Fix reboot loop

src/charm.py

@@ -273,6 +273,12 @@ def _on_install(self, _event: InstallEvent) -> None:
         """
         self.unit.status = MaintenanceStatus("Installing packages")
 
+        # Temporary solution: Upgrade the kernel due to a kernel bug in 5.15. Kernel upgrade
+        # not needed for container-based end-to-end tests.
+        if not LXD_PROFILE_YAML.exists():
+            self.unit.status = MaintenanceStatus("Upgrading kernel")
+            self._upgrade_kernel()
+
         try:
             # The `_start_services`, `_install_deps` includes retry.
             self._install_deps()
@@ -301,11 +307,6 @@ def _on_install(self, _event: InstallEvent) -> None:
                 self.unit.status = MaintenanceStatus(f"Failed to update runner binary: {err}")
                 return
 
-            # Temporary solution: Upgrade the kernel due to a kernel bug in 5.15. Kernel upgrade
-            # not needed for container-based end-to-end tests.
-            if not LXD_PROFILE_YAML.exists():
-                self._upgrade_kernel()
-
             self.unit.status = MaintenanceStatus("Starting runners")
             try:
                 self._reconcile_runners(runner_manager)
@@ -320,7 +321,9 @@ def _upgrade_kernel(self) -> None:
         """Upgrade the Linux kernel."""
         execute_command(["/usr/bin/apt-get", "update"])
         execute_command(["/usr/bin/apt-get", "install", "-qy", "linux-generic-hwe-22.04"])
-        execute_command(["reboot"])
+        _, exit_code = execute_command(["ls", "/var/run/reboot-required"], check_exit=False)
+        if exit_code == 0:
+            execute_command(["reboot"])
 
     @catch_charm_errors
     def _on_upgrade_charm(self, _event: UpgradeCharmEvent) -> None:

src/firewall.py

@@ -61,7 +61,7 @@ def get_host_ip(self) -> str:
         Returns:
             The host IP address.
         """
-        address = execute_command(
+        address, _ = execute_command(
             ["/snap/bin/lxc", "network", "get", self._network, "ipv4.address"]
         )
         return str(ipaddress.IPv4Interface(address.strip()).ip)

src/utilities.py

@@ -123,7 +123,7 @@ def secure_run_subprocess(cmd: Sequence[str], **kwargs) -> subprocess.CompletedP
     return result
 
 
-def execute_command(cmd: Sequence[str], check_exit: bool = True, **kwargs) -> str:
+def execute_command(cmd: Sequence[str], check_exit: bool = True, **kwargs) -> tuple[str, int]:
     """Execute a command on a subprocess.
 
     The command is executed with `subprocess.run`, additional arguments can be passed to it as
@@ -136,7 +136,7 @@ def execute_command(cmd: Sequence[str], check_exit: bool = True, **kwargs) -> st
         kwargs: Additional keyword arguments for the `subprocess.run` call.
 
     Returns:
-        Output on stdout.
+        Output on stdout, and the exit code.
     """
     result = secure_run_subprocess(cmd, **kwargs)
 
@@ -153,11 +153,10 @@ def execute_command(cmd: Sequence[str], check_exit: bool = True, **kwargs) -> st
 
             raise SubprocessError(cmd, err.returncode, err.stdout, err.stderr) from err
 
-    return (
-        result.stdout
-        if isinstance(result.stdout, str)
-        else result.stdout.decode(kwargs.get("encoding", "utf-8"))
-    )
+    if isinstance(result.stdout, str):
+        return (result.stdout, result.returncode)
+
+    return (result.stdout.decode(kwargs.get("encoding", "utf-8")), result.returncode)
 
 
 def get_env_var(env_var: str) -> Optional[str]: