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authorZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2013-01-12 16:55:04 -0500
committerZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2013-02-14 10:40:45 -0500
commit1fd961211df69ce672252d543bf4777738647048 (patch)
treeabb3cba616bdfcc7f2e58b6c87a75c2eb0f1347e
parenta860325e7ed7ea2bd688b2f002021123a05af084 (diff)
nspawn: print PID and show how to enter the namespace
systemd-nspawn will now print the PID of the child. An example showing how to enter the container is added to the man page. Support for nsenter without an explicit command was added in https://github.com/karelzak/util-linux/commit/5758069 (post v2.22.2). So this example requires both a new kernel and the latest util-linux.
-rw-r--r--man/systemd-nspawn.xml30
-rw-r--r--src/nspawn/nspawn.c26
2 files changed, 47 insertions, 9 deletions
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 6a01ffd450..5cba40bcd4 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -49,7 +49,10 @@
<refsynopsisdiv>
<cmdsynopsis>
- <command>systemd-nspawn <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="opt">COMMAND</arg> <arg choice="opt" rep="repeat">ARGS</arg></command>
+ <command>systemd-nspawn</command>
+ <arg choice="opt" rep="repeat">OPTIONS</arg>
+ <arg choice="opt">COMMAND</arg>
+ <arg choice="opt" rep="repeat">ARGS</arg>
</cmdsynopsis>
</refsynopsisdiv>
@@ -114,7 +117,10 @@
see each other. The PID namespace separation of the
two containers is complete and the containers will
share very few runtime objects except for the
- underlying file system.</para>
+ underlying file system. It is however possible to
+ enter an existing container, see
+ <link linkend='example-nsenter'>Example 4</link> below.
+ </para>
<para><command>systemd-nspawn</command> implements the
<ulink
@@ -318,7 +324,6 @@
distribution into the directory
<filename>~/debian-tree/</filename> and then spawns a
shell in a namespace container in it.</para>
-
</refsect1>
<refsect1>
@@ -332,6 +337,24 @@
boots an OS in a namespace container in it.</para>
</refsect1>
+ <refsect1 id='example-nsenter'>
+ <title>Example 4</title>
+
+ <para>To enter the container, PID of one of the
+ processes sharing the new namespaces must be used.
+ <command>systemd-nspawn</command> prints the PID
+ (as viewed from the outside) of the launched process,
+ and it can be used to enter the container.</para>
+
+ <programlisting># nsenter -muinpt $PID</programlisting>
+
+ <para><citerefentry><refentrytitle>nsenter</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ is part of
+ <ulink url="https://github.com/karelzak/util-linux">util-linux</ulink>.
+ Kernel support for entering namespaces was added in
+ Linux 3.8.</para>
+ </refsect1>
+
<refsect1>
<title>Exit status</title>
@@ -344,6 +367,7 @@
<para>
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>chroot</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+ <citerefentry><refentrytitle>unshare</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
<citerefentry><refentrytitle>yum</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>debootstrap</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
<citerefentry><refentrytitle>pacman</refentrytitle><manvolnum>8</manvolnum></citerefentry>
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 1d602a5b31..2fec9023a1 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -33,6 +33,7 @@
#include <sys/prctl.h>
#include <sys/capability.h>
#include <getopt.h>
+#include <sys/poll.h>
#include <sys/epoll.h>
#include <termios.h>
#include <sys/signalfd.h>
@@ -1204,12 +1205,11 @@ int main(int argc, char *argv[]) {
for (;;) {
siginfo_t status;
+ int pipefd[2];
- if (saved_attr_valid) {
- if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_attr) < 0) {
- log_error("Failed to set terminal attributes: %m");
- goto finish;
- }
+ if(pipe2(pipefd, O_NONBLOCK|O_CLOEXEC) < 0) {
+ log_error("pipe2(): %m");
+ goto finish;
}
pid = syscall(__NR_clone, SIGCHLD|CLONE_NEWIPC|CLONE_NEWNS|CLONE_NEWPID|CLONE_NEWUTS|(arg_private_network ? CLONE_NEWNET : 0), NULL);
@@ -1224,7 +1224,6 @@ int main(int argc, char *argv[]) {
if (pid == 0) {
/* child */
-
const char *home = NULL;
uid_t uid = (uid_t) -1;
gid_t gid = (gid_t) -1;
@@ -1245,9 +1244,20 @@ int main(int argc, char *argv[]) {
envp[2] = strv_find_prefix(environ, "TERM=");
n_env = 3;
+ close(pipefd[1]);
+ fd_wait_for_event(pipefd[0], POLLHUP, -1);
+ close(pipefd[0]);
+
close_nointr_nofail(master);
master = -1;
+ if (saved_attr_valid) {
+ if (tcsetattr(STDIN_FILENO, TCSANOW, &raw_attr) < 0) {
+ log_error("Failed to set terminal attributes: %m");
+ goto child_fail;
+ }
+ }
+
close_nointr(STDIN_FILENO);
close_nointr(STDOUT_FILENO);
close_nointr(STDERR_FILENO);
@@ -1482,6 +1492,10 @@ int main(int argc, char *argv[]) {
_exit(EXIT_FAILURE);
}
+ log_info("Init process in the container running as PID %d", pid);
+ close(pipefd[0]);
+ close(pipefd[1]);
+
fdset_free(fds);
fds = NULL;