nspawn: support custom container service name

We were hardcoding "systemd-nspawn" as the value of the $container env
variable and "nspawn" as the service string in machined registration.

This commit allows the user to configure it by setting the
$SYSTEMD_NSPAWN_CONTAINER_SERVICE env variable when calling
systemd-nspawn.

If $SYSTEMD_NSPAWN_CONTAINER_SERVICE is not set, we use the string
"systemd-nspawn" for both, fixing the previous inconsistency.

1 files changed, 13 insertions, 4 deletions

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index ff12ca6498..4c426e6874 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -178,6 +178,7 @@ static bool arg_unified_cgroup_hierarchy = false;
 static SettingsMask arg_settings_mask = 0;
 static int arg_settings_trusted = -1;
 static char **arg_parameters = NULL;
+static const char *arg_container_service_name = "systemd-nspawn";
 
 static void help(void) {
         printf("%s [OPTIONS...] [PATH] [ARGUMENTS...]\n\n"
@@ -387,7 +388,7 @@ static int parse_argv(int argc, char *argv[]) {
         };
 
         int c, r;
-        const char *p;
+        const char *p, *e;
         uint64_t plus = 0, minus = 0;
         bool mask_all_settings = false, mask_no_settings = false;
 
@@ -909,6 +910,10 @@ static int parse_argv(int argc, char *argv[]) {
         if (r < 0)
                 return r;
 
+        e = getenv("SYSTEMD_NSPAWN_CONTAINER_SERVICE");
+        if (e)
+                arg_container_service_name = e;
+
         return 1;
 }
 
@@ -2404,10 +2409,10 @@ static int inner_child(
                 FDSet *fds) {
 
         _cleanup_free_ char *home = NULL;
-        unsigned n_env = 2;
+        unsigned n_env = 1;
         const char *envp[] = {
                 "PATH=" DEFAULT_PATH_SPLIT_USR,
-                "container=systemd-nspawn", /* LXC sets container=lxc, so follow the scheme here */
+                NULL, /* container */
                 NULL, /* TERM */
                 NULL, /* HOME */
                 NULL, /* USER */
@@ -2508,6 +2513,9 @@ static int inner_child(
         if (r < 0)
                 return r;
 
+        /* LXC sets container=lxc, so follow the scheme here */
+        envp[n_env++] = strjoina("container=", arg_container_service_name);
+
         envp[n_env] = strv_find_prefix(environ, "TERM=");
         if (envp[n_env])
                 n_env ++;
@@ -3426,7 +3434,8 @@ int main(int argc, char *argv[]) {
                                         arg_custom_mounts, arg_n_custom_mounts,
                                         arg_kill_signal,
                                         arg_property,
-                                        arg_keep_unit);
+                                        arg_keep_unit,
+                                        arg_container_service_name);
                         if (r < 0)
                                 goto finish;
                 }