systemctl: drop hardcoded chkconfig invocation

Introduce /usr/lib/systemd/systemd-sysv-install [--root=] <action> <name>
abstraction, replacing the direct calling of chkconfig. This allows
distributions to call their specific tools like update-rc.d without patching
systemd.

Ship systemd-sysv-install.SKELETON as an example for packagers how to implement
this.

Drop the --enable-chkconfig configure option.

Document this in README and point to it in NEWS.

2 files changed, 52 insertions, 6 deletions

diff --git a/src/systemctl/systemctl.c b/src/systemctl/systemctl.c
index f8e10a4710..f0ba83dabf 100644
--- a/src/systemctl/systemctl.c
+++ b/src/systemctl/systemctl.c
@@ -5098,7 +5098,7 @@ static int import_environment(sd_bus *bus, char **args) {
 static int enable_sysv_units(const char *verb, char **args) {
         int r = 0;
 
-#if defined(HAVE_SYSV_COMPAT) && defined(HAVE_CHKCONFIG)
+#if defined(HAVE_SYSV_COMPAT)
         unsigned f = 0;
         _cleanup_lookup_paths_free_ LookupPaths paths = {};
 
@@ -5123,7 +5123,7 @@ static int enable_sysv_units(const char *verb, char **args) {
                 _cleanup_free_ char *p = NULL, *q = NULL, *l = NULL;
                 bool found_native = false, found_sysv;
                 unsigned c = 1;
-                const char *argv[6] = { "/sbin/chkconfig", NULL, NULL, NULL, NULL };
+                const char *argv[6] = { ROOTLIBEXECDIR "/systemd-sysv-install", NULL, NULL, NULL, NULL };
                 char **k;
                 int j;
                 pid_t pid;
@@ -5161,15 +5161,13 @@ static int enable_sysv_units(const char *verb, char **args) {
                 if (!found_sysv)
                         continue;
 
-                log_info("%s is not a native service, redirecting to /sbin/chkconfig.", name);
+                log_info("%s is not a native service, redirecting to systemd-sysv-install", name);
 
                 if (!isempty(arg_root))
                         argv[c++] = q = strappend("--root=", arg_root);
 
+                argv[c++] = verb;
                 argv[c++] = basename(p);
-                argv[c++] =
-                        streq(verb, "enable") ? "on" :
-                        streq(verb, "disable") ? "off" : "--level=5";
                 argv[c] = NULL;
 
                 l = strv_join((char**)argv, " ");
@@ -5185,6 +5183,7 @@ static int enable_sysv_units(const char *verb, char **args) {
                         /* Child */
 
                         execv(argv[0], (char**) argv);
+                        log_error("Failed to execute %s: %m", argv[0]);
                         _exit(EXIT_FAILURE);
                 }
 
diff --git a/src/systemctl/systemd-sysv-install.SKELETON b/src/systemctl/systemd-sysv-install.SKELETON
new file mode 100755
index 0000000000..a53a3e6221
--- /dev/null
+++ b/src/systemctl/systemd-sysv-install.SKELETON
@@ -0,0 +1,47 @@
+#!/bin/sh
+# This script is called by "systemctl enable/disable" when the given unit is a
+# SysV init.d script. It needs to call the distribution's mechanism for
+# enabling/disabling those, such as chkconfig, update-rc.d, or similar. This
+# can optionally take a --root argument for enabling a SysV init script
+# in a chroot or similar.
+set -e
+
+usage() {
+    echo "Usage: $0 [--root=path] enable|disable|is-enabled <sysv script name>" >&2
+    exit 1
+}
+
+# parse options
+eval set -- "$(getopt -o r: --long root: -- "$@")"
+while true; do
+    case "$1" in
+        -r|--root)
+            ROOT="$2"
+            shift 2 ;;
+        --) shift ; break ;;
+        *) usage ;;
+    esac
+done
+
+NAME="$2"
+[ -n "$NAME" ] || usage
+
+case "$1" in
+    enable)
+        # call the command to enable SysV init script $NAME here
+        # (consider optional $ROOT)
+        echo "IMPLEMENT ME: enabling SysV init.d script $NAME"
+        ;;
+    disable)
+        # call the command to disable SysV init script $NAME here
+        # (consider optional $ROOT)
+        echo "IMPLEMENT ME: disabling SysV init.d script $NAME"
+        ;;
+    is-enabled)
+        # exit with 0 if $NAME is enabled, non-zero if it is disabled
+        # (consider optional $ROOT)
+        echo "IMPLEMENT ME: checking SysV init.d script $NAME"
+        ;;
+    *)
+        usage ;;
+esac