Fix problem with packer's shutdown command when finished building

[ddelnano]

Fix problem with packer's shutdown command when finished building

[ddelnano]

I applied this change and created a build. It doesn't appear gracefully runs the shutdown command. Instead it seems to swallow the error that is currently produced.

Here is the output when run with this code change

==> xenserver-iso: Connected to SSH!
2021/03/29 23:07:43 packer-plugin-xenserver plugin: 2021/03/29 23:07:43 Running the provision hook
==> xenserver-iso: Step: Shutting down VM
    xenserver-iso: Executing shutdown command...
2021/03/29 23:07:43 packer-plugin-xenserver plugin: 2021/03/29 23:07:43 [DEBUG] Opening new ssh session
2021/03/29 23:07:43 packer-plugin-xenserver plugin: 2021/03/29 23:07:43 [DEBUG] starting remote command: /sbin/shutdown
==> xenserver-iso: Failed to set wall message, ignoring: Interactive authentication required.
2021/03/29 23:07:46 packer-plugin-xenserver plugin: 2021/03/29 23:07:46 [ERROR] Remote command exited with '1': /sbin/shutdown
==> xenserver-iso: Failed to call ScheduleShutdown in logind, proceeding with immediate shutdown: Interactive authentication required.
    xenserver-iso: Waiting for VM to enter Halted state...
==> xenserver-iso: Error waiting for VM to halt: Timed out
==> xenserver-iso: WARNING: Forcing hard shutdown of the VM...
    xenserver-iso: Successfully shut down VM
    xenserver-iso: Successfully set VM as a template

Here is the output when run from the latest release (v0.3.2)

==> xenserver-iso: Connected to SSH!
==> xenserver-iso: Step: Shutting down VM
    xenserver-iso: Executing shutdown command...
==> xenserver-iso: Shutdown command failed: Process exited with status 1
==> xenserver-iso: WARNING: Forcing hard shutdown of the VM...
    xenserver-iso: Successfully shut down VM
    xenserver-iso: Successfully set VM as a template

So the RemoteCmd.RunWithUi seems to not return an error even though the command itself did fail. It seems the underlying issue is actually the following lines from the output above

==> xenserver-iso: Failed to set wall message, ignoring: Interactive authentication required.
2021/03/29 23:07:46 packer-plugin-xenserver plugin: 2021/03/29 23:07:46 [ERROR] Remote command exited with '1': /sbin/shutdown
==> xenserver-iso: Failed to call ScheduleShutdown in logind, proceeding with immediate shutdown: Interactive authentication required.

[ddelnano]

It seems that the better solution would be to use the XAPI's graceful vm shutdown rather than expecting user's of this plugin to supply their own shutdown command. In fact the plugin already has the code for this 😄 (here).

This is used when the shutdown command is omitted from the packer config. I removed it from the centos example and re-ran the build and see that it is working as expected.

==> xenserver-iso: Connected to SSH!
2021/03/29 23:41:27 packer-plugin-xenserver plugin: 2021/03/29 23:41:27 Running the provision hook
==> xenserver-iso: Step: Shutting down VM
    xenserver-iso: Attempting to cleanly shutdown the VM...
    xenserver-iso: Successfully shut down VM
    xenserver-iso: Successfully set VM as a template
2021/03/29 23:41:37 packer-plugin-xenserver plugin: 2021/03/29 23:41:37 Skipping detach of 'iso_vdi_uuid'
2021/03/29 23:41:37 packer-plugin-xenserver plugin: 2021/03/29 23:41:37 Could not find VDI record in VBD 'OpaqueRef:ad300ce7-00c5-453c-91f5-4fb453dc43b9'
2021/03/29 23:41:37 packer-plugin-xenserver plugin: 2021/03/29 23:41:37 Detached VDI '696250ff-7d32-4993-a141-5823d6af859a'
2021/03/29 23:41:37 packer-plugin-xenserver plugin: 2021/03/29 23:41:37 Detached VDI 'feea5dbe-55d8-429f-a978-92cf4e3725e1'
2021/03/29 23:41:37 packer-plugin-xenserver plugin: 2021/03/29 23:41:37 Skipping detach of 'floppy_vdi_uuid'
==> xenserver-iso: Step: export artifact
==> xenserver-iso: Getting XVA https://xen.internal.ddelnano.com/export?uuid=e84eea49-60c4-9ec4-8570-7aa13474950d&session_id=OpaqueRef:b8e115c2-e8c4-4c78-8570-0bb73ce7c547
==> xenserver-iso: Download completed: packer-centos-8.3-x86_64-xenserver
2021/03/29 23:43:39 [INFO] (telemetry) ending xenserver-iso
Build 'xenserver-iso' finished after 23 minutes 2 seconds.

In order to resolve this issue, I think the documentation should be updated to reflect that without a shutdown command it is still a graceful shutdown, however, if your VM requires special shutdown handling then you can customize it if you need to.