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nspawn: beef up nspawn with some btrfs magic

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This adds --template= to duplicate an OS tree as btrfs snpashot and run
it

This also adds --ephemeral or -x to create a snapshot of an OS tree and
boot that, removing it after exit.
This commit is contained in:
Lennart Poettering 2014-12-12 03:50:59 +01:00
parent 0254b455e9
commit ec16945ebf
3 changed files with 285 additions and 99 deletions
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98
man/systemd-nspawn.xml
View file

@ -165,14 +165,78 @@
<term><option>--directory=</option></term>
<listitem><para>Directory to use as
file system root for the container. If
neither <option>--directory=</option>
nor <option>--image=</option> are
file system root for the container.</para>
<para>If neither
<option>--directory=</option>, nor
<option>--image=</option> is specified
the directory is determined as
<filename>/var/lib/container/</filename>
suffixed by the machine name as
specified with
<option>--machine=</option>. If
neither <option>--directory=</option>,
<option>--image=</option>, nor
<option>--machine=</option> are
specified, the current directory will
be used. May not be specified together with
be used. May not be specified together
with
<option>--image=</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>--template=</option></term>
<listitem><para>Directory or
<literal>btrfs</literal> subvolume to
use as template for the container's
root directory. If this is specified
and the container's root directory (as
configured by
<option>--directory=</option>) does
not yet exist it is created as
<literal>btrfs</literal> subvolume and
populated from this template
tree. Ideally, the specified template
path refers to the root of a
<literal>btrfs</literal> subvolume, in
which case a simple copy-on-write
snapshot is taken, and populating the
root directory is instant. If the
specified template path does not refer
to the root of a
<literal>btrfs</literal> subvolume (or
not even to a <literal>btrfs</literal>
file system at all), the tree is
copied, which can be substantially
more time-consuming. Note that if this
option is used the container's root
directory (in contrast to the template
directory!) must be located on a
<literal>btrfs</literal> file system,
so that the <literal>btrfs</literal>
subvolume may be created. May not be
specified together with
<option>--image=</option> or
<option>--ephemeral</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-x</option></term>
<term><option>--ephemeral</option></term>
<listitem><para>If specified, the
container is run with a temporary
<literal>btrfs</literal> snapshot of
its root directory (as configured with
<option>--directory=</option>), that
is removed immediately when the
container terminates. May not be
specified together with
<option>--image=</option> or
<option>--template=</option>.</para></listitem>
</varlistentry>
<varlistentry>
<term><option>-i</option></term>
<term><option>--image=</option></term>
@ -197,7 +261,9 @@
partitions, swap partitions or EFI
system partitions are not mounted. May
not be specified together with
<option>--directory=</option>.</para></listitem>
<option>--directory=</option>,
<option>--template=</option> or
<option>--ephemeral</option>.</para></listitem>
</varlistentry>
<varlistentry>
@ -653,13 +719,13 @@
<term><option>--volatile</option><replaceable>=MODE</replaceable></term>
<listitem><para>Boots the container in
volatile (ephemeral) mode. When no
mode parameter is passed or when mode
is specified as <literal>yes</literal>
full volatile mode is enabled. This
means the root directory is mounted as
mostly unpopulated
<literal>tmpfs</literal> instance, and
volatile mode. When no mode parameter
is passed or when mode is specified as
<literal>yes</literal> full volatile
mode is enabled. This means the root
directory is mounted as mostly
unpopulated <literal>tmpfs</literal>
instance, and
<filename>/usr</filename> from the OS
tree is mounted into it, read-only
(the system thus starts up with
@ -677,8 +743,8 @@
changes to the latter are lost on
shutdown). When the mode parameter is
specified as <literal>no</literal>
(the default) the whole OS tree is made
available writable.</para>
(the default) the whole OS tree is
made available writable.</para>
<para>Note that setting this to
<literal>yes</literal> or
@ -748,13 +814,13 @@
</example>
<example>
<title>Boot into a btrfs snapshot of the host system</title>
<title>Boot into a <literal>btrfs</literal> snapshot of the host system</title>
<programlisting># btrfs subvolume snapshot / /.tmp
# systemd-nspawn --private-network -D /.tmp -b</programlisting>
<para>This runs a copy of the host system in a
btrfs snapshot.</para>
<literal>btrfs</literal> snapshot.</para>
</example>
<example>

285
src/nspawn/nspawn.c
View file

@ -91,6 +91,7 @@
#include "barrier.h"
#include "event-util.h"
#include "cap-list.h"
#include "btrfs-util.h"
#ifdef HAVE_SECCOMP
#include "seccomp-util.h"
@ -115,6 +116,7 @@ typedef enum Volatile {
} Volatile;
static char *arg_directory = NULL;
static char *arg_template = NULL;
static char *arg_user = NULL;
static sd_id128_t arg_uuid = {};
static char *arg_machine = NULL;
@ -124,6 +126,7 @@ static const char *arg_slice = NULL;
static bool arg_private_network = false;
static bool arg_read_only = false;
static bool arg_boot = false;
static bool arg_ephemeral = false;
static LinkJournal arg_link_journal = LINK_AUTO;
static bool arg_link_journal_try = false;
static uint64_t arg_retain =
@ -166,7 +169,7 @@ static char **arg_network_macvlan = NULL;
static bool arg_network_veth = false;
static const char *arg_network_bridge = NULL;
static unsigned long arg_personality = 0xffffffffLU;
static const char *arg_image = NULL;
static char *arg_image = NULL;
static Volatile arg_volatile = VOLATILE_NO;
static void help(void) {
@ -176,7 +179,11 @@ static void help(void) {
" --version Print version string\n"
" -q --quiet Do not show status information\n"
" -D --directory=PATH Root directory for the container\n"
" -i --image=PATH File system device or image for the container\n"
" --template=PATH Initialize root directory from template directory,\n"
" if missing\n"
" -x --ephemeral Run container with snapshot of root directory, and\n"
" remove it after exit\n"
" -i --image=PATH File system device or disk image for the container\n"
" -b --boot Boot up full system (i.e. invoke init)\n"
" -u --user=USER Run the command under specified user or uid\n"
" -M --machine=NAME Set the machine name for the container\n"
@ -221,6 +228,27 @@ static void help(void) {
program_invocation_short_name);
}
static int set_sanitized_path(char **b, const char *path) {
char *p;
assert(b);
assert(path);
p = canonicalize_file_name(path);
if (!p) {
if (errno != ENOENT)
return -errno;
p = path_make_absolute_cwd(path);
if (!p)
return -ENOMEM;
}
free(*b);
*b = path_kill_slashes(p);
return 0;
}
static int parse_argv(int argc, char *argv[]) {
enum {
@ -244,12 +272,15 @@ static int parse_argv(int argc, char *argv[]) {
ARG_NETWORK_BRIDGE,
ARG_PERSONALITY,
ARG_VOLATILE,
ARG_TEMPLATE,
};
static const struct option options[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, ARG_VERSION },
{ "directory", required_argument, NULL, 'D' },
{ "template", required_argument, NULL, ARG_TEMPLATE },
{ "ephemeral", no_argument, NULL, 'x' },
{ "user", required_argument, NULL, 'u' },
{ "private-network", no_argument, NULL, ARG_PRIVATE_NETWORK },
{ "boot", no_argument, NULL, 'b' },
@ -286,7 +317,7 @@ static int parse_argv(int argc, char *argv[]) {
assert(argc >= 0);
assert(argv);
while ((c = getopt_long(argc, argv, "+hD:u:bL:M:jS:Z:qi:", options, NULL)) >= 0)
while ((c = getopt_long(argc, argv, "+hD:u:bL:M:jS:Z:qi:x", options, NULL)) >= 0)
switch (c) {
@ -300,17 +331,28 @@ static int parse_argv(int argc, char *argv[]) {
return 0;
case 'D':
free(arg_directory);
arg_directory = canonicalize_file_name(optarg);
if (!arg_directory) {
log_error_errno(errno, "Invalid root directory: %m");
return -ENOMEM;
}
r = set_sanitized_path(&arg_directory, optarg);
if (r < 0)
return log_error_errno(r, "Invalid root directory: %m");
break;
case ARG_TEMPLATE:
r = set_sanitized_path(&arg_template, optarg);
if (r < 0)
return log_error_errno(r, "Invalid template directory: %m");
break;
case 'i':
arg_image = optarg;
r = set_sanitized_path(&arg_image, optarg);
if (r < 0)
return log_error_errno(r, "Invalid image path: %m");
break;
case 'x':
arg_ephemeral = true;
break;
case 'u':
@ -621,6 +663,26 @@ static int parse_argv(int argc, char *argv[]) {
return -EINVAL;
}
if (arg_template && arg_image) {
log_error("--template= and --image= may not be combined.");
return -EINVAL;
}
if (arg_template && !(arg_directory || arg_machine)) {
log_error("--template= needs --directory= or --machine=.");
return -EINVAL;
}
if (arg_ephemeral && arg_template) {
log_error("--ephemeral and --template= may not be combined.");
return -EINVAL;
}
if (arg_ephemeral && arg_image) {
log_error("--ephemeral and --image= may not be combined.");
return -EINVAL;
}
if (arg_volatile != VOLATILE_NO && arg_read_only) {
log_error("Cannot combine --read-only with --volatile. Note that --volatile already implies a read-only base hierarchy.");
return -EINVAL;
@ -2019,6 +2081,7 @@ static int setup_image(char **device_path, int *loop_nr) {
assert(device_path);
assert(loop_nr);
assert(arg_image);
fd = open(arg_image, O_CLOEXEC|(arg_read_only ? O_RDONLY : O_RDWR)|O_NONBLOCK|O_NOCTTY);
if (fd < 0)
@ -2117,6 +2180,7 @@ static int dissect_image(
assert(home_device);
assert(srv_device);
assert(secondary);
assert(arg_image);
b = blkid_new_probe();
if (!b)
@ -2784,6 +2848,35 @@ static int on_orderly_shutdown(sd_event_source *s, const struct signalfd_siginfo
return 0;
}
static int determine_names(void) {
if (!arg_image && !arg_directory) {
if (arg_machine)
arg_directory = strappend("/var/lib/container/", arg_machine);
else
arg_directory = get_current_dir_name();
if (!arg_directory) {
log_error("Failed to determine path, please use -D.");
return -EINVAL;
}
}
if (!arg_machine) {
arg_machine = strdup(basename(arg_image ?: arg_directory));
if (!arg_machine)
return log_oom();
hostname_cleanup(arg_machine, false);
if (!machine_name_is_valid(arg_machine)) {
log_error("Failed to determine machine name automatically, please use -M.");
return -EINVAL;
}
}
return 0;
}
int main(int argc, char *argv[]) {
_cleanup_free_ char *device_path = NULL, *root_device = NULL, *home_device = NULL, *srv_device = NULL;
@ -2791,71 +2884,43 @@ int main(int argc, char *argv[]) {
_cleanup_close_ int master = -1, image_fd = -1;
_cleanup_close_pair_ int kmsg_socket_pair[2] = { -1, -1 };
_cleanup_fdset_free_ FDSet *fds = NULL;
int r = EXIT_FAILURE, k, n_fd_passed, loop_nr = -1;
int r, n_fd_passed, loop_nr = -1;
const char *console = NULL;
char veth_name[IFNAMSIZ];
bool secondary = false;
bool secondary = false, remove_subvol = false;
sigset_t mask, mask_chld;
pid_t pid = 0;
int ret = EXIT_SUCCESS;
log_parse_environment();
log_open();
k = parse_argv(argc, argv);
if (k < 0)
r = parse_argv(argc, argv);
if (r <= 0)
goto finish;
else if (k == 0) {
r = EXIT_SUCCESS;
r = determine_names();
if (r < 0)
goto finish;
}
if (!arg_image) {
if (arg_directory) {
char *p;
p = path_make_absolute_cwd(arg_directory);
free(arg_directory);
arg_directory = p;
} else
arg_directory = get_current_dir_name();
if (!arg_directory) {
log_error("Failed to determine path, please use -D.");
goto finish;
}
path_kill_slashes(arg_directory);
}
if (!arg_machine) {
arg_machine = strdup(basename(arg_image ? arg_image : arg_directory));
if (!arg_machine) {
log_oom();
goto finish;
}
hostname_cleanup(arg_machine, false);
if (isempty(arg_machine)) {
log_error("Failed to determine machine name automatically, please use -M.");
goto finish;
}
}
if (geteuid() != 0) {
log_error("Need to be root.");
r = -EPERM;
goto finish;
}
if (sd_booted() <= 0) {
log_error("Not running on a systemd system.");
r = -EINVAL;
goto finish;
}
log_close();
n_fd_passed = sd_listen_fds(false);
if (n_fd_passed > 0) {
k = fdset_new_listen_fds(&fds, false);
if (k < 0) {
log_error_errno(k, "Failed to collect file descriptors: %m");
r = fdset_new_listen_fds(&fds, false);
if (r < 0) {
log_error_errno(r, "Failed to collect file descriptors: %m");
goto finish;
}
}
@ -2863,14 +2928,53 @@ int main(int argc, char *argv[]) {
log_open();
if (arg_directory) {
assert(!arg_image);
if (path_equal(arg_directory, "/")) {
log_error("Spawning container on root directory not supported.");
r = -EINVAL;
goto finish;
}
if (arg_template) {
r = btrfs_subvol_snapshot(arg_template, arg_directory, arg_read_only, true);
if (r == -EEXIST) {
if (!arg_quiet)
log_info("Directory %s already exists, not populating from template %s.", arg_directory, arg_template);
} else if (r < 0) {
log_error_errno(r, "Couldn't create snapshort %s from %s: %m", arg_directory, arg_template);
goto finish;
} else {
if (!arg_quiet)
log_info("Populated %s from template %s.", arg_directory, arg_template);
}
} else if (arg_ephemeral) {
char *np;
r = tempfn_random(arg_directory, &np);
if (r < 0) {
log_error_errno(r, "Failed to generate name for snapshot: %m");
goto finish;
}
r = btrfs_subvol_snapshot(arg_directory, np, arg_read_only, true);
if (r < 0) {
free(np);
log_error_errno(r, "Failed to create snapshot %s from %s: %m", np, arg_directory);
goto finish;
}
free(arg_directory);
arg_directory = np;
remove_subvol = true;
}
if (arg_boot) {
if (path_is_os_tree(arg_directory) <= 0) {
log_error("Directory %s doesn't look like an OS root directory (os-release file is missing). Refusing.", arg_directory);
r = -EINVAL;
goto finish;
}
} else {
@ -2880,13 +2984,17 @@ int main(int argc, char *argv[]) {
argc > optind && path_is_absolute(argv[optind]) ? argv[optind] : "/usr/bin/");
if (access(p, F_OK) < 0) {
log_error("Directory %s lacks the binary to execute or doesn't look like a binary tree. Refusing.", arg_directory);
r = -EINVAL;
goto finish;
}
}
} else {
char template[] = "/tmp/nspawn-root-XXXXXX";
assert(arg_image);
assert(!arg_template);
if (!mkdtemp(template)) {
log_error_errno(errno, "Failed to create temporary directory: %m");
r = -errno;
@ -2916,27 +3024,27 @@ int main(int argc, char *argv[]) {
master = posix_openpt(O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY);
if (master < 0) {
log_error_errno(errno, "Failed to acquire pseudo tty: %m");
r = log_error_errno(errno, "Failed to acquire pseudo tty: %m");
goto finish;
}
console = ptsname(master);
if (!console) {
log_error_errno(errno, "Failed to determine tty name: %m");
r = log_error_errno(errno, "Failed to determine tty name: %m");
goto finish;
}
if (!arg_quiet)
log_info("Spawning container %s on %s.\nPress ^] three times within 1s to kill container.",
arg_machine, arg_image ? arg_image : arg_directory);
arg_machine, arg_image ?: arg_directory);
if (unlockpt(master) < 0) {
log_error_errno(errno, "Failed to unlock tty: %m");
r = log_error_errno(errno, "Failed to unlock tty: %m");
goto finish;
}
if (socketpair(AF_UNIX, SOCK_DGRAM|SOCK_NONBLOCK|SOCK_CLOEXEC, 0, kmsg_socket_pair) < 0) {
log_error_errno(errno, "Failed to create kmsg socket pair: %m");
r = log_error_errno(errno, "Failed to create kmsg socket pair: %m");
goto finish;
}
@ -2970,13 +3078,13 @@ int main(int argc, char *argv[]) {
* give it a chance to call wait() and terminate. */
r = sigprocmask(SIG_UNBLOCK, &mask_chld, NULL);
if (r < 0) {
log_error_errno(errno, "Failed to change the signal mask: %m");
r = log_error_errno(errno, "Failed to change the signal mask: %m");
goto finish;
}
r = sigaction(SIGCHLD, &sa, NULL);
if (r < 0) {
log_error_errno(errno, "Failed to install SIGCHLD handler: %m");
r = log_error_errno(errno, "Failed to install SIGCHLD handler: %m");
goto finish;
}
@ -2985,11 +3093,10 @@ int main(int argc, char *argv[]) {
(arg_private_network ? CLONE_NEWNET : 0), NULL);
if (pid < 0) {
if (errno == EINVAL)
log_error_errno(errno, "clone() failed, do you have namespace support enabled in your kernel? (You need UTS, IPC, PID and NET namespacing built in): %m");
r = log_error_errno(errno, "clone() failed, do you have namespace support enabled in your kernel? (You need UTS, IPC, PID and NET namespacing built in): %m");
else
log_error_errno(errno, "clone() failed: %m");
r = log_error_errno(errno, "clone() failed: %m");
r = pid;
goto finish;
}
@ -3028,14 +3135,14 @@ int main(int argc, char *argv[]) {
reset_all_signal_handlers();
reset_signal_mask();
k = open_terminal(console, O_RDWR);
if (k != STDIN_FILENO) {
if (k >= 0) {
safe_close(k);
k = -EINVAL;
r = open_terminal(console, O_RDWR);
if (r != STDIN_FILENO) {
if (r >= 0) {
safe_close(r);
r = -EINVAL;
}
log_error_errno(k, "Failed to open console: %m");
log_error_errno(r, "Failed to open console: %m");
_exit(EXIT_FAILURE);
}
@ -3090,9 +3197,9 @@ int main(int argc, char *argv[]) {
_exit(EXIT_FAILURE);
if (arg_read_only) {
k = bind_remount_recursive(arg_directory, true);
if (k < 0) {
log_error_errno(k, "Failed to make tree read-only: %m");
r = bind_remount_recursive(arg_directory, true);
if (r < 0) {
log_error_errno(r, "Failed to make tree read-only: %m");
_exit(EXIT_FAILURE);
}
}
@ -3196,9 +3303,9 @@ int main(int argc, char *argv[]) {
}
if (fdset_size(fds) > 0) {
k = fdset_cloexec(fds, false);
if (k < 0) {
log_error("Failed to unset O_CLOEXEC for file descriptors.");
r = fdset_cloexec(fds, false);
if (r < 0) {
log_error_errno(r, "Failed to unset O_CLOEXEC for file descriptors.");
_exit(EXIT_FAILURE);
}
@ -3350,8 +3457,10 @@ int main(int argc, char *argv[]) {
}
r = sd_event_loop(event);
if (r < 0)
return log_error_errno(r, "Failed to run event loop: %m");
if (r < 0) {
log_error_errno(r, "Failed to run event loop: %m");
goto finish;
}
forward = pty_forward_free(forward);
@ -3368,16 +3477,17 @@ int main(int argc, char *argv[]) {
r = wait_for_container(pid, &container_status);
pid = 0;
if (r < 0) {
if (r < 0)
/* We failed to wait for the container, or the
* container exited abnormally */
r = EXIT_FAILURE;
break;
} else if (r > 0 || container_status == CONTAINER_TERMINATED)
goto finish;
else if (r > 0 || container_status == CONTAINER_TERMINATED){
/* The container exited with a non-zero
* status, or with zero status and no reboot
* was requested. */
ret = r;
break;
}
/* CONTAINER_REBOOTED, loop again */
@ -3392,7 +3502,8 @@ int main(int argc, char *argv[]) {
* restart. This is necessary since we might
* have cgroup parameters set we want to have
* flushed out. */
r = 133;
ret = 133;
r = 0;
break;
}
}
@ -3407,7 +3518,17 @@ finish:
if (pid > 0)
kill(pid, SIGKILL);
if (remove_subvol && arg_directory) {
int k;
k = btrfs_subvol_remove(arg_directory);
if (k < 0)
log_warning_errno(k, "Cannot remove subvolume '%s', ignoring: %m", arg_directory);
}
free(arg_directory);
free(arg_template);
free(arg_image);
free(arg_machine);
free(arg_user);
strv_free(arg_setenv);
@ -3417,5 +3538,5 @@ finish:
strv_free(arg_bind_ro);
strv_free(arg_tmpfs);
return r;
return r < 0 ? EXIT_FAILURE : ret;
}

1
src/shared/copy.c
View file

@ -82,7 +82,6 @@ int copy_bytes(int fdf, int fdt, off_t max_bytes) {
r = loop_write(fdt, buf, (size_t) n, false);
if (r < 0)
return r;
}
next: