debug-generator: add new kernel cmdline option systemd.wants= to add units to the initial transaction

man/kernel-command-line.xml

@@ -100,14 +100,15 @@
 
                         <varlistentry>
                                 <term><varname>systemd.mask=</varname></term>
+                                <term><varname>systemd.wants=</varname></term>
                                 <term><varname>systemd.debug-shell</varname></term>
                                 <listitem>
                                         <para>Additional parameters
                                         understood by
                                         <citerefentry><refentrytitle>systemd-debug-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
-                                        to mask specific units at
+                                        to mask or start specific
-                                        boot, or invoke a debug shell
+                                        units at boot, or invoke a
-                                        on tty9.</para>
+                                        debug shell on tty9.</para>
                                 </listitem>
                         </varlistentry>
 

man/systemd-debug-generator.xml

@@ -53,7 +53,8 @@
                 <title>Description</title>
 
                 <para><filename>systemd-debug-generator</filename> is
-                a generator that reads the kernel command line and understands two options:</para>
+                a generator that reads the kernel command line and
+                understands three options:</para>
 
                 <para>If the <option>systemd.mask=</option> option is
                 specified and followed by a unit name this unit is
@@ -61,7 +62,14 @@
                 <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
                 <command>mask</command> command. This is useful to
                 boot with certain units removed from the initial boot
-                transaction for debugging system startup.</para>
+                transaction for debugging system startup. May be
+                specified more than once.</para>
+
+                <para>If the <option>systemd.wants=</option> option is
+                specified and followed by a unit name a start job for
+                this unit is added to the initial transaction. This is
+                useful to start one ore more additional units at
+                boot. May be specified more than once.</para>
 
                 <para>If the <option>systemd.debug-shell</option>
                 option is specified the debug shell service

src/debug-generator/debug-generator.c

@@ -26,11 +26,14 @@
 
 static const char *arg_dest = "/tmp";
 static char **arg_mask = NULL;
+static char **arg_wants = NULL;
 static bool arg_debug_shell = false;
 
 static int parse_proc_cmdline_item(const char *key, const char *value) {
         int r;
 
+        assert(key);
+
         if (streq(key, "systemd.mask")) {
 
                 if (!value)
@@ -38,7 +41,7 @@ static int parse_proc_cmdline_item(const char *key, const char *value) {
                 else {
                         char *n;
 
-                        n = strdup(value);
+                        n = unit_name_mangle(value, MANGLE_NOGLOB);
                         if (!n)
                                 return log_oom();
 
@@ -46,6 +49,23 @@ static int parse_proc_cmdline_item(const char *key, const char *value) {
                         if (r < 0)
                                 return log_oom();
                 }
+
+        } else if (streq(key, "systemd.wants")) {
+
+                if (!value)
+                        log_error("Missing argument for systemd.want= kernel command line parameter.");
+                else {
+                        char *n;
+
+                        n = unit_name_mangle(value, MANGLE_NOGLOB);
+                        if (!n)
+                                return log_oom();
+
+                        r = strv_consume(&arg_wants, n);
+                        if (r < 0)
+                                return log_oom();
+                }
+
         } else if (streq(key, "systemd.debug-shell")) {
 
                 if (value) {
@@ -69,13 +89,9 @@ static int generate_mask_symlinks(void) {
                 return 0;
 
         STRV_FOREACH(u, arg_mask) {
-                _cleanup_free_ char *m = NULL, *p = NULL;
+                _cleanup_free_ char *p = NULL;
 
-                m = unit_name_mangle(*u, MANGLE_NOGLOB);
+                p = strjoin(arg_dest, "/", *u, NULL);
-                if (!m)
-                        return log_oom();
-
-                p = strjoin(arg_dest, "/", m, NULL);
                 if (!p)
                         return log_oom();
 
@@ -88,22 +104,33 @@ static int generate_mask_symlinks(void) {
         return r;
 }
 
-static int generate_debug_shell_symlink(void) {
+static int generate_wants_symlinks(void) {
-        const char *p;
+        char **u;
+        int r = 0;
 
-        if (!arg_debug_shell)
+        if (strv_isempty(arg_wants))
                 return 0;
 
-        p = strappenda(arg_dest, "/default.target.wants/debug-shell.service");
+        STRV_FOREACH(u, arg_wants) {
+                _cleanup_free_ char *p = NULL, *f = NULL;
 
-        mkdir_parents_label(p, 0755);
+                p = strjoin(arg_dest, "/default.target.wants/", *u, NULL);
+                if (!p)
+                        return log_oom();
 
-        if (symlink(SYSTEM_DATA_UNIT_PATH "/debug-shell.service", p) < 0) {
+                f = strappend(SYSTEM_DATA_UNIT_PATH "/", *u);
-                log_error("Failed to create %s symlink: %m", p);
+                if (!f)
-                return -errno;
+                        return log_oom();
+
+                mkdir_parents_label(p, 0755);
+
+                if (symlink(f, p) < 0) {
+                        log_error("Failed to create wants symlink %s: %m", p);
+                        r = -errno;
+                }
         }
 
-        return 0;
+        return r;
 }
 
 int main(int argc, char *argv[]) {
@@ -126,12 +153,21 @@ int main(int argc, char *argv[]) {
         if (parse_proc_cmdline(parse_proc_cmdline_item) < 0)
                 return EXIT_FAILURE;
 
+        if (arg_debug_shell) {
+                r = strv_extend(&arg_wants, "debug-shell.service");
+                if (r < 0) {
+                        r = log_oom();
+                        goto finish;
+                }
+        }
+
         r = generate_mask_symlinks();
 
-        q = generate_debug_shell_symlink();
+        q = generate_wants_symlinks();
         if (q < 0)
                 r = q;
 
+finish:
         return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
 
 }