nspawn: add new .nspawn files for container settings

.nspawn fiels are simple settings files that may accompany container
images and directories and contain settings otherwise passed on the
nspawn command line. This provides an efficient way to attach execution
data directly to containers.

1 files changed, 528 insertions, 220 deletions

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 1c64c3e771..a8afcd1466 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -102,12 +102,8 @@
 #include "seccomp-util.h"
 #endif
 
-typedef struct ExposePort {
-        int protocol;
-        uint16_t host_port;
-        uint16_t container_port;
-        LIST_FIELDS(struct ExposePort, ports);
-} ExposePort;
+#include "nspawn.h"
+#include "nspawn-settings.h"
 
 typedef enum ContainerStatus {
         CONTAINER_TERMINATED,
@@ -121,28 +117,6 @@ typedef enum LinkJournal {
         LINK_GUEST
 } LinkJournal;
 
-typedef enum Volatile {
-        VOLATILE_NO,
-        VOLATILE_YES,
-        VOLATILE_STATE,
-} Volatile;
-
-typedef enum CustomMountType {
-        CUSTOM_MOUNT_BIND,
-        CUSTOM_MOUNT_TMPFS,
-        CUSTOM_MOUNT_OVERLAY,
-} CustomMountType;
-
-typedef struct CustomMount {
-        CustomMountType type;
-        bool read_only;
-        char *source; /* for overlayfs this is the upper directory */
-        char *destination;
-        char *options;
-        char *work_dir;
-        char **lower;
-} CustomMount;
-
 static char *arg_directory = NULL;
 static char *arg_template = NULL;
 static char *arg_user = NULL;
@@ -195,16 +169,19 @@ static char **arg_network_interfaces = NULL;
 static char **arg_network_macvlan = NULL;
 static char **arg_network_ipvlan = NULL;
 static bool arg_network_veth = false;
-static const char *arg_network_bridge = NULL;
+static char *arg_network_bridge = NULL;
 static unsigned long arg_personality = PERSONALITY_INVALID;
 static char *arg_image = NULL;
-static Volatile arg_volatile = VOLATILE_NO;
+static VolatileMode arg_volatile_mode = VOLATILE_NO;
 static ExposePort *arg_expose_ports = NULL;
 static char **arg_property = NULL;
 static uid_t arg_uid_shift = UID_INVALID, arg_uid_range = 0x10000U;
 static bool arg_userns = false;
 static int arg_kill_signal = 0;
 static bool arg_unified_cgroup_hierarchy = false;
+static SettingsMask arg_settings_mask = 0;
+static int arg_settings_trusted = -1;
+static char **arg_parameters = NULL;
 
 static void help(void) {
         printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
@@ -275,30 +252,36 @@ static void help(void) {
                "     --keep-unit            Do not register a scope for the machine, reuse\n"
                "                            the service unit nspawn is running in\n"
                "     --volatile[=MODE]      Run the system in volatile mode\n"
+               "     --settings=BOOLEAN     Load additional settings from .nspawn file\n"
                , program_invocation_short_name);
 }
 
-static CustomMount* custom_mount_add(CustomMountType t) {
+static CustomMount* custom_mount_add(CustomMount **l, unsigned *n, CustomMountType t) {
         CustomMount *c, *ret;
 
-        c = realloc(arg_custom_mounts, (arg_n_custom_mounts + 1) * sizeof(CustomMount));
+        assert(l);
+        assert(n);
+        assert(t >= 0);
+        assert(t < _CUSTOM_MOUNT_TYPE_MAX);
+
+        c = realloc(*l, (*n + 1) * sizeof(CustomMount));
         if (!c)
                 return NULL;
 
-        arg_custom_mounts = c;
-        ret = arg_custom_mounts + arg_n_custom_mounts;
-        arg_n_custom_mounts++;
+        *l = c;
+        ret = *l + *n;
+        (*n)++;
 
         *ret = (CustomMount) { .type = t };
 
         return ret;
 }
 
-static void custom_mount_free_all(void) {
+void custom_mount_free_all(CustomMount *l, unsigned n) {
         unsigned i;
 
-        for (i = 0; i < arg_n_custom_mounts; i++) {
-                CustomMount *m = &arg_custom_mounts[i];
+        for (i = 0; i < n; i++) {
+                CustomMount *m = l + i;
 
                 free(m->source);
                 free(m->destination);
@@ -312,8 +295,7 @@ static void custom_mount_free_all(void) {
                 strv_free(m->lower);
         }
 
-        arg_custom_mounts = mfree(arg_custom_mounts);
-        arg_n_custom_mounts = 0;
+        free(l);
 }
 
 static int custom_mount_compare(const void *a, const void *b) {
@@ -410,6 +392,161 @@ static int detect_unified_cgroup_hierarchy(void) {
         return 0;
 }
 
+VolatileMode volatile_mode_from_string(const char *s) {
+        int b;
+
+        if (isempty(s))
+                return _VOLATILE_MODE_INVALID;
+
+        b = parse_boolean(s);
+        if (b > 0)
+                return VOLATILE_YES;
+        if (b == 0)
+                return VOLATILE_NO;
+
+        if (streq(s, "state"))
+                return VOLATILE_STATE;
+
+        return _VOLATILE_MODE_INVALID;
+}
+
+int expose_port_parse(ExposePort **l, const char *s) {
+
+        const char *split, *e;
+        uint16_t container_port, host_port;
+        int protocol;
+        ExposePort *p;
+        int r;
+
+        if ((e = startswith(s, "tcp:")))
+                protocol = IPPROTO_TCP;
+        else if ((e = startswith(s, "udp:")))
+                protocol = IPPROTO_UDP;
+        else {
+                e = s;
+                protocol = IPPROTO_TCP;
+        }
+
+        split = strchr(e, ':');
+        if (split) {
+                char v[split - e + 1];
+
+                memcpy(v, e, split - e);
+                v[split - e] = 0;
+
+                r = safe_atou16(v, &host_port);
+                if (r < 0 || host_port <= 0)
+                        return -EINVAL;
+
+                r = safe_atou16(split + 1, &container_port);
+        } else {
+                r = safe_atou16(e, &container_port);
+                host_port = container_port;
+        }
+
+        if (r < 0 || container_port <= 0)
+                return -EINVAL;
+
+        LIST_FOREACH(ports, p, arg_expose_ports)
+                if (p->protocol == protocol && p->host_port == host_port)
+                        return -EEXIST;
+
+        p = new(ExposePort, 1);
+        if (!p)
+                return -ENOMEM;
+
+        p->protocol = protocol;
+        p->host_port = host_port;
+        p->container_port = container_port;
+
+        LIST_PREPEND(ports, *l, p);
+
+        return 0;
+}
+
+int bind_mount_parse(CustomMount **l, unsigned *n, const char *s, bool read_only) {
+        _cleanup_free_ char *source = NULL, *destination = NULL, *opts = NULL;
+        const char *p = s;
+        CustomMount *m;
+        int r;
+
+        assert(l);
+        assert(n);
+
+        r = extract_many_words(&p, ":", EXTRACT_DONT_COALESCE_SEPARATORS, &source, &destination, NULL);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EINVAL;
+
+        if (r == 1) {
+                destination = strdup(source);
+                if (!destination)
+                        return -ENOMEM;
+        }
+
+        if (r == 2 && !isempty(p)) {
+                opts = strdup(p);
+                if (!opts)
+                        return -ENOMEM;
+        }
+
+        if (!path_is_absolute(source))
+                return -EINVAL;
+
+        if (!path_is_absolute(destination))
+                return -EINVAL;
+
+        m = custom_mount_add(l, n, CUSTOM_MOUNT_BIND);
+        if (!m)
+                return log_oom();
+
+        m->source = source;
+        m->destination = destination;
+        m->read_only = read_only;
+        m->options = opts;
+
+        source = destination = opts = NULL;
+        return 0;
+}
+
+int tmpfs_mount_parse(CustomMount **l, unsigned *n, const char *s) {
+        _cleanup_free_ char *path = NULL, *opts = NULL;
+        const char *p = s;
+        CustomMount *m;
+        int r;
+
+        assert(l);
+        assert(n);
+        assert(s);
+
+        r = extract_first_word(&p, &path, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EINVAL;
+
+        if (isempty(p))
+                opts = strdup("mode=0755");
+        else
+                opts = strdup(p);
+        if (!opts)
+                return -ENOMEM;
+
+        if (!path_is_absolute(path))
+                return -EINVAL;
+
+        m = custom_mount_add(l, n, CUSTOM_MOUNT_TMPFS);
+        if (!m)
+                return -ENOMEM;
+
+        m->destination = path;
+        m->options = opts;
+
+        path = opts = NULL;
+        return 0;
+}
+
 static int parse_argv(int argc, char *argv[]) {
 
         enum {
@@ -439,6 +576,7 @@ static int parse_argv(int argc, char *argv[]) {
                 ARG_PROPERTY,
                 ARG_PRIVATE_USERS,
                 ARG_KILL_SIGNAL,
+                ARG_SETTINGS,
         };
 
         static const struct option options[] = {
@@ -481,11 +619,13 @@ static int parse_argv(int argc, char *argv[]) {
                 { "property",              required_argument, NULL, ARG_PROPERTY          },
                 { "private-users",         optional_argument, NULL, ARG_PRIVATE_USERS     },
                 { "kill-signal",           required_argument, NULL, ARG_KILL_SIGNAL       },
+                { "settings",              required_argument, NULL, ARG_SETTINGS          },
                 {}
         };
 
         int c, r;
         uint64_t plus = 0, minus = 0;
+        bool mask_all_settings = false, mask_no_settings = false;
 
         assert(argc >= 0);
         assert(argv);
@@ -533,16 +673,20 @@ static int parse_argv(int argc, char *argv[]) {
                         if (r < 0)
                                 return log_oom();
 
+                        arg_settings_mask |= SETTING_USER;
                         break;
 
                 case ARG_NETWORK_BRIDGE:
-                        arg_network_bridge = optarg;
+                        r = free_and_strdup(&arg_network_bridge, optarg);
+                        if (r < 0)
+                                return log_oom();
 
                         /* fall through */
 
                 case 'n':
                         arg_network_veth = true;
                         arg_private_network = true;
+                        arg_settings_mask |= SETTING_NETWORK;
                         break;
 
                 case ARG_NETWORK_INTERFACE:
@@ -550,6 +694,7 @@ static int parse_argv(int argc, char *argv[]) {
                                 return log_oom();
 
                         arg_private_network = true;
+                        arg_settings_mask |= SETTING_NETWORK;
                         break;
 
                 case ARG_NETWORK_MACVLAN:
@@ -557,6 +702,7 @@ static int parse_argv(int argc, char *argv[]) {
                                 return log_oom();
 
                         arg_private_network = true;
+                        arg_settings_mask |= SETTING_NETWORK;
                         break;
 
                 case ARG_NETWORK_IPVLAN:
@@ -567,10 +713,12 @@ static int parse_argv(int argc, char *argv[]) {
 
                 case ARG_PRIVATE_NETWORK:
                         arg_private_network = true;
+                        arg_settings_mask |= SETTING_NETWORK;
                         break;
 
                 case 'b':
                         arg_boot = true;
+                        arg_settings_mask |= SETTING_BOOT;
                         break;
 
                 case ARG_UUID:
@@ -579,6 +727,8 @@ static int parse_argv(int argc, char *argv[]) {
                                 log_error("Invalid UUID: %s", optarg);
                                 return r;
                         }
+
+                        arg_settings_mask |= SETTING_MACHINE_ID;
                         break;
 
                 case 'S':
@@ -611,6 +761,7 @@ static int parse_argv(int argc, char *argv[]) {
 
                 case ARG_READ_ONLY:
                         arg_read_only = true;
+                        arg_settings_mask |= SETTING_READ_ONLY;
                         break;
 
                 case ARG_CAPABILITY:
@@ -646,6 +797,7 @@ static int parse_argv(int argc, char *argv[]) {
                                 }
                         }
 
+                        arg_settings_mask |= SETTING_CAPABILITY;
                         break;
                 }
 
@@ -681,83 +833,21 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case ARG_BIND:
-                case ARG_BIND_RO: {
-                        const char *current = optarg;
-                        _cleanup_free_ char *source = NULL, *destination = NULL, *opts = NULL;
-                        CustomMount *m;
-
-                        r = extract_many_words(&current, ":", EXTRACT_DONT_COALESCE_SEPARATORS, &source, &destination, &opts, NULL);
-                        switch (r) {
-                        case 1:
-                                destination = strdup(source);
-                        case 2:
-                        case 3:
-                                break;
-                        case -ENOMEM:
-                                return log_oom();
-                        default:
-                                log_error("Invalid bind mount specification: %s", optarg);
-                                return -EINVAL;
-                        }
-
-                        if (!source || !destination)
-                                return log_oom();
-
-                        if (!path_is_absolute(source) || !path_is_absolute(destination)) {
-                                log_error("Invalid bind mount specification: %s", optarg);
-                                return -EINVAL;
-                        }
-
-                        m = custom_mount_add(CUSTOM_MOUNT_BIND);
-                        if (!m)
-                                return log_oom();
-
-                        m->source = source;
-                        m->destination = destination;
-                        m->read_only = c == ARG_BIND_RO;
-                        m->options = opts;
-
-                        source = destination = opts = NULL;
+                case ARG_BIND_RO:
+                        r = bind_mount_parse(&arg_custom_mounts, &arg_n_custom_mounts, optarg, c == ARG_BIND_RO);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --bind(-ro)= argument %s: %m", optarg);
 
+                        arg_settings_mask |= SETTING_CUSTOM_MOUNTS;
                         break;
-                }
-
-                case ARG_TMPFS: {
-                        const char *current = optarg;
-                        _cleanup_free_ char *path = NULL, *opts = NULL;
-                        CustomMount *m;
-
-                        r = extract_first_word(&current, &path, ":", EXTRACT_DONT_COALESCE_SEPARATORS);
-                        if (r == -ENOMEM)
-                                return log_oom();
-                        else if (r < 0) {
-                                log_error("Invalid tmpfs specification: %s", optarg);
-                                return r;
-                        }
-                        if (r)
-                                opts = strdup(current);
-                        else
-                                opts = strdup("mode=0755");
-
-                        if (!path || !opts)
-                                return log_oom();
-
-                        if (!path_is_absolute(path)) {
-                                log_error("Invalid tmpfs specification: %s", optarg);
-                                return -EINVAL;
-                        }
-
-                        m = custom_mount_add(CUSTOM_MOUNT_TMPFS);
-                        if (!m)
-                                return log_oom();
-
-                        m->destination = path;
-                        m->options = opts;
 
-                        path = opts = NULL;
+                case ARG_TMPFS:
+                        r = tmpfs_mount_parse(&arg_custom_mounts, &arg_n_custom_mounts, optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --tmpfs= argument %s: %m", optarg);
 
+                        arg_settings_mask |= SETTING_CUSTOM_MOUNTS;
                         break;
-                }
 
                 case ARG_OVERLAY:
                 case ARG_OVERLAY_RO: {
@@ -808,7 +898,7 @@ static int parse_argv(int argc, char *argv[]) {
                                 lower[n - 2] = NULL;
                         }
 
-                        m = custom_mount_add(CUSTOM_MOUNT_OVERLAY);
+                        m = custom_mount_add(&arg_custom_mounts, &arg_n_custom_mounts, CUSTOM_MOUNT_OVERLAY);
                         if (!m)
                                 return log_oom();
 
@@ -820,6 +910,7 @@ static int parse_argv(int argc, char *argv[]) {
                         upper = destination = NULL;
                         lower = NULL;
 
+                        arg_settings_mask |= SETTING_CUSTOM_MOUNTS;
                         break;
                 }
 
@@ -837,6 +928,8 @@ static int parse_argv(int argc, char *argv[]) {
 
                         strv_free(arg_setenv);
                         arg_setenv = n;
+
+                        arg_settings_mask |= SETTING_ENVIRONMENT;
                         break;
                 }
 
@@ -870,85 +963,36 @@ static int parse_argv(int argc, char *argv[]) {
                                 return -EINVAL;
                         }
 
+                        arg_settings_mask |= SETTING_PERSONALITY;
                         break;
 
                 case ARG_VOLATILE:
 
                         if (!optarg)
-                                arg_volatile = VOLATILE_YES;
+                                arg_volatile_mode = VOLATILE_YES;
                         else {
-                                r = parse_boolean(optarg);
-                                if (r < 0) {
-                                        if (streq(optarg, "state"))
-                                                arg_volatile = VOLATILE_STATE;
-                                        else {
-                                                log_error("Failed to parse --volatile= argument: %s", optarg);
-                                                return r;
-                                        }
-                                } else
-                                        arg_volatile = r ? VOLATILE_YES : VOLATILE_NO;
-                        }
+                                VolatileMode m;
 
-                        break;
-
-                case 'p': {
-                        const char *split, *e;
-                        uint16_t container_port, host_port;
-                        int protocol;
-                        ExposePort *p;
-
-                        if ((e = startswith(optarg, "tcp:")))
-                                protocol = IPPROTO_TCP;
-                        else if ((e = startswith(optarg, "udp:")))
-                                protocol = IPPROTO_UDP;
-                        else {
-                                e = optarg;
-                                protocol = IPPROTO_TCP;
-                        }
-
-                        split = strchr(e, ':');
-                        if (split) {
-                                char v[split - e + 1];
-
-                                memcpy(v, e, split - e);
-                                v[split - e] = 0;
-
-                                r = safe_atou16(v, &host_port);
-                                if (r < 0 || host_port <= 0) {
-                                        log_error("Failed to parse host port: %s", optarg);
-                                        return -EINVAL;
-                                }
-
-                                r = safe_atou16(split + 1, &container_port);
-                        } else {
-                                r = safe_atou16(e, &container_port);
-                                host_port = container_port;
-                        }
-
-                        if (r < 0 || container_port <= 0) {
-                                log_error("Failed to parse host port: %s", optarg);
-                                return -EINVAL;
-                        }
-
-                        LIST_FOREACH(ports, p, arg_expose_ports) {
-                                if (p->protocol == protocol && p->host_port == host_port) {
-                                        log_error("Duplicate port specification: %s", optarg);
+                                m = volatile_mode_from_string(optarg);
+                                if (m < 0) {
+                                        log_error("Failed to parse --volatile= argument: %s", optarg);
                                         return -EINVAL;
-                                }
+                                } else
+                                        arg_volatile_mode = m;
                         }
 
-                        p = new(ExposePort, 1);
-                        if (!p)
-                                return log_oom();
-
-                        p->protocol = protocol;
-                        p->host_port = host_port;
-                        p->container_port = container_port;
+                        arg_settings_mask |= SETTING_VOLATILE_MODE;
+                        break;
 
-                        LIST_PREPEND(ports, arg_expose_ports, p);
+                case 'p':
+                        r = expose_port_parse(&arg_expose_ports, optarg);
+                        if (r == -EEXIST)
+                                return log_error_errno(r, "Duplicate port specification: %s", optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse host port %s: %m", optarg);
 
+                        arg_settings_mask |= SETTING_EXPOSE_PORTS;
                         break;
-                }
 
                 case ARG_PROPERTY:
                         if (strv_extend(&arg_property, optarg) < 0)
@@ -992,6 +1036,42 @@ static int parse_argv(int argc, char *argv[]) {
                                 return -EINVAL;
                         }
 
+                        arg_settings_mask |= SETTING_KILL_SIGNAL;
+                        break;
+
+                case ARG_SETTINGS:
+
+                        /* no               → do not read files
+                         * yes              → read files, do not override cmdline, trust only subset
+                         * override         → read files, override cmdline, trust only subset
+                         * trusted          → read files, do not override cmdline, trust all
+                         */
+
+                        r = parse_boolean(optarg);
+                        if (r < 0) {
+                                if (streq(optarg, "trusted")) {
+                                        mask_all_settings = false;
+                                        mask_no_settings = false;
+                                        arg_settings_trusted = true;
+
+                                } else if (streq(optarg, "override")) {
+                                        mask_all_settings = false;
+                                        mask_no_settings = true;
+                                        arg_settings_trusted = -1;
+                                } else
+                                        return log_error_errno(r, "Failed to parse --settings= argument: %s", optarg);
+                        } else if (r > 0) {
+                                /* yes */
+                                mask_all_settings = false;
+                                mask_no_settings = false;
+                                arg_settings_trusted = -1;
+                        } else {
+                                /* no */
+                                mask_all_settings = true;
+                                mask_no_settings = false;
+                                arg_settings_trusted = false;
+                        }
+
                         break;
 
                 case '?':
@@ -1044,7 +1124,37 @@ static int parse_argv(int argc, char *argv[]) {
                 return -EINVAL;
         }
 
-        if (arg_volatile != VOLATILE_NO && arg_read_only) {
+        if (arg_userns && access("/proc/self/uid_map", F_OK) < 0)
+                return log_error_errno(EOPNOTSUPP, "--private-users= is not supported, kernel compiled without user namespace support.");
+
+        if (argc > optind) {
+                arg_parameters = strv_copy(argv + optind);
+                if (!arg_parameters)
+                        return log_oom();
+
+                arg_settings_mask |= SETTING_BOOT;
+        }
+
+        /* Load all settings from .nspawn files */
+        if (mask_no_settings)
+                arg_settings_mask = 0;
+
+        /* Don't load any settings from .nspawn files */
+        if (mask_all_settings)
+                arg_settings_mask = _SETTINGS_MASK_ALL;
+
+        arg_retain = (arg_retain | plus | (arg_private_network ? 1ULL << CAP_NET_ADMIN : 0)) & ~minus;
+
+        r = detect_unified_cgroup_hierarchy();
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static int verify_arguments(void) {
+
+        if (arg_volatile_mode != VOLATILE_NO && arg_read_only) {
                 log_error("Cannot combine --read-only with --volatile. Note that --volatile already implies a read-only base hierarchy.");
                 return -EINVAL;
         }
@@ -1054,19 +1164,10 @@ static int parse_argv(int argc, char *argv[]) {
                 return -EINVAL;
         }
 
-        if (arg_userns && access("/proc/self/uid_map", F_OK) < 0)
-                return log_error_errno(EOPNOTSUPP, "--private-users= is not supported, kernel compiled without user namespace support.");
-
-        arg_retain = (arg_retain | plus | (arg_private_network ? 1ULL << CAP_NET_ADMIN : 0)) & ~minus;
-
         if (arg_boot && arg_kill_signal <= 0)
                 arg_kill_signal = SIGRTMIN+3;
 
-        r = detect_unified_cgroup_hierarchy();
-        if (r < 0)
-                return r;
-
-        return 1;
+        return 0;
 }
 
 static int tmpfs_patch_options(const char *options, char **ret) {
@@ -1743,7 +1844,7 @@ static int setup_volatile_state(const char *directory) {
 
         assert(directory);
 
-        if (arg_volatile != VOLATILE_STATE)
+        if (arg_volatile_mode != VOLATILE_STATE)
                 return 0;
 
         /* --volatile=state means we simply overmount /var
@@ -1780,7 +1881,7 @@ static int setup_volatile(const char *directory) {
 
         assert(directory);
 
-        if (arg_volatile != VOLATILE_YES)
+        if (arg_volatile_mode != VOLATILE_YES)
                 return 0;
 
         /* --volatile=yes means we mount a tmpfs to the root dir, and
@@ -2208,6 +2309,15 @@ static int expose_ports(sd_netlink *rtnl, union in_addr_union *exposed) {
         return 0;
 }
 
+void expose_port_free_all(ExposePort *p) {
+
+        while (p) {
+                ExposePort *q = p;
+                LIST_REMOVE(ports, p, q);
+                free(q);
+        }
+}
+
 static int on_address_change(sd_netlink *rtnl, sd_netlink_message *m, void *userdata) {
         union in_addr_union *exposed = userdata;
 
@@ -4254,9 +4364,7 @@ static int inner_child(
                 bool secondary,
                 int kmsg_socket,
                 int rtnl_socket,
-                FDSet *fds,
-                int argc,
-                char *argv[]) {
+                FDSet *fds) {
 
         _cleanup_free_ char *home = NULL;
         unsigned n_env = 2;
@@ -4412,9 +4520,12 @@ static int inner_child(
 
                 /* Automatically search for the init system */
 
-                m = 1 + argc - optind;
+                m = 1 + strv_length(arg_parameters);
                 a = newa(char*, m + 1);
-                memcpy(a + 1, argv + optind, m * sizeof(char*));
+                if (strv_isempty(arg_parameters))
+                        a[1] = NULL;
+                else
+                        memcpy(a + 1, arg_parameters, m * sizeof(char*));
 
                 a[0] = (char*) "/usr/lib/systemd/systemd";
                 execve(a[0], a, env_use);
@@ -4424,10 +4535,10 @@ static int inner_child(
 
                 a[0] = (char*) "/sbin/init";
                 execve(a[0], a, env_use);
-        } else if (argc > optind)
-                execvpe(argv[optind], argv + optind, env_use);
+        } else if (!strv_isempty(arg_parameters))
+                execvpe(arg_parameters[0], arg_parameters, env_use);
         else {
-                chdir(home ? home : "/root");
+                chdir(home ?: "/root");
                 execle("/bin/bash", "-bash", NULL, env_use);
                 execle("/bin/sh", "-sh", NULL, env_use);
         }
@@ -4449,9 +4560,7 @@ static int outer_child(
                 int kmsg_socket,
                 int rtnl_socket,
                 int uid_shift_socket,
-                FDSet *fds,
-                int argc,
-                char *argv[]) {
+                FDSet *fds) {
 
         pid_t pid;
         ssize_t l;
@@ -4604,7 +4713,7 @@ static int outer_child(
                  * requested, so that we all are owned by the user if
                  * user namespaces are turned on. */
 
-                r = inner_child(barrier, directory, secondary, kmsg_socket, rtnl_socket, fds, argc, argv);
+                r = inner_child(barrier, directory, secondary, kmsg_socket, rtnl_socket, fds);
                 if (r < 0)
                         _exit(EXIT_FAILURE);
 
@@ -4780,6 +4889,202 @@ static int create_subcgroup(pid_t pid) {
         return 0;
 }
 
+static int load_settings(void) {
+        _cleanup_(settings_freep) Settings *settings = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        _cleanup_free_ char *p = NULL;
+        const char *fn, *i;
+        int r;
+
+        /* If all settings are masked, there's no point in looking for
+         * the settings file */
+        if ((arg_settings_mask & _SETTINGS_MASK_ALL) == _SETTINGS_MASK_ALL)
+                return 0;
+
+        fn = strjoina(arg_machine, ".nspawn");
+
+        /* We first look in the admin's directories in /etc and /run */
+        FOREACH_STRING(i, "/etc/systemd/nspawn", "/run/systemd/nspawn") {
+                _cleanup_free_ char *j = NULL;
+
+                j = strjoin(i, "/", fn, NULL);
+                if (!j)
+                        return log_oom();
+
+                f = fopen(j, "re");
+                if (f) {
+                        p = j;
+                        j = NULL;
+
+                        /* By default we trust configuration from /etc and /run */
+                        if (arg_settings_trusted < 0)
+                                arg_settings_trusted = true;
+
+                        break;
+                }
+
+                if (errno != ENOENT)
+                        return log_error_errno(errno, "Failed to open %s: %m", j);
+        }
+
+        if (!f) {
+                /* After that, let's look for a file next to the
+                 * actual image we shall boot. */
+
+                if (arg_image) {
+                        p = file_in_same_dir(arg_image, fn);
+                        if (!p)
+                                return log_oom();
+                } else if (arg_directory) {
+                        p = file_in_same_dir(arg_directory, fn);
+                        if (!p)
+                                return log_oom();
+                }
+
+                if (p) {
+                        f = fopen(p, "re");
+                        if (!f && errno != ENOENT)
+                                return log_error_errno(errno, "Failed to open %s: %m", p);
+
+                        /* By default we do not trust configuration from /var/lib/machines */
+                        if (arg_settings_trusted < 0)
+                                arg_settings_trusted = false;
+                }
+        }
+
+        if (!f)
+                return 0;
+
+        log_debug("Settings are trusted: %s", yes_no(arg_settings_trusted));
+
+        r = settings_load(f, p, &settings);
+        if (r < 0)
+                return r;
+
+        /* Copy over bits from the settings, unless they have been
+         * explicitly masked by command line switches. */
+
+        if ((arg_settings_mask & SETTING_BOOT) == 0 &&
+            settings->boot >= 0) {
+                arg_boot = settings->boot;
+
+                strv_free(arg_parameters);
+                arg_parameters = settings->parameters;
+                settings->parameters = NULL;
+        }
+
+        if ((arg_settings_mask & SETTING_ENVIRONMENT) == 0 &&
+            settings->environment) {
+                strv_free(arg_setenv);
+                arg_setenv = settings->environment;
+                settings->environment = NULL;
+        }
+
+        if ((arg_settings_mask & SETTING_USER) == 0 &&
+            settings->user) {
+                free(arg_user);
+                arg_user = settings->user;
+                settings->user = NULL;
+        }
+
+        if ((arg_settings_mask & SETTING_CAPABILITY) == 0) {
+
+                if (!arg_settings_trusted && settings->capability != 0)
+                        log_warning("Ignoring Capability= setting, file %s is not trusted.", p);
+                else
+                        arg_retain |= settings->capability;
+
+                arg_retain &= ~settings->drop_capability;
+        }
+
+        if ((arg_settings_mask & SETTING_KILL_SIGNAL) == 0 &&
+            settings->kill_signal > 0)
+                arg_kill_signal = settings->kill_signal;
+
+        if ((arg_settings_mask & SETTING_PERSONALITY) == 0 &&
+            settings->personality != PERSONALITY_INVALID)
+                arg_personality = settings->personality;
+
+        if ((arg_settings_mask & SETTING_MACHINE_ID) == 0 &&
+            !sd_id128_is_null(settings->machine_id)) {
+
+                if (!arg_settings_trusted)
+                        log_warning("Ignoring MachineID= setting, file %s is not trusted.", p);
+                else
+                        arg_uuid = settings->machine_id;
+        }
+
+        if ((arg_settings_mask & SETTING_READ_ONLY) == 0 &&
+            settings->read_only >= 0)
+                arg_read_only = settings->read_only;
+
+        if ((arg_settings_mask & SETTING_VOLATILE_MODE) == 0 &&
+            settings->volatile_mode != _VOLATILE_MODE_INVALID)
+                arg_volatile_mode = settings->volatile_mode;
+
+        if ((arg_settings_mask & SETTING_CUSTOM_MOUNTS) == 0 &&
+            settings->n_custom_mounts > 0) {
+
+                if (!arg_settings_trusted)
+                        log_warning("Ignoring TemporaryFileSystem=, Bind= and BindReadOnly= settings, file %s is not trusted.", p);
+                else {
+                        custom_mount_free_all(arg_custom_mounts, arg_n_custom_mounts);
+                        arg_custom_mounts = settings->custom_mounts;
+                        arg_n_custom_mounts = settings->n_custom_mounts;
+
+                        settings->custom_mounts = NULL;
+                        settings->n_custom_mounts = 0;
+                }
+        }
+
+        if ((arg_settings_mask & SETTING_NETWORK) == 0 &&
+            (settings->private_network >= 0 ||
+             settings->network_veth >= 0 ||
+             settings->network_bridge ||
+             settings->network_interfaces ||
+             settings->network_macvlan ||
+             settings->network_ipvlan)) {
+
+                if (!arg_settings_trusted)
+                        log_warning("Ignoring network settings, file %s is not trusted.", p);
+                else {
+                        strv_free(arg_network_interfaces);
+                        arg_network_interfaces = settings->network_interfaces;
+                        settings->network_interfaces = NULL;
+
+                        strv_free(arg_network_macvlan);
+                        arg_network_macvlan = settings->network_macvlan;
+                        settings->network_macvlan = NULL;
+
+                        strv_free(arg_network_ipvlan);
+                        arg_network_ipvlan = settings->network_ipvlan;
+                        settings->network_ipvlan = NULL;
+
+                        free(arg_network_bridge);
+                        arg_network_bridge = settings->network_bridge;
+                        settings->network_bridge = NULL;
+
+                        arg_network_veth = settings->network_veth > 0 || settings->network_bridge;
+
+                        arg_private_network = true; /* all these settings imply private networking */
+                }
+        }
+
+        if ((arg_settings_mask & SETTING_EXPOSE_PORTS) == 0 &&
+            settings->expose_ports) {
+
+                if (!arg_settings_trusted)
+                        log_warning("Ignoring Port= setting, file %s is not trusted.", p);
+                else {
+                        expose_port_free_all(arg_expose_ports);
+                        arg_expose_ports = settings->expose_ports;
+                        settings->expose_ports = NULL;
+                }
+        }
+
+        return 0;
+}
+
 int main(int argc, char *argv[]) {
 
         _cleanup_free_ char *device_path = NULL, *root_device = NULL, *home_device = NULL, *srv_device = NULL, *console = NULL;
@@ -4803,15 +5108,22 @@ int main(int argc, char *argv[]) {
         if (r <= 0)
                 goto finish;
 
-        r = determine_names();
-        if (r < 0)
-                goto finish;
-
         if (geteuid() != 0) {
                 log_error("Need to be root.");
                 r = -EPERM;
                 goto finish;
         }
+        r = determine_names();
+        if (r < 0)
+                goto finish;
+
+        r = load_settings();
+        if (r < 0)
+                goto finish;
+
+        r = verify_arguments();
+        if (r < 0)
+                goto finish;
 
         n_fd_passed = sd_listen_fds(false);
         if (n_fd_passed > 0) {
@@ -5092,8 +5404,7 @@ int main(int argc, char *argv[]) {
                                         kmsg_socket_pair[1],
                                         rtnl_socket_pair[1],
                                         uid_shift_socket_pair[1],
-                                        fds,
-                                        argc, argv);
+                                        fds);
                         if (r < 0)
                                 _exit(EXIT_FAILURE);
 
@@ -5342,24 +5653,21 @@ finish:
                 (void) rm_rf(p, REMOVE_ROOT);
         }
 
+        flush_ports(&exposed);
+
         free(arg_directory);
         free(arg_template);
         free(arg_image);
         free(arg_machine);
         free(arg_user);
         strv_free(arg_setenv);
+        free(arg_network_bridge);
         strv_free(arg_network_interfaces);
         strv_free(arg_network_macvlan);
         strv_free(arg_network_ipvlan);
-        custom_mount_free_all();
-
-        flush_ports(&exposed);
-
-        while (arg_expose_ports) {
-                ExposePort *p = arg_expose_ports;
-                LIST_REMOVE(ports, arg_expose_ports, p);
-                free(p);
-        }
+        strv_free(arg_parameters);
+        custom_mount_free_all(arg_custom_mounts, arg_n_custom_mounts);
+        expose_port_free_all(arg_expose_ports);
 
         return r < 0 ? EXIT_FAILURE : ret;
 }