tests: add GuestDistro to Microvm

Add a new member of the Microvm class, GuestDisrto, which contains
distro-specific information. The currently included fields are
hostname (set in rootfs build), ssh_service (Ubuntu uses ssh.service vs
AL2023's sshd.service), os_release_token (displayed as part of
/etc/os-release), and shell_prompt.

These fields are used a few different tests. The GuestDistro class makes
it easier to extend if new fields are required.

Signed-off-by: James Curtis <jxcurtis@amazon.co.uk>

Author: JamesC1305

tests/framework/guest.py

@@ -0,0 +1,25 @@
+# Copyright 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Guest distro detection and distro-specific properties."""
+
+from pathlib import Path
+
+
+class GuestDistro:
+    """Distro-specific guest properties, inferred from rootfs filename."""
+
+    def __init__(self, rootfs_path: Path):
+        name = rootfs_path.stem.lower()
+        if "ubuntu" in name:
+            self.hostname = "ubuntu-fc-uvm"
+            self.ssh_service = "ssh.service"
+            self.os_release_token = "ID=ubuntu"
+            self.shell_prompt = f"{self.hostname}:~#"
+        elif "amazon" in name or "al2023" in name:
+            self.hostname = "al2023-fc-uvm"
+            self.ssh_service = "sshd.service"
+            self.os_release_token = 'ID="amzn"'
+            self.shell_prompt = f"[root@{self.hostname} ~]#"
+        else:
+            raise ValueError(f"Unknown guest distro for rootfs: {rootfs_path}")

tests/framework/microvm.py

@@ -34,6 +34,7 @@
 import host_tools.network as net_tools
 from framework import utils
 from framework.defs import DEFAULT_BINARY_DIR, MAX_API_CALL_DURATION_MS
+from framework.guest import GuestDistro
 from framework.http_api import Api
 from framework.jailer import JailerContext
 from framework.microvm_helpers import MicrovmHelpers
@@ -221,6 +222,7 @@ def __init__(
 
         self.kernel_file = None
         self.rootfs_file = None
+        self.distro = None
         self.ssh_key = None
         self.initrd_file = None
         self.boot_args = None
@@ -1062,6 +1064,7 @@ def make_snapshot(
             snapshot_type=snapshot_type,
             meta={
                 "kernel_file": str(self.kernel_file),
+                "rootfs_file": str(self.rootfs_file) if self.rootfs_file else None,
                 "vcpus_count": self.vcpus_count,
             },
         )
@@ -1125,6 +1128,9 @@ def restore_from_snapshot(
             setattr(self, key, value)
         # Adjust things just in case
         self.kernel_file = Path(self.kernel_file)
+        if self.rootfs_file:
+            self.rootfs_file = Path(self.rootfs_file)
+            self.distro = GuestDistro(self.rootfs_file)
 
         iface_overrides = []
         if rename_interfaces is not None:
@@ -1306,6 +1312,7 @@ def build(self, kernel=None, rootfs=None, **kwargs):
                 rootfs_path = Path(vm.path) / rootfs.name
                 shutil.copyfile(rootfs, rootfs_path)
             vm.rootfs_file = rootfs_path
+            vm.distro = GuestDistro(rootfs_path)
             vm.ssh_key = ssh_key
         return vm
 

tests/framework/utils_vsock.py

@@ -163,7 +163,7 @@ def check_guest_connections(vm, server_port_path, blob_path, blob_hash):
         # Needed to execute the bash script that tests for concurrent
         # vsock guest initiated connections.
         vm.ssh.check_output(
-            "echo 1024 > /sys/fs/cgroup/system.slice/ssh.service/pids.max"
+            f"echo 1024 > /sys/fs/cgroup/system.slice/{vm.distro.ssh_service}/pids.max"
         )
 
         # Build the guest worker sub-command.

tests/integration_tests/functional/test_kernel_cmdline.py

@@ -18,14 +18,14 @@ def test_init_params(uvm_plain):
     vm.memory_monitor = None
 
     # We will override the init with /bin/cat so that we try to read the
-    # Ubuntu version from the /etc/issue file.
+    # distro info from the /etc/os-release file.
     vm.basic_config(
         vcpu_count=1,
-        boot_args="console=ttyS0 reboot=k panic=1 swiotlb=noforce init=/bin/cat -- /etc/issue",
+        boot_args="console=ttyS0 reboot=k panic=1 swiotlb=noforce init=/bin/cat -- /etc/os-release",
     )
 
     vm.start()
     serial = Serial(vm)
     serial.open()
     # If the string does not show up, the test will fail.
-    serial.rx(token="Ubuntu 24.04")
+    serial.rx(token=vm.distro.os_release_token)

tests/integration_tests/functional/test_serial_io.py

@@ -31,7 +31,7 @@ def test_serial_after_snapshot(uvm_plain, microvm_factory):
     microvm.start()
 
     # looking for the # prompt at the end
-    serial.rx("ubuntu-fc-uvm:~#")
+    serial.rx(microvm.distro.shell_prompt)
 
     # Create snapshot.
     snapshot = microvm.snapshot_full()
@@ -99,7 +99,7 @@ def test_serial_active_tx_snapshot(uvm_plain, microvm_factory):
     # Send Ctrl-C to the guest to stop the ongoing transmission and regain the shell
     serial.tx("\x03", end="")
     # looking for the # prompt at the end
-    serial.rx("ubuntu-fc-uvm:~#")
+    serial.rx(vm.distro.shell_prompt)
     serial.tx("pwd")
     res = serial.rx("#")
     assert "/root" in res
@@ -124,7 +124,7 @@ def test_serial_console_login(uvm_plain_any):
 
     serial = Serial(microvm)
     serial.open()
-    serial.rx("ubuntu-fc-uvm:")
+    serial.rx(microvm.distro.shell_prompt)
     serial.tx("id")
     serial.rx("uid=0(root) gid=0(root) groups=0(root)")