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fstab-generator: add support for volatile boots 

This adds support for a new kernel command line option "systemd.volatile=" that
provides the same functionality that systemd-nspawn's --volatile= switch
provides, but for host systems (i.e. systems booting with a kernel).

It takes the same parameter and has the same effect.

In order to implement systemd.volatile=yes a new service
systemd-volatile-root.service is introduced that only runs in the initrd and
rearranges the root directory as needed to become a tmpfs instance. Note that
systemd.volatile=state is implemented different: it simply generates a
var.mount unit file that is part of the normal boot and has no effect on the
initrd execution.

The way this is implemented ensures that other explicit configuration for /var
can always override the effect of these options.  Specifically, the var.mount
unit is generated in the "late" generator directory, so that it only is in
effect if nothing else overrides it.
This commit is contained in:
Lennart Poettering 2016-12-13 12:45:19 +01:00
parent e5b4220341
commit 91214a37ef
14 changed files with 456 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
.gitignore vendored
View File

@ -126,6 +126,7 @@
/systemd-update-utmp
/systemd-user-sessions
/systemd-vconsole-setup
/systemd-volatile-root
/tags
/test-acd
/test-acl-util

7
Makefile-man.am
View File

@ -142,6 +142,7 @@ MANPAGES += \
man/systemd-tty-ask-password-agent.1 \
man/systemd-udevd.service.8 \
man/systemd-update-done.service.8 \
man/systemd-volatile-root.service.8 \
man/systemd.1 \
man/systemd.automount.5 \
man/systemd.device.5 \
@ -482,6 +483,7 @@ MANPAGES_ALIAS += \
man/systemd-udevd.8 \
man/systemd-update-done.8 \
man/systemd-user.conf.5 \
man/systemd-volatile-root.8 \
man/udev_device_get_action.3 \
man/udev_device_get_devlinks_list_entry.3 \
man/udev_device_get_devnode.3 \
@ -837,6 +839,7 @@ man/systemd-udevd-kernel.socket.8: man/systemd-udevd.service.8
man/systemd-udevd.8: man/systemd-udevd.service.8
man/systemd-update-done.8: man/systemd-update-done.service.8
man/systemd-user.conf.5: man/systemd-system.conf.5
man/systemd-volatile-root.8: man/systemd-volatile-root.service.8
man/udev_device_get_action.3: man/udev_device_get_syspath.3
man/udev_device_get_devlinks_list_entry.3: man/udev_device_has_tag.3
man/udev_device_get_devnode.3: man/udev_device_get_syspath.3
@ -1790,6 +1793,9 @@ man/systemd-update-done.html: man/systemd-update-done.service.html
man/systemd-user.conf.html: man/systemd-system.conf.html
$(html-alias)
man/systemd-volatile-root.html: man/systemd-volatile-root.service.html
$(html-alias)
man/udev_device_get_action.html: man/udev_device_get_syspath.html
$(html-alias)
@ -2804,6 +2810,7 @@ EXTRA_DIST += \
man/systemd-update-utmp.service.xml \
man/systemd-user-sessions.service.xml \
man/systemd-vconsole-setup.service.xml \
man/systemd-volatile-root.service.xml \
man/systemd.automount.xml \
man/systemd.device.xml \
man/systemd.exec.xml \

10
Makefile.am
View File

@ -397,6 +397,7 @@ rootlibexec_PROGRAMS = \
systemd-initctl \
systemd-shutdown \
systemd-remount-fs \
systemd-volatile-root \
systemd-reply-password \
systemd-fsck \
systemd-ac-power \
@ -538,6 +539,7 @@ nodist_systemunit_DATA = \
units/system-update-cleanup.service \
units/systemd-initctl.service \
units/systemd-remount-fs.service \
units/systemd-volatile-root.service \
units/systemd-ask-password-wall.service \
units/systemd-ask-password-console.service \
units/systemd-sysctl.service \
@ -602,6 +604,7 @@ EXTRA_DIST += \
units/system-update-cleanup.service.in \
units/systemd-initctl.service.in \
units/systemd-remount-fs.service.in \
units/systemd-volatile-root.service.in \
units/systemd-update-utmp.service.in \
units/systemd-update-utmp-runlevel.service.in \
units/systemd-ask-password-wall.service.in \
@ -3067,6 +3070,13 @@ systemd_remount_fs_SOURCES = \
systemd_remount_fs_LDADD = \
libsystemd-shared.la
# ------------------------------------------------------------------------------
systemd_volatile_root_SOURCES = \
src/volatile-root/volatile-root.c
systemd_volatile_root_LDADD = \
libsystemd-shared.la
# ------------------------------------------------------------------------------
systemd_cgroups_agent_SOURCES = \
src/cgroups-agent/cgroups-agent.c

23
man/kernel-command-line.xml
View File

@ -124,6 +124,28 @@
</listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.volatile=</varname></term>
<listitem>
<para>This parameter controls whether the system shall boot up in volatile mode. Takes a boolean argument, or
the special value <literal>state</literal>. If false (the default), normal boot mode is selected, the root
directory and <filename>/var</filename> are mounted as specified on the kernel command line or
<filename>/etc/fstab</filename>, or otherwise configured. If true, full state-less boot mode is selected. In
this case the root directory is mounted as volatile memory file system (<literal>tmpfs</literal>), and only
<filename>/usr</filename> is mounted from the file system configured as root device, in read-only mode. This
enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
configuration and no stored state in effect, as <filename>/etc</filename> and <filename>/var</filename> (as
well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
setting is set to <literal>state</literal> the root file system is mounted as usual, however
<filename>/var</filename> is mounted as a volatile memory file system (<literal>tmpfs</literal>), so that the
system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. For details,
see
<citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
and
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>quiet</varname></term>
<listitem>
@ -382,6 +404,7 @@
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-gpt-auto-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-modules-load.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-backlight@.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-rfkill.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,

46
man/systemd-fstab-generator.xml
View File

@ -89,12 +89,13 @@
<listitem><para>Takes a boolean argument. Defaults to
<literal>yes</literal>. If <literal>no</literal>, causes the
generator to ignore any mounts or swaps configured in
generator to ignore any mounts or swap devices configured in
<filename>/etc/fstab</filename>. <varname>rd.fstab=</varname>
is honored only by initial RAM disk (initrd) while
is honored only by the initial RAM disk (initrd) while
<varname>fstab=</varname> is honored by both the main system
and the initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>root=</varname></term>
@ -102,6 +103,7 @@
initrd. <varname>root=</varname> is honored by the
initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>rootfstype=</varname></term>
@ -109,6 +111,7 @@
passed to the mount command. <varname>rootfstype=</varname> is
honored by the initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>rootflags=</varname></term>
@ -116,6 +119,7 @@
use. <varname>rootflags=</varname> is honored by the
initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>mount.usr=</varname></term>
@ -133,6 +137,7 @@
<para><varname>mount.usr=</varname> is honored by the initrd.
</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>mount.usrfstype=</varname></term>
@ -150,6 +155,7 @@
<para><varname>mount.usrfstype=</varname> is honored by the
initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>mount.usrflags=</varname></term>
@ -166,6 +172,39 @@
<para><varname>mount.usrflags=</varname> is honored by the
initrd.</para></listitem>
</varlistentry>
<varlistentry>
<term><varname>systemd.volatile=</varname></term>
<listitem><para>Controls whether the system shall boot up in volatile mode. Takes a boolean argument or the
special value <option>state</option>.</para>
<para>If false (the default), this generator makes no changes to the mount tree and the system is booted up in
normal mode.</para>
<para>If true the generator ensures
<citerefentry><refentrytitle>systemd-volatile-root.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
is run as part of the initial RAM disk ("initrd"). This service changes the mount table before transitioning to
the host system, so that a volatile memory file system (<literal>tmpfs</literal>) is used as root directory,
with only <filename>/usr</filename> mounted into it from the configured root file system, in read-only
mode. This way the system operates in fully stateless mode, with all configuration and state reset at boot and
lost at shutdown, as <filename>/etc</filename> and <filename>/var</filename> will be served from the (initially
unpopulated) volatile memory file system.</para>
<para>If set to <option>state</option> the generator will leave the root
directory mount point unaltered, however will mount a <literal>tmpfs</literal> file system to
<filename>/var</filename>. In this mode the normal system configuration (i.e the contents of
<literal>/etc</literal>) is in effect (and may be modified during system runtime), however the system state
(i.e. the contents of <literal>/var</literal>) is reset at boot and lost at shutdown.</para>
<para>Note that in none of these modes the root directory, <filename>/etc</filename>, <filename>/var</filename>
or any other resources stored in the root file system are physically removed. It's thus safe to boot a system
that is normally operated in non-volatile mode temporarily into volatile mode, without losing data.</para>
<para>Note that enabling this setting will only work correctly on operating systems that can boot up with only
<filename>/usr</filename> mounted, and are able to automatically populate <filename>/etc</filename>, and also
<filename>/var</filename> in case of <literal>systemd.volatile=yes</literal>.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>
@ -176,7 +215,8 @@
<citerefentry project='man-pages'><refentrytitle>fstab</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.mount</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd.swap</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>
<citerefentry><refentrytitle>systemd-cryptsetup-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>

15
man/systemd-nspawn.xml
View File

@ -939,12 +939,15 @@
<option>no</option> (the default), the whole OS tree is made
available writable.</para>
<para>Note that setting this to <option>yes</option> or
<option>state</option> will only work correctly with
operating systems in the container that can boot up with only
<filename>/usr</filename> mounted, and are able to populate
<filename>/var</filename> automatically, as
needed.</para></listitem>
<para>This option provides similar functionality for containers as the <literal>systemd.volatile=</literal>
kernel command line switch provides for host systems. See
<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
details.</para>
<para>Note that enabling this setting will only work correctly with operating systems in the container that can
boot up with only <filename>/usr</filename> mounted, and are able to automatically populate
<filename>/var</filename>, and also <filename>/etc</filename> in case of
<literal>--volatile=yes</literal>.</para></listitem>
</varlistentry>
<varlistentry>

79
man/systemd-volatile-root.service.xml Normal file
View File

@ -0,0 +1,79 @@
<?xml version="1.0"?>
<!--*-nxml-*-->
<!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 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
-->
<refentry id="systemd-volatile-root.service">
<refentryinfo>
<title>systemd-volatile-root.service</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>systemd-volatile-root.service</refentrytitle>
<manvolnum>8</manvolnum>
</refmeta>
<refnamediv>
<refname>systemd-volatile-root.service</refname>
<refname>systemd-volatile-root</refname>
<refpurpose>Make the root file system volatile</refpurpose>
</refnamediv>
<refsynopsisdiv>
<para><filename>systemd-volatile-root.service</filename></para>
<para><filename>/usr/lib/systemd/systemd-volatile-root</filename></para>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><filename>systemd-volatile-root.service</filename> is a service that replaces the root directory with a
volatile memory file system (<literal>tmpfs</literal>), mounting the original (non-volatile)
<filename>/usr</filename> inside it read-only. This way, vendor data from <filename>/usr</filename> is available as
usual, but all configuration data in <filename>/etc</filename>, all state data in <filename>/var</filename> and all
other resources stored directly under the root directory are reset on boot and lost at shutdown, enabling fully
stateless systems.</para>
<para>This service is only enabled if full volatile mode is selected, for example by specifying
<literal>systemd.volatile=yes</literal> on the kernel command line. This service runs only in the initial RAM disk
("initrd"), before the system transitions to the host's root directory. Note that this service is not used if
<literal>systemd.volatile=state</literal> is used, as in that mode the root directory is non-volatile.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>systemd-fstab-generator</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>kernel-command-line</refentrytitle><manvolnum>7</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>

85
src/fstab-generator/fstab-generator.c
View File

@ -42,8 +42,10 @@
#include "unit-name.h"
#include "util.h"
#include "virt.h"
#include "volatile-util.h"
static const char *arg_dest = "/tmp";
static const char *arg_dest_late = "/tmp";
static bool arg_fstab_enabled = true;
static char *arg_root_what = NULL;
static char *arg_root_fstype = NULL;
@ -52,6 +54,7 @@ static int arg_root_rw = -1;
static char *arg_usr_what = NULL;
static char *arg_usr_fstype = NULL;
static char *arg_usr_options = NULL;
static VolatileMode arg_volatile_mode = _VOLATILE_MODE_INVALID;
static int add_swap(
const char *what,
@ -235,6 +238,7 @@ static int write_requires_mounts_for(FILE *f, const char *opts) {
}
static int add_mount(
const char *dest,
const char *what,
const char *where,
const char *fstype,
@ -286,7 +290,7 @@ static int add_mount(
if (r < 0)
return log_error_errno(r, "Failed to generate unit name: %m");
unit = strjoin(arg_dest, "/", name);
unit = strjoin(dest, "/", name);
if (!unit)
return log_oom();
@ -318,7 +322,7 @@ static int add_mount(
}
if (passno != 0) {
r = generator_write_fsck_deps(f, arg_dest, what, where, fstype);
r = generator_write_fsck_deps(f, dest, what, where, fstype);
if (r < 0)
return r;
}
@ -334,7 +338,7 @@ static int add_mount(
if (!isempty(fstype) && !streq(fstype, "auto"))
fprintf(f, "Type=%s\n", fstype);
r = generator_write_timeouts(arg_dest, what, where, opts, &filtered);
r = generator_write_timeouts(dest, what, where, opts, &filtered);
if (r < 0)
return r;
@ -350,7 +354,7 @@ static int add_mount(
return log_error_errno(r, "Failed to write unit file %s: %m", unit);
if (!noauto && !automount) {
lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", name);
lnk = strjoin(dest, "/", post, nofail ? ".wants/" : ".requires/", name);
if (!lnk)
return log_oom();
@ -364,7 +368,7 @@ static int add_mount(
if (r < 0)
return log_error_errno(r, "Failed to generate unit name: %m");
automount_unit = strjoin(arg_dest, "/", automount_name);
automount_unit = strjoin(dest, "/", automount_name);
if (!automount_unit)
return log_oom();
@ -406,7 +410,7 @@ static int add_mount(
return log_error_errno(r, "Failed to write unit file %s: %m", automount_unit);
free(lnk);
lnk = strjoin(arg_dest, "/", post, nofail ? ".wants/" : ".requires/", automount_name);
lnk = strjoin(dest, "/", post, nofail ? ".wants/" : ".requires/", automount_name);
if (!lnk)
return log_oom();
@ -479,7 +483,8 @@ static int parse_fstab(bool initrd) {
else
post = SPECIAL_LOCAL_FS_TARGET;
k = add_mount(what,
k = add_mount(arg_dest,
what,
where,
me->mnt_type,
me->mnt_opts,
@ -540,7 +545,8 @@ static int add_sysroot_mount(void) {
return r;
}
return add_mount(what,
return add_mount(arg_dest,
what,
"/sysroot",
arg_root_fstype,
opts,
@ -593,7 +599,8 @@ static int add_sysroot_usr_mount(void) {
opts = arg_usr_options;
log_debug("Found entry what=%s where=/sysroot/usr type=%s", what, strna(arg_usr_fstype));
return add_mount(what,
return add_mount(arg_dest,
what,
"/sysroot/usr",
arg_usr_fstype,
opts,
@ -605,6 +612,46 @@ static int add_sysroot_usr_mount(void) {
"/proc/cmdline");
}
static int add_volatile_root(void) {
const char *from, *to;
if (arg_volatile_mode != VOLATILE_YES)
return 0;
/* Let's add in systemd-remount-volatile.service which will remount the root device to tmpfs if this is
* requested, leaving only /usr from the root mount inside. */
from = strjoina(SYSTEM_DATA_UNIT_PATH "/systemd-volatile-root.service");
to = strjoina(arg_dest, "/" SPECIAL_INITRD_ROOT_FS_TARGET, ".requires/systemd-volatile-root.service");
(void) mkdir_parents(to, 0755);
if (symlink(from, to) < 0)
return log_error_errno(errno, "Failed to hook in volatile remount service: %m");
return 0;
}
static int add_volatile_var(void) {
if (arg_volatile_mode != VOLATILE_STATE)
return 0;
/* If requested, mount /var as tmpfs, but do so only if there's nothing else defined for this. */
return add_mount(arg_dest_late,
"tmpfs",
"/var",
"tmpfs",
"mode=0755",
0,
false,
false,
false,
SPECIAL_LOCAL_FS_TARGET,
"/proc/cmdline");
}
static int parse_proc_cmdline_item(const char *key, const char *value, void *data) {
int r;
@ -686,6 +733,18 @@ static int parse_proc_cmdline_item(const char *key, const char *value, void *dat
arg_root_rw = true;
else if (streq(key, "ro") && !value)
arg_root_rw = false;
else if (streq(key, "systemd.volatile")) {
VolatileMode m;
if (value) {
m = volatile_mode_from_string(value);
if (m < 0)
log_warning("Failed to parse systemd.volatile= argument: %s", value);
else
arg_volatile_mode = m;
} else
arg_volatile_mode = VOLATILE_YES;
}
return 0;
}
@ -700,6 +759,8 @@ int main(int argc, char *argv[]) {
if (argc > 1)
arg_dest = argv[1];
if (argc > 3)
arg_dest_late = argv[3];
log_set_target(LOG_TARGET_SAFE);
log_parse_environment();
@ -720,8 +781,12 @@ int main(int argc, char *argv[]) {
k = add_sysroot_usr_mount();
if (k < 0)
r = k;
k = add_volatile_root();
if (k < 0)
r = k;
} else
r = 0;
r = add_volatile_var();
/* Honour /etc/fstab only when that's enabled */
if (arg_fstab_enabled) {

27
src/shared/volatile-util.c
View File

@ -17,8 +17,10 @@
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "alloc-util.h"
#include "macro.h"
#include "parse-util.h"
#include "proc-cmdline.h"
#include "string-util.h"
#include "volatile-util.h"
@ -39,3 +41,28 @@ VolatileMode volatile_mode_from_string(const char *s) {
return _VOLATILE_MODE_INVALID;
}
int query_volatile_mode(VolatileMode *ret) {
_cleanup_free_ char *mode = NULL;
VolatileMode m = VOLATILE_NO;
int r;
r = proc_cmdline_get_key("systemd.volatile", PROC_CMDLINE_VALUE_OPTIONAL, &mode);
if (r < 0)
return r;
if (r == 0)
goto finish;
if (mode) {
m = volatile_mode_from_string(mode);
if (m < 0)
return -EINVAL;
} else
m = VOLATILE_YES;
r = 1;
finish:
*ret = m;
return r;
}

2
src/shared/volatile-util.h
View File

@ -28,3 +28,5 @@ typedef enum VolatileMode {
} VolatileMode;
VolatileMode volatile_mode_from_string(const char *s);
int query_volatile_mode(VolatileMode *ret);

1
src/volatile-root/Makefile Symbolic link
View File

@ -0,0 +1 @@
../Makefile

157
src/volatile-root/volatile-root.c Normal file
View File

@ -0,0 +1,157 @@
/***
This file is part of systemd.
Copyright 2016 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <sys/mount.h>
#include "alloc-util.h"
#include "fs-util.h"
#include "mkdir.h"
#include "mount-util.h"
#include "stat-util.h"
#include "volatile-util.h"
#include "string-util.h"
#include "path-util.h"
static int make_volatile(const char *path) {
_cleanup_free_ char *old_usr = NULL;
int r;
r = path_is_mount_point(path, NULL, AT_SYMLINK_FOLLOW);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a mount point: %m", path);
if (r == 0) {
log_error("%s is not a mount point.", path);
return -EINVAL;
}
r = path_is_temporary_fs(path);
if (r < 0)
return log_error_errno(r, "Couldn't determine whether %s is a temporary file system: %m", path);
if (r > 0) {
log_info("%s already is a temporary file system.", path);
return 0;
}
r = chase_symlinks("/usr", path, CHASE_PREFIX_ROOT, &old_usr);
if (r < 0)
return log_error_errno(r, "/usr not available in old root: %m");
r = mkdir_p("/run/systemd/volatile-sysroot", 0700);
if (r < 0)
return log_error_errno(r, "Couldn't generate volatile sysroot directory: %m");
r = mount_verbose(LOG_ERR, "tmpfs", "/run/systemd/volatile-sysroot", "tmpfs", MS_STRICTATIME, "mode=755");
if (r < 0)
goto finish_rmdir;
if (mkdir("/run/systemd/volatile-sysroot/usr", 0755) < 0) {
r = -errno;
goto finish_umount;
}
r = mount_verbose(LOG_ERR, old_usr, "/run/systemd/volatile-sysroot/usr", NULL, MS_BIND|MS_REC, NULL);
if (r < 0)
goto finish_umount;
r = bind_remount_recursive("/run/systemd/volatile-sysroot/usr", true, NULL);
if (r < 0)
goto finish_umount;
r = umount_recursive(path, 0);
if (r < 0) {
log_error_errno(r, "Failed to unmount %s: %m", path);
goto finish_umount;
}
if (mount(NULL, "/", NULL, MS_SLAVE|MS_REC, NULL) < 0)
log_warning_errno(errno, "Failed to remount %s MS_SLAVE|MS_REC: %m", path);
r = mount_verbose(LOG_ERR, "/run/systemd/volatile-sysroot", path, NULL, MS_MOVE, NULL);
finish_umount:
(void) umount_recursive("/run/systemd/volatile-sysroot", 0);
finish_rmdir:
(void) rmdir("/run/systemd/volatile-sysroot");
return r;
}
int main(int argc, char *argv[]) {
VolatileMode m = _VOLATILE_MODE_INVALID;
const char *path;
int r;
log_set_target(LOG_TARGET_AUTO);
log_parse_environment();
log_open();
if (argc > 3) {
log_error("Too many arguments. Expected directory and mode.");
r = -EINVAL;
goto finish;
}
r = query_volatile_mode(&m);
if (r < 0) {
log_error_errno(r, "Failed to determine volatile mode from kernel command line.");
goto finish;
}
if (r == 0 && argc >= 2) {
/* The kernel command line always wins. However if nothing was set there, the argument passed here wins instead. */
m = volatile_mode_from_string(argv[1]);
if (m < 0) {
log_error("Couldn't parse volatile mode: %s", argv[1]);
r = -EINVAL;
goto finish;
}
}
if (argc < 3)
path = "/sysroot";
else {
path = argv[2];
if (isempty(path)) {
log_error("Directory name cannot be empty.");
r = -EINVAL;
goto finish;
}
if (!path_is_absolute(path)) {
log_error("Directory must be specified as absolute path.");
r = -EINVAL;
goto finish;
}
if (path_equal(path, "/")) {
log_error("Directory cannot be the root directory.");
r = -EINVAL;
goto finish;
}
}
if (m != VOLATILE_YES) {
r = 0;
goto finish;
}
r = make_volatile(path);
finish:
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}

1
units/.gitignore vendored
View File

@ -75,5 +75,6 @@
/systemd-update-utmp.service
/systemd-user-sessions.service
/systemd-vconsole-setup.service
/systemd-volatile-root.service
/tmp.mount
/user@.service

21
units/systemd-volatile-root.service.in Normal file
View File

@ -0,0 +1,21 @@
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Enforce Volatile Root File Systems
Documentation=man:systemd-volatile-root.service(8)
DefaultDependencies=no
Conflicts=shutdown.target
After=sysroot.mount
Before=initrd-root-fs.target shutdown.target
Conflicts=shutdown.target
AssertPathExists=/etc/initrd-release
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=@rootlibexecdir@/systemd-volatile-root yes /sysroot