Revert "WIP: restore /nix/var/nix as source of truth for profiles"

This reverts commit fbeef68d63.

this codebase fucking confuses me.

src/libstore/local-store.cc

@@ -217,8 +217,6 @@ LocalStore::LocalStore(const Params & params)
         }
     }
 
-    createUser(getUserName(), getuid());
-
     /* Optionally, create directories and set permissions for a
        multi-user install. */
     if (getuid() == 0 && settings.buildUsersGroup != "") {
@@ -1795,21 +1793,6 @@ void LocalStore::signRealisation(Realisation & realisation)
     }
 }
 
-void LocalStore::createUser(std::string_view userName, uid_t userId)
-{
-    // XXX: previously created gcroots/per-user; should this too?
-    auto const perUserProfile = fmt("%s/profiles/per-user/%s", stateDir, userName);
-    createDirs(perUserProfile);
-
-    if (chmod(perUserProfile.c_str(), 0755) == -1) {
-        throw SysError(errno, "changing permissions of directory '%s'", perUserProfile);
-    }
-
-    if (chown(perUserProfile.c_str(), userId, getgid()) == -1) {
-        throw SysError(errno, "changing owner of directory '%s'", perUserProfile);
-    }
-}
-
 void LocalStore::signPathInfo(ValidPathInfo & info)
 {
     // FIXME: keep secret keys in memory.

src/libstore/local-store.hh

@@ -366,8 +366,6 @@ private:
     void signPathInfo(ValidPathInfo & info);
     void signRealisation(Realisation &);
 
-    void createUser(std::string_view userName, uid_t userId) override;
-
     // XXX: Make a generic `Store` method
     ContentAddress hashCAPath(
         const ContentAddressMethod & method,

src/libstore/profiles.cc

@@ -304,95 +304,15 @@ std::string optimisticLockProfile(const Path & profile)
     return pathExists(profile) ? readLink(profile) : "";
 }
 
-/**
- * Migrates a set of profiles from one directory to another.
- *
- * Intended for migration from ~/.local/state/nix/profiles
- * to /nix/var/nix/profiles/per-user/foo
- */
-void migrateProfiles(Path const & profilesFrom, Path const & profilesTo)
-{
-    auto const oldProfiles = readDirectory(profilesFrom);
-    for (DirEntry const & oldProfileEnt : oldProfiles) {
-        auto const oldGenPath = profilesFrom + "/" + oldProfileEnt.name;
-        if (!isLink(oldGenPath)) {
-            // This is not a profile and we should not touch it.
-            continue;
-        }
-
-        auto const newGenPath = fmt("%s/%s", profilesTo, oldProfileEnt.name);
-        auto const genTarget = readLink(oldGenPath);
-        printTalkative("migrating XDG profile '%s' to '%s'", oldGenPath, newGenPath);
-        replaceSymlink(genTarget, newGenPath);
-
-        deletePath(oldGenPath);
-    }
-
-    // Now that we've deleted all the profile symlinks in ~/.local/state/nix/profiles,
-    // it's time to make ~/.local/state/nix/profiles itself a symlink.
-    if (readDirectory(profilesFrom).empty()) {
-        removeFile(profilesFrom);
-        replaceSymlink(profilesTo, profilesFrom);
-    } else {
-        // But if that directory had stuff other than profiles in it, we shouldn't delete that.
-        // Back them up for the user.
-        warn("non-profiles found in '%s'; backing up instead of deleting", profilesFrom);
-        Path backupName = profilesFrom + ".bak";
-        if (pathExists(backupName)) {
-            unsigned suffix = 0;
-            do {
-                assert(suffix < UINT_MAX);
-                suffix += 1;
-                backupName = fmt("%s.bak-%u", profilesFrom, suffix);
-            } while (pathExists(backupName));
-        }
-
-        printTalkative("backed up as '%s'", backupName);
-        renameFile(profilesFrom, backupName);
-    }
-}
-
-Path ensureProfilesDir()
-{
-    // root is special.
-    if (getuid() == 0) {
-        auto profileRoot = rootProfilesDir();
-        createDirs(profileRoot);
-        return profileRoot;
-    }
-
-    auto const localNixStateDir = createNixStateDir();
-
-    auto const homeStateProfiles = localNixStateDir + "/profiles";
-
-    auto const nixVarProfiles = fmt(
-        "%s/profiles/per-user/%s",
-        settings.nixStateDir,
-        getUserName()
-    );
-
-    if (pathExists(homeStateProfiles)) {
-        if (!isLink(homeStateProfiles)) {
-            migrateProfiles(homeStateProfiles, nixVarProfiles);
-            // The XDG-style profiles put the default profile *outside* of the directory
-            // with the rest of the profile symlinks.
-            replaceSymlink(nixVarProfiles + "/profile", localNixStateDir + "/profile");
-        }
-    } else {
-        replaceSymlink(nixVarProfiles, homeStateProfiles);
-    }
-
-    return nixVarProfiles;
-}
 
 Path profilesDir()
 {
-    try {
-        return ensureProfilesDir();
-    } catch (Error const & e) {
-        printInfo("ignoring error initializing user profiles: %s", e.what());
-        return fmt("%s/profiles/per-user/%s", settings.nixStateDir, getUserName());
-    }
+    auto profileRoot =
+        (getuid() == 0)
+        ? rootProfilesDir()
+        : createNixStateDir() + "/profiles";
+    createDirs(profileRoot);
+    return profileRoot;
 }
 
 Path rootProfilesDir()
@@ -400,10 +320,25 @@ Path rootProfilesDir()
     return settings.nixStateDir + "/profiles/per-user/root";
 }
 
+
 Path getDefaultProfile()
 {
-    return profilesDir() + "/profile";
-    Path userProfiles = profilesDir();
+    Path profileLink = settings.useXDGBaseDirectories ? createNixStateDir() + "/profile" : getHome() + "/.nix-profile";
+    try {
+        auto profile = profilesDir() + "/profile";
+        if (!pathExists(profileLink)) {
+            replaceSymlink(profile, profileLink);
+        }
+        // Backwards compatibiliy measure: Make root's profile available as
+        // `.../default` as it's what NixOS and most of the init scripts expect
+        Path globalProfileLink = settings.nixStateDir + "/profiles/default";
+        if (getuid() == 0 && !pathExists(globalProfileLink)) {
+            replaceSymlink(profile, globalProfileLink);
+        }
+        return absPath(readLink(profileLink), dirOf(profileLink));
+    } catch (Error &) {
+        return profileLink;
+    }
 }
 
 Path defaultChannelsDir()

src/libstore/store-api.hh

@@ -859,11 +859,6 @@ public:
         return toRealPath(printStorePath(storePath));
     }
 
-    virtual void createUser(std::string_view userName, uid_t userId)
-    {
-        warn("base class Store called unimplemented createUser()");
-    }
-
     /**
      * Synchronises the options of the client with those of the daemon
      * (a no-op when there’s no daemon)

src/libutil/util.hh

@@ -240,15 +240,11 @@ std::optional<Path> getSelfExe();
 
 /**
  * @return $XDG_STATE_HOME or $HOME/.local/state.
- *
- * @note Completely unrelated to settings.nixStateDir.
  */
 Path getStateDir();
 
 /**
  * Create the Nix state directory and return the path to it.
- *
- * @note Completely unrelated to settings.nixStateDir
  */
 Path createNixStateDir();
 

src/nix/daemon.cc

@@ -357,14 +357,6 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
                 //  Restore normal handling of SIGCHLD.
                 setSigChldAction(false);
 
-                auto store = openUncachedStore();
-
-                try {
-                    store->createUser(user, peer.uid);
-                } catch (SysError const & e) {
-                    printError("ignoring error while creating store per-user state: %s", e.what());
-                }
-
                 //  For debugging, stuff the pid into argv[1].
                 if (peer.pidKnown && savedArgv[1]) {
                     auto processName = std::to_string(peer.pid);
@@ -374,7 +366,7 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
                 //  Handle the connection.
                 FdSource from(remote.get());
                 FdSink to(remote.get());
-                processConnection(store, from, to, trusted, NotRecursive);
+                processConnection(openUncachedStore(), from, to, trusted, NotRecursive);
 
                 exit(0);
             }, options);