[systemd-devel] Antw: [EXT] Re: Run "ipmitool power cycle" after lib/systemd/system-shutdown scripts

[Ulrich Windl]

>>> Paul Menzel <pmenzel+systemd-devel at molgen.mpg.de> schrieb am 11.02.2022 um
11:39 in Nachricht <e1361c39-5f56-e89d-f5c9-c9dafd08b81d at molgen.mpg.de>:
> Dear Adam,
> 
> 
> First, just a note (for myself), `ipmitool power` is a shortcut for 
> `ipmitool chassis power`.
> 
> 
> Am 11.02.22 um 10:54 schrieb Adam Nielsen:
>>>> After flashing the firmware of some pcie card I need to power cycle
>>>> the server to finish the flashing process.
>>>
>>> Can you please tell us the PCIe device, where a normal system reboot is
>>> not enough to reset it, so I can avoid buying it?
>> 
>> Most remote access cards work like this by design.  You might be
>> connected to a remote computer via a web browser, and need to get into
>> the BIOS to change some settings.  If you reboot the machine, the last
>> thing you want is the card to reset as well, causing your remote
>> session to drop out.  By the time the card's firmware has started and
>> you reconnect, you've probably missed the prompt to press F2/DEL/etc.
> 
> Then these remote management cards should allow to be restarted 
> separately. The BMC I had to deal with allow that.
> 
>> A lot of server hardware (e.g. SAS controllers) have onboard firmware
>> which may or may not restart during a reboot.  This is also by design,
>> because the cards can take many minutes for the firmware to boot up, so
>> by continuing to run the firmware across a restart they can cut the
>> server boot time down by many minutes, which makes a big difference if
>> you're running an OS that requires frequent reboots.
> 
> Why should the firmware need more than one second? There is no reason 
> for that. So, one more point to avoid such a device.

Well, I think (for example) that Dell's iDRAC are complete Linux systems (or similar) with a web server and other services. So it takes minutes instead of seconds until everything is loaded.

> 
>> I think most hardware vendors (at least in the server space) view a
>> reboot as a means to apply operating system updates rather than a means
>> to actually reset hardware.  This would no doubt be why programs like
>> ipmitool have an option to automatically power cycle the machine, for
>> the rare cases where you do want the hardware reset as well.
> 
> Hmm, that would be very strange. Luckily until now, a normal reboot was 
> totally fine in my experience with Dell and Supermicro servers.

The thing with LOM (Lights Out management) is that the LOM is available when the server is powered down, so it makes no sense the roboot the LOM with the server.
But usually LOM can restart itself witthout affecting the OS (Dell's IPMI watchdog excepted, maybe).

> 
>> It's only really a problem when you try to use this server hardware in
>> consumer machines, which don't really have a means to automatically
>> power cycle themselves.  Most servers seem to be configurable, to do
>> things like intercept a hardware reset and turn it into a power cycle
>> automatically, or have an "always on" mode configured where you just
>> tell the OS to shut down and power off, and the server will
>> automatically power itself back on a few seconds later, or at the very
>> least the server will have one of those remote access controllers that
>> you can use to remotely power it back on again after you've done a
>> normal shut down + power off.
>> 
>> So if you don't like the idea of parts of the system continuing to run
>> across reboots, just stay clear of hardware designed for enterprise
>> servers and you'll likely never encounter it.
> 
> Yes, that is why I asked, so I will never buy such crappy hardware. With 
> Dell and Supermicro servers, rebooting the system was all I needed. (The 
> BMC is not reset, but can be done separately while the server itself is 
> still running.)
> 
> 
> Kind regards,
> 
> Paul