Add 'nix daemon' command

src/nix/command.hh

@@ -13,6 +13,8 @@ namespace nix {
 
 extern std::string programPath;
 
+extern char * * savedArgv;
+
 class EvalState;
 struct Pos;
 class Store;

src/nix/daemon.cc

@@ -1,3 +1,4 @@
+#include "command.hh"
 #include "shared.hh"
 #include "local-store.hh"
 #include "remote-store.hh"
@@ -150,7 +151,7 @@ static ref<Store> openUncachedStore()
 }
 
 
-static void daemonLoop(char * * argv)
+static void daemonLoop()
 {
     if (chdir("/") == -1)
         throw SysError("cannot change current directory");
@@ -232,9 +233,9 @@ static void daemonLoop(char * * argv)
                 setSigChldAction(false);
 
                 //  For debugging, stuff the pid into argv[1].
-                if (peer.pidKnown && argv[1]) {
+                if (peer.pidKnown && savedArgv[1]) {
                     string processName = std::to_string(peer.pid);
-                    strncpy(argv[1], processName.c_str(), strlen(argv[1]));
+                    strncpy(savedArgv[1], processName.c_str(), strlen(savedArgv[1]));
                 }
 
                 //  Handle the connection.
@@ -264,27 +265,8 @@ static void daemonLoop(char * * argv)
     }
 }
 
-
-static int main_nix_daemon(int argc, char * * argv)
+static void runDaemon(bool stdio)
 {
-    {
-        auto stdio = false;
-
-        parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
-            if (*arg == "--daemon")
-                ; //  ignored for backwards compatibility
-            else if (*arg == "--help")
-                showManPage("nix-daemon");
-            else if (*arg == "--version")
-                printVersion("nix-daemon");
-            else if (*arg == "--stdio")
-                stdio = true;
-            else return false;
-            return true;
-        });
-
-        initPlugins();
-
     if (stdio) {
         if (auto store = openUncachedStore().dynamic_pointer_cast<RemoteStore>()) {
             auto conn = store->openConnectionWrapper();
@@ -311,7 +293,7 @@ static int main_nix_daemon(int argc, char * * argv)
                     if (res == -1)
                         throw SysError("splicing data from stdin to daemon socket");
                     else if (res == 0)
-                            return 0;
+                        return;
                 }
             }
         } else {
@@ -322,12 +304,58 @@ static int main_nix_daemon(int argc, char * * argv)
                not `nix-daemon`'s responsibility. */
             processConnection(openUncachedStore(), from, to, Trusted, NotRecursive, [&](Store & _){});
         }
-        } else {
-            daemonLoop(argv);
-        }
+    } else
+        daemonLoop();
+}
+
+static int main_nix_daemon(int argc, char * * argv)
+{
+    {
+        auto stdio = false;
+
+        parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
+            if (*arg == "--daemon")
+                ; //  ignored for backwards compatibility
+            else if (*arg == "--help")
+                showManPage("nix-daemon");
+            else if (*arg == "--version")
+                printVersion("nix-daemon");
+            else if (*arg == "--stdio")
+                stdio = true;
+            else return false;
+            return true;
+        });
+
+        initPlugins();
+
+        runDaemon(stdio);
 
         return 0;
     }
 }
 
 static RegisterLegacyCommand r_nix_daemon("nix-daemon", main_nix_daemon);
+
+struct CmdDaemon : StoreCommand
+{
+    std::string description() override
+    {
+        return "daemon to perform store operations on behalf of non-root clients";
+    }
+
+    Category category() override { return catUtility; }
+
+    std::string doc() override
+    {
+        return
+          #include "daemon.md"
+          ;
+    }
+
+    void run(ref<Store> store) override
+    {
+        runDaemon(false);
+    }
+};
+
+static auto rCmdDaemon = registerCommand2<CmdDaemon>({"daemon"});

src/nix/daemon.md

@@ -0,0 +1,21 @@
+R""(
+
+# Example
+
+* Run the daemon in the foreground:
+
+  ```console
+  # nix daemon
+  ```
+
+# Description
+
+This command runs the Nix daemon, which is a required component in
+multi-user Nix installations. It performs build actions and other
+operations on the Nix store on behalf of non-root users. Usually you
+don't run the daemon directly; instead it's managed by a service
+management framework such as `systemd`.
+
+Note that this daemon does not fork into the background.
+
+)""

src/nix/main.cc

@@ -52,6 +52,7 @@ static bool haveInternet()
 }
 
 std::string programPath;
+char * * savedArgv;
 
 struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
 {
@@ -232,6 +233,8 @@ static auto rCmdHelp = registerCommand<CmdHelp>("help");
 
 void mainWrapped(int argc, char * * argv)
 {
+    savedArgv = argv;
+
     /* The chroot helper needs to be run before any threads have been
        started. */
     if (argc > 0 && argv[0] == chrootHelperName) {

tests/common.sh.in

@@ -73,7 +73,7 @@ startDaemon() {
     # Start the daemon, wait for the socket to appear.  !!!
     # ‘nix-daemon’ should have an option to fork into the background.
     rm -f $NIX_STATE_DIR/daemon-socket/socket
-    nix-daemon &
+    nix daemon &
     for ((i = 0; i < 30; i++)); do
         if [ -e $NIX_DAEMON_SOCKET_PATH ]; then break; fi
         sleep 1