diff --git a/src/basic/namespace-util.c b/src/basic/namespace-util.c
index 6a73eed913..f156bfdf24 100644
--- a/src/basic/namespace-util.c
+++ b/src/basic/namespace-util.c
@@ -68,6 +68,11 @@ static int pidref_namespace_open_by_type_internal(const PidRef *pidref, Namespac
 
         if (pidref->fd >= 0) {
                 r = pidfd_get_namespace(pidref->fd, namespace_info[type].pidfd_get_ns_ioctl_cmd);
+                if (r == -ENOPKG)
+                        return log_debug_errno(
+                                        r,
+                                        "Cannot open %s namespace for PID "PID_FMT" as the namespace type is not supported by the kernel",
+                                        namespace_info[type].proc_name, pidref->pid);
                 if (!ERRNO_IS_NEG_NOT_SUPPORTED(r))
                         return r;
         }
@@ -83,10 +88,17 @@ static int pidref_namespace_open_by_type_internal(const PidRef *pidref, Namespac
         if (nsfd == -ENOENT) {
                 r = proc_mounted();
                 if (r == 0)
-                        return -ENOSYS;  /* /proc/ is not available or not set up properly, we're most likely
-                                            in some chroot environment. */
+                        /* /proc/ is not available or not set up properly, we're most likely in some chroot environment. */
+                        return log_debug_errno(
+                                        SYNTHETIC_ERRNO(ENOSYS),
+                                        "Cannot open %s namespace for PID "PID_FMT" as /proc is not mounted",
+                                        namespace_info[type].proc_name, pidref->pid);
                 if (r > 0)
-                        return -ENOPKG;  /* If /proc/ is definitely around then this means the namespace type is not supported */
+                        /* If /proc/ is definitely around then this means the namespace type is not supported */
+                        return log_debug_errno(
+                                        SYNTHETIC_ERRNO(ENOPKG),
+                                        "Cannot open %s namespace for PID "PID_FMT" via /proc as the namespace type is not supported by the kernel",
+                                        namespace_info[type].proc_name, pidref->pid);
 
                 /* can't determine? then propagate original error */
         }
@@ -216,33 +228,39 @@ int namespace_open(
         return pidref_namespace_open(&pidref, ret_pidns_fd, ret_mntns_fd, ret_netns_fd, ret_userns_fd, ret_root_fd);
 }
 
-static int namespace_enter_one_idempotent(int nsfd, NamespaceType type) {
-        int r;
-
-        /* Join a namespace, but only if we're not part of it already. This is important if we don't necessarily
-         * own the namespace in question, as kernel would unconditionally return EPERM otherwise. */
-
-        assert(nsfd >= 0);
-        assert(type >= 0 && type < _NAMESPACE_TYPE_MAX);
-
-        r = is_our_namespace(nsfd, type);
-        if (r < 0)
-                return r;
-        if (r > 0)
-                return 0;
-
-        if (setns(nsfd, namespace_info[type].clone_flag) < 0)
-                return -errno;
-
-        return 1;
-}
-
 int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int root_fd) {
         int r;
 
         /* Block dlopen() now, to avoid us inadvertently loading shared library from another namespace */
         block_dlopen();
 
+         /* Join namespaces, but only if we're not part of them already. This is important if we don't
+          * necessarily own the namespace in question, as kernel would unconditionally return EPERM otherwise. */
+
+        if (pidns_fd >= 0) {
+                r = is_our_namespace(pidns_fd, NAMESPACE_PID);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        pidns_fd = -EBADF;
+        }
+
+        if (mntns_fd >= 0) {
+                r = is_our_namespace(mntns_fd, NAMESPACE_MOUNT);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        mntns_fd = -EBADF;
+        }
+
+        if (netns_fd >= 0) {
+                r = is_our_namespace(netns_fd, NAMESPACE_NET);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        netns_fd = -EBADF;
+        }
+
         if (userns_fd >= 0) {
                 /* Can't setns to your own userns, since then you could escalate from non-root to root in
                  * your own namespace, so check if namespaces are equal before attempting to enter. */
@@ -275,23 +293,17 @@ int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int
                         return -errno;
         }
 
-        if (pidns_fd >= 0) {
-                r = namespace_enter_one_idempotent(pidns_fd, NAMESPACE_PID);
-                if (r < 0)
-                        return r;
-        }
+        if (pidns_fd >= 0)
+                if (setns(pidns_fd, CLONE_NEWPID) < 0)
+                        return -errno;
 
-        if (mntns_fd >= 0) {
-                r = namespace_enter_one_idempotent(mntns_fd, NAMESPACE_MOUNT);
-                if (r < 0)
-                        return r;
-        }
+        if (mntns_fd >= 0)
+                if (setns(mntns_fd, CLONE_NEWNS) < 0)
+                        return -errno;
 
-        if (netns_fd >= 0) {
-                r = namespace_enter_one_idempotent(netns_fd, NAMESPACE_NET);
-                if (r < 0)
-                        return r;
-        }
+        if (netns_fd >= 0)
+                if (setns(netns_fd, CLONE_NEWNET) < 0)
+                        return -errno;
 
         if (userns_fd >= 0 && have_cap_sys_admin)
                 if (setns(userns_fd, CLONE_NEWUSER) < 0)
@@ -361,6 +373,42 @@ int is_our_namespace(int fd, NamespaceType type) {
         return fd_inode_same(fd, our_ns);
 }
 
+int are_our_namespaces(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int root_fd) {
+        int r;
+
+        if (pidns_fd >= 0) {
+                r = is_our_namespace(pidns_fd, NAMESPACE_PID);
+                if (r <= 0)
+                        return r;
+        }
+
+        if (mntns_fd >= 0) {
+                r = is_our_namespace(mntns_fd, NAMESPACE_MOUNT);
+                if (r <= 0)
+                        return r;
+        }
+
+        if (netns_fd >= 0) {
+                r = is_our_namespace(netns_fd, NAMESPACE_NET);
+                if (r <= 0)
+                        return r;
+        }
+
+        if (userns_fd >= 0) {
+                r = is_our_namespace(userns_fd, NAMESPACE_USER);
+                if (r <= 0)
+                        return r;
+        }
+
+        if (root_fd >= 0) {
+                r = dir_fd_is_root(root_fd);
+                if (r <= 0)
+                        return r;
+        }
+
+        return true;
+}
+
 int namespace_is_init(NamespaceType type) {
         int r;
 
diff --git a/src/basic/namespace-util.h b/src/basic/namespace-util.h
index 32e64fa9e6..cd2ea78692 100644
--- a/src/basic/namespace-util.h
+++ b/src/basic/namespace-util.h
@@ -50,6 +50,7 @@ int namespace_enter(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int
 
 int fd_is_namespace(int fd, NamespaceType type);
 int is_our_namespace(int fd, NamespaceType type);
+int are_our_namespaces(int pidns_fd, int mntns_fd, int netns_fd, int userns_fd, int root_fd);
 
 int namespace_is_init(NamespaceType type);
 
diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index 9d77e96b1a..3f2c2d3b23 100644
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -25,13 +25,11 @@
 #include "cgroup-util.h"
 #include "dirent-util.h"
 #include "dlfcn-util.h"
-#include "env-file.h"
 #include "errno-util.h"
 #include "escape.h"
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
-#include "hostname-util.h"
 #include "io-util.h"
 #include "iovec-util.h"
 #include "locale-util.h"
@@ -53,6 +51,7 @@
 #include "stdio-util.h"
 #include "string-table.h"
 #include "string-util.h"
+#include "strv.h"
 #include "time-util.h"
 #include "user-util.h"
 
@@ -349,47 +348,6 @@ int pidref_get_cmdline_strv(const PidRef *pid, ProcessCmdlineFlags flags, char *
         return 0;
 }
 
-int container_get_leader(const char *machine, pid_t *pid) {
-        _cleanup_free_ char *s = NULL, *class = NULL;
-        const char *p;
-        pid_t leader;
-        int r;
-
-        assert(machine);
-        assert(pid);
-
-        if (streq(machine, ".host")) {
-                *pid = 1;
-                return 0;
-        }
-
-        if (!hostname_is_valid(machine, 0))
-                return -EINVAL;
-
-        p = strjoina("/run/systemd/machines/", machine);
-        r = parse_env_file(NULL, p,
-                           "LEADER", &s,
-                           "CLASS", &class);
-        if (r == -ENOENT)
-                return -EHOSTDOWN;
-        if (r < 0)
-                return r;
-        if (!s)
-                return -EIO;
-
-        if (!streq_ptr(class, "container"))
-                return -EIO;
-
-        r = parse_pid(s, &leader);
-        if (r < 0)
-                return r;
-        if (leader <= 1)
-                return -EIO;
-
-        *pid = leader;
-        return 0;
-}
-
 int pid_is_kernel_thread(pid_t pid) {
         int r;
 
diff --git a/src/basic/process-util.h b/src/basic/process-util.h
index b3f6120053..9d16055d5e 100644
--- a/src/basic/process-util.h
+++ b/src/basic/process-util.h
@@ -54,8 +54,6 @@ int pid_get_start_time(pid_t pid, usec_t *ret);
 int pidref_get_start_time(const PidRef *pid, usec_t *ret);
 int get_process_umask(pid_t pid, mode_t *ret);
 
-int container_get_leader(const char *machine, pid_t *pid);
-
 static inline bool SIGINFO_CODE_IS_DEAD(int code) {
         return IN_SET(code, CLD_EXITED, CLD_KILLED, CLD_DUMPED);
 }
diff --git a/src/coredump/coredump-send.c b/src/coredump/coredump-send.c
index 12c781d05a..0174be69a4 100644
--- a/src/coredump/coredump-send.c
+++ b/src/coredump/coredump-send.c
@@ -241,7 +241,7 @@ int coredump_send_to_container(CoredumpContext *context) {
         _cleanup_(pidref_done) PidRef leader_pid = PIDREF_NULL;
         r = namespace_get_leader(&context->pidref, NAMESPACE_PID, &leader_pid);
         if (r < 0)
-                return log_debug_errno(r, "Failed to get namespace leader: %m");
+                return log_error_errno(r, "Failed to get namespace leader: %m");
 
         r = can_forward_coredump(&context->pidref, &leader_pid);
         if (r <= 0)
@@ -258,33 +258,33 @@ int coredump_send_to_container(CoredumpContext *context) {
 
         r = RET_NERRNO(socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, pair));
         if (r < 0)
-                return log_debug_errno(r, "Failed to create socket pair: %m");
+                return log_error_errno(r, "Failed to create socket pair: %m");
 
         r = setsockopt_int(pair[1], SOL_SOCKET, SO_PASSCRED, true);
         if (r < 0)
-                return log_debug_errno(r, "Failed to set SO_PASSCRED: %m");
+                return log_error_errno(r, "Failed to set SO_PASSCRED: %m");
 
         r = pidref_namespace_open(&leader_pid, &pidnsfd, &mntnsfd, &netnsfd, &usernsfd, &rootfd);
         if (r < 0)
-                return log_debug_errno(r, "Failed to open namespaces of PID " PID_FMT ": %m", leader_pid.pid);
+                return log_error_errno(r, "Failed to open namespaces of PID " PID_FMT ": %m", leader_pid.pid);
 
         r = namespace_fork("(sd-coredumpns)", "(sd-coredump)",
                            FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM,
                            pidnsfd, mntnsfd, netnsfd, usernsfd, rootfd, &child);
         if (r < 0)
-                return log_debug_errno(r, "Failed to fork into namespaces of PID " PID_FMT ": %m", leader_pid.pid);
+                return log_error_errno(r, "Failed to fork into namespaces of PID " PID_FMT ": %m", leader_pid.pid);
         if (r == 0) {
                 pair[0] = safe_close(pair[0]);
 
                 r = access_nofollow("/run/systemd/coredump", W_OK);
                 if (r < 0) {
-                        log_debug_errno(r, "Cannot find coredump socket, exiting: %m");
+                        log_error_errno(r, "Cannot find coredump socket, exiting: %m");
                         _exit(EXIT_FAILURE);
                 }
 
                 r = receive_ucred(pair[1], &ucred);
                 if (r < 0) {
-                        log_debug_errno(r, "Failed to receive ucred and fd: %m");
+                        log_error_errno(r, "Failed to receive ucred and fd: %m");
                         _exit(EXIT_FAILURE);
                 }
 
@@ -309,7 +309,7 @@ int coredump_send_to_container(CoredumpContext *context) {
 
                 r = coredump_send(context);
                 if (r < 0) {
-                        log_debug_errno(r, "Failed to send iovec to coredump socket: %m");
+                        log_error_errno(r, "Failed to send iovec to coredump socket: %m");
                         _exit(EXIT_FAILURE);
                 }
 
@@ -324,13 +324,13 @@ int coredump_send_to_container(CoredumpContext *context) {
          * container. The kernel will perform the translation for us. */
         r = send_ucred(pair[0], &ucred);
         if (r < 0)
-                return log_debug_errno(r, "Failed to send metadata to container: %m");
+                return log_error_errno(r, "Failed to send metadata to container: %m");
 
-        r = pidref_wait_for_terminate_and_check("(sd-coredumpns)", &child, 0);
+        r = pidref_wait_for_terminate_and_check("(sd-coredumpns)", &child, WAIT_LOG);
         if (r < 0)
-                return log_debug_errno(r, "Failed to wait for child to terminate: %m");
+                return r;
         if (r != EXIT_SUCCESS)
-                return log_debug_errno(SYNTHETIC_ERRNO(EPROTO), "Failed to process coredump in container.");
+                return -EPROTO;
 
         return 1; /* sent */
 }
diff --git a/src/libsystemd/sd-bus/bus-container.c b/src/libsystemd/sd-bus/bus-container.c
index 3bbcbb81c6..475e855462 100644
--- a/src/libsystemd/sd-bus/bus-container.c
+++ b/src/libsystemd/sd-bus/bus-container.c
@@ -5,20 +5,99 @@
 #include "bus-container.h"
 #include "bus-internal.h"
 #include "bus-socket.h"
+#include "env-file.h"
+#include "errno-util.h"
 #include "fd-util.h"
 #include "format-util.h"
+#include "hostname-util.h"
 #include "log.h"
 #include "namespace-util.h"
-#include "pidref.h"
+#include "parse-util.h"
+#include "path-lookup.h"
+#include "path-util.h"
 #include "process-util.h"
 #include "string-util.h"
 
+int container_get_leader(RuntimeScope scope, const char *machine, pid_t *ret) {
+        _cleanup_free_ char *p = NULL, *s = NULL, *class = NULL;
+        pid_t leader;
+        int r;
+
+        assert(machine);
+        assert(ret);
+
+        if (streq(machine, ".host")) {
+                if (scope == RUNTIME_SCOPE_USER)
+                        return -EHOSTDOWN;
+
+                *ret = 1;
+                return 0;
+        }
+
+        if (!hostname_is_valid(machine, 0))
+                return -EINVAL;
+
+        r = runtime_directory_generic(scope, "systemd/machines", &p);
+        if (r < 0)
+                return r;
+
+        if (!path_extend(&p, machine))
+                return -ENOMEM;
+
+        r = parse_env_file(NULL, p,
+                           "LEADER", &s,
+                           "CLASS", &class);
+        if (r == -ENOENT)
+                return -EHOSTDOWN;
+        if (r < 0)
+                return r;
+        if (!s)
+                return -ESRCH;
+
+        if (!streq_ptr(class, "container"))
+                return -EMEDIUMTYPE;
+
+        r = parse_pid(s, &leader);
+        if (r < 0)
+                return r;
+        if (leader <= 1)
+                return -EBADMSG;
+
+        *ret = leader;
+        return 0;
+}
+
+static int bus_container_connect_namespace(sd_bus *b, int pidnsfd, int mntnsfd, int usernsfd, int rootfd) {
+        _cleanup_close_pair_ int errno_pipe_fd[2] = EBADF_PAIR;
+        int r;
+
+        if (pipe2(errno_pipe_fd, O_CLOEXEC) < 0)
+                return log_debug_errno(errno, "Failed to create pipe: %m");
+
+        r = namespace_fork("(sd-buscntrns)", "(sd-buscntr)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL|FORK_WAIT,
+                           pidnsfd, mntnsfd, /* netns_fd= */ -EBADF, usernsfd, rootfd, /* ret= */ NULL);
+        if (r == -EPROTO) {
+                errno_pipe_fd[1] = safe_close(errno_pipe_fd[1]);
+
+                int k = read_errno(errno_pipe_fd[0]);
+                if (k < 0 && k != -EIO)
+                        return k;
+        }
+        if (r < 0)
+                return log_debug_errno(r, "Failed to create namespace for (sd-buscntr): %m");
+        if (r == 0) {
+                errno_pipe_fd[0] = safe_close(errno_pipe_fd[0]);
+
+                r = RET_NERRNO(connect(b->input_fd, &b->sockaddr.sa, b->sockaddr_size));
+                report_errno_and_exit(errno_pipe_fd[1], r);
+        }
+
+        return 0;
+}
+
 int bus_container_connect_socket(sd_bus *b) {
         _cleanup_close_ int pidnsfd = -EBADF, mntnsfd = -EBADF, usernsfd = -EBADF, rootfd = -EBADF;
-        _cleanup_(pidref_done) PidRef child = PIDREF_NULL;
-        _cleanup_close_pair_ int pair[2] = EBADF_PAIR;
-        int r, error_buf = 0;
-        ssize_t n;
+        int r;
 
         assert(b);
         assert(b->input_fd < 0);
@@ -29,7 +108,9 @@ int bus_container_connect_socket(sd_bus *b) {
                 log_debug("sd-bus: connecting bus%s%s to machine %s...",
                           b->description ? " " : "", strempty(b->description), b->machine);
 
-                r = container_get_leader(b->machine, &b->nspid);
+                r = container_get_leader(RUNTIME_SCOPE_USER, b->machine, &b->nspid);
+                if (IN_SET(r, -EHOSTDOWN, -ENXIO))
+                        r = container_get_leader(RUNTIME_SCOPE_SYSTEM, b->machine, &b->nspid);
                 if (r < 0)
                         return r;
         } else
@@ -50,56 +131,17 @@ int bus_container_connect_socket(sd_bus *b) {
 
         bus_socket_setup(b);
 
-        if (socketpair(AF_UNIX, SOCK_SEQPACKET|SOCK_CLOEXEC, 0, pair) < 0)
-                return log_debug_errno(errno, "Failed to create a socket pair: %m");
-
-        r = namespace_fork("(sd-buscntrns)", "(sd-buscntr)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL,
-                           pidnsfd, mntnsfd, -1, usernsfd, rootfd, &child);
+        r = are_our_namespaces(pidnsfd, mntnsfd, /* netns_fd= */ -EBADF, usernsfd, rootfd);
         if (r < 0)
-                return log_debug_errno(r, "Failed to create namespace for (sd-buscntr): %m");
-        if (r == 0) {
-                pair[0] = safe_close(pair[0]);
-
-                r = connect(b->input_fd, &b->sockaddr.sa, b->sockaddr_size);
-                if (r < 0) {
-                        /* Try to send error up */
-                        error_buf = errno;
-                        (void) write(pair[1], &error_buf, sizeof(error_buf));
-                        _exit(EXIT_FAILURE);
-                }
-
-                _exit(EXIT_SUCCESS);
-        }
-
-        pair[1] = safe_close(pair[1]);
-
-        r = pidref_wait_for_terminate_and_check("(sd-buscntrns)", &child, 0);
+                return log_debug_errno(r, "Failed to check if already in PID "PID_FMT" namespaces: %m", b->nspid);
+        if (r > 0)
+                r = RET_NERRNO(connect(b->input_fd, &b->sockaddr.sa, b->sockaddr_size));
+        else
+                r = bus_container_connect_namespace(b, pidnsfd, mntnsfd, usernsfd, rootfd);
+        if (r == -EINPROGRESS)
+                return 1;
         if (r < 0)
-                return r;
-        bool nonzero_exit_status = r != EXIT_SUCCESS;
-
-        n = read(pair[0], &error_buf, sizeof(error_buf));
-        if (n < 0)
-                return log_debug_errno(errno, "Failed to read error status from (sd-buscntr): %m");
-
-        if (n > 0) {
-                if (n != sizeof(error_buf))
-                        return log_debug_errno(SYNTHETIC_ERRNO(EIO),
-                                               "Read error status of unexpected length %zd from (sd-buscntr).", n);
-
-                if (error_buf < 0)
-                        return log_debug_errno(SYNTHETIC_ERRNO(EBADMSG),
-                                               "Got unexpected error status from (sd-buscntr).");
-
-                if (error_buf == EINPROGRESS)
-                        return 1;
-
-                if (error_buf > 0)
-                        return log_debug_errno(error_buf, "(sd-buscntr) failed to connect to D-Bus socket: %m");
-        }
-
-        if (nonzero_exit_status)
-                return -EPROTO;
+                return log_debug_errno(r, "Failed to connect to D-Bus socket in namespaces of PID "PID_FMT": %m", b->nspid);
 
         return bus_socket_start_auth(b);
 }
diff --git a/src/libsystemd/sd-bus/bus-container.h b/src/libsystemd/sd-bus/bus-container.h
index 2e933bd9a7..f6ede2ecd6 100644
--- a/src/libsystemd/sd-bus/bus-container.h
+++ b/src/libsystemd/sd-bus/bus-container.h
@@ -3,4 +3,6 @@
 
 #include "sd-forward.h"
 
+int container_get_leader(RuntimeScope scope, const char *machine, pid_t *ret);
+
 int bus_container_connect_socket(sd_bus *b);
diff --git a/src/libsystemd/sd-id128/id128-util.c b/src/libsystemd/sd-id128/id128-util.c
index 0cae92b728..9d406a45d1 100644
--- a/src/libsystemd/sd-id128/id128-util.c
+++ b/src/libsystemd/sd-id128/id128-util.c
@@ -5,6 +5,7 @@
 #include <sys/socket.h>
 #include <unistd.h>
 
+#include "bus-container.h"
 #include "fd-util.h"
 #include "fs-util.h"
 #include "hash-funcs.h"
@@ -13,6 +14,7 @@
 #include "namespace-util.h"
 #include "pidref.h"
 #include "process-util.h"
+#include "runtime-scope.h"
 #include "sha256.h"
 #include "siphash24.h"
 #include "string-util.h"
@@ -287,7 +289,7 @@ int id128_get_boot_for_machine(const char *machine, sd_id128_t *ret) {
         if (isempty(machine))
                 return sd_id128_get_boot(ret);
 
-        r = container_get_leader(machine, &pid);
+        r = container_get_leader(RUNTIME_SCOPE_SYSTEM, machine, &pid);
         if (r < 0)
                 return r;
 
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 1c0ab6e712..296b12bb90 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -4368,15 +4368,8 @@ static int outer_child(
                 /* The inner child has all namespaces that are requested, so that we all are owned by the
                  * user if user namespaces are turned on. */
 
-                if (arg_network_namespace_path) {
-                        r = namespace_enter(/* pidns_fd= */ -EBADF,
-                                            /* mntns_fd= */ -EBADF,
-                                            netns_fd,
-                                            /* userns_fd= */ -EBADF,
-                                            /* root_fd= */ -EBADF);
-                        if (r < 0)
-                                return log_error_errno(r, "Failed to join network namespace: %m");
-                }
+                if (arg_network_namespace_path && setns(netns_fd, CLONE_NEWNET) < 0)
+                        return log_error_errno(errno, "Failed to join network namespace: %m");
 
                 if (arg_userns_mode == USER_NAMESPACE_MANAGED) {
                         /* In managed usernamespace operation, sysfs + procfs are special, we'll have to