receiving, with a rack-controller, via a first network, an application program interface (API) request, wherein:

the rack-controller is configured to control a plurality of rack-mounted computing devices mounted in a plurality of different rack units of one or more racks;

the rack-controller is configured to control the rack-mounted computing devices via a second network, different from the first network;

the rack-controller includes a gateway between the first network and the second network;

the second network is an out-of-band network distinct from an in-band network with which data is conveyed between rack-mounted computing devices or between rack-mounted computing devices and the internet; and

the API request is encoded in a first protocol;

based on the API request, selecting, with the rack-controller, one of a plurality of routines to effectuate control via the second network of at least some of the plurality of rack-mounted computing devices, the plurality of routines including:

a first routine that reads a sensor via the second network on one of the rack-mounted computing devices;

a second routine that reads a sensor via the second network on the rack but not on one of the rack-mounted computing devices;

a third routine that scans computing devices on the second network and produces an inventory of the scanned computing devices on the second network;

a fourth routine by which a configuration of an extensible firmware interface (EFI) of a given one of the rack-mounted computing device is adjusted; and

executing, with the rack-controller, the selected routine and, as a result, sending one or more commands via the second network encoded in a second protocol different from the first protocol to effectuate an action indicated by the API request.

the rack-controller is an out-of-band computer having a processor, memory, an operating system stored in persistent memory;

the rack-controller is coupled to a rack in which the rack-mounted computing devices are disposed;

the number of rack-mounted computing devices controlled by the rack-controller exceeds seven;

the rack-controller is not on the in-band network;

the first network is an out-of-band Ethernet network;

the second network is a direct-current (DC) power-line network with which both power and data are conveyed via a DC power bus;

the first protocol is a hypertext transport protocol and the API is a representational state transfer API;

the sensor is a temperature sensor;

the configuration of the EFI specifies a boot device of the given rack-mounted computing device;

at least some of the routines do not use a baseboard management controller of the rack-mounted computing devices;

the selected routine is the first routine;

the operations comprise:

receiving, with the rack-controller, a response from the temperature sensor in units other than units of temperature;

converting, with the rack-controller, the response into units of temperature; and

sending, with the rack-controller, via the first network, an HTTP response including the converted response in units of temperature.

the second network connects a control plane of a rack over which a plurality of servers mounted in the rack are controlled; and

the first network is an out-of-band network over which a data center is managed based on workload and environmental data gathered from a plurality of racks via a plurality of respective instances of the first network.

the plurality of routines comprises a fifth routine by which a rack-mounted computing device is power cycled;

the fifth routine is selected; and

the operations comprise:

sending, with the rack-controller, via the second network, an instruction that causes a given rack-mounted computing device to power cycle;

receiving, with the rack-controller, via the second network, one or more power-on-self-test (POST) codes; and

sending, with the rack-controller, via the first network, an indication of the one or more POST codes.

the third routine is selected;

the operations comprise:

sending, with the rack-controller, via the second network, to each device on the second network, a command to send an identifier;

receiving, with the rack-controller, during each of a plurality of durations of time reserved for respective ones of the devices to use a shared physical medium of the second network, an identifier from the respective devices.

the third routine is selected;

the operations comprise:

sending, with the rack-controller, via the second network, and a modem coupled a mid-plane of a server, a command to a computing device coupled to the server and the modem, the command causing the computing device to execute a scan of other computing devices coupled to a system management bus of server;

receiving, with the rack-controller, from the modem, via the second network, identifiers of at least some computing devices detected in scan.

the fourth routine is selected;

the operations comprise:

receiving, with the rack-controller, via the first network, an a new version of the EFI;

sending, with the rack-controller, via the second network, the new version of the EFI to a given one of the rack-mounted computing devices and instructions to store the new version of the EFI at given boot target of a plurality of candidate boot targets of the given one of the rack-mounted computing devices;

sending, with the rack-controller, via the second network, to the given rack-mounted computing device, an instruction to change a boot target of the EFT to the given boot target; and

sending, with the rack-controller, via the second network, an instruction reboot the given one of the rack-mounted computing devices.

the fourth routine is selected; and

the operations comprise:

changing a boot target of an EFI of at least one of the rack-mounted computing devices without making the change via an Intelligent Platform Management Interface (IPMI) of at least one of the rack-mounted computing devices.

gathering, with the rack-controller, via the second network, agentless monitoring metrics from each of the rack-mounted computing devices, the metrics including processor utilization of the respective rack-mounted computing devices.

wherein the agentless monitoring metrics are not reported by an operating system or a process running within the operating system of the rack-mounted computing devices, and wherein the metrics include memory utilization and an indication of processor temperature.

the second network is power-line network by which both electrical power is supplied to the rack-mounted computing devices and by which data is exchanged.

the second network is an Ethernet network.

at least two of the routines are not effectuated via a baseboard management controller of the rack-mounted computing devices.

causing a component identifier of a component of one of the rack-mounted computing devices to be read from a register of the component and conveyed via a system management bus of the one of the rack-mounted computing devices before being sent to the rack-controller via the second network.

receiving, with the rack-controller, the component identifier;

selecting a command corresponding to a capability of the component based on the component identifier; and

sending, with the rack-controller, via the second network, the selected command.

reading from the register comprises incrementing an address through an address space of the system management bus until an address of the component is found.

the routines comprise a routine by which TTY access to a remote console executing on one of the rack-mounted computing devices is provided, wherein the rack-controller operates as a web proxy in the TTY access.

the first routine is selected with means for selecting a routine based on an API request;

the sensor comprises means for sensing; and

the rack-controller comprises means for controlling a rack.

the rack controller is executed in an out-of-band computer having a processor and memory storing instructions that when executed effectuate at least some of the operations of claim 1;

the rack controller is configured to manage rack-mounted computing devices via the second network with a power-line communication network.

the rack controller is configured to be executed in a rack-mounted computing device; and

the second network is an Ethernet network.

the rack controller is configured to be executed in a rack-mounted computing device; and

the rack controller is configured to manage rack-mounted computing devices via the second network with a power-line communication network.

the rack controller is executed in an out-of-band computer having a processor and memory storing instructions that when executed effectuate at least some of the operations of claim 1; and

the second network is an Ethernet network.

receiving, with a rack-controller, via a first network, an application program interface (API) request, wherein:

the rack-controller is configured to control a plurality of rack-mounted computing devices mounted in a plurality of different rack units of one or more racks;

the rack-controller is configured to control the rack-mounted computing devices via a second network, different from the first network;

the rack-controller includes a gateway between the first network and the second network;

the second network is an out-of-band network distinct from an in-band network with which data is conveyed between rack-mounted computing devices or between rack-mounted computing devices and the internet; and

the API request is encoded in a first protocol;

based on the API request, selecting, with the rack-controller, one of a plurality of routines to effectuate control via the second network of at least some of the plurality of rack-mounted computing devices, the plurality of routines including:

a first routine that reads a sensor via the second network on one of the rack-mounted computing devices;

a second routine that reads a sensor via the second network on the rack but not on one of the rack-mounted computing devices;

a third routine that scans computing devices on the second network and produces an inventory of the scanned computing devices on the second network;

a fourth routine by which a configuration of an extensible firmware interface (EFI) of a given one of the rack-mounted computing device is adjusted; and

executing, with the rack-controller, the selected routine and, as a result, sending one or more commands via the second network encoded in a second protocol different from the first protocol to effectuate an action indicated by the API request.

a data center management computing device communicatively coupled to an out-of-band network; and

a plurality of racks, each rack comprising:

a plurality of rack-mounted computing devices within the plurality of racks and communicatively coupled to an in-band network;

a rack-controller communicatively coupled to the data center management computing device via the out-of-band network;

a powerline network having a rack-specific network address space independent of address spaces of other powerline networks of other racks;

a plurality of powerline modems each associated with a respective one or more of the rack-mounted computing devices; and

a tangible, non-transitory, machine-readable medium of the rack controller storing instructions that when executed by the rack-controller effectuate operations comprising:

receiving, with a rack-controller, via the out-of-band network, a request;

based on the request, selecting, with the rack-controller, one of a plurality of routines to effectuate control via the second network of at least some of the plurality of rack-mounted computing devices, the plurality of routines including at least two of the following:

a first routine that reads a sensor via the second network on one of the rack-mounted computing devices;

a second routine that reads a sensor via the second network on the rack but not on one of the rack-mounted computing devices;

a third routine that scans computing devices on the second network and produces an inventory of the scanned computing devices on the second network; or

a fourth routine by which a configuration of an extensible firmware interface (EFI) of a given one of the rack-mounted computing device is adjusted; and

executing, with the rack-controller, the selected routine and, as a result, sending one or more commands via the powerline network to effectuate an action in response to the request.