diff --git a/doc/manual/src/installation/installing-binary.md b/doc/manual/src/installation/installing-binary.md
index ed0f65177..2d007ca1b 100644
--- a/doc/manual/src/installation/installing-binary.md
+++ b/doc/manual/src/installation/installing-binary.md
@@ -13,7 +13,7 @@ for your platform:
 - multi-user on macOS
 
   > **Notes on read-only filesystem root in macOS 10.15 Catalina +**
-  > 
+  >
   > - It took some time to support this cleanly. You may see posts,
   >   examples, and tutorials using obsolete workarounds.
   > - Supporting it cleanly made macOS installs too complex to qualify
@@ -31,8 +31,8 @@ $ sh <(curl -L https://nixos.org/nix/install) --no-daemon
 ```
 
 This will perform a single-user installation of Nix, meaning that `/nix`
-is owned by the invoking user. You should run this under your usual user
-account, *not* as root. The script will invoke `sudo` to create `/nix`
+is owned by the invoking user. You can run this under your usual user
+account or root. The script will invoke `sudo` to create `/nix`
 if it doesn’t already exist. If you don’t have `sudo`, you should
 manually create `/nix` first as root, e.g.:
 
@@ -71,11 +71,11 @@ $ sh <(curl -L https://nixos.org/nix/install) --daemon
 
 The multi-user installation of Nix will create build users between the
 user IDs 30001 and 30032, and a group with the group ID 30000. You
-should run this under your usual user account, *not* as root. The script
+can run this under your usual user account or root. The script
 will invoke `sudo` as needed.
 
 > **Note**
-> 
+>
 > If you need Nix to use a different group ID or user ID set, you will
 > have to download the tarball manually and [edit the install
 > script](#installing-from-a-binary-tarball).
@@ -168,7 +168,7 @@ and `/etc/zshrc` which you may remove.
    removed next.
 
 7. Remove the Nix Store volume:
-   
+
    ```console
    sudo diskutil apfs deleteVolume /nix
    ```
@@ -189,7 +189,7 @@ and `/etc/zshrc` which you may remove.
    identifier.
 
 > **Note**
-> 
+>
 > After you complete the steps here, you will still have an empty `/nix`
 > directory. This is an expected sign of a successful uninstall. The empty
 > `/nix` directory will disappear the next time you reboot.
diff --git a/scripts/install-multi-user.sh b/scripts/install-multi-user.sh
index e6864eaaf..a9f3e74dc 100644
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@@ -59,6 +59,30 @@ headless() {
     fi
 }
 
+is_root() {
+    if [ "$EUID" -eq 0 ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+is_os_linux() {
+    if [ "$(uname -s)" = "Linux" ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
+is_os_darwin() {
+    if [ "$(uname -s)" = "Darwin" ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
 contact_us() {
     echo "You can open an issue at https://github.com/nixos/nix/issues"
     echo ""
@@ -313,10 +337,15 @@ __sudo() {
 _sudo() {
     local expl="$1"
     shift
-    if ! headless; then
+    if ! headless || is_root; then
         __sudo "$expl" "$*" >&2
     fi
-    sudo "$@"
+
+    if is_root; then
+        env "$@"
+    else
+        sudo "$@"
+    fi
 }
 
 
@@ -423,7 +452,7 @@ EOF
         fi
     done
 
-    if [ "$(uname -s)" = "Linux" ] && [ ! -e /run/systemd/system ]; then
+    if is_os_linux && [ ! -e /run/systemd/system ]; then
         warning <<EOF
 We did not detect systemd on your system. With a multi-user install
 without systemd you will have to manually configure your init system to
@@ -865,24 +894,14 @@ EOF
           install -m 0664 "$SCRATCH/nix.conf" /etc/nix/nix.conf
 }
 
-main() {
-    # TODO: I've moved this out of validate_starting_assumptions so we
-    # can fail faster in this case. Sourcing install-darwin... now runs
-    # `touch /` to detect Read-only root, but it could update times on
-    # pre-Catalina macOS if run as root user.
-    if [ "$EUID" -eq 0 ]; then
-        failure <<EOF
-Please do not run this script with root privileges. I will call sudo
-when I need to.
-EOF
-    fi
 
+main() {
     check_selinux
 
-    if [ "$(uname -s)" = "Darwin" ]; then
+    if is_os_darwin; then
         # shellcheck source=./install-darwin-multi-user.sh
         . "$EXTRACTED_NIX_PATH/install-darwin-multi-user.sh"
-    elif [ "$(uname -s)" = "Linux" ]; then
+    elif is_os_linux; then
         # shellcheck source=./install-systemd-multi-user.sh
         . "$EXTRACTED_NIX_PATH/install-systemd-multi-user.sh" # most of this works on non-systemd distros also
     else
@@ -890,7 +909,10 @@ EOF
     fi
 
     welcome_to_nix
-    chat_about_sudo
+
+    if ! is_root; then
+        chat_about_sudo
+    fi
 
     cure_artifacts
     # TODO: there's a tension between cure and validate. I moved the
diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 405135d5a..17246ccbc 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -913,12 +913,6 @@ void DerivationGoal::buildDone()
             outputPaths
         );
 
-        if (buildMode == bmCheck) {
-            cleanupPostOutputsRegisteredModeCheck();
-            done(BuildResult::Built, std::move(builtOutputs));
-            return;
-        }
-
         cleanupPostOutputsRegisteredModeNonCheck();
 
         /* Repeat the build if necessary. */
diff --git a/src/nix/bundle.md b/src/nix/bundle.md
index 2bb70711f..a18161a3c 100644
--- a/src/nix/bundle.md
+++ b/src/nix/bundle.md
@@ -44,7 +44,7 @@ flake output attributes:
 
 * `bundlers.<system>.default`
 
-If an attribute *name* is given, `nix run` tries the following flake
+If an attribute *name* is given, `nix bundle` tries the following flake
 output attributes:
 
 * `bundlers.<system>.<name>`
diff --git a/tests/check.sh b/tests/check.sh
index ab48ff865..495202781 100644
--- a/tests/check.sh
+++ b/tests/check.sh
@@ -40,6 +40,14 @@ nix-build check.nix -A deterministic --argstr checkBuildId $checkBuildId \
 if grep -q 'may not be deterministic' $TEST_ROOT/log; then false; fi
 checkBuildTempDirRemoved $TEST_ROOT/log
 
+nix build -f check.nix deterministic --rebuild --repeat 1 \
+    --argstr checkBuildId $checkBuildId --keep-failed --no-link \
+    2> $TEST_ROOT/log
+if grep -q 'checking is not possible' $TEST_ROOT/log; then false; fi
+# Repeat is set to 1, ie. nix should build deterministic twice.
+if [ "$(grep "checking outputs" $TEST_ROOT/log | wc -l)" -ne 2 ]; then false; fi
+checkBuildTempDirRemoved $TEST_ROOT/log
+
 nix-build check.nix -A nondeterministic --argstr checkBuildId $checkBuildId \
     --no-out-link 2> $TEST_ROOT/log
 checkBuildTempDirRemoved $TEST_ROOT/log
@@ -50,6 +58,12 @@ grep 'may not be deterministic' $TEST_ROOT/log
 [ "$status" = "104" ]
 checkBuildTempDirRemoved $TEST_ROOT/log
 
+nix build -f check.nix nondeterministic --rebuild --repeat 1 \
+    --argstr checkBuildId $checkBuildId --keep-failed --no-link \
+    2> $TEST_ROOT/log || status=$?
+grep 'may not be deterministic' $TEST_ROOT/log
+checkBuildTempDirRemoved $TEST_ROOT/log
+
 nix-build check.nix -A nondeterministic --argstr checkBuildId $checkBuildId \
     --no-out-link --check --keep-failed 2> $TEST_ROOT/log || status=$?
 grep 'may not be deterministic' $TEST_ROOT/log