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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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#include <sys/types.h>
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#include <sys/syscall.h>
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#include <sys/mount.h>
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#include <sys/prctl.h>
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#include <sys/capability.h>
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#include <sys/epoll.h>
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#include <sys/signalfd.h>
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#include <systemd/sd-daemon.h>
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#include "cgroup-util.h"
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#include "loopback-setup.h"
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static char *arg_directory = NULL;
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static char *arg_user = NULL;
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static bool arg_private_network = false;
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static int help(void) {
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printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
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"Spawn a minimal namespace container for debugging, testing and building.\n\n"
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" -h --help Show this help\n"
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" -D --directory=NAME Root directory for the container\n"
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" -u --user=USER Run the command under specified user or uid\n"
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" --private-network Disable network in container\n",
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program_invocation_short_name);
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static int parse_argv(int argc, char *argv[]) {
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ARG_PRIVATE_NETWORK = 0x100
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static const struct option options[] = {
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{ "help", no_argument, NULL, 'h' },
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{ "directory", required_argument, NULL, 'D' },
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{ "user", required_argument, NULL, 'u' },
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{ "private-network", no_argument, NULL, ARG_PRIVATE_NETWORK },
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while ((c = getopt_long(argc, argv, "+hD:u:", options, NULL)) >= 0) {
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if (!(arg_directory = strdup(optarg))) {
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log_error("Failed to duplicate root directory.");
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if (!(arg_user = strdup(optarg))) {
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log_error("Failed to duplicate user name.");
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case ARG_PRIVATE_NETWORK:
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arg_private_network = true;
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log_error("Unknown option code %c", c);
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static int mount_all(const char *dest) {
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typedef struct MountPoint {
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static const MountPoint mount_table[] = {
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{ "proc", "/proc", "proc", NULL, MS_NOSUID|MS_NOEXEC|MS_NODEV, true },
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{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND, true }, /* Bind mount first */
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{ "/proc/sys", "/proc/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, true }, /* Then, make it r/o */
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{ "/sys", "/sys", "bind", NULL, MS_BIND, true }, /* Bind mount first */
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{ "/sys", "/sys", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, true }, /* Then, make it r/o */
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{ "tmpfs", "/dev", "tmpfs", "mode=755", MS_NOSUID, true },
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{ "/dev/pts", "/dev/pts", "bind", NULL, MS_BIND, true },
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{ "tmpfs", "/run", "tmpfs", "mode=755", MS_NOSUID|MS_NODEV, true },
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{ "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND, false }, /* Bind mount first */
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{ "/sys/fs/selinux", "/sys/fs/selinux", "bind", NULL, MS_BIND|MS_RDONLY|MS_REMOUNT, false }, /* Then, make it r/o */
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for (k = 0; k < ELEMENTSOF(mount_table); k++) {
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if (asprintf(&where, "%s/%s", dest, mount_table[k].where) < 0) {
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log_error("Out of memory");
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if ((t = path_is_mount_point(where, false)) < 0) {
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log_error("Failed to detect whether %s is a mount point: %s", where, strerror(-t));
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mkdir_p(where, 0755);
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if (mount(mount_table[k].what,
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mount_table[k].flags,
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mount_table[k].options) < 0 &&
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mount_table[k].fatal) {
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log_error("mount(%s) failed: %m", where);
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/* Fix the timezone, if possible */
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if (asprintf(&where, "%s/etc/localtime", dest) >= 0) {
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if (mount("/etc/localtime", where, "bind", MS_BIND, NULL) >= 0)
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mount("/etc/localtime", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);
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if (asprintf(&where, "%s/etc/timezone", dest) >= 0) {
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if (mount("/etc/timezone", where, "bind", MS_BIND, NULL) >= 0)
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mount("/etc/timezone", where, "bind", MS_BIND|MS_REMOUNT|MS_RDONLY, NULL);
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static int copy_devnodes(const char *dest, const char *console) {
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static const char devnodes[] =
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char *from = NULL, *to = NULL;
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NULSTR_FOREACH(d, devnodes) {
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asprintf(&from, "/dev/%s", d);
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asprintf(&to, "%s/dev/%s", dest, d);
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log_error("Failed to allocate devnode path");
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if (stat(from, &st) < 0) {
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if (errno != ENOENT) {
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log_error("Failed to stat %s: %m", from);
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} else if (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode)) {
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log_error("%s is not a char or block device, cannot copy.", from);
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} else if (mknod(to, st.st_mode, st.st_rdev) < 0) {
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log_error("mknod(%s) failed: %m", dest);
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if (stat(console, &st) < 0) {
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log_error("Failed to stat %s: %m", console);
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} else if (!S_ISCHR(st.st_mode)) {
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log_error("/dev/console is not a char device.");
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if (asprintf(&to, "%s/dev/console", dest) < 0) {
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log_error("Out of memory");
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/* We need to bind mount the right tty to /dev/console since
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* ptys can only exist on pts file systems. To have something
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* to bind mount things on we create a device node first, that
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* has the right major/minor (note that the major minor
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* doesn't actually matter here, since we mount it over
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if (mknod(to, (st.st_mode & ~07777) | 0600, st.st_rdev) < 0)
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log_error("mknod for /dev/console failed: %m");
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if (mount(console, to, "bind", MS_BIND, NULL) < 0) {
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log_error("bind mount for /dev/console failed: %m");
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if ((k = chmod_and_chown(console, 0600, 0, 0)) < 0) {
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log_error("Failed to correct access mode for TTY: %s", strerror(-k));
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static int drop_capabilities(void) {
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static const unsigned long retain[] = {
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CAP_NET_BIND_SERVICE,
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for (l = 0; l <= cap_last_cap(); l++) {
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for (i = 0; i < ELEMENTSOF(retain); i++)
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if (i < ELEMENTSOF(retain))
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if (prctl(PR_CAPBSET_DROP, l) < 0) {
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log_error("PR_CAPBSET_DROP failed: %m");
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static int is_os_tree(const char *path) {
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/* We use /bin/sh as flag file if something is an OS */
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if (asprintf(&p, "%s/bin/sh", path) < 0)
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return r < 0 ? 0 : 1;
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static int process_pty(int master, sigset_t *mask) {
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char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
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size_t in_buffer_full = 0, out_buffer_full = 0;
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struct epoll_event stdin_ev, stdout_ev, master_ev, signal_ev;
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bool stdin_readable = false, stdout_writable = false, master_readable = false, master_writable = false;
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int ep = -1, signal_fd = -1, r;
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fd_nonblock(STDIN_FILENO, 1);
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fd_nonblock(STDOUT_FILENO, 1);
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fd_nonblock(master, 1);
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if ((signal_fd = signalfd(-1, mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
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log_error("signalfd(): %m");
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if ((ep = epoll_create1(EPOLL_CLOEXEC)) < 0) {
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log_error("Failed to create epoll: %m");
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stdin_ev.events = EPOLLIN|EPOLLET;
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stdin_ev.data.fd = STDIN_FILENO;
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stdout_ev.events = EPOLLOUT|EPOLLET;
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stdout_ev.data.fd = STDOUT_FILENO;
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master_ev.events = EPOLLIN|EPOLLOUT|EPOLLET;
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master_ev.data.fd = master;
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signal_ev.events = EPOLLIN;
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signal_ev.data.fd = signal_fd;
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if (epoll_ctl(ep, EPOLL_CTL_ADD, STDIN_FILENO, &stdin_ev) < 0 ||
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epoll_ctl(ep, EPOLL_CTL_ADD, STDOUT_FILENO, &stdout_ev) < 0 ||
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epoll_ctl(ep, EPOLL_CTL_ADD, master, &master_ev) < 0 ||
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epoll_ctl(ep, EPOLL_CTL_ADD, signal_fd, &signal_ev) < 0) {
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log_error("Failed to regiser fds in epoll: %m");
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struct epoll_event ev[16];
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if ((nfds = epoll_wait(ep, ev, ELEMENTSOF(ev), -1)) < 0) {
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if (errno == EINTR || errno == EAGAIN)
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log_error("epoll_wait(): %m");
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for (i = 0; i < nfds; i++) {
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if (ev[i].data.fd == STDIN_FILENO) {
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if (ev[i].events & (EPOLLIN|EPOLLHUP))
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stdin_readable = true;
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} else if (ev[i].data.fd == STDOUT_FILENO) {
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if (ev[i].events & (EPOLLOUT|EPOLLHUP))
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stdout_writable = true;
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} else if (ev[i].data.fd == master) {
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if (ev[i].events & (EPOLLIN|EPOLLHUP))
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master_readable = true;
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if (ev[i].events & (EPOLLOUT|EPOLLHUP))
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master_writable = true;
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} else if (ev[i].data.fd == signal_fd) {
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struct signalfd_siginfo sfsi;
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if ((n = read(signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {
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log_error("Failed to read from signalfd: invalid block size");
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if (errno != EINTR && errno != EAGAIN) {
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log_error("Failed to read from signalfd: %m");
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if (sfsi.ssi_signo == SIGWINCH) {
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/* The window size changed, let's forward that. */
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if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)
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ioctl(master, TIOCSWINSZ, &ws);
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while ((stdin_readable && in_buffer_full <= 0) ||
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(master_writable && in_buffer_full > 0) ||
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(master_readable && out_buffer_full <= 0) ||
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(stdout_writable && out_buffer_full > 0)) {
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if (stdin_readable && in_buffer_full < LINE_MAX) {
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if ((k = read(STDIN_FILENO, in_buffer + in_buffer_full, LINE_MAX - in_buffer_full)) < 0) {
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if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
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stdin_readable = false;
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log_error("read(): %m");
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in_buffer_full += (size_t) k;
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if (master_writable && in_buffer_full > 0) {
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if ((k = write(master, in_buffer, in_buffer_full)) < 0) {
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if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
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master_writable = false;
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log_error("write(): %m");
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assert(in_buffer_full >= (size_t) k);
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memmove(in_buffer, in_buffer + k, in_buffer_full - k);
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if (master_readable && out_buffer_full < LINE_MAX) {
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if ((k = read(master, out_buffer + out_buffer_full, LINE_MAX - out_buffer_full)) < 0) {
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if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
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master_readable = false;
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log_error("read(): %m");
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out_buffer_full += (size_t) k;
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if (stdout_writable && out_buffer_full > 0) {
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if ((k = write(STDOUT_FILENO, out_buffer, out_buffer_full)) < 0) {
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if (errno == EAGAIN || errno == EPIPE || errno == ECONNRESET || errno == EIO)
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stdout_writable = false;
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log_error("write(): %m");
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assert(out_buffer_full >= (size_t) k);
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memmove(out_buffer, out_buffer + k, out_buffer_full - k);
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out_buffer_full -= k;
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close_nointr_nofail(ep);
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close_nointr_nofail(signal_fd);
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int main(int argc, char *argv[]) {
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int r = EXIT_FAILURE, k;
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char *oldcg = NULL, *newcg = NULL;
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const char *console = NULL;
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struct termios saved_attr, raw_attr;
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bool saved_attr_valid = false;
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log_parse_environment();
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if ((r = parse_argv(argc, argv)) <= 0)
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p = path_make_absolute_cwd(arg_directory);
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arg_directory = get_current_dir_name();
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if (!arg_directory) {
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log_error("Failed to determine path");
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path_kill_slashes(arg_directory);
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if (geteuid() != 0) {
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log_error("Need to be root.");
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if (sd_booted() <= 0) {
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log_error("Not running on a systemd system.");
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if (path_equal(arg_directory, "/")) {
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log_error("Spawning container on root directory not supported.");
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if (is_os_tree(arg_directory) <= 0) {
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log_error("Directory %s doesn't look like an OS root directory. Refusing.", arg_directory);
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if ((k = cg_get_by_pid(SYSTEMD_CGROUP_CONTROLLER, 0, &oldcg)) < 0) {
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log_error("Failed to determine current cgroup: %s", strerror(-k));
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if (asprintf(&newcg, "%s/nspawn-%lu", oldcg, (unsigned long) getpid()) < 0) {
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log_error("Failed to allocate cgroup path.");
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if ((k = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, newcg, 0)) < 0) {
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log_error("Failed to create cgroup: %s", strerror(-k));
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if ((master = posix_openpt(O_RDWR|O_NOCTTY|O_CLOEXEC|O_NDELAY)) < 0) {
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log_error("Failed to acquire pseudo tty: %m");
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if (!(console = ptsname(master))) {
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log_error("Failed to determine tty name: %m");
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log_info("Spawning namespace container on %s (console is %s).", arg_directory, console);
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if (ioctl(STDIN_FILENO, TIOCGWINSZ, &ws) >= 0)
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ioctl(master, TIOCSWINSZ, &ws);
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if (unlockpt(master) < 0) {
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log_error("Failed to unlock tty: %m");
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if (tcgetattr(STDIN_FILENO, &saved_attr) < 0) {
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log_error("Failed to get terminal attributes: %m");
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saved_attr_valid = true;
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raw_attr = saved_attr;
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cfmakeraw(&raw_attr);
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raw_attr.c_lflag &= ~ECHO;
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if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_attr) < 0) {
709
log_error("Failed to set terminal attributes: %m");
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assert_se(sigemptyset(&mask) == 0);
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sigset_add_many(&mask, SIGCHLD, SIGWINCH, SIGTERM, SIGINT, -1);
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assert_se(sigprocmask(SIG_BLOCK, &mask, NULL) == 0);
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pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|(arg_private_network ? CLONE_NEWNET : 0), NULL);
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log_error("clone() failed, do you have namespace support enabled in your kernel? (You need UTS, IPC, PID and NET namespacing built in): %m");
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log_error("clone() failed: %m");
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const char *home = NULL;
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uid_t uid = (uid_t) -1;
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gid_t gid = (gid_t) -1;
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const char *envp[] = {
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"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
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"container=systemd-nspawn", /* LXC sets container=lxc, so follow the scheme here */
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envp[2] = strv_find_prefix(environ, "TERM=");
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close_nointr_nofail(master);
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close_nointr(STDIN_FILENO);
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close_nointr(STDOUT_FILENO);
750
close_nointr(STDERR_FILENO);
752
close_all_fds(NULL, 0);
754
reset_all_signal_handlers();
756
assert_se(sigemptyset(&mask) == 0);
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assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
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if (prctl(PR_SET_PDEATHSIG, SIGKILL) < 0)
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/* Mark / as private, in case somebody marked it shared */
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if (mount(NULL, "/", NULL, MS_PRIVATE|MS_REC, NULL) < 0)
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if (mount_all(arg_directory) < 0)
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if (copy_devnodes(arg_directory, console) < 0)
775
if (chdir(arg_directory) < 0) {
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log_error("chdir(%s) failed: %m", arg_directory);
780
if (open_terminal("dev/console", O_RDWR) != STDIN_FILENO ||
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dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO ||
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dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO)
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if (mount(arg_directory, "/", "bind", MS_BIND|MS_MOVE, NULL) < 0) {
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log_error("mount(MS_MOVE) failed: %m");
790
if (chroot(".") < 0) {
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log_error("chroot() failed: %m");
795
if (chdir("/") < 0) {
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log_error("chdir() failed: %m");
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if (drop_capabilities() < 0)
809
if (get_user_creds((const char**)&arg_user, &uid, &gid, &home) < 0) {
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log_error("get_user_creds() failed: %m");
814
if (mkdir_parents(home, 0775) < 0) {
815
log_error("mkdir_parents() failed: %m");
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if (safe_mkdir(home, 0775, uid, gid) < 0) {
820
log_error("safe_mkdir() failed: %m");
824
if (initgroups((const char*)arg_user, gid) < 0) {
825
log_error("initgroups() failed: %m");
829
if (setresgid(gid, gid, gid) < 0) {
830
log_error("setregid() failed: %m");
834
if (setresuid(uid, uid, uid) < 0) {
835
log_error("setreuid() failed: %m");
840
if ((asprintf((char**)(envp + 3), "HOME=%s", home? home: "/root") < 0) ||
841
(asprintf((char**)(envp + 4), "USER=%s", arg_user? arg_user : "root") < 0) ||
842
(asprintf((char**)(envp + 5), "LOGNAME=%s", arg_user? arg_user : "root") < 0)) {
843
log_error("Out of memory");
847
if ((hn = file_name_from_path(arg_directory)))
848
sethostname(hn, strlen(hn));
851
execvpe(argv[optind], argv + optind, (char**) envp);
853
chdir(home ? home : "/root");
854
execle("/bin/bash", "-bash", NULL, (char**) envp);
857
log_error("execv() failed: %m");
863
if (process_pty(master, &mask) < 0)
866
if (saved_attr_valid) {
867
tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);
868
saved_attr_valid = false;
871
r = wait_for_terminate_and_warn(argc > optind ? argv[optind] : "bash", pid);
877
if (saved_attr_valid)
878
tcsetattr(STDIN_FILENO, TCSANOW, &saved_attr);
881
close_nointr_nofail(master);
884
cg_attach(SYSTEMD_CGROUP_CONTROLLER, oldcg, 0);
887
cg_kill_recursive_and_wait(SYSTEMD_CGROUP_CONTROLLER, newcg, true);
added
removed
src/nspawn.c
