nvme-discover(1)
================

NAME
----
nvme-discover - Send Get Log Page request to Discovery Controller.

SYNOPSIS
--------
[verse]
'nvme discover'
		[--transport=<trtype>     | -t <trtype>]
		[--traddr=<traddr>        | -a <traddr>]
		[--trsvcid=<trsvcid>      | -s <trsvcid>]
		[--host-traddr=<traddr>   | -w <traddr>]
		[--hostnqn=<hostnqn>      | -q <hostnqn>]
		[--hostid=<hostid>        | -I <hostid>]
		[--raw=<filename>	  | -r <filename>]
		[--device=<device>        | -d <device>]
		[--keep-alive-tmo=<sec>   | -k <sec>]
		[--reconnect-delay=<#>	  | -c <#>]
		[--ctrl-loss-tmo=<#>	  | -l <#>]
		[--hdr_digest             | -g]
		[--data_digest            | -G]
		[--nr-io-queues=<#>       | -i <#>]
		[--nr-write-queues=<#>    | -W <#>]
		[--nr-poll-queues=<#>     | -P <#>]
		[--queue-size=<#>         | -Q <#>]
		[--persistent             | -p]
		[--quiet                  | -S]
		[--output-format=<fmt>    | -o <fmt>]

DESCRIPTION
-----------
Send one or more Get Log Page requests to a NVMe-over-Fabrics Discovery
Controller.

If no parameters are given, then 'nvme discover' will attempt to 
find a /etc/nvme/discovery.conf file to use to supply a list of
Discovery commands to run.  If no /etc/nvme/discovery.conf file
exists, the command will quit with an error.

Otherwise, a specific Discovery Controller should be specified using the
--transport, --traddr, and if necessary the --trsvcid flags. A Diѕcovery
request will then be sent to the specified Discovery Controller.

BACKGROUND
----------
The NVMe-over-Fabrics specification defines the concept of a 
Discovery Controller that an NVMe Host can query on a fabric
network to discover NVMe subsystems contained in NVMe Targets
which it can connect to on the network.  The Discovery Controller
will return Discovery Log Pages that provide the NVMe Host
with specific information (such as network address and unique
subsystem NQN) the NVMe Host can use to issue an
NVMe connect command to connect itself to a storage resource
contained in that NVMe subsystem on the NVMe Target.

Note that the base NVMe specification defines the NQN (NVMe Qualified
Name) format which an NVMe endpoint (device, subsystem, etc) must
follow to guarantee a unique name under the NVMe standard.
In particular, the Host NQN uniquely identifies the NVMe Host, and
may be used by the the Discovery Controller to control what NVMe Target
resources are allocated to the NVMe Host for a connection.

A Discovery Controller has it's own NQN defined in the NVMe-over-Fabrics
specification, *nqn.2014-08.org.nvmexpress.discovery*.  All Discovery
Controllers must use this NQN name. This NQN is used by default by
nvme-cli for the 'discover' command. 

OPTIONS
-------
-t <trtype>::
--transport=<trtype>::
	This field specifies the network fabric being used for
	a NVMe-over-Fabrics network.  Current string values include:
+
[]
|=================
|Value|Definition
|rdma|The network fabric is an rdma network (RoCE, iWARP, Infiniband, basic rdma, etc)
|fc  |*WIP* The network fabric is a Fibre Channel network.
|tcp |The network fabric is a TCP/IP network.
|loop|Connect to a NVMe over Fabrics target on the local host
|=================

-a <traddr>::
--traddr=<traddr>::
	This field specifies the network address of the Discovery Controller.
	For transports using IP addressing (e.g. rdma) this should be an
	IP-based (ex. IPv4) address.

-s <trsvcid>::
--trsvcid=<trsvcid>::
	This field specifies the transport service id.  For transports using IP
	addressing (e.g. rdma) this field is the port number. By default, the IP
	port number for the RDMA transport is 4420.

-w <traddr>::
--host-traddr=<traddr>::
	This field specifies the network address used on the host to connect
	to the Discovery Controller.
 
-q <hostnqn>::
--hostnqn=<hostnqn>::
	Overrides the default host NQN that identifies the NVMe Host.  
	If this option is not specified, the default is read from
	/etc/nvme/hostnqn first. If that does not exist, the autogenerated
	NQN value from the NVMe Host kernel module is used next.

-I <hostid>::
--hostid=<hostid>::
	UUID(Universally Unique Identifier) to be discovered which should be
	formatted.

-r <filename>::
--raw=<filename>::
	This field will take the output of the 'nvme discover' command
	and dump it to a raw binary file. By default 'nvme discover' will
	dump the output to stdout.

-d <device>::
--device=<device>::
	This field takes a device as input. Device is in the format of nvme*,
	eg. nvme0, nvme1

-k <#>::
--keep-alive-tmo=<#>::
	Overrides the default dealy (in seconds) for keep alive.
	This option will be ignored for the discovery, and it is only
	implemented for completeness.

-c <#>::
--reconnect-delay=<#>::
	Overrides the default delay (in seconds) before reconnect is attempted
	after a connect loss.

-l <#>::
--ctrl-loss-tmo=<#>::
	Overrides the default controller loss timeout period (in seconds).

-g::
--hdr_digest::
	Generates/verifies header digest (TCP).

-G::
--data_digest::
	Generates/verifies data digest (TCP).

-i <#>::
--nr-io-queues=<#>::
	Overrides the default number of I/O queues create by the driver.
	This option will be ignored for the discovery, and it is only
	implemented for completeness.

-W <#>::
--nr-write-queues=<#>::
	Adds additional queues that will be used for write I/O.

-P <#>::
--nr-poll-queues=<#>::
	Adds additional queues that will be used for polling latency sensitive I/O.

-Q <#>::
--queue-size=<#>::
	Overrides the default number of elements in the I/O queues created
	by the driver which can be found at drivers/nvme/host/fabrics.h.
	This option will be ignored for the discovery, and it is only
	implemented for completeness.

-p::
--persistent::
	Persistent discovery connection.

-S::
--quiet::
	Suppress already connected errors.

-o <format>::
--output-format=<format>::
              Set the reporting format to 'normal', 'json', or
              'binary'. Only one output format can be used at a time.

EXAMPLES
--------
* Query the Discover Controller with IP4 address 192.168.1.3 for all
resources allocated for NVMe Host name host1-rogue-nqn on the RDMA network.
Port 4420 is used by default:
+
------------
# nvme discover --transport=rdma --traddr=192.168.1.3 \
--hostnqn=host1-rogue-nqn
------------
+
* Issue a 'nvme discover' command using a /etc/nvme/discovery.conf file:
+
-----------
# Machine default 'nvme discover' commands.  Query the
# Discovery Controller's two ports (some resources may only
# be accessible on a single port).  Note an official
# nqn (Host) name defined in the NVMe specification is being used
# in this example.
-t rdma -a 192.168.69.33 -s 4420 -q nqn.2014-08.com.example:nvme:nvm-subsystem-sn-d78432
-t rdma -a 192.168.1.4   -s 4420 -q nqn.2014-08.com.example:nvme:nvm-subsystem-sn-d78432

At the prompt type "nvme discover".

------------

SEE ALSO
--------
nvme-connect(1)
nvme-connect-all(1)

AUTHORS
-------
This was written by mailto:james.p.freyensee@intel.com[Jay Freyensee]

NVME
----
Part of the nvme-user suite
