Add support for systemd-nspawn containers

This adds support for running OpenRC in a container created by
the systemd-nspawn utility.

This fixes #52.

X-Gentoo-Bug: 548058
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=548058

etc/rc.conf.Linux

@@ -2,14 +2,15 @@
 # LINUX SPECIFIC OPTIONS
 
 # This is the subsystem type. Valid options on Linux:
-# ""        - nothing special
-# "lxc"     - Linux Containers
-# "openvz"  - Linux OpenVZ
-# "prefix"  - Prefix
-# "uml"     - Usermode Linux
-# "vserver" - Linux vserver
-# "xen0"    - Xen0 Domain
-# "xenU"    - XenU Domain
+# ""               - nothing special
+# "lxc"            - Linux Containers
+# "openvz"         - Linux OpenVZ
+# "prefix"         - Prefix
+# "uml"            - Usermode Linux
+# "vserver"        - Linux vserver
+# "systemd-nspawn" - Container created by the systemd-nspawn utility
+# "xen0"           - Xen0 Domain
+# "xenU"           - XenU Domain
 # If this is commented out, automatic detection will be used.
 #
 # This should be set to the value representing the environment this file is

sh/openrc-run.sh.in

@@ -34,7 +34,10 @@ sourcex()
 
 sourcex "@LIBEXECDIR@/sh/functions.sh"
 sourcex "@LIBEXECDIR@/sh/rc-functions.sh"
-[ "$RC_SYS" != "PREFIX" ] && sourcex -e "@LIBEXECDIR@/sh/rc-cgroup.sh"
+case $RC_SYS in
+	PREFIX|SYSTEMD-NSPAWN) ;;
+	*) sourcex -e "@LIBEXECDIR@/sh/rc-cgroup.sh";;
+esac
 
 # Support LiveCD foo
 if sourcex -e "/sbin/livecd-functions.sh"; then

src/librc/librc.c

@@ -294,6 +294,8 @@ rc_sys_v1(void)
 		return RC_SYS_OPENVZ; /* old test */
 	else if (file_regex("/proc/1/environ", "container=lxc"))
 		return RC_SYS_LXC;
+	else if (file_regex("/proc/1/environ", "container=systemd-nspawn"))
+		return RC_SYS_SYSTEMD_NSPAWN;
 #endif
 
 	return NULL;

src/librc/rc.h.in

@@ -332,6 +332,7 @@ bool rc_service_daemons_crashed(const char *);
 #define RC_SYS_OPENVZ  "OPENVZ"
 #define RC_SYS_LXC     "LXC"
 #define RC_SYS_PREFIX  "PREFIX"
+#define RC_SYS_SYSTEMD_NSPAWN "SYSTEMD-NSPAWN"
 #define RC_SYS_UML     "UML"
 #define RC_SYS_VSERVER "VSERVER"
 #define RC_SYS_XEN0    "XEN0"