+static int get_boot_id_for_machine(const char *machine, sd_id128_t *boot_id) {
+ _cleanup_close_pair_ int pair[2] = { -1, -1 };
+ _cleanup_close_ int pidnsfd = -1, mntnsfd = -1, rootfd = -1;
+ pid_t pid, child;
+ siginfo_t si;
+ char buf[37];
+ ssize_t k;
+ int r;
+
+ assert(machine);
+ assert(boot_id);
+
+ if (!filename_is_safe(machine))
+ return -EINVAL;
+
+ r = container_get_leader(machine, &pid);
+ if (r < 0)
+ return r;
+
+ r = namespace_open(pid, &pidnsfd, &mntnsfd, NULL, &rootfd);
+ if (r < 0)
+ return r;
+
+ if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pair) < 0)
+ return -errno;
+
+ child = fork();
+ if (child < 0)
+ return -errno;
+
+ if (child == 0) {
+ int fd;
+
+ pair[0] = safe_close(pair[0]);
+
+ r = namespace_enter(pidnsfd, mntnsfd, -1, rootfd);
+ if (r < 0)
+ _exit(EXIT_FAILURE);
+
+ fd = open("/proc/sys/kernel/random/boot_id", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+ if (fd < 0)
+ _exit(EXIT_FAILURE);
+
+ k = loop_read(fd, buf, 36, false);
+ safe_close(fd);
+ if (k != 36)
+ _exit(EXIT_FAILURE);
+
+ k = send(pair[1], buf, 36, MSG_NOSIGNAL);
+ if (k != 36)
+ _exit(EXIT_FAILURE);
+
+ _exit(EXIT_SUCCESS);
+ }
+
+ pair[1] = safe_close(pair[1]);
+
+ r = wait_for_terminate(child, &si);
+ if (r < 0 || si.si_code != CLD_EXITED || si.si_status != EXIT_SUCCESS)
+ return r < 0 ? r : -EIO;
+
+ k = recv(pair[0], buf, 36, 0);
+ if (k != 36)
+ return -EIO;
+
+ buf[36] = 0;
+ r = sd_id128_from_string(buf, boot_id);
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+int add_match_this_boot(sd_journal *j, const char *machine) {