From 1fd961211df69ce672252d543bf4777738647048 Mon Sep 17 00:00:00 2001
From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Sat, 12 Jan 2013 16:55:04 -0500
Subject: 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.
---
 src/nspawn/nspawn.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

(limited to 'src')

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;
 
-- 
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