main: introduce /etc/machine-id

This is supposed to play the same roles /var/lib/dbus/machine-id,
however fixes a couple of problems:

- It is available during early boot since it is stored in /etc

- Removes the ID from the D-Bus context and moves it into a system
  context, thus hopefully lowering hesitation by people to use it.

- It is generated at installation time. If the file is empty at boot
  time it will be mounted over with a randomly generated ID, which is
  not saved to disk. This is useful to support state-less machines with
  no transient or writable /etc configuration.

7 files changed, 349 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index adee97f6ce..c5bb5755cc 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+systemd-machine-id-setup
 systemd-detect-virt
 systemd-sysctl
 test-strv
diff --git a/Makefile.am b/Makefile.am
index 1841ad5c5a..3d32df2e46 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -98,7 +98,8 @@ rootbin_PROGRAMS = \
 	systemd-notify \
 	systemd-ask-password \
 	systemd-tty-ask-password-agent \
-	systemd-tmpfiles
+	systemd-tmpfiles \
+	systemd-machine-id-setup
 
 bin_PROGRAMS = \
 	systemd-cgls
@@ -434,6 +435,7 @@ libsystemd_core_la_SOURCES = \
 	src/loopback-setup.c \
 	src/kmod-setup.c \
 	src/locale-setup.c \
+	src/machine-id-setup.c \
 	src/specifier.c \
 	src/unit-name.c \
 	src/fdset.c \
@@ -523,6 +525,7 @@ MANPAGES = \
 	man/systemd.conf.5 \
 	man/tmpfiles.d.5 \
 	man/hostname.5 \
+	man/machine-id.5 \
 	man/vconsole.conf.5 \
 	man/locale.conf.5 \
 	man/os-release.5 \
@@ -737,6 +740,16 @@ systemd_tmpfiles_CFLAGS = \
 systemd_tmpfiles_LDADD = \
 	libsystemd-basic.la
 
+systemd_machine_id_setup_SOURCES = \
+	src/machine-id-setup.c \
+	src/machine-id-main.c
+
+systemd_machine_id_setup_CFLAGS = \
+	$(AM_CFLAGS)
+
+systemd_machine_id_setup_LDADD = \
+	libsystemd-basic.la
+
 systemd_sysctl_SOURCES = \
 	src/sysctl.c
 
diff --git a/man/machine-id.xml b/man/machine-id.xml
new file mode 100644
index 0000000000..fefeb66fd6
--- /dev/null
+++ b/man/machine-id.xml
@@ -0,0 +1,104 @@
+<?xml version='1.0'?> <!--*-nxml-*-->
+<?xml-stylesheet type="text/xsl" href="http://docbook.sourceforge.net/release/xsl/current/xhtml/docbook.xsl"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+        "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+
+<!--
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<refentry id="machine-id">
+        <refentryinfo>
+                <title>/etc/machine-id</title>
+                <productname>systemd</productname>
+
+                <authorgroup>
+                        <author>
+                                <contrib>Developer</contrib>
+                                <firstname>Lennart</firstname>
+                                <surname>Poettering</surname>
+                                <email>lennart@poettering.net</email>
+                        </author>
+                </authorgroup>
+        </refentryinfo>
+
+        <refmeta>
+                <refentrytitle>machine-id</refentrytitle>
+                <manvolnum>5</manvolnum>
+        </refmeta>
+
+        <refnamediv>
+                <refname>machine-id</refname>
+                <refpurpose>local machine ID configuration file</refpurpose>
+        </refnamediv>
+
+        <refsynopsisdiv>
+                <para><filename>/etc/machine-id</filename></para>
+        </refsynopsisdiv>
+
+        <refsect1>
+                <title>Description</title>
+
+                <para>The <filename>/etc/machine-id</filename> file
+                configures the unique machine id of the local system
+                that is set during installation. It should contain a
+                single newline-terminated, hexadecimal, lowercase 16
+                character machine ID string.</para>
+
+                <para>The machine ID is usually generated from a
+                random source during system installation and stays
+                constant for all subsequent boots. Optionally, for
+                stateless systems it is generated during runtime at
+                boot.</para>
+
+                <para>The machine ID does not change based on user
+                configuration, or when hardware is replaced.</para>
+
+                <para>This machine id follows the same format and
+                logic as the D-Bus machine ID.</para>
+
+                <para>Programs may use this ID to identify the host
+                with a globally unique ID in the network, that does
+                not change even if the local network configuration
+                changes. Due to this and its greater length it is
+                a more useful replacement than the
+                <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                call POSIX specifies.</para>
+        </refsect1>
+
+        <refsect1>
+                <title>History</title>
+
+                <para>The simple configuration file format of
+                <filename>/etc/machine-id</filename> originates in the
+                <filename>/var/lib/dbus/machine-id</filename> file
+                introduced by D-Bus. In fact this latter file might be a
+                symlink to the
+                <varname>/etc/machine-id</varname>.</para>
+        </refsect1>
+
+        <refsect1>
+                  <title>See Also</title>
+                  <para>
+                          <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>gethostid</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+                          <citerefentry><refentrytitle>hostname</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+                  </para>
+        </refsect1>
+
+</refentry>
diff --git a/src/machine-id-main.c b/src/machine-id-main.c
new file mode 100644
index 0000000000..03970a2b06
--- /dev/null
+++ b/src/machine-id-main.c
@@ -0,0 +1,35 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <unistd.h>
+#include <stdlib.h>
+
+#include "machine-id-setup.h"
+#include "log.h"
+
+int main(int argc, char *argv[]) {
+
+        log_set_target(LOG_TARGET_AUTO);
+        log_parse_environment();
+        log_open();
+
+        return machine_id_setup() < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+}
diff --git a/src/machine-id-setup.c b/src/machine-id-setup.c
new file mode 100644
index 0000000000..940670b339
--- /dev/null
+++ b/src/machine-id-setup.c
@@ -0,0 +1,166 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <sys/mount.h>
+
+#include "machine-id-setup.h"
+#include "macro.h"
+#include "util.h"
+#include "log.h"
+
+static int generate(char id[34]) {
+        int fd;
+        char buf[16];
+        char *p, *q;
+        ssize_t k;
+
+        assert(id);
+
+        /* First, try reading the D-Bus machine id, unless it is a symlink */
+        if ((fd = open("/var/lib/dbus/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW)) >= 0) {
+
+                k = loop_read(fd, id, 33, false);
+                close_nointr_nofail(fd);
+
+                if (k >= 32) {
+                        id[32] = '\n';
+                        id[33] = 0;
+
+                        log_info("Initializing machine ID from D-Bus machine ID.");
+                        return 0;
+                }
+        }
+
+        /* If that didn't work, generate a random machine id */
+        if ((fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+                log_error("Failed to open /dev/urandom: %m");
+                return -errno;
+        }
+
+        k = loop_read(fd, buf, sizeof(buf), false);
+        close_nointr_nofail(fd);
+
+        if (k != sizeof(buf)) {
+                log_error("Failed to read /dev/urandom: %s", strerror(k < 0 ? -k : EIO));
+                return k < 0 ? (int) k : -EIO;
+        }
+
+        for (p = buf, q = id; p < buf + sizeof(buf); p++, q += 2) {
+                q[0] = hexchar(*p >> 4);
+                q[1] = hexchar(*p & 15);
+        }
+
+        id[32] = '\n';
+        id[33] = 0;
+
+        log_info("Initializing machine ID from random generator.");
+
+        return 0;
+}
+
+int machine_id_setup(void) {
+        int fd, r;
+        bool writable;
+        struct stat st;
+        char id[34]; /* 32 + \n + \0 */
+        mode_t m;
+
+        m = umask(0000);
+
+        if ((fd = open("/etc/machine-id", O_RDWR|O_CREAT|O_CLOEXEC|O_NOCTTY, 0644)) >= 0)
+                writable = true;
+        else {
+                if ((fd = open("/etc/machine-id", O_RDONLY|O_CLOEXEC|O_NOCTTY)) < 0) {
+                        umask(m);
+                        log_error("Cannot open /etc/machine-id: %m");
+                        return -errno;
+                }
+
+                writable = false;
+        }
+
+        umask(m);
+
+        if (fstat(fd, &st) < 0) {
+                log_error("fstat() failed: %m");
+                r = -errno;
+                goto finish;
+        }
+
+        if (S_ISREG(st.st_mode)) {
+                if (loop_read(fd, id, 32, false) >= 32) {
+                        r = 0;
+                        goto finish;
+                }
+        }
+
+        /* Hmm, so, the id currently stored is not useful, then let's
+         * generate one */
+
+        if ((r = generate(id)) < 0)
+                goto finish;
+
+        if (S_ISREG(st.st_mode) && writable) {
+                lseek(fd, 0, SEEK_SET);
+
+                if (loop_write(fd, id, 33, false) == 33) {
+                        r = 0;
+                        goto finish;
+                }
+        }
+
+        close_nointr_nofail(fd);
+        fd = -1;
+
+        /* Hmm, we couldn't write it? So let's write it to
+         * /dev/.systemd/machine-id as a replacement */
+
+        mkdir_p("/dev/.systemd", 0755);
+
+        if ((r = write_one_line_file("/dev/.systemd/machine-id", id)) < 0) {
+                log_error("Cannot write /dev/.systemd/machine-id: %s", strerror(-r));
+
+                unlink("/dev/.systemd/machine-id");
+                goto finish;
+        }
+
+        /* And now, let's mount it over */
+        r = mount("/dev/.systemd/machine-id", "/etc/machine-id", "bind", MS_BIND|MS_RDONLY, NULL) < 0 ? -errno : 0;
+        unlink("/dev/.systemd/machine-id");
+
+        if (r < 0)
+                log_error("Failed to mount /etc/machine-id: %s", strerror(-r));
+        else
+                log_info("Installed non-transient /etc/machine-id file.");
+
+finish:
+
+        if (fd >= 0)
+                close_nointr_nofail(fd);
+
+        return r;
+}
diff --git a/src/machine-id-setup.h b/src/machine-id-setup.h
new file mode 100644
index 0000000000..4d0a9cf331
--- /dev/null
+++ b/src/machine-id-setup.h
@@ -0,0 +1,27 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#ifndef foomachineidsetuphfoo
+#define foomachineidsetuphfoo
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+int machine_id_setup(void);
+
+#endif
diff --git a/src/main.c b/src/main.c
index ef6e681771..a041a22eda 100644
--- a/src/main.c
+++ b/src/main.c
@@ -41,6 +41,7 @@
 #include "kmod-setup.h"
 #include "locale-setup.h"
 #include "selinux-setup.h"
+#include "machine-id-setup.h"
 #include "load-fragment.h"
 #include "fdset.h"
 #include "special.h"
@@ -1127,6 +1128,7 @@ int main(int argc, char *argv[]) {
 
                 kmod_setup();
                 hostname_setup();
+                machine_id_setup();
                 loopback_setup();
 
                 mkdir_p("/dev/.systemd/ask-password/", 0755);