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machinectl: implement "bind" command to create additional bind mounts from host to container during runtime

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This commit is contained in:
Lennart Poettering 2014-12-17 21:51:45 +01:00
parent 60e1651a31
commit 785890acf6
3 changed files with 339 additions and 38 deletions
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44
man/machinectl.xml
View File

@ -146,6 +146,25 @@
footer.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--mkdir</option></term>
<listitem><para>When used with
<command>bind</command> creates the
destination directory before applying
the bind mount.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--read-only</option></term>
<listitem><para>When used with
<command>bind</command> applies a
read-only bind
mount.</para></listitem>
</varlistentry>
<xi:include href="user-system-options.xml" xpointer="host" />
<xi:include href="user-system-options.xml" xpointer="machine" />
@ -270,6 +289,31 @@
instance.</para></listitem>
</varlistentry>
<varlistentry>
<term><command>bind</command> <replaceable>ID</replaceable> <replaceable>DIRECTORY</replaceable> [<replaceable>DIRECTORY</replaceable>]</term>
<listitem><para>Bind mounts a
directory from the host into the
specified container. The first
directory argument is the source
directory on the host, the second
directory argument the source
directory on the host. When the latter
is omitted the destination path in the
container is the same as the source
path on the host. When combined with
the <option>--read-only</option>
switch a ready-only bind mount is
created. When combined with the
<option>--mkdir</option> switch the
destination path is first created
before the mount is applied. Note that
this option is currently only
supported for
<citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>
containers.</para></listitem>
</varlistentry>
</variablelist>
</refsect1>

302
src/machine/machinectl.c
View File

@ -30,6 +30,7 @@
#include <netinet/in.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <sys/mount.h>
#include "sd-bus.h"
#include "log.h"
@ -45,6 +46,8 @@
#include "cgroup-util.h"
#include "ptyfwd.h"
#include "event-util.h"
#include "path-util.h"
#include "mkdir.h"
static char **arg_property = NULL;
static bool arg_all = false;
@ -55,6 +58,8 @@ static const char *arg_kill_who = NULL;
static int arg_signal = SIGTERM;
static BusTransport arg_transport = BUS_TRANSPORT_LOCAL;
static char *arg_host = NULL;
static bool arg_read_only = false;
static bool arg_mkdir = false;
static void pager_open_if_enabled(void) {
@ -572,6 +577,241 @@ static int terminate_machine(sd_bus *bus, char **args, unsigned n) {
return 0;
}
static int machine_get_leader(sd_bus *bus, const char *name, pid_t *ret) {
_cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_bus_message_unref_ sd_bus_message *reply = NULL, *reply2 = NULL;
const char *object;
uint32_t leader;
int r;
assert(bus);
assert(name);
assert(ret);
r = sd_bus_call_method(
bus,
"org.freedesktop.machine1",
"/org/freedesktop/machine1",
"org.freedesktop.machine1.Manager",
"GetMachine",
&error,
&reply,
"s", name);
if (r < 0) {
log_error("Could not get path to machine: %s", bus_error_message(&error, -r));
return r;
}
r = sd_bus_message_read(reply, "o", &object);
if (r < 0)
return bus_log_parse_error(r);
r = sd_bus_get_property(
bus,
"org.freedesktop.machine1",
object,
"org.freedesktop.machine1.Machine",
"Leader",
&error,
&reply2,
"u");
if (r < 0)
return log_error_errno(r, "Failed to retrieve PID of leader: %m");
r = sd_bus_message_read(reply2, "u", &leader);
if (r < 0)
return bus_log_parse_error(r);
*ret = leader;
return 0;
}
static int bind_mount(sd_bus *bus, char **args, unsigned n) {
char mount_slave[] = "/tmp/propagate.XXXXXX", *mount_tmp, *mount_outside, *p;
pid_t child, leader;
const char *dest;
siginfo_t si;
bool mount_slave_created = false, mount_slave_mounted = false,
mount_tmp_created = false, mount_tmp_mounted = false,
mount_outside_created = false, mount_outside_mounted = false;
int r;
/* One day, when bind mounting /proc/self/fd/n works across
* namespace boundaries we should rework this logic to make
* use of it... */
if (n > 4) {
log_error("Too many arguments.");
return -EINVAL;
}
dest = args[3] ?: args[2];
if (!path_is_absolute(dest)) {
log_error("Destination path not absolute.");
return -EINVAL;
}
p = strappenda("/run/systemd/nspawn/propagate/", args[1], "/");
if (access(p, F_OK) < 0) {
log_error("Container does not allow propagation of mount points.");
return -ENOTSUP;
}
r = machine_get_leader(bus, args[1], &leader);
if (r < 0)
return r;
/* Our goal is to install a new bind mount into the container,
possibly read-only. This is irritatingly complex
unfortunately, currently.
First, we start by creating a private playground in /tmp,
that we can mount MS_SLAVE. (Which is necessary, since
MS_MOUNT cannot be applied to mounts with MS_SHARED parent
mounts.) */
if (!mkdtemp(mount_slave))
return log_error_errno(errno, "Failed to create playground: %m");
mount_slave_created = true;
if (mount(mount_slave, mount_slave, NULL, MS_BIND, NULL) < 0) {
r = log_error_errno(errno, "Failed to make bind mount: %m");
goto finish;
}
mount_slave_mounted = true;
if (mount(NULL, mount_slave, NULL, MS_SLAVE, NULL) < 0) {
r = log_error_errno(errno, "Failed to remount slave: %m");
goto finish;
}
/* Second, we mount the source directory to a directory inside
of our MS_SLAVE playground. */
mount_tmp = strappenda(mount_slave, "/mount");
if (mkdir(mount_tmp, 0700) < 0) {
r = log_error_errno(errno, "Failed to create temporary mount: %m");
goto finish;
}
mount_tmp_created = true;
if (mount(args[2], mount_tmp, NULL, MS_BIND, NULL) < 0) {
r = log_error_errno(errno, "Failed to overmount: %m");
goto finish;
}
mount_tmp_mounted = true;
/* Third, we remount the new bind mount read-only if requested. */
if (arg_read_only)
if (mount(NULL, mount_tmp, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0) {
r = log_error_errno(errno, "Failed to mark read-only: %m");
goto finish;
}
/* Fourth, we move the new bind mount into the propagation
* directory. This way it will appear there read-only
* right-away. */
mount_outside = strappenda("/run/systemd/nspawn/propagate/", args[1], "/XXXXXX");
if (!mkdtemp(mount_outside)) {
r = log_error_errno(errno, "Cannot create propagation directory: %m");
goto finish;
}
mount_outside_created = true;
if (mount(mount_tmp, mount_outside, NULL, MS_MOVE, NULL) < 0) {
r = log_error_errno(errno, "Failed to move: %m");
goto finish;
}
mount_outside_mounted = true;
mount_tmp_mounted = false;
(void) rmdir(mount_tmp);
mount_tmp_created = false;
(void) umount(mount_slave);
mount_slave_mounted = false;
(void) rmdir(mount_slave);
mount_slave_created = false;
child = fork();
if (child < 0) {
r = log_error_errno(errno, "Failed to fork(): %m");
goto finish;
}
if (child == 0) {
const char *mount_inside;
int mntfd;
const char *q;
q = procfs_file_alloca(leader, "ns/mnt");
mntfd = open(q, O_RDONLY|O_NOCTTY|O_CLOEXEC);
if (mntfd < 0) {
log_error_errno(errno, "Failed to open mount namespace of leader: %m");
_exit(EXIT_FAILURE);
}
if (setns(mntfd, CLONE_NEWNS) < 0) {
log_error_errno(errno, "Failed to join namespace of leader: %m");
_exit(EXIT_FAILURE);
}
if (arg_mkdir)
mkdir_p(dest, 0755);
/* Fifth, move the mount to the right place inside */
mount_inside = strappenda("/run/systemd/nspawn/incoming/", basename(mount_outside));
if (mount(mount_inside, dest, NULL, MS_MOVE, NULL) < 0) {
log_error_errno(errno, "Failed to mount: %m");
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
r = wait_for_terminate(child, &si);
if (r < 0) {
log_error_errno(r, "Failed to wait for client: %m");
goto finish;
}
if (si.si_code != CLD_EXITED) {
log_error("Client died abnormally.");
r = -EIO;
goto finish;
}
if (si.si_status != EXIT_SUCCESS) {
r = -EIO;
goto finish;
}
r = 0;
finish:
if (mount_outside_mounted)
umount(mount_outside);
if (mount_outside_created)
rmdir(mount_outside);
if (mount_tmp_mounted)
umount(mount_tmp);
if (mount_tmp_created)
umount(mount_tmp);
if (mount_slave_mounted)
umount(mount_slave);
if (mount_slave_created)
umount(mount_slave);
return r;
}
static int openpt_in_namespace(pid_t pid, int flags) {
_cleanup_close_pair_ int pair[2] = { -1, -1 };
_cleanup_close_ int pidnsfd = -1, mntnsfd = -1, rootfd = -1;
@ -658,15 +898,15 @@ static int openpt_in_namespace(pid_t pid, int flags) {
}
static int login_machine(sd_bus *bus, char **args, unsigned n) {
_cleanup_bus_message_unref_ sd_bus_message *reply = NULL, *reply2 = NULL, *reply3 = NULL;
_cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
_cleanup_bus_close_unref_ sd_bus *container_bus = NULL;
_cleanup_(pty_forward_freep) PTYForward *forward = NULL;
_cleanup_event_unref_ sd_event *event = NULL;
_cleanup_close_ int master = -1;
_cleanup_free_ char *getty = NULL;
const char *path, *pty, *p;
uint32_t leader;
const char *pty, *p;
pid_t leader;
sigset_t mask;
int r, ret = 0;
@ -686,39 +926,9 @@ static int login_machine(sd_bus *bus, char **args, unsigned n) {
if (r < 0)
return log_error_errno(r, "Failed to attach bus to event loop: %m");
r = sd_bus_call_method(
bus,
"org.freedesktop.machine1",
"/org/freedesktop/machine1",
"org.freedesktop.machine1.Manager",
"GetMachine",
&error,
&reply,
"s", args[1]);
if (r < 0) {
log_error("Could not get path to machine: %s", bus_error_message(&error, -r));
r = machine_get_leader(bus, args[1], &leader);
if (r < 0)
return r;
}
r = sd_bus_message_read(reply, "o", &path);
if (r < 0)
return bus_log_parse_error(r);
r = sd_bus_get_property(
bus,
"org.freedesktop.machine1",
path,
"org.freedesktop.machine1.Machine",
"Leader",
&error,
&reply2,
"u");
if (r < 0)
return log_error_errno(r, "Failed to retrieve PID of leader: %m");
r = sd_bus_message_read(reply2, "u", &leader);
if (r < 0)
return bus_log_parse_error(r);
master = openpt_in_namespace(leader, O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY);
if (master < 0)
@ -750,7 +960,7 @@ static int login_machine(sd_bus *bus, char **args, unsigned n) {
"/org/freedesktop/systemd1",
"org.freedesktop.systemd1.Manager",
"StartUnit",
&error, &reply3,
&error, &reply,
"ss", getty, "replace");
if (r < 0) {
log_error("Failed to start getty service: %s", bus_error_message(&error, r));
@ -799,7 +1009,9 @@ static void help(void) {
" -a --all Show all properties, including empty ones\n"
" -l --full Do not ellipsize output\n"
" --kill-who=WHO Who to send signal to\n"
" -s --signal=SIGNAL Which signal to send\n\n"
" -s --signal=SIGNAL Which signal to send\n"
" --read-only Create read-only bind mount\n"
" --mkdir Create directory before bind mounting, if missing\n\n"
"Commands:\n"
" list List running VMs and containers\n"
" status NAME... Show VM/container status\n"
@ -808,7 +1020,8 @@ static void help(void) {
" poweroff NAME... Power off one or more containers\n"
" reboot NAME... Reboot one or more containers\n"
" kill NAME... Send signal to processes of a VM/container\n"
" terminate NAME... Terminate one or more VMs/containers\n",
" terminate NAME... Terminate one or more VMs/containers\n"
" bind NAME PATH [PATH] Bind mount a path from the host into a container\n",
program_invocation_short_name);
}
@ -819,6 +1032,8 @@ static int parse_argv(int argc, char *argv[]) {
ARG_NO_PAGER,
ARG_NO_LEGEND,
ARG_KILL_WHO,
ARG_READ_ONLY,
ARG_MKDIR,
};
static const struct option options[] = {
@ -833,6 +1048,8 @@ static int parse_argv(int argc, char *argv[]) {
{ "signal", required_argument, NULL, 's' },
{ "host", required_argument, NULL, 'H' },
{ "machine", required_argument, NULL, 'M' },
{ "read-only", no_argument, NULL, ARG_READ_ONLY },
{ "mkdir", no_argument, NULL, ARG_MKDIR },
{}
};
@ -903,6 +1120,14 @@ static int parse_argv(int argc, char *argv[]) {
arg_host = optarg;
break;
case ARG_READ_ONLY:
arg_read_only = true;
break;
case ARG_MKDIR:
arg_mkdir = true;
break;
case '?':
return -EINVAL;
@ -933,6 +1158,7 @@ static int machinectl_main(sd_bus *bus, int argc, char *argv[]) {
{ "poweroff", MORE, 2, poweroff_machine },
{ "kill", MORE, 2, kill_machine },
{ "login", MORE, 2, login_machine },
{ "bind", MORE, 3, bind_mount },
};
int left;

31
src/nspawn/nspawn.c
View File

@ -2082,6 +2082,27 @@ finish:
}
static int setup_propagate(const char *root) {
const char *p, *q;
(void) mkdir_p("/run/systemd/nspawn/", 0755);
(void) mkdir_p("/run/systemd/nspawn/propagate", 0600);
p = strappenda("/run/systemd/nspawn/propagate/", arg_machine);
(void) mkdir_p(p, 0600);
q = strappenda(root, "/run/systemd/nspawn/incoming");
mkdir_parents(q, 0755);
mkdir_p(q, 0600);
if (mount(p, q, NULL, MS_BIND, NULL) < 0)
return log_error_errno(errno, "Failed to install propagation bind mount.");
if (mount(NULL, q, NULL, MS_BIND|MS_REMOUNT|MS_RDONLY, NULL) < 0)
return log_error_errno(errno, "Failed to make propagation mount read-only");
return 0;
}
static int setup_image(char **device_path, int *loop_nr) {
struct loop_info64 info = {
.lo_flags = LO_FLAGS_AUTOCLEAR|LO_FLAGS_PARTSCAN
@ -3260,6 +3281,9 @@ int main(int argc, char *argv[]) {
dev_setup(arg_directory);
if (setup_propagate(arg_directory) < 0)
_exit(EXIT_FAILURE);
if (setup_seccomp() < 0)
_exit(EXIT_FAILURE);
@ -3571,6 +3595,13 @@ finish:
log_warning_errno(k, "Cannot remove subvolume '%s', ignoring: %m", arg_directory);
}
if (arg_machine) {
const char *p;
p = strappenda("/run/systemd/nspawn/propagate", arg_machine);
(void) rm_rf(p, false, true, false);
}
free(arg_directory);
free(arg_template);
free(arg_image);