docs/src/content/docs/advanced/bmc.md
:::caution[Beta] Reading — power state and sensors — has been verified against exactly one machine, and power control against none by anything automated. Both work; how much of the hardware in the world they work on is not yet known. See Hardware this has run against.
Treat the power operations the way you would treat a physical button on a machine you are not standing next to. :::
A BMC is a small computer on the server's motherboard with its own power rail and its own network port. It answers while the host is off, hung, or has no operating system on it at all — which is the one thing SSH and a monitor agent cannot do.
ServerBox talks to it over Redfish, the HTTPS API most enterprise hardware from roughly 2016 on provides. Older machines that only speak IPMI are not supported; see How it works for why that line is where it is.
Power: on means the
machine is running and something else is wrong; Power: off means it is off.
Those are different problems and the server card cannot otherwise tell them
apart.A BMC sits beside SSH rather than instead of it. One server can have both, and normally does.
https://10.0.0.9.
Only the scheme, host and port are used; the rest of the path is fixed by
the specification.The BMC card then appears on the server's detail page, and the power button gains the hardware operations.
A BMC account is a record of its own, not a username and password typed into each server. BMCs are provisioned a rack at a time and usually answer to one account, so twenty machines share one — and rotating that password is one edit rather than twenty.
Manage them at Settings → BMC accounts. Each entry shows how many servers use it, because editing one changes what all of them use.
Deleting an account does not delete the servers that used it. They keep their address and lose the account, which the editor then says.
BMCs ship self-signed certificates, so there is nothing for a certificate authority to vouch for. ServerBox does not offer an "ignore the certificate" switch here — a management interface holding power control is the worst place to have one.
Instead it works the way SSH host keys already do in this app: you look at the certificate once and accept it, and from then on only that exact certificate is accepted.
Compare the fingerprint against the BMC's own web interface before accepting. That is the step that makes this worth anything.
If the fingerprint later changes, the app refuses the connection and says so. That happens legitimately when a BMC regenerates its certificate or its firmware is updated — and it is also what an interception looks like. Check before accepting the new one.
Many BMCs ship certificates that expired years ago. ServerBox says so and lets you accept anyway; refusing them would refuse most of the hardware this is for.
The power button offers the OS operations and the hardware ones together. They are not the same thing:
| Goes through the OS | Effect | |
|---|---|---|
| Shut down | yes | asks the OS to shut down; needs a running OS |
| Restart | yes | asks the OS to restart |
| Power on | no | the only one that works on a machine that is off |
| Force off | no | cuts power. Unsaved work is lost, filesystems are not unmounted |
| Power cycle | no | off, then on |
A graceful operation is a request, not a result. ServerBox sends it and then watches the reported power state rather than trusting the HTTP response — some firmware accepts a graceful shutdown and reports success without the OS having done anything. When the state does not move within the wait, the app reports accepted rather than confirmed, and means it.
What the service actually allows differs per vendor, and ServerBox asks rather than assumes: an operation this machine has no equivalent for is not offered at all, instead of failing when pressed.
The event log, storage inventory, boot device override and virtual media are not implemented. Neither is reaching a BMC through a monitor agent, which is what a BMC on an isolated management network would need — the phone has to be able to route to the BMC directly.
Guests of one physical host are not modelled. Several virtual machines running on one server would all point at that server's BMC, where a power operation on any of them cuts all of them and the reported power state is the host's rather than the guest's. Configure the BMC on the host.