nspawn: optionally run a stub init process as PID 1

This adds a new switch --as-pid2, which allows running commands as PID 2, while a stub init process is run as PID 1.
This is useful in order to run arbitrary commands in a container, as PID1's semantics are different from all other
processes regarding reaping of unknown children or signal handling.

1 files changed, 24 insertions, 14 deletions

diff --git a/src/nspawn/nspawn-settings.h b/src/nspawn/nspawn-settings.h
index 236a1baa4f..fdb07486da 100644
--- a/src/nspawn/nspawn-settings.h
+++ b/src/nspawn/nspawn-settings.h
@@ -27,26 +27,34 @@
 #include "nspawn-expose-ports.h"
 #include "nspawn-mount.h"
 
+typedef enum StartMode {
+        START_PID1, /* Run parameters as command line as process 1 */
+        START_PID2, /* Use stub init process as PID 1, run parameters as command line as process 2 */
+        START_BOOT, /* Search for init system, pass arguments as parameters */
+        _START_MODE_MAX,
+        _START_MODE_INVALID = -1
+} StartMode;
+
 typedef enum SettingsMask {
-        SETTING_BOOT          = 1 << 0,
-        SETTING_ENVIRONMENT   = 1 << 1,
-        SETTING_USER          = 1 << 2,
-        SETTING_CAPABILITY    = 1 << 3,
-        SETTING_KILL_SIGNAL   = 1 << 4,
-        SETTING_PERSONALITY   = 1 << 5,
-        SETTING_MACHINE_ID    = 1 << 6,
-        SETTING_NETWORK       = 1 << 7,
-        SETTING_EXPOSE_PORTS  = 1 << 8,
-        SETTING_READ_ONLY     = 1 << 9,
-        SETTING_VOLATILE_MODE = 1 << 10,
-        SETTING_CUSTOM_MOUNTS = 1 << 11,
+        SETTING_START_MODE        = 1 << 0,
+        SETTING_ENVIRONMENT       = 1 << 1,
+        SETTING_USER              = 1 << 2,
+        SETTING_CAPABILITY        = 1 << 3,
+        SETTING_KILL_SIGNAL       = 1 << 4,
+        SETTING_PERSONALITY       = 1 << 5,
+        SETTING_MACHINE_ID        = 1 << 6,
+        SETTING_NETWORK           = 1 << 7,
+        SETTING_EXPOSE_PORTS      = 1 << 8,
+        SETTING_READ_ONLY         = 1 << 9,
+        SETTING_VOLATILE_MODE     = 1 << 10,
+        SETTING_CUSTOM_MOUNTS     = 1 << 11,
         SETTING_WORKING_DIRECTORY = 1 << 12,
-        _SETTINGS_MASK_ALL    = (1 << 13) -1
+        _SETTINGS_MASK_ALL        = (1 << 13) -1
 } SettingsMask;
 
 typedef struct Settings {
         /* [Run] */
-        int boot;
+        StartMode start_mode;
         char **parameters;
         char **environment;
         char *user;
@@ -91,3 +99,5 @@ int config_parse_volatile_mode(const char *unit, const char *filename, unsigned
 int config_parse_bind(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_tmpfs(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_veth_extra(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_boot(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_pid2(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);