From 3e56a78b50e4794f89295278d477ad605c22471b Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Sun, 22 Apr 2012 13:37:24 +0200
Subject: [PATCH] nspawn: add -b switch to automatically look for an init
 binary (cherry picked from commit
 0f0dbc46ccf5aaaf3131446d0a4d78bc97a37295)

Conflicts:

	TODO
---
 man/systemd-nspawn.xml |   10 ++++++++++
 src/nspawn/nspawn.c    |   29 +++++++++++++++++++++++++++--
 src/shared/util.h      |    2 ++
 3 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 47aa4a7..31baa01 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -142,6 +142,16 @@
                         </varlistentry>
 
                         <varlistentry>
+                                <term><option>--boot</option></term>
+                                <term><option>-b</option></term>
+
+                                <listitem><para>Automatically search
+                                for an init binary and invoke it
+                                instead of a shell or a user supplied
+                                program.</para></listitem>
+                        </varlistentry>
+
+                        <varlistentry>
                                 <term><option>--user=</option></term>
                                 <term><option>-u</option></term>
 
diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index 0d0d987..c1b1dc7 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -56,6 +56,7 @@ static char *arg_directory = NULL;
 static char *arg_user = NULL;
 static char **arg_controllers = NULL;
 static bool arg_private_network = false;
+static bool arg_boot = false;
 
 static int help(void) {
 
@@ -63,6 +64,7 @@ static int help(void) {
                "Spawn a minimal namespace container for debugging, testing and building.\n\n"
                "  -h --help             Show this help\n"
                "  -D --directory=NAME   Root directory 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"
                "  -C --controllers=LIST Put the container in specified comma-separated cgroup hierarchies\n"
                "     --private-network  Disable network in container\n",
@@ -83,6 +85,7 @@ static int parse_argv(int argc, char *argv[]) {
                 { "user",            required_argument, NULL, 'u'                 },
                 { "controllers",     required_argument, NULL, 'C'                 },
                 { "private-network", no_argument,       NULL, ARG_PRIVATE_NETWORK },
+                { "boot",            no_argument,       NULL, 'b'                 },
                 { NULL,              0,                 NULL, 0                   }
         };
 
@@ -91,7 +94,7 @@ static int parse_argv(int argc, char *argv[]) {
         assert(argc >= 0);
         assert(argv);
 
-        while ((c = getopt_long(argc, argv, "+hD:u:C:", options, NULL)) >= 0) {
+        while ((c = getopt_long(argc, argv, "+hD:u:C:b", options, NULL)) >= 0) {
 
                 switch (c) {
 
@@ -133,6 +136,10 @@ static int parse_argv(int argc, char *argv[]) {
                         arg_private_network = true;
                         break;
 
+                case 'b':
+                        arg_boot = true;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -1024,7 +1031,25 @@ int main(int argc, char *argv[]) {
 
                 setup_hostname();
 
-                if (argc > optind)
+                if (arg_boot) {
+                        char **a;
+                        size_t l;
+
+                        /* Automatically search for the init system */
+
+                        l = 1 + argc - optind;
+                        a = newa(char*, l + 1);
+                        memcpy(a + 1, argv + optind, l * sizeof(char*));
+
+                        a[0] = (char*) "/usr/lib/systemd/systemd";
+                        execve(a[0], a, (char**) envp);
+
+                        a[0] = (char*) "/lib/systemd/systemd";
+                        execve(a[0], a, (char**) envp);
+
+                        a[0] = (char*) "/sbin/init";
+                        execve(a[0], a, (char**) envp);
+                } else if (argc > optind)
                         execvpe(argv[optind], argv + optind, (char**) envp);
                 else {
                         chdir(home ? home : "/root");
diff --git a/src/shared/util.h b/src/shared/util.h
index 42d1f0c..f4190a3 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -100,6 +100,8 @@ bool streq_ptr(const char *a, const char *b);
 
 #define new0(t, n) ((t*) calloc((n), sizeof(t)))
 
+#define newa(t, n) ((t*) alloca(sizeof(t)*(n)))
+
 #define newdup(t, p, n) ((t*) memdup(p, sizeof(t)*(n))
 
 #define malloc0(n) (calloc((n), 1))