check_grub_legacy: inhibit when GRUB legacy is present

Adds a new actor checking for whether any of the GRUB devices
have the old GRUB Legacy installed. If any of such devices
is detected, the upgrade is inhibited. The GRUB Legacy is detected
by searching for the string 'GRUB version 0.94' in `file -s`
of the device.

repos/system_upgrade/el7toel8/actors/checklegacygrub/actor.py

@@ -0,0 +1,20 @@
+from leapp.actors import Actor
+from leapp.libraries.actor import check_legacy_grub as check_legacy_grub_lib
+from leapp.reporting import Report
+from leapp.tags import ChecksPhaseTag, IPUWorkflowTag
+
+
+class CheckLegacyGrub(Actor):
+    """
+    Check whether GRUB Legacy is installed in the MBR.
+
+    GRUB Legacy is deprecated since RHEL 7 in favour of GRUB2.
+    """
+
+    name = 'check_grub_legacy'
+    consumes = ()
+    produces = (Report,)
+    tags = (ChecksPhaseTag, IPUWorkflowTag)
+
+    def process(self):
+        check_legacy_grub_lib.check_grub_disks_for_legacy_grub()

repos/system_upgrade/el7toel8/actors/checklegacygrub/libraries/check_legacy_grub.py

@@ -0,0 +1,53 @@
+from leapp import reporting
+from leapp.exceptions import StopActorExecution
+from leapp.libraries.common import grub as grub_lib
+from leapp.libraries.stdlib import api, CalledProcessError, run
+from leapp.reporting import create_report
+
+# There is no grub legacy package on RHEL7, therefore, the system must have been upgraded from RHEL6
+MIGRATION_TO_GRUB2_GUIDE_URL = 'https://access.redhat.com/solutions/2643721'
+
+
+def has_legacy_grub(device):
+    try:
+        output = run(['file', '-s', device])
+    except CalledProcessError as err:
+        msg = 'Failed to determine the file type for the special device `{0}`. Full error: `{1}`'
+        api.current_logger().warning(msg.format(device, str(err)))
+
+        # According to `file` manpage, the exit code > 0 iff the file does not exists (meaning)
+        # that grub_lib.get_grub_devices() is unreliable for some reason (better stop the upgrade),
+        # or because the file type could not be determined. However, its manpage directly gives examples
+        # of file -s being used on block devices, so this should be unlikely - especially if one would
+        # consider that get_grub_devices was able to determine that it is a grub device.
+        raise StopActorExecution()
+
+    grub_legacy_version_string = 'GRUB version 0.94'
+    return grub_legacy_version_string in output['stdout']
+
+
+def check_grub_disks_for_legacy_grub():
+    # Both GRUB2 and Grub Legacy are recognized by `get_grub_devices`
+    grub_devices = grub_lib.get_grub_devices()
+
+    legacy_grub_devices = []
+    for device in grub_devices:
+        if has_legacy_grub(device):
+            legacy_grub_devices.append(device)
+
+    if legacy_grub_devices:
+        details = ('Leapp detected GRUB Legacy to be installed on the system. '
+                   'The GRUB Legacy bootloader is unsupported on RHEL7 and GRUB2 should be used instead. '
+                   'GRUB Legacy has been detected on following devices:\n'
+                   '{block_devices_fmt}\n')
+        block_devices_fmt = '\n'.join(legacy_grub_devices)
+        create_report([
+            reporting.Title("GRUB Legacy is used on the system"),
+            reporting.Summary(details.format(block_devices_fmt=block_devices_fmt)),
+            reporting.Severity(reporting.Severity.HIGH),
+            reporting.Groups([reporting.Groups.BOOT]),
+            reporting.Remediation(hint='Migrate to the GRUB2 bootloader on the reported devices.'),
+            reporting.Groups([reporting.Groups.INHIBITOR]),
+            reporting.ExternalLink(url=MIGRATION_TO_GRUB2_GUIDE_URL,
+                                   title='How to install GRUB2 after a RHEL6 to RHEL7 upgrade'),
+        ])

repos/system_upgrade/el7toel8/actors/checklegacygrub/tests/test_check_legacy_grub.py

@@ -0,0 +1,45 @@
+import pytest
+
+from leapp.libraries.actor import check_legacy_grub as check_legacy_grub_lib
+from leapp.libraries.common import grub as grub_lib
+from leapp.libraries.common.testutils import create_report_mocked
+from leapp.utils.report import is_inhibitor
+
+VDA_WITH_LEGACY_GRUB = (
+    '/dev/vda: x86 boot sector; GRand Unified Bootloader, stage1 version 0x3, '
+    'stage2 address 0x2000, stage2 segment 0x200, GRUB version 0.94; partition 1: ID=0x83, '
+    'active, starthead 32, startsector 2048, 1024000 sectors; partition 2: ID=0x83, starthead 221, '
+    'startsector 1026048, 19945472 sectors, code offset 0x48\n'
+)
+
+NVME0N1_VDB_WITH_GRUB = (
+    '/dev/nvme0n1: x86 boot sector; partition 1: ID=0x83, active, starthead 32, startsector 2048, 6291456 sectors; '
+    'partition 2: ID=0x83, starthead 191, startsector 6293504, 993921024 sectors, code offset 0x63'
+)
+
+
+@pytest.mark.parametrize(
+    ('grub_device_to_file_output', 'should_inhibit'),
+    [
+        ({'/dev/vda': VDA_WITH_LEGACY_GRUB}, True),
+        ({'/dev/nvme0n1': NVME0N1_VDB_WITH_GRUB}, False),
+        ({'/dev/vda': VDA_WITH_LEGACY_GRUB, '/dev/nvme0n1': NVME0N1_VDB_WITH_GRUB}, True)
+    ]
+)
+def test_check_legacy_grub(monkeypatch, grub_device_to_file_output, should_inhibit):
+
+    def file_cmd_mock(cmd, *args, **kwargs):
+        assert cmd[:2] == ['file', '-s']
+        return {'stdout': grub_device_to_file_output[cmd[2]]}
+
+    monkeypatch.setattr(check_legacy_grub_lib, 'create_report', create_report_mocked())
+    monkeypatch.setattr(grub_lib, 'get_grub_devices', lambda: list(grub_device_to_file_output.keys()))
+    monkeypatch.setattr(check_legacy_grub_lib, 'run', file_cmd_mock)
+
+    check_legacy_grub_lib.check_grub_disks_for_legacy_grub()
+
+    assert bool(check_legacy_grub_lib.create_report.called) == should_inhibit
+    if should_inhibit:
+        assert len(check_legacy_grub_lib.create_report.reports) == 1
+        report = check_legacy_grub_lib.create_report.reports[0]
+        assert is_inhibitor(report)