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nspawn: optionally run a stub init process as PID 1

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This adds a new switch --as-pid2, which allows running commands as PID 2, while a stub init process is run as PID 1.
This is useful in order to run arbitrary commands in a container, as PID1's semantics are different from all other
processes regarding reaping of unknown children or signal handling.
This commit is contained in:
Lennart Poettering
2016-02-03 23:58:24 +01:00
parent 021dd87bc0
commit 7732f92bad
9 changed files with 426 additions and 43 deletions
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src/nspawn/nspawn-gperf.gperf
+2 -1
View File
@@ -15,7 +15,8 @@ struct ConfigPerfItem;
%struct-type
%includes
%%
Exec.Boot, config_parse_tristate, 0, offsetof(Settings, boot)
Exec.Boot, config_parse_boot, 0, 0
Exec.ProcessTwo, config_parse_pid2, 0, 0,
Exec.Parameters, config_parse_strv, 0, offsetof(Settings, parameters)
Exec.Environment, config_parse_strv, 0, offsetof(Settings, environment)
Exec.User, config_parse_string, 0, offsetof(Settings, user)
src/nspawn/nspawn-settings.c
+92 -1
View File
@@ -24,6 +24,7 @@
#include "conf-parser.h"
#include "nspawn-network.h"
#include "nspawn-settings.h"
#include "parse-util.h"
#include "process-util.h"
#include "strv.h"
#include "util.h"
@@ -39,7 +40,7 @@ int settings_load(FILE *f, const char *path, Settings **ret) {
if (!s)
return -ENOMEM;
s->boot = -1;
s->start_mode = _START_MODE_INVALID;
s->personality = PERSONALITY_INVALID;
s->read_only = -1;
@@ -303,3 +304,93 @@ int config_parse_veth_extra(
return 0;
}
int config_parse_boot(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = parse_boolean(rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse Boot= parameter %s, ignoring: %m", rvalue);
return 0;
}
if (r > 0) {
if (settings->start_mode == START_PID2)
goto conflict;
settings->start_mode = START_BOOT;
} else {
if (settings->start_mode == START_BOOT)
goto conflict;
if (settings->start_mode < 0)
settings->start_mode = START_PID1;
}
return 0;
conflict:
log_syntax(unit, LOG_ERR, filename, line, r, "Conflicting Boot= or ProcessTwo= setting found. Ignoring.");
return 0;
}
int config_parse_pid2(
const char *unit,
const char *filename,
unsigned line,
const char *section,
unsigned section_line,
const char *lvalue,
int ltype,
const char *rvalue,
void *data,
void *userdata) {
Settings *settings = data;
int r;
assert(filename);
assert(lvalue);
assert(rvalue);
r = parse_boolean(rvalue);
if (r < 0) {
log_syntax(unit, LOG_ERR, filename, line, r, "Failed to parse ProcessTwo= parameter %s, ignoring: %m", rvalue);
return 0;
}
if (r > 0) {
if (settings->start_mode == START_BOOT)
goto conflict;
settings->start_mode = START_PID2;
} else {
if (settings->start_mode == START_PID2)
goto conflict;
if (settings->start_mode < 0)
settings->start_mode = START_PID1;
}
return 0;
conflict:
log_syntax(unit, LOG_ERR, filename, line, r, "Conflicting Boot= or ProcessTwo= setting found. Ignoring.");
return 0;
}
src/nspawn/nspawn-settings.h
+24 -14
View File
@@ -27,26 +27,34 @@
#include "nspawn-expose-ports.h"
#include "nspawn-mount.h"
typedef enum StartMode {
START_PID1, /* Run parameters as command line as process 1 */
START_PID2, /* Use stub init process as PID 1, run parameters as command line as process 2 */
START_BOOT, /* Search for init system, pass arguments as parameters */
_START_MODE_MAX,
_START_MODE_INVALID = -1
} StartMode;
typedef enum SettingsMask {
SETTING_BOOT = 1 << 0,
SETTING_ENVIRONMENT = 1 << 1,
SETTING_USER = 1 << 2,
SETTING_CAPABILITY = 1 << 3,
SETTING_KILL_SIGNAL = 1 << 4,
SETTING_PERSONALITY = 1 << 5,
SETTING_MACHINE_ID = 1 << 6,
SETTING_NETWORK = 1 << 7,
SETTING_EXPOSE_PORTS = 1 << 8,
SETTING_READ_ONLY = 1 << 9,
SETTING_VOLATILE_MODE = 1 << 10,
SETTING_CUSTOM_MOUNTS = 1 << 11,
SETTING_START_MODE = 1 << 0,
SETTING_ENVIRONMENT = 1 << 1,
SETTING_USER = 1 << 2,
SETTING_CAPABILITY = 1 << 3,
SETTING_KILL_SIGNAL = 1 << 4,
SETTING_PERSONALITY = 1 << 5,
SETTING_MACHINE_ID = 1 << 6,
SETTING_NETWORK = 1 << 7,
SETTING_EXPOSE_PORTS = 1 << 8,
SETTING_READ_ONLY = 1 << 9,
SETTING_VOLATILE_MODE = 1 << 10,
SETTING_CUSTOM_MOUNTS = 1 << 11,
SETTING_WORKING_DIRECTORY = 1 << 12,
_SETTINGS_MASK_ALL = (1 << 13) -1
_SETTINGS_MASK_ALL = (1 << 13) -1
} SettingsMask;
typedef struct Settings {
/* [Run] */
int boot;
StartMode start_mode;
char **parameters;
char **environment;
char *user;
@@ -91,3 +99,5 @@ int config_parse_volatile_mode(const char *unit, const char *filename, unsigned
int config_parse_bind(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_tmpfs(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_veth_extra(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_boot(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
int config_parse_pid2(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
src/nspawn/nspawn-stub-pid1.c
+170
View File
@@ -0,0 +1,170 @@
/***
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/reboot.h>
#include <sys/unistd.h>
#include <sys/wait.h>
#include "fd-util.h"
#include "log.h"
#include "nspawn-stub-pid1.h"
#include "process-util.h"
#include "signal-util.h"
#include "time-util.h"
#include "def.h"
int stub_pid1(void) {
enum {
STATE_RUNNING,
STATE_REBOOT,
STATE_POWEROFF,
} state = STATE_RUNNING;
sigset_t fullmask, oldmask, waitmask;
usec_t quit_usec = USEC_INFINITY;
pid_t pid;
int r;
/* Implements a stub PID 1, that reaps all processes and processes a couple of standard signals. This is useful
* for allowing arbitrary processes run in a container, and still have all zombies reaped. */
assert_se(sigfillset(&fullmask) >= 0);
assert_se(sigprocmask(SIG_BLOCK, &fullmask, &oldmask) >= 0);
pid = fork();
if (pid < 0)
return log_error_errno(errno, "Failed to fork child pid: %m");
if (pid == 0) {
/* Return in the child */
assert_se(sigprocmask(SIG_SETMASK, &oldmask, NULL) >= 0);
setsid();
return 0;
}
reset_all_signal_handlers();
log_close();
close_all_fds(NULL, 0);
log_open();
rename_process("STUBINIT");
assert_se(sigemptyset(&waitmask) >= 0);
assert_se(sigset_add_many(&waitmask,
SIGCHLD, /* posix: process died */
SIGINT, /* sysv: ctrl-alt-del */
SIGRTMIN+3, /* systemd: halt */
SIGRTMIN+4, /* systemd: poweroff */
SIGRTMIN+5, /* systemd: reboot */
SIGRTMIN+6, /* systemd: kexec */
SIGRTMIN+13, /* systemd: halt */
SIGRTMIN+14, /* systemd: poweroff */
SIGRTMIN+15, /* systemd: reboot */
SIGRTMIN+16, /* systemd: kexec */
-1) >= 0);
/* Note that we ignore SIGTERM (sysv's reexec), SIGHUP (reload), and all other signals here, since we don't
* support reexec/reloading in this stub process. */
for (;;) {
siginfo_t si;
usec_t current_usec;
si.si_pid = 0;
r = waitid(P_ALL, 0, &si, WEXITED|WNOHANG);
if (r < 0) {
r = log_error_errno(errno, "Failed to reap children: %m");
goto finish;
}
current_usec = now(CLOCK_MONOTONIC);
if (si.si_pid == pid || current_usec >= quit_usec) {
/* The child we started ourselves died or we reached a timeout. */
if (state == STATE_REBOOT) { /* dispatch a queued reboot */
(void) reboot(RB_AUTOBOOT);
r = log_error_errno(errno, "Failed to reboot: %m");
goto finish;
} else if (state == STATE_POWEROFF)
(void) reboot(RB_POWER_OFF); /* if this fails, fall back to normal exit. */
if (si.si_pid == pid && si.si_code == CLD_EXITED)
r = si.si_status; /* pass on exit code */
else
r = 255; /* signal, coredump, timeout, … */
goto finish;
}
if (si.si_pid != 0)
/* We reaped something. Retry until there's nothing more to reap. */
continue;
if (quit_usec == USEC_INFINITY)
r = sigwaitinfo(&waitmask, &si);
else {
struct timespec ts;
r = sigtimedwait(&waitmask, &si, timespec_store(&ts, quit_usec - current_usec));
}
if (r < 0) {
if (errno == EINTR) /* strace -p attach can result in EINTR, let's handle this nicely. */
continue;
if (errno == EAGAIN) /* timeout reached */
continue;
r = log_error_errno(errno, "Failed to wait for signal: %m");
goto finish;
}
if (si.si_signo == SIGCHLD)
continue; /* Let's reap this */
if (state != STATE_RUNNING)
continue;
/* Would love to use a switch() statement here, but SIGRTMIN is actually a function call, not a
* constant… */
if (si.si_signo == SIGRTMIN+3 ||
si.si_signo == SIGRTMIN+4 ||
si.si_signo == SIGRTMIN+13 ||
si.si_signo == SIGRTMIN+14)
state = STATE_POWEROFF;
else if (si.si_signo == SIGINT ||
si.si_signo == SIGRTMIN+5 ||
si.si_signo == SIGRTMIN+6 ||
si.si_signo == SIGRTMIN+15 ||
si.si_signo == SIGRTMIN+16)
state = STATE_REBOOT;
else
assert_not_reached("Got unexpected signal");
/* (void) kill_and_sigcont(pid, SIGTERM); */
quit_usec = now(CLOCK_MONOTONIC) + DEFAULT_TIMEOUT_USEC;
}
finish:
_exit(r < 0 ? EXIT_FAILURE : r);
}
src/nspawn/nspawn-stub-pid1.h
+22
View File
@@ -0,0 +1,22 @@
#pragma once
/***
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/>.
***/
int stub_pid1(void);
src/nspawn/nspawn.c
+40 -12
View File
@@ -79,6 +79,7 @@
#include "nspawn-register.h"
#include "nspawn-settings.h"
#include "nspawn-setuid.h"
#include "nspawn-stub-pid1.h"
#include "parse-util.h"
#include "path-util.h"
#include "process-util.h"
@@ -123,7 +124,7 @@ static const char *arg_selinux_apifs_context = NULL;
static const char *arg_slice = NULL;
static bool arg_private_network = false;
static bool arg_read_only = false;
static bool arg_boot = false;
static StartMode arg_start_mode = START_PID1;
static bool arg_ephemeral = false;
static LinkJournal arg_link_journal = LINK_AUTO;
static bool arg_link_journal_try = false;
@@ -193,6 +194,7 @@ static void help(void) {
" -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"
" -a --as-pid2 Maintain a stub init as PID1, invoke binary as PID2\n"
" -b --boot Boot up full system (i.e. invoke init)\n"
" --chdir=PATH Set working directory in the container\n"
" -u --user=USER Run the command under specified user or uid\n"
@@ -358,6 +360,7 @@ static int parse_argv(int argc, char *argv[]) {
{ "ephemeral", no_argument, NULL, 'x' },
{ "user", required_argument, NULL, 'u' },
{ "private-network", no_argument, NULL, ARG_PRIVATE_NETWORK },
{ "as-pid2", no_argument, NULL, 'a' },
{ "boot", no_argument, NULL, 'b' },
{ "uuid", required_argument, NULL, ARG_UUID },
{ "read-only", no_argument, NULL, ARG_READ_ONLY },
@@ -404,7 +407,7 @@ 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:xp:n", options, NULL)) >= 0)
while ((c = getopt_long(argc, argv, "+hD:u:abL:M:jS:Z:qi:xp:n", options, NULL)) >= 0)
switch (c) {
@@ -495,8 +498,23 @@ static int parse_argv(int argc, char *argv[]) {
break;
case 'b':
arg_boot = true;
arg_settings_mask |= SETTING_BOOT;
if (arg_start_mode == START_PID2) {
log_error("--boot and --as-pid2 may not be combined.");
return -EINVAL;
}
arg_start_mode = START_BOOT;
arg_settings_mask |= SETTING_START_MODE;
break;
case 'a':
if (arg_start_mode == START_BOOT) {
log_error("--boot and --as-pid2 may not be combined.");
return -EINVAL;
}
arg_start_mode = START_PID2;
arg_settings_mask |= SETTING_START_MODE;
break;
case ARG_UUID:
@@ -876,7 +894,7 @@ static int parse_argv(int argc, char *argv[]) {
if (arg_share_system)
arg_register = false;
if (arg_boot && arg_share_system) {
if (arg_start_mode != START_PID1 && arg_share_system) {
log_error("--boot and --share-system may not be combined.");
return -EINVAL;
}
@@ -924,7 +942,7 @@ static int parse_argv(int argc, char *argv[]) {
if (!arg_parameters)
return log_oom();
arg_settings_mask |= SETTING_BOOT;
arg_settings_mask |= SETTING_START_MODE;
}
/* Load all settings from .nspawn files */
@@ -960,7 +978,7 @@ static int verify_arguments(void) {
return -EINVAL;
}
if (arg_boot && arg_kill_signal <= 0)
if (arg_start_mode == START_BOOT && arg_kill_signal <= 0)
arg_kill_signal = SIGRTMIN+3;
return 0;
@@ -2584,6 +2602,12 @@ static int inner_child(
if (chdir(arg_chdir) < 0)
return log_error_errno(errno, "Failed to change to specified working directory %s: %m", arg_chdir);
if (arg_start_mode == START_PID2) {
r = stub_pid1();
if (r < 0)
return r;
}
/* Now, explicitly close the log, so that we
* then can close all remaining fds. Closing
* the log explicitly first has the benefit
@@ -2595,7 +2619,7 @@ static int inner_child(
log_close();
(void) fdset_close_others(fds);
if (arg_boot) {
if (arg_start_mode == START_BOOT) {
char **a;
size_t m;
@@ -2917,9 +2941,9 @@ static int load_settings(void) {
/* Copy over bits from the settings, unless they have been
* explicitly masked by command line switches. */
if ((arg_settings_mask & SETTING_BOOT) == 0 &&
settings->boot >= 0) {
arg_boot = settings->boot;
if ((arg_settings_mask & SETTING_START_MODE) == 0 &&
settings->start_mode >= 0) {
arg_start_mode = settings->start_mode;
strv_free(arg_parameters);
arg_parameters = settings->parameters;
@@ -3074,6 +3098,10 @@ int main(int argc, char *argv[]) {
log_parse_environment();
log_open();
/* Make sure rename_process() in the stub init process can work */
saved_argv = argv;
saved_argc = argc;
r = parse_argv(argc, argv);
if (r <= 0)
goto finish;
@@ -3180,7 +3208,7 @@ int main(int argc, char *argv[]) {
}
}
if (arg_boot) {
if (arg_start_mode == START_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;