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main: introduce /etc/machine-id

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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.
This commit is contained in:
Lennart Poettering 2011-03-04 21:53:19 +01:00
parent 63a723f3a7
commit d7ccca2e3f
7 changed files with 349 additions and 1 deletions
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1
.gitignore vendored
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@ -1,3 +1,4 @@
systemd-machine-id-setup
systemd-detect-virt
systemd-sysctl
test-strv

15
Makefile.am
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@ -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

104
man/machine-id.xml Normal file
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@ -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>

35
src/machine-id-main.c Normal file
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@ -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;
}

166
src/machine-id-setup.c Normal file
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@ -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;
}

27
src/machine-id-setup.h Normal file
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@ -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

2
src/main.c
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@ -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);