {
-               make_err_msg("bad number of intervals  %i", conf.num_intervals_arg);
-               return -E_INVALID_NUMBER;
-       }
-       DSS_DEBUG_LOG("number of intervals: %i\n", conf.num_intervals_arg);
+       dss_get_snapshot_list(&sl);
+       FOR_EACH_SNAPSHOT(s, i, &sl) {
+               int64_t d = 0;
+               if (s->flags & SS_COMPLETE)
+                       d = (s->completion_time - s->creation_time) / 60;
+               dss_msg("%u\t%s\t%3" PRId64 ":%02" PRId64 "\n", s->interval, s->name, d/60, d%60);
+       };
+       free_snapshot_list(&sl);
        return 1;
 }
 
-static void setup_signal_handling(void)
+static int setup_signal_handling(void)
 {
        int ret;
 
@@ -1041,43 +1031,45 @@ static void setup_signal_handling(void)
        signal_pipe = signal_init(); /* always successful */
        ret = install_sighandler(SIGINT);
        if (ret < 0)
-               goto err;
+               return ret;
        ret = install_sighandler(SIGTERM);
        if (ret < 0)
-               goto err;
-       ret = install_sighandler(SIGCHLD);
-       if (ret < 0)
-               goto err;
-       return;
-err:
-       DSS_EMERG_LOG("could not install signal handlers\n");
-       exit(EXIT_FAILURE);
+               return ret;
+       return install_sighandler(SIGCHLD);
 }
 
+/**
+ * The main function of dss.
+ *
+ * \param argc Usual argument count.
+ * \param argv Usual argument vector.
+ */
 int main(int argc, char **argv)
 {
        int ret;
+       struct cmdline_parser_params params = {
+               .override = 0,
+               .initialize = 1,
+               .check_required = 0,
+               .check_ambiguity = 0,
+               .print_errors = 1
+       };
 
-       cmdline_parser(argc, argv, &conf); /* aborts on errors */
-       ret = read_config_file();
+       cmdline_parser_ext(argc, argv, &conf, &params); /* aborts on errors */
+       ret = parse_config_file(0);
        if (ret < 0)
                goto out;
-       ret = check_config();
+       if (conf.daemon_given)
+               daemon_init();
+       ret = change_to_dest_dir();
        if (ret < 0)
                goto out;
-       if (conf.logfile_given) {
-               logfile = open_log(conf.logfile_arg);
-               log_welcome(conf.loglevel_arg);
-       }
-       ret = dss_chdir(conf.dest_dir_arg);
+       ret = setup_signal_handling();
        if (ret < 0)
                goto out;
-       if (conf.daemon_given)
-               daemon_init();
-       setup_signal_handling();
        ret = call_command_handler();
 out:
        if (ret < 0)
-               log_err_msg(EMERG, -ret);
-       clean_exit(ret >= 0? EXIT_SUCCESS : EXIT_FAILURE);
+               DSS_EMERG_LOG("%s\n", dss_strerror(-ret));
+       exit(ret >= 0? EXIT_SUCCESS : EXIT_FAILURE);
 }