Merge pull request #4835 from poettering/unit-name-printf

Various specifier resolution fixes.

5 files changed, 128 insertions, 92 deletions

diff --git a/src/core/load-fragment-gperf.gperf.m4 b/src/core/load-fragment-gperf.gperf.m4
index f4ef5a0140..2610442b91 100644
--- a/src/core/load-fragment-gperf.gperf.m4
+++ b/src/core/load-fragment-gperf.gperf.m4
@@ -191,13 +191,13 @@ Unit.IgnoreOnIsolate,            config_parse_bool,                  0,
 Unit.IgnoreOnSnapshot,           config_parse_warn_compat,           DISABLED_LEGACY,               0
 Unit.JobTimeoutSec,              config_parse_sec_fix_0,             0,                             offsetof(Unit, job_timeout)
 Unit.JobTimeoutAction,           config_parse_emergency_action,      0,                             offsetof(Unit, job_timeout_action)
-Unit.JobTimeoutRebootArgument,   config_parse_string,                0,                             offsetof(Unit, job_timeout_reboot_arg)
+Unit.JobTimeoutRebootArgument,   config_parse_unit_string_printf,    0,                             offsetof(Unit, job_timeout_reboot_arg)
 Unit.StartLimitIntervalSec,      config_parse_sec,                   0,                             offsetof(Unit, start_limit.interval)
 m4_dnl The following is a legacy alias name for compatibility
 Unit.StartLimitInterval,         config_parse_sec,                   0,                             offsetof(Unit, start_limit.interval)
 Unit.StartLimitBurst,            config_parse_unsigned,              0,                             offsetof(Unit, start_limit.burst)
 Unit.StartLimitAction,           config_parse_emergency_action,      0,                             offsetof(Unit, start_limit_action)
-Unit.RebootArgument,             config_parse_string,                0,                             offsetof(Unit, reboot_arg)
+Unit.RebootArgument,             config_parse_unit_string_printf,    0,                             offsetof(Unit, reboot_arg)
 Unit.ConditionPathExists,        config_parse_unit_condition_path,   CONDITION_PATH_EXISTS,         offsetof(Unit, conditions)
 Unit.ConditionPathExistsGlob,    config_parse_unit_condition_path,   CONDITION_PATH_EXISTS_GLOB,    offsetof(Unit, conditions)
 Unit.ConditionPathIsDirectory,   config_parse_unit_condition_path,   CONDITION_PATH_IS_DIRECTORY,   offsetof(Unit, conditions)
@@ -254,7 +254,7 @@ m4_dnl The following three only exist for compatibility, they moved into Unit, s
 Service.StartLimitInterval,      config_parse_sec,                   0,                             offsetof(Unit, start_limit.interval)
 Service.StartLimitBurst,         config_parse_unsigned,              0,                             offsetof(Unit, start_limit.burst)
 Service.StartLimitAction,        config_parse_emergency_action,      0,                             offsetof(Unit, start_limit_action)
-Service.RebootArgument,          config_parse_string,                0,                             offsetof(Unit, reboot_arg)
+Service.RebootArgument,          config_parse_unit_path_printf,      0,                             offsetof(Unit, reboot_arg)
 Service.FailureAction,           config_parse_emergency_action,      0,                             offsetof(Service, emergency_action)
 Service.Type,                    config_parse_service_type,          0,                             offsetof(Service, type)
 Service.Restart,                 config_parse_service_restart,       0,                             offsetof(Service, restart)
@@ -272,8 +272,8 @@ Service.FileDescriptorStoreMax,  config_parse_unsigned,              0,
 Service.NotifyAccess,            config_parse_notify_access,         0,                             offsetof(Service, notify_access)
 Service.Sockets,                 config_parse_service_sockets,       0,                             0
 Service.BusPolicy,               config_parse_warn_compat,           DISABLED_LEGACY,               0
-Service.USBFunctionDescriptors,  config_parse_path,                  0,                             offsetof(Service, usb_function_descriptors)
-Service.USBFunctionStrings,      config_parse_path,                  0,                             offsetof(Service, usb_function_strings)
+Service.USBFunctionDescriptors,  config_parse_unit_path_printf,      0,                             offsetof(Service, usb_function_descriptors)
+Service.USBFunctionStrings,      config_parse_unit_path_printf,      0,                             offsetof(Service, usb_function_strings)
 EXEC_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
 CGROUP_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
 KILL_CONTEXT_CONFIG_ITEMS(Service)m4_dnl
@@ -332,9 +332,9 @@ Socket.Service,                  config_parse_socket_service,        0,
 Socket.TriggerLimitIntervalSec,  config_parse_sec,                   0,                             offsetof(Socket, trigger_limit.interval)
 Socket.TriggerLimitBurst,        config_parse_unsigned,              0,                             offsetof(Socket, trigger_limit.burst)
 m4_ifdef(`HAVE_SMACK',
-`Socket.SmackLabel,              config_parse_string,                0,                             offsetof(Socket, smack)
-Socket.SmackLabelIPIn,           config_parse_string,                0,                             offsetof(Socket, smack_ip_in)
-Socket.SmackLabelIPOut,          config_parse_string,                0,                             offsetof(Socket, smack_ip_out)',
+`Socket.SmackLabel,              config_parse_unit_string_printf,    0,                             offsetof(Socket, smack)
+Socket.SmackLabelIPIn,           config_parse_unit_string_printf,    0,                             offsetof(Socket, smack_ip_in)
+Socket.SmackLabelIPOut,          config_parse_unit_string_printf,    0,                             offsetof(Socket, smack_ip_out)',
 `Socket.SmackLabel,              config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
 Socket.SmackLabelIPIn,           config_parse_warn_compat,           DISABLED_CONFIGURATION,        0
 Socket.SmackLabelIPOut,          config_parse_warn_compat,           DISABLED_CONFIGURATION,        0')
@@ -354,9 +354,9 @@ BusName.AllowWorld,              config_parse_bus_policy_world,      0,
 BusName.SELinuxContext,          config_parse_exec_selinux_context,  0,                             0
 BusName.AcceptFileDescriptors,   config_parse_bool,                  0,                             offsetof(BusName, accept_fd)
 m4_dnl
-Mount.What,                      config_parse_string,                0,                             offsetof(Mount, parameters_fragment.what)
+Mount.What,                      config_parse_unit_string_printf,    0,                             offsetof(Mount, parameters_fragment.what)
 Mount.Where,                     config_parse_path,                  0,                             offsetof(Mount, where)
-Mount.Options,                   config_parse_string,                0,                             offsetof(Mount, parameters_fragment.options)
+Mount.Options,                   config_parse_unit_string_printf,    0,                             offsetof(Mount, parameters_fragment.options)
 Mount.Type,                      config_parse_string,                0,                             offsetof(Mount, parameters_fragment.fstype)
 Mount.TimeoutSec,                config_parse_sec,                   0,                             offsetof(Mount, timeout_usec)
 Mount.DirectoryMode,             config_parse_mode,                  0,                             offsetof(Mount, directory_mode)
@@ -373,7 +373,7 @@ Automount.TimeoutIdleSec,        config_parse_sec,                   0,
 m4_dnl
 Swap.What,                       config_parse_path,                  0,                             offsetof(Swap, parameters_fragment.what)
 Swap.Priority,                   config_parse_int,                   0,                             offsetof(Swap, parameters_fragment.priority)
-Swap.Options,                    config_parse_string,                0,                             offsetof(Swap, parameters_fragment.options)
+Swap.Options,                    config_parse_unit_string_printf,    0,                             offsetof(Swap, parameters_fragment.options)
 Swap.TimeoutSec,                 config_parse_sec,                   0,                             offsetof(Swap, timeout_usec)
 EXEC_CONTEXT_CONFIG_ITEMS(Swap)m4_dnl
 CGROUP_CONTEXT_CONFIG_ITEMS(Swap)m4_dnl
diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 970eed27c1..6b36b2fc3a 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -579,6 +579,7 @@ int config_parse_exec(
                 void *userdata) {
 
         ExecCommand **e = data;
+        Unit *u = userdata;
         const char *p;
         bool semicolon;
         int r;
@@ -604,7 +605,7 @@ int config_parse_exec(
                 _cleanup_free_ ExecCommand *nce = NULL;
                 _cleanup_strv_free_ char **n = NULL;
                 size_t nlen = 0, nbufsize = 0;
-                char *f;
+                const char *f;
                 int i;
 
                 semicolon = false;
@@ -631,47 +632,47 @@ int config_parse_exec(
                         f++;
                 }
 
-                if (isempty(f)) {
+                r = unit_full_printf(u, f, &path);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve unit specifiers on %s, ignoring: %m", f);
+                        return 0;
+                }
+
+                if (isempty(path)) {
                         /* First word is either "-" or "@" with no command. */
                         log_syntax(unit, LOG_ERR, filename, line, 0, "Empty path in command line, ignoring: \"%s\"", rvalue);
                         return 0;
                 }
-                if (!string_is_safe(f)) {
+                if (!string_is_safe(path)) {
                         log_syntax(unit, LOG_ERR, filename, line, 0, "Executable path contains special characters, ignoring: %s", rvalue);
                         return 0;
                 }
-                if (!path_is_absolute(f)) {
+                if (!path_is_absolute(path)) {
                         log_syntax(unit, LOG_ERR, filename, line, 0, "Executable path is not absolute, ignoring: %s", rvalue);
                         return 0;
                 }
-                if (endswith(f, "/")) {
+                if (endswith(path, "/")) {
                         log_syntax(unit, LOG_ERR, filename, line, 0, "Executable path specifies a directory, ignoring: %s", rvalue);
                         return 0;
                 }
 
-                if (f == firstword) {
-                        path = firstword;
-                        firstword = NULL;
-                } else {
-                        path = strdup(f);
-                        if (!path)
-                                return log_oom();
-                }
-
                 if (!separate_argv0) {
+                        char *w = NULL;
+
                         if (!GREEDY_REALLOC(n, nbufsize, nlen + 2))
                                 return log_oom();
-                        f = strdup(path);
-                        if (!f)
+
+                        w = strdup(path);
+                        if (!w)
                                 return log_oom();
-                        n[nlen++] = f;
+                        n[nlen++] = w;
                         n[nlen] = NULL;
                 }
 
                 path_kill_slashes(path);
 
                 while (!isempty(p)) {
-                        _cleanup_free_ char *word = NULL;
+                        _cleanup_free_ char *word = NULL, *resolved = NULL;
 
                         /* Check explicitly for an unquoted semicolon as
                          * command separator token.  */
@@ -682,18 +683,21 @@ int config_parse_exec(
                                 break;
                         }
 
-                        /* Check for \; explicitly, to not confuse it with \\;
-                         * or "\;" or "\\;" etc.  extract_first_word would
-                         * return the same for all of those.  */
+                        /* Check for \; explicitly, to not confuse it with \\; or "\;" or "\\;" etc.
+                         * extract_first_word() would return the same for all of those.  */
                         if (p[0] == '\\' && p[1] == ';' && (!p[2] || strchr(WHITESPACE, p[2]))) {
+                                char *w;
+
                                 p += 2;
                                 p += strspn(p, WHITESPACE);
+
                                 if (!GREEDY_REALLOC(n, nbufsize, nlen + 2))
                                         return log_oom();
-                                f = strdup(";");
-                                if (!f)
+
+                                w = strdup(";");
+                                if (!w)
                                         return log_oom();
-                                n[nlen++] = f;
+                                n[nlen++] = w;
                                 n[nlen] = NULL;
                                 continue;
                         }
@@ -701,14 +705,20 @@ int config_parse_exec(
                         r = extract_first_word_and_warn(&p, &word, NULL, EXTRACT_QUOTES|EXTRACT_CUNESCAPE, unit, filename, line, rvalue);
                         if (r == 0)
                                 break;
-                        else if (r < 0)
+                        if (r < 0)
                                 return 0;
 
+                        r = unit_full_printf(u, word, &resolved);
+                        if (r < 0) {
+                                log_syntax(unit, LOG_ERR, filename, line, 0, "Failed to resolve unit specifiers on %s, ignoring: %m", word);
+                                return 0;
+                        }
+
                         if (!GREEDY_REALLOC(n, nbufsize, nlen + 2))
                                 return log_oom();
-                        n[nlen++] = word;
+                        n[nlen++] = resolved;
                         n[nlen] = NULL;
-                        word = NULL;
+                        resolved = NULL;
                 }
 
                 if (!n || !n[0]) {
@@ -1326,7 +1336,7 @@ int config_parse_exec_selinux_context(
         } else
                 ignore = false;
 
-        r = unit_name_printf(u, rvalue, &k);
+        r = unit_full_printf(u, rvalue, &k);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve specifiers, ignoring: %m");
                 return 0;
@@ -1374,7 +1384,7 @@ int config_parse_exec_apparmor_profile(
         } else
                 ignore = false;
 
-        r = unit_name_printf(u, rvalue, &k);
+        r = unit_full_printf(u, rvalue, &k);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve specifiers, ignoring: %m");
                 return 0;
@@ -1422,7 +1432,7 @@ int config_parse_exec_smack_process_label(
         } else
                 ignore = false;
 
-        r = unit_name_printf(u, rvalue, &k);
+        r = unit_full_printf(u, rvalue, &k);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve specifiers, ignoring: %m");
                 return 0;
@@ -1689,7 +1699,7 @@ int config_parse_fdname(
                 return 0;
         }
 
-        r = unit_name_printf(UNIT(s), rvalue, &p);
+        r = unit_full_printf(UNIT(s), rvalue, &p);
         if (r < 0) {
                 log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve specifiers, ignoring: %s", rvalue);
                 return 0;
@@ -2555,7 +2565,7 @@ int config_parse_unit_requires_mounts_for(
         assert(data);
 
         for (p = rvalue;; ) {
-                _cleanup_free_ char *word = NULL;
+                _cleanup_free_ char *word = NULL, *resolved = NULL;
 
                 r = extract_first_word(&p, &word, NULL, EXTRACT_QUOTES);
                 if (r == 0)
@@ -2573,9 +2583,15 @@ int config_parse_unit_requires_mounts_for(
                         continue;
                 }
 
-                r = unit_require_mounts_for(u, word);
+                r = unit_full_printf(u, word, &resolved);
                 if (r < 0) {
-                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to add required mount \"%s\", ignoring: %m", word);
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve unit name \"%s\", ignoring: %m", word);
+                        continue;
+                }
+
+                r = unit_require_mounts_for(u, resolved);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to add required mount \"%s\", ignoring: %m", resolved);
                         continue;
                 }
         }
@@ -3710,7 +3726,7 @@ int config_parse_runtime_directory(
                         return 0;
                 }
 
-                r = unit_name_printf(u, word, &k);
+                r = unit_full_printf(u, word, &k);
                 if (r < 0) {
                         log_syntax(unit, LOG_ERR, filename, line, r,
                                    "Failed to resolve specifiers in \"%s\", ignoring: %m", word);
@@ -3812,8 +3828,8 @@ int config_parse_namespace_path_strv(
                 void *data,
                 void *userdata) {
 
+        Unit *u = userdata;
         char*** sv = data;
-        const char *prev;
         const char *cur;
         int r;
 
@@ -3828,10 +3844,10 @@ int config_parse_namespace_path_strv(
                 return 0;
         }
 
-        prev = cur = rvalue;
+        cur = rvalue;
         for (;;) {
-                _cleanup_free_ char *word = NULL;
-                int offset;
+                _cleanup_free_ char *word = NULL, *resolved = NULL, *joined = NULL;
+                bool ignore_enoent;
 
                 r = extract_first_word(&cur, &word, NULL, EXTRACT_QUOTES);
                 if (r == 0)
@@ -3839,31 +3855,37 @@ int config_parse_namespace_path_strv(
                 if (r == -ENOMEM)
                         return log_oom();
                 if (r < 0) {
-                        log_syntax(unit, LOG_ERR, filename, line, r, "Trailing garbage, ignoring: %s", prev);
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to extract first word, ignoring: %s", rvalue);
                         return 0;
                 }
 
                 if (!utf8_is_valid(word)) {
                         log_syntax_invalid_utf8(unit, LOG_ERR, filename, line, word);
-                        prev = cur;
                         continue;
                 }
 
-                offset = word[0] == '-';
-                if (!path_is_absolute(word + offset)) {
-                        log_syntax(unit, LOG_ERR, filename, line, 0, "Not an absolute path, ignoring: %s", word);
-                        prev = cur;
+                ignore_enoent = word[0] == '-';
+
+                r = unit_full_printf(u, word + ignore_enoent, &resolved);
+                if (r < 0) {
+                        log_syntax(unit, LOG_ERR, filename, line, r, "Failed to resolve specifiers in %s: %m", word);
+                        continue;
+                }
+
+                if (!path_is_absolute(resolved)) {
+                        log_syntax(unit, LOG_ERR, filename, line, 0, "Not an absolute path, ignoring: %s", resolved);
                         continue;
                 }
 
-                path_kill_slashes(word + offset);
+                path_kill_slashes(resolved);
 
-                r = strv_push(sv, word);
+                joined = strjoin(ignore_enoent ? "-" : "", resolved);
+
+                r = strv_push(sv, joined);
                 if (r < 0)
                         return log_oom();
 
-                prev = cur;
-                word = NULL;
+                joined = NULL;
         }
 
         return 0;
diff --git a/src/core/service.c b/src/core/service.c
index 61246d831d..576416ad29 100644
--- a/src/core/service.c
+++ b/src/core/service.c
@@ -49,7 +49,6 @@
 #include "string-util.h"
 #include "strv.h"
 #include "unit-name.h"
-#include "unit-printf.h"
 #include "unit.h"
 #include "utf8.h"
 #include "util.h"
@@ -1205,7 +1204,7 @@ static int service_spawn(
                 ExecFlags flags,
                 pid_t *_pid) {
 
-        _cleanup_strv_free_ char **argv = NULL, **final_env = NULL, **our_env = NULL, **fd_names = NULL;
+        _cleanup_strv_free_ char **final_env = NULL, **our_env = NULL, **fd_names = NULL;
         _cleanup_free_ int *fds = NULL;
         unsigned n_fds = 0, n_env = 0;
         const char *path;
@@ -1263,10 +1262,6 @@ static int service_spawn(
         if (r < 0)
                 return r;
 
-        r = unit_full_printf_strv(UNIT(s), c->argv, &argv);
-        if (r < 0)
-                return r;
-
         our_env = new0(char*, 9);
         if (!our_env)
                 return -ENOMEM;
@@ -1349,7 +1344,7 @@ static int service_spawn(
         } else
                 path = UNIT(s)->cgroup_path;
 
-        exec_params.argv = argv;
+        exec_params.argv = c->argv;
         exec_params.environment = final_env;
         exec_params.fds = fds;
         exec_params.fd_names = fd_names;
diff --git a/src/core/socket.c b/src/core/socket.c
index 1a53d47f21..fee9b702e6 100644
--- a/src/core/socket.c
+++ b/src/core/socket.c
@@ -54,7 +54,6 @@
 #include "string-util.h"
 #include "strv.h"
 #include "unit-name.h"
-#include "unit-printf.h"
 #include "unit.h"
 #include "user-util.h"
 #include "in-addr-util.h"
@@ -1740,7 +1739,6 @@ static int socket_coldplug(Unit *u) {
 }
 
 static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {
-        _cleanup_free_ char **argv = NULL;
         pid_t pid;
         int r;
         ExecParameters exec_params = {
@@ -1772,11 +1770,7 @@ static int socket_spawn(Socket *s, ExecCommand *c, pid_t *_pid) {
         if (r < 0)
                 return r;
 
-        r = unit_full_printf_strv(UNIT(s), c->argv, &argv);
-        if (r < 0)
-                return r;
-
-        exec_params.argv = argv;
+        exec_params.argv = c->argv;
         exec_params.environment = UNIT(s)->manager->environment;
         exec_params.confirm_spawn = manager_get_confirm_spawn(UNIT(s)->manager);
         exec_params.cgroup_supported = UNIT(s)->manager->cgroup_supported;
diff --git a/src/core/unit-printf.c b/src/core/unit-printf.c
index 1f5dc6fd88..746e1a46ef 100644
--- a/src/core/unit-printf.c
+++ b/src/core/unit-printf.c
@@ -78,12 +78,18 @@ static int specifier_filename(char specifier, void *data, void *userdata, char *
                 return unit_name_to_path(u->id, ret);
 }
 
+static void bad_specifier(Unit *u, char specifier) {
+        log_unit_warning(u, "Specifier '%%%c' used in unit configuration, which is deprecated. Please update your unit file, as it does not work as intended.", specifier);
+}
+
 static int specifier_cgroup(char specifier, void *data, void *userdata, char **ret) {
         Unit *u = userdata;
         char *n;
 
         assert(u);
 
+        bad_specifier(u, specifier);
+
         if (u->cgroup_path)
                 n = strdup(u->cgroup_path);
         else
@@ -101,6 +107,8 @@ static int specifier_cgroup_root(char specifier, void *data, void *userdata, cha
 
         assert(u);
 
+        bad_specifier(u, specifier);
+
         n = strdup(u->manager->cgroup_root);
         if (!n)
                 return -ENOMEM;
@@ -115,6 +123,8 @@ static int specifier_cgroup_slice(char specifier, void *data, void *userdata, ch
 
         assert(u);
 
+        bad_specifier(u, specifier);
+
         if (UNIT_ISSET(u->slice)) {
                 Unit *slice;
 
@@ -194,13 +204,20 @@ static int specifier_user_shell(char specifier, void *data, void *userdata, char
 int unit_name_printf(Unit *u, const char* format, char **ret) {
 
         /*
-         * This will use the passed string as format string and
-         * replace the following specifiers:
+         * This will use the passed string as format string and replace the following specifiers (which should all be
+         * safe for inclusion in unit names):
          *
          * %n: the full id of the unit                 (foo@bar.waldo)
          * %N: the id of the unit without the suffix   (foo@bar)
          * %p: the prefix                              (foo)
          * %i: the instance                            (bar)
+         *
+         * %U: the UID of the running user
+         * %u: the username of the running user
+         *
+         * %m: the machine ID of the running system
+         * %H: the host name of the running system
+         * %b: the boot ID of the running system
          */
 
         const Specifier table[] = {
@@ -208,7 +225,14 @@ int unit_name_printf(Unit *u, const char* format, char **ret) {
                 { 'N', specifier_prefix_and_instance, NULL },
                 { 'p', specifier_prefix,              NULL },
                 { 'i', specifier_string,              u->instance },
-                { 0, NULL, NULL }
+
+                { 'U', specifier_user_id,             NULL },
+                { 'u', specifier_user_name,           NULL },
+
+                { 'm', specifier_machine_id,          NULL },
+                { 'H', specifier_host_name,           NULL },
+                { 'b', specifier_boot_id,             NULL },
+                {}
         };
 
         assert(u);
@@ -220,22 +244,23 @@ int unit_name_printf(Unit *u, const char* format, char **ret) {
 
 int unit_full_printf(Unit *u, const char *format, char **ret) {
 
-        /* This is similar to unit_name_printf() but also supports
-         * unescaping. Also, adds a couple of additional codes:
+        /* This is similar to unit_name_printf() but also supports unescaping. Also, adds a couple of additional codes
+         * (which are likely not suitable for unescaped inclusion in unit names):
+         *
+         * %f: the unescaped instance if set, otherwise the id unescaped as path
+         * %c: cgroup path of unit (deprecated)
+         * %r: where units in this slice are placed in the cgroup tree (deprecated)
+         * %R: the root of this systemd's instance tree (deprecated)
+         * %t: the runtime directory to place sockets in (e.g. "/run" or $XDG_RUNTIME_DIR)
+         *
+         * %h: the homedir of the running user
+         * %s: the shell of the running user
+         *
+         * %v: `uname -r` of the running system
          *
-         * %f the instance if set, otherwise the id
-         * %c cgroup path of unit
-         * %r where units in this slice are placed in the cgroup tree
-         * %R the root of this systemd's instance tree
-         * %t the runtime directory to place sockets in (e.g. "/run" or $XDG_RUNTIME_DIR)
-         * %U the UID of the running user
-         * %u the username of the running user
-         * %h the homedir of the running user
-         * %s the shell of the running user
-         * %m the machine ID of the running system
-         * %H the host name of the running system
-         * %b the boot ID of the running system
-         * %v `uname -r` of the running system
+         * NOTICE: When you add new entries here, please be careful: specifiers which depend on settings of the unit
+         * file itself are broken by design, as they would resolve differently depending on whether they are used
+         * before or after the relevant configuration setting. Hence: don't add them.
          */
 
         const Specifier table[] = {