diff --git a/nixos/tests/all-tests.nix b/nixos/tests/all-tests.nix
index f09c4b473b53..a33c791a9f69 100644
--- a/nixos/tests/all-tests.nix
+++ b/nixos/tests/all-tests.nix
@@ -63,7 +63,7 @@ let
       - `config.node.pkgs.<name>` or `config.nodes.foo.nixpkgs.pkgs.<name>` to refer
         to the Nixpkgs used on the VM guest(s).
       - `hostPkgs.<name>` when invoking commands on the VM host (e.g. in Python
-        `os.system("foo")`)
+        `subprocess.run(["foo"])`)
     - Since the runTest argument is a module instead of a function, arguments
       must be passed as option definitions.
       You may declare explicit `options` for the test parameter(s), or use the
diff --git a/nixos/tests/boot.nix b/nixos/tests/boot.nix
index a59f94b94edf..ecc6240fc888 100644
--- a/nixos/tests/boot.nix
+++ b/nixos/tests/boot.nix
@@ -203,11 +203,26 @@ in
     makeTest {
       name = "boot-uboot-extlinux";
       nodes = { };
-      testScript = ''
-        import os
+      testScript = /* py */ ''
+        import subprocess
 
         # Create a mutable linked image backed by the read-only SD image
-        if os.system("${pkgs.qemu}/bin/qemu-img create -f qcow2 -F raw -b ${sdImage} ${mutableImage}") != 0:
+        if (
+            subprocess.run(
+                [
+                    "${pkgs.qemu}/bin/qemu-img",
+                    "create",
+                    "-f",
+                    "qcow2",
+                    "-F",
+                    "raw",
+                    "-b",
+                    "${sdImage}",
+                    "${mutableImage}",
+                ]
+            ).returncode
+            != 0
+        ):
             raise RuntimeError("Could not create mutable linked image")
 
         machine = create_machine("${startCommand}")
diff --git a/nixos/tests/ec2-image.nix b/nixos/tests/ec2-image.nix
index df07d14b8ba7..b711ceadc2d5 100644
--- a/nixos/tests/ec2-image.nix
+++ b/nixos/tests/ec2-image.nix
@@ -135,7 +135,17 @@ in
               public_key = os.path.join(key_dir, "id_ed25519.pub")
 
               # Generate key pair using host SSH tools
-              ret = os.system(f"${hostPkgs.openssh}/bin/ssh-keygen -t ed25519 -f {private_key} -N \"\"")
+              ret = subprocess.run(
+                  [
+                      "${hostPkgs.openssh}/bin/ssh-keygen",
+                      "-t",
+                      "ed25519",
+                      "-f",
+                      private_key,
+                      "-N",
+                      ""
+                  ]
+              ).returncode
               if ret != 0:
                   raise Exception("Failed to generate SSH key pair")
 
diff --git a/nixos/tests/ghostunnel-modular.nix b/nixos/tests/ghostunnel-modular.nix
index bb4cef2a9f08..7fa301168a46 100644
--- a/nixos/tests/ghostunnel-modular.nix
+++ b/nixos/tests/ghostunnel-modular.nix
@@ -54,13 +54,13 @@
   };
 
   testScript = ''
-    import os
+    import subprocess
 
     # prepare certificates
 
     def cmd(command):
       print(f"+{command}")
-      r = os.system(command)
+      r = subprocess.run(command, shell=True).returncode
       if r != 0:
         raise Exception(f"Command {command} failed with exit code {r}")
 
diff --git a/nixos/tests/ghostunnel.nix b/nixos/tests/ghostunnel.nix
index acd9c4331835..58749591ffbc 100644
--- a/nixos/tests/ghostunnel.nix
+++ b/nixos/tests/ghostunnel.nix
@@ -48,13 +48,13 @@
   };
 
   testScript = ''
-    import os
+    import subprocess
 
     # prepare certificates
 
     def cmd(command):
       print(f"+{command}")
-      r = os.system(command)
+      r = subprocess.run(command, shell=True).returncode
       if r != 0:
         raise Exception(f"Command {command} failed with exit code {r}")
 
diff --git a/nixos/tests/haproxy.nix b/nixos/tests/haproxy.nix
index 107010528737..20bcd700bb58 100644
--- a/nixos/tests/haproxy.nix
+++ b/nixos/tests/haproxy.nix
@@ -69,12 +69,12 @@
       };
   };
   testScript = ''
-    import os
+    import subprocess
 
     # Helpers
     def cmd(command):
       print(f"+{command}")
-      r = os.system(command)
+      r = subprocess.run(command, shell=True).returncode
       if r != 0:
         raise Exception(f"Command {command} failed with exit code {r}")
 
diff --git a/pkgs/os-specific/linux/usbrelay/test.nix b/pkgs/os-specific/linux/usbrelay/test.nix
index b7894b0da773..60118dee1cd3 100644
--- a/pkgs/os-specific/linux/usbrelay/test.nix
+++ b/pkgs/os-specific/linux/usbrelay/test.nix
@@ -45,9 +45,11 @@ import ../../../../nixos/tests/make-test-python.nix (
       documentation.nixos.enable = false; # building nixos manual takes long time
     };
 
-    testScript = ''
+    testScript = /* py */ ''
       import os
-      if os.waitstatus_to_exitcode(os.system("lsusb -d 16c0:05df")) != 0:
+      import subprocess
+
+      if os.waitstatus_to_exitcode(subprocess.run(["lsusb", "-d", "16c0:05df"]).returncode) != 0:
           print("No USB relay detected, skipping test")
           import sys
           sys.exit(2)