diff --git a/src/decman/core/command.py b/src/decman/core/command.py
index 5e36023..bbcc708 100644
--- a/src/decman/core/command.py
+++ b/src/decman/core/command.py
@@ -4,6 +4,7 @@ import os
 import pty
 import pwd
 import select
+import shlex
 import shutil
 import struct
 import subprocess
@@ -13,6 +14,7 @@ import tty
 import typing
 
 import decman.core.error as errors
+import decman.core.output as output
 
 
 def get_user_info(user: str) -> tuple[int, int]:
@@ -55,6 +57,8 @@ def pty_run(
     if not sys.stdin.isatty():
         raise OSError(errno.ENOTTY, "Stdin is not a TTY.")
 
+    output.print_debug(f"Running command '{shlex.join(command)}'")
+
     env = _build_env(user=user, env_overrides=env_overrides, mimic_login=mimic_login)
 
     pid, master_fd = pty.fork()
@@ -90,6 +94,8 @@ def run(
     if not command:
         return 0, ""
 
+    output.print_debug(f"Running command '{shlex.join(command)}'")
+
     env = _build_env(user=user, env_overrides=env_overrides, mimic_login=mimic_login)
     uid, gid = None, None
 
@@ -104,9 +110,9 @@ def run(
     except OSError as error:
         # Mirror PTY behavior: "<cmd>: <error>\n" and errno-based exit code
         msg = error.strerror or str(error)
-        output = f"{command[0]}: {msg}\n"
+        text_output = f"{command[0]}: {msg}\n"
         code = error.errno if error.errno and error.errno < 128 else 127
-        return code, output
+        return code, text_output
 
     return process.returncode, stdout.decode("utf-8", errors="replace")
 
diff --git a/src/decman/core/output.py b/src/decman/core/output.py
index 5b4ccfe..a36267e 100644
--- a/src/decman/core/output.py
+++ b/src/decman/core/output.py
@@ -133,6 +133,14 @@ def print_debug(msg: str):
         print(f"{_tag()} {_gray('DEBUG')}: {msg}")
 
 
+def print_command_output(msg: str):
+    """
+    Prints command output without a DECMAN tag if debug messages are enabled.
+    """
+    if config.debug_output:
+        print(msg)
+
+
 # ─────────────────────────────
 # List printing
 # ─────────────────────────────
diff --git a/src/decman/plugins/__init__.py b/src/decman/plugins/__init__.py
index f46779c..e264087 100644
--- a/src/decman/plugins/__init__.py
+++ b/src/decman/plugins/__init__.py
@@ -1,4 +1,5 @@
 import importlib.metadata as metadata
+import typing
 
 import decman.core.module as module
 import decman.core.store as _store
@@ -45,6 +46,24 @@ class Plugin:
         """
 
 
+def run_method_with_attribute(mod: module.Module, attribute: str) -> typing.Any:
+    """
+    Runs the method with the given attribute in the module and returns its returned value.
+    Returns none if no such method is found.
+
+    Only the first found method with the attribute is ran.
+    """
+    for name in dir(mod):
+        attr = getattr(mod, name)
+        if not callable(attr):
+            continue
+        func = getattr(attr, "__func__", attr)
+        if getattr(func, attribute, False):
+            return attr()
+
+    return None
+
+
 def available_plugins() -> dict[str, Plugin]:
     """
     Returns all available plugins.
diff --git a/src/decman/plugins/systemd.py b/src/decman/plugins/systemd.py
index 27c84e2..70d1f40 100644
--- a/src/decman/plugins/systemd.py
+++ b/src/decman/plugins/systemd.py
@@ -1,5 +1,296 @@
+import shutil
+
+import decman.core.command as command
+import decman.core.module as module
+import decman.core.output as output
+import decman.core.store as _store
 import decman.plugins as plugins
 
 
+def units(fn):
+    """
+    Annotate that this function returns a set of systemd unit names that should be enabled.
+    """
+    fn.__systemd__units__ = True
+    return fn
+
+
+def user_units(fn):
+    """
+    Annotate that this function returns a dict of users and systemd user unit names that should be
+    enabled.
+    """
+    fn.__systemd__user__units__ = True
+    return fn
+
+
+class SystemdCommands:
+    """
+    Default commands for the Systemd plugin.
+    """
+
+    def enable_units(self, units: set[str]) -> list[str]:
+        """
+        Running this command enables the given systemd units.
+        """
+        return ["systemctl", "enable"] + list(units)
+
+    def disable_units(self, units: set[str]) -> list[str]:
+        """
+        Running this command disables the given systemd units.
+        """
+        return ["systemctl", "disable"] + list(units)
+
+    def enable_user_units(self, units: set[str], user: str) -> list[str]:
+        """
+        Running this command enables the given systemd units for the user.
+        """
+        return ["systemctl", "--user", "-M", f"{user}@", "enable"] + list(units)
+
+    def disable_user_units(self, units: set[str], user: str) -> list[str]:
+        """
+        Running this command disables the given systemd units for the user.
+        """
+        return ["systemctl", "--user", "-M", f"{user}@", "disable"] + list(units)
+
+    def daemon_reload(self) -> list[str]:
+        """
+        Running this command reloads the systemd daemon.
+        """
+        return ["systemctl", "daemon-reload"]
+
+    def user_daemon_reload(self, user: str) -> list[str]:
+        """
+        Running this command reloads the systemd daemon for the given user.
+        """
+        return ["systemctl", "--user", "-M", f"{user}@", "daemon-reload"]
+
+
 class Systemd(plugins.Plugin):
     NAME = "systemd"
+
+    def __init__(self) -> None:
+        self.enabled_systemd_units: set[str] = set()
+        self.enabled_systemd_user_units: dict[str, set[str]] = {}
+        self.commands = SystemdCommands()
+
+    def available(self) -> bool:
+        return shutil.which("systemctl") is not None
+
+    def process_modules(self, store: _store.Store, modules: set[module.Module]):
+        # These store keys are used to track changes in modules.
+        # This way when these change, module can be marked as changed
+        store.ensure("systemd_units_for_module", {})
+        store.ensure("systemd_user_units_for_module", {})
+
+        for mod in modules:
+            store["systemd_units_for_module"].setdefault(mod.name, set())
+            store["systemd_user_units_for_module"].setdefault(mod.name, {})
+
+            units = plugins.run_method_with_attribute(mod, "__systemd__units__") or set()
+            user_units = plugins.run_method_with_attribute(mod, "__systemd__user__units__") or {}
+
+            if store["systemd_units_for_module"][mod.name] != units:
+                mod._changed = True
+
+            if store["systemd_user_units_for_module"][mod.name] != user_units:
+                mod._changed = True
+
+            self.enabled_systemd_units |= units
+            for user, u_units in user_units.items():
+                self.enabled_systemd_user_units.setdefault(user, set()).update(u_units)
+
+            store["systemd_units_for_module"][mod.name] = units
+            store["systemd_user_units_for_module"][mod.name] = user_units
+
+    def apply(
+        self, store: _store.Store, dry_run: bool = False, params: list[str] | None = None
+    ) -> bool:
+        store.ensure("systemd_units", set())
+        store.ensure("systemd_user_units", {})
+
+        units_to_enable = set()
+        units_to_disable = set()
+        user_units_to_enable: dict[str, set[str]] = {}
+        user_units_to_disable: dict[str, set[str]] = {}
+
+        for unit in self.enabled_systemd_units:
+            if unit not in store["systemd_units"]:
+                units_to_enable.add(unit)
+
+        for unit in store["systemd_units"]:
+            if unit not in self.enabled_systemd_units:
+                units_to_disable.add(unit)
+
+        for user, units in self.enabled_systemd_user_units.items():
+            store["systemd_user_units"].setdefault(user, set())
+            user_units_to_enable.setdefault(user, set())
+
+            for unit in units:
+                if unit not in store["systemd_user_units"][user]:
+                    user_units_to_enable[user].add(unit)
+
+        for user, units in store["systemd_user_units"].items():
+            self.enabled_systemd_user_units.setdefault(user, set())
+            user_units_to_disable.setdefault(user, set())
+
+            for unit in units:
+                if unit not in self.enabled_systemd_user_units[user]:
+                    user_units_to_disable[user].add(unit)
+
+        output.print_info("Reloading systemd daemon.")
+        if not dry_run:
+            if not self.reload_daemon():
+                return False
+
+        output.print_info("Reloading systemd daemon for users.")
+        if not dry_run:
+            for user in user_units_to_enable.keys() | user_units_to_disable.keys():
+                if not self.reload_user_daemon(user):
+                    return False
+
+        output.print_list("Enabling systemd units:", list(units_to_enable))
+        if not dry_run:
+            if not self.enable_units(store, units_to_enable):
+                return False
+
+        output.print_list("Disabling systemd units:", list(units_to_disable))
+        if not dry_run:
+            if not self.disable_units(store, units_to_disable):
+                return False
+
+        for user, units in user_units_to_enable.items():
+            output.print_list(f"Enabling systemd units for {user}:", list(units))
+            if not dry_run:
+                if not self.enable_user_units(store, units, user):
+                    return False
+
+        for user, units in user_units_to_disable.items():
+            output.print_list(f"Disabling systemd units for {user}:", list(units))
+            if not dry_run:
+                if not self.disable_user_units(store, units, user):
+                    return False
+
+        return True
+
+    def enable_units(self, store: _store.Store, units: set[str]) -> bool:
+        """
+        Enables the given units.
+
+        Returns ``True`` if the operation was successful.
+        """
+        if not units:
+            return True
+
+        code, text = command.run(self.commands.enable_units(units))
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error(f"Failed to enable systemd units '{' '.join(units)}'.")
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+
+        store["systemd_units"] |= units
+
+        return True
+
+    def disable_units(self, store: _store.Store, units: set[str]) -> bool:
+        """
+        Disables the given units.
+
+        Returns ``True`` if the operation was successful.
+        """
+        if not units:
+            return True
+
+        code, text = command.run(self.commands.disable_units(units))
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error(f"Failed to disable systemd units '{' '.join(units)}'.")
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+
+        store["systemd_units"] -= units
+
+        return True
+
+    def enable_user_units(self, store: _store.Store, units: set[str], user: str) -> bool:
+        """
+        Enables the given units for the given user.
+
+        Returns ``True`` if the operation was successful.
+        """
+        if not units:
+            return True
+
+        code, text = command.run(self.commands.enable_user_units(units, user))
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error(
+                f"Failed to enable systemd units '{' '.join(units)}' for user {user}."
+            )
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+
+        store["systemd_user_units"].setdefault(user, set())
+        store["systemd_user_units"][user] |= units
+
+        return True
+
+    def disable_user_units(self, store: _store.Store, units: set[str], user: str) -> bool:
+        """
+        Disables the given units for the given user.
+
+        Returns ``True`` if the operation was successful.
+        """
+        if not units:
+            return True
+
+        code, text = command.run(self.commands.disable_user_units(units, user))
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error(
+                f"Failed to disable systemd units '{' '.join(units)}' for user {user}."
+            )
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+
+        store["systemd_user_units"].setdefault(user, set())
+        store["systemd_user_units"][user] -= units
+
+        return True
+
+    def reload_user_daemon(self, user: str) -> bool:
+        """
+        Reloads the user's systemd daemon.
+
+        Returns ``True`` if the operation was successful.
+        """
+
+        code, text = command.run(self.commands.user_daemon_reload(user))
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error(f"Failed to reload systemd daemon for {user}.")
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+        return True
+
+    def reload_daemon(self) -> bool:
+        """
+        Reloads the systemd daemon.
+
+        Returns ``True`` if the operation was successful.
+        """
+
+        code, text = command.run(self.commands.daemon_reload())
+        output.print_command_output(text)
+        if code != 0:
+            output.print_error("Failed to reload systemd daemon.")
+            output.print_error(f"Command exited with code: {code}")
+            output.print_error(f"{text}")
+            return False
+        return True
diff --git a/tests/test_decman_plugins.py b/tests/test_decman_plugins.py
new file mode 100644
index 0000000..a024a02
--- /dev/null
+++ b/tests/test_decman_plugins.py
@@ -0,0 +1,26 @@
+from decman.core.module import Module
+from decman.plugins import run_method_with_attribute
+
+
+def mark(attr):
+    attr.__flag__ = True
+    return attr
+
+
+def test_runs_marked_method_and_returns_value():
+    class M(Module):
+        @mark
+        def foo(self):
+            return 123
+
+    m = M("m")
+    assert run_method_with_attribute(m, "__flag__") == 123
+
+
+def test_returns_none_if_no_method_has_attribute():
+    class M(Module):
+        def foo(self):
+            return 1
+
+    m = M("m")
+    assert run_method_with_attribute(m, "__flag__") is None
diff --git a/tests/test_decman_plugins_systemd.py b/tests/test_decman_plugins_systemd.py
new file mode 100644
index 0000000..285f010
--- /dev/null
+++ b/tests/test_decman_plugins_systemd.py
@@ -0,0 +1,366 @@
+import pytest
+
+from decman.plugins import systemd as systemd_mod
+
+
+class DummyStore(dict):
+    def ensure(self, key, default):
+        if key not in self:
+            self[key] = default
+
+
+class DummyModule:
+    def __init__(self, name: str):
+        self.name = name
+        self._changed = False
+
+
+@pytest.fixture
+def store():
+    return DummyStore()
+
+
+@pytest.fixture
+def systemd():
+    return systemd_mod.Systemd()
+
+
+def test_units_decorator_sets_attribute():
+    @systemd_mod.units
+    def fn():
+        pass
+
+    assert getattr(fn, "__systemd__units__", False) is True
+
+
+def test_user_units_decorator_sets_attribute():
+    @systemd_mod.user_units
+    def fn():
+        pass
+
+    assert getattr(fn, "__systemd__user__units__", False) is True
+
+
+def test_available_true_if_systemctl_found(monkeypatch, systemd):
+    called = {}
+
+    def fake_which(name):
+        called["name"] = name
+        return "/bin/systemctl"
+
+    monkeypatch.setattr(systemd_mod.shutil, "which", fake_which)
+    assert systemd.available() is True
+    assert called["name"] == "systemctl"
+
+
+def test_available_false_if_systemctl_missing(monkeypatch, systemd):
+    monkeypatch.setattr(systemd_mod.shutil, "which", lambda name: None)
+    assert systemd.available() is False
+
+
+def test_process_modules_marks_changed_and_updates_store(monkeypatch, store, systemd):
+    # initial store empty; ensure keys will be created
+    m1 = DummyModule("mod1")
+    m2 = DummyModule("mod2")
+
+    def fake_run_method(mod, attr):
+        if mod is m1 and attr == "__systemd__units__":
+            return {"a.service"}
+        if mod is m1 and attr == "__systemd__user__units__":
+            return {"alice": {"u1.service"}}
+        # m2 has no units
+        return None
+
+    monkeypatch.setattr(systemd_mod.plugins, "run_method_with_attribute", fake_run_method)
+
+    systemd.process_modules(store, {m1, m2})
+
+    # m1 changed from default -> marked _changed
+    assert m1._changed is True
+    # m2 had no units
+    assert m2._changed is False
+
+    # enabled units aggregated
+    assert systemd.enabled_systemd_units == {"a.service"}
+    assert systemd.enabled_systemd_user_units == {"alice": {"u1.service"}}
+
+    # store updated per module
+    assert store["systemd_units_for_module"]["mod1"] == {"a.service"}
+    assert store["systemd_user_units_for_module"]["mod1"] == {"alice": {"u1.service"}}
+    assert store["systemd_units_for_module"]["mod2"] == set()
+    assert store["systemd_user_units_for_module"]["mod2"] == {}
+
+
+def test_process_modules_no_change_second_run(monkeypatch, store, systemd):
+    m1 = DummyModule("mod1")
+
+    def fake_run_method(mod, attr):
+        if attr == "__systemd__units__":
+            return {"a.service"}
+        if attr == "__systemd__user__units__":
+            return {"alice": {"u1.service"}}
+        return None
+
+    monkeypatch.setattr(systemd_mod.plugins, "run_method_with_attribute", fake_run_method)
+
+    # first run populates store
+    systemd.process_modules(store, {m1})
+    m1._changed = False
+
+    # new instance (fresh per-process in real usage)
+    systemd2 = systemd_mod.Systemd()
+    monkeypatch.setattr(systemd_mod.plugins, "run_method_with_attribute", fake_run_method)
+
+    systemd2.process_modules(store, {m1})
+
+    # values in store are same -> _changed stays False
+    assert m1._changed is False
+
+
+def test_apply_enables_and_disables_units_and_user_units(store):
+    s = systemd_mod.Systemd()
+
+    # Current enabled according to modules
+    s.enabled_systemd_units = {"new.service"}
+    s.enabled_systemd_user_units = {"alice": {"newuser.service"}}
+
+    # Store says we had an old unit enabled before
+    store["systemd_units"] = {"old.service"}
+    store["systemd_user_units"] = {"alice": {"olduser.service"}}
+
+    calls = []
+
+    def fake_reload_daemon():
+        calls.append(("reload_daemon",))
+        return True
+
+    def fake_reload_user_daemon(user):
+        calls.append(("reload_user_daemon", user))
+        return True
+
+    def fake_enable_units(store_arg, units_arg):
+        calls.append(("enable_units", frozenset(units_arg)))
+        store_arg["systemd_units"] |= units_arg
+        return True
+
+    def fake_disable_units(store_arg, units_arg):
+        calls.append(("disable_units", frozenset(units_arg)))
+        store_arg["systemd_units"] -= units_arg
+        return True
+
+    def fake_enable_user_units(store_arg, units_arg, user):
+        calls.append(("enable_user_units", user, frozenset(units_arg)))
+        store_arg["systemd_user_units"].setdefault(user, set()).update(units_arg)
+        return True
+
+    def fake_disable_user_units(store_arg, units_arg, user):
+        calls.append(("disable_user_units", user, frozenset(units_arg)))
+        store_arg["systemd_user_units"].setdefault(user, set()).difference_update(units_arg)
+        return True
+
+    # patch instance methods (no self parameter expected)
+    s.reload_daemon = fake_reload_daemon
+    s.reload_user_daemon = fake_reload_user_daemon
+    s.enable_units = fake_enable_units
+    s.disable_units = fake_disable_units
+    s.enable_user_units = fake_enable_user_units
+    s.disable_user_units = fake_disable_user_units
+
+    result = s.apply(store, dry_run=False, params=None)
+    assert result is True
+
+    # reloads called once
+    assert ("reload_daemon",) in calls
+    assert ("reload_user_daemon", "alice") in calls
+
+    # enable/disable correct units
+    assert ("enable_units", frozenset({"new.service"})) in calls
+    assert ("disable_units", frozenset({"old.service"})) in calls
+    assert ("enable_user_units", "alice", frozenset({"newuser.service"})) in calls
+    assert ("disable_user_units", "alice", frozenset({"olduser.service"})) in calls
+
+    # store reconciled
+    assert store["systemd_units"] == {"new.service"}
+    assert store["systemd_user_units"]["alice"] == {"newuser.service"}
+
+
+def test_apply_dry_run_does_not_mutate_store_or_call_commands(store):
+    s = systemd_mod.Systemd()
+    s.enabled_systemd_units = {"new.service"}
+    s.enabled_systemd_user_units = {"alice": {"newuser.service"}}
+
+    store["systemd_units"] = {"old.service"}
+    store["systemd_user_units"] = {"alice": {"olduser.service"}}
+
+    called = {"reload": False, "enable": False, "disable": False}
+
+    s.reload_daemon = lambda: called.__setitem__("reload", True) or True
+    s.reload_user_daemon = lambda user: called.__setitem__("reload", True) or True
+    s.enable_units = lambda st, u: called.__setitem__("enable", True) or True
+    s.disable_units = lambda st, u: called.__setitem__("disable", True) or True
+    s.enable_user_units = lambda st, u, user: called.__setitem__("enable", True) or True
+    s.disable_user_units = lambda st, u, user: called.__setitem__("disable", True) or True
+
+    result = s.apply(store, dry_run=True, params=None)
+    assert result is True
+
+    # no commands should be called
+    assert called == {"reload": False, "enable": False, "disable": False}
+
+    # store unchanged
+    assert store["systemd_units"] == {"old.service"}
+    assert store["systemd_user_units"]["alice"] == {"olduser.service"}
+
+
+def test_enable_units_success(monkeypatch, store, systemd):
+    store["systemd_units"] = {"old.service"}
+
+    def fake_run(cmd):
+        assert cmd[0] == "systemctl"
+        assert cmd[1] == "enable"
+        assert "new.service" in cmd[2:]
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.enable_units(store, {"new.service"})
+    assert result is True
+    assert store["systemd_units"] == {"old.service", "new.service"}
+
+
+def test_enable_units_failure_does_not_update_store(monkeypatch, store, systemd):
+    store["systemd_units"] = {"old.service"}
+
+    def fake_run(cmd):
+        return 1, "error"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.enable_units(store, {"new.service"})
+    assert result is False
+    # unchanged
+    assert store["systemd_units"] == {"old.service"}
+
+
+def test_disable_units_success(monkeypatch, store, systemd):
+    store["systemd_units"] = {"old.service", "new.service"}
+
+    def fake_run(cmd):
+        assert cmd[0] == "systemctl"
+        assert cmd[1] == "disable"
+        assert "new.service" in cmd[2:]
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.disable_units(store, {"new.service"})
+    assert result is True
+    assert store["systemd_units"] == {"old.service"}
+
+
+def test_disable_units_failure_does_not_update_store(monkeypatch, store, systemd):
+    store["systemd_units"] = {"old.service", "new.service"}
+
+    def fake_run(cmd):
+        return 1, "error"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.disable_units(store, {"new.service"})
+    assert result is False
+    assert store["systemd_units"] == {"old.service", "new.service"}
+
+
+def test_enable_user_units_success(monkeypatch, store, systemd):
+    store["systemd_user_units"] = {"alice": {"olduser.service"}}
+
+    def fake_run(cmd):
+        assert cmd[0] == "systemctl"
+        assert "--user" in cmd
+        assert "enable" in cmd
+        assert "newuser.service" in cmd
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.enable_user_units(store, {"newuser.service"}, "alice")
+    assert result is True
+    assert store["systemd_user_units"]["alice"] == {
+        "olduser.service",
+        "newuser.service",
+    }
+
+
+def test_enable_user_units_failure_does_not_update_store(monkeypatch, store, systemd):
+    store["systemd_user_units"] = {"alice": {"olduser.service"}}
+
+    def fake_run(cmd):
+        return 1, "error"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.enable_user_units(store, {"newuser.service"}, "alice")
+    assert result is False
+    assert store["systemd_user_units"]["alice"] == {"olduser.service"}
+
+
+def test_disable_user_units_success(monkeypatch, store, systemd):
+    store["systemd_user_units"] = {"alice": {"olduser.service", "newuser.service"}}
+
+    def fake_run(cmd):
+        assert cmd[0] == "systemctl"
+        assert "--user" in cmd
+        assert "disable" in cmd
+        assert "newuser.service" in cmd
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.disable_user_units(store, {"newuser.service"}, "alice")
+    assert result is True
+    assert store["systemd_user_units"]["alice"] == {"olduser.service"}
+
+
+def test_disable_user_units_failure_does_not_update_store(monkeypatch, store, systemd):
+    store["systemd_user_units"] = {"alice": {"olduser.service", "newuser.service"}}
+
+    def fake_run(cmd):
+        return 1, "error"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+
+    result = systemd.disable_user_units(store, {"newuser.service"}, "alice")
+    assert result is False
+    assert store["systemd_user_units"]["alice"] == {
+        "olduser.service",
+        "newuser.service",
+    }
+
+
+def test_reload_daemon_uses_command_run(monkeypatch, systemd):
+    called = {}
+
+    def fake_run(cmd):
+        called["cmd"] = cmd
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+    result = systemd.reload_daemon()
+    assert result is True
+    assert called["cmd"][:2] == ["systemctl", "daemon-reload"]
+
+
+def test_reload_user_daemon_uses_command_run(monkeypatch, systemd):
+    called = {}
+
+    def fake_run(cmd):
+        called["cmd"] = cmd
+        return 0, "ok"
+
+    monkeypatch.setattr(systemd_mod.command, "run", fake_run)
+    result = systemd.reload_user_daemon("alice")
+    assert result is True
+    cmd = called["cmd"]
+    assert cmd[0] == "systemctl"
+    assert "--user" in cmd
+    assert "daemon-reload" in cmd