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nvmetcli - Configure NVMe-over-Fabrics Target.

nvmetcli clear
nvmetcli restore [filename.json]

*nvmetcli* is a program used for viewing, editing, saving,
and starting a Linux kernel NVMe Target, used for an NVMe-over-Fabrics
network configuration.  It allows an administrator to export
a storage resource (such as NVMe devices, files, and volumes)
to a local block device and expose them to remote systems
based on the NVMe-over-Fabrics specification from

*nvmetcli* is run as root and has two modes:

1. An interactive configuration shell
2. Command-line mode which uses an argument

The term *NQN* used throughout this man page is the *NVMe Qualified
Name* format which an NVMe endpoint (device, subsystem, etc) must
follow to guarantee a unique name under the NVMe standard.  Any
name in a network system setup can be used, but if it does not
follow the NQN format, it may not be unique on an NVMe-over-Fabrics network.

Note that some of the fields set for an NVMe Target port under
interactive mode are defined in the "Discovery Log Page" section of
NVMe-over-Fabrics specification. Each NVMe Target has a
discovery controller mechanism that an NVMe Host can use to determine
the NVM subsystems it can access.  *nvmetcli* can be used to add
a new record to the discovery controller upon each new subsystem
entry and port entry that the newly created subsystem entry binds
to (see *OPTIONS* and *EXAMPLES* sections).  Each NVMe
Host only gets to see the discovery entries defined in
*/subsystems/[NQN NAME]/allowed_hosts* and the IP port it is connected
to the NVMe Target.  An NVMe Host can retrieve these discovery logs via
the nvme-cli tool (

*Interactive Configuration Shell*

To start the interactive configuration shell, type *nvmetcli* on
the command-line.  nvmetcli interacts with the Linux kernel
NVMe Target configfs subsystem starting at base
nvmetcli directories **/port**, **/subsystem**, and **/host**.
Configuration changes entered by the administrator are made
immediately to the kernel target configuration.  The
following commands can be used while in the interactive configuration
shell mode:
| cd                    | Allows to move around the tree. 
| ls                    | Lists contents of current tree node.
| create [NQN name]/[#] | Create a new object using the specified name
                          or number. If a [NQN name]/[#] is not specified,
                          a random entry will be used.
| delete [NQN name]/[#] | Delete an object with the specified name or number.
| set attr allow_any_host=[0/1] | Used under */subsystems/[NQN name]* to
                                  specify if any NVMe Host can connect to
                                  the subsystem.
| set device path=[device path] | Used under
                                  */subsystems/[NQN name]/namespaces*
                                  to set the (storage) device to be used.
| set device nguid=[string]     | Used under
                                  */subsystems/[NQN name]/namespaces*
                                  to set the unique id of the device to
                                  the defined namespace.
| enable/disable                | Used under
                                  */subsystems/[NQN name]/namespaces*
                                  to enable and disable the namespace.
| set addr [discovery log page field]=[string] | Used under */ports/[#]*
                                                 to create a port which
                                                 access is allowed. See
                                                 *EXAMPLES* for more
| saveconfig [filename.json]    | Save the NVMe Target configuration in .json
                                  format.  Without specifying the
                                  filename this will save as
                                  */etc/nvmet/config.json*.  This file
                                  is in JSON format and can be edited directly
                                  using a prefered file editor.
| exit                          | Quits interactive configuration shell mode.

*Command Line Mode*

Typing *nvmetcli [cmd]* on the command-line will execute a command
and not enter the interactive configuration shell.

| restore [filename.json] | Loads a saved NVMe Target configuration.
                            Without specifying the filename this will use
| clear                   | Clears a current NVMe Target configuration.
| ls                      | Dumps the current NVMe Target configuration.


Make sure to run nvmetcli as root, the nvmet module is loaded,
your devices and all dependent modules are loaded,
and configfs is mounted on /sys/kernel/config

	mount -t configs none /sys/kernel/config

The following section walks through a configuration example.

* To get started with the interactive mode and the nvmetcli command prompt,
type (in root):
# ./nvmetcli

* Create a subsystem.  If you do not specify a name a NQN will be generated,
which is probably the best choice. We don't do it here as the name
would be random:
> cd /subsystems
...> create testnqn

* Add access for a specific NVMe Host by it's NQN:
...> cd /hosts
...> create hostnqn
...> cd /subsystems/testnqn
...> set attr allow_any_host=0
...> cd /subsystems/testnqn/allowed_hosts/
...> create hostnqn

* Remove access of a subsystem by deleting the Host NQN:
...> cd /subsystems/testnqn/allowed_hosts/
...> delete hostnqn

* Alternatively this allows any Host to connect to the subsystsem.  Only
use this in tightly controlled environments:
...> cd /subsystems/testnqn/
...> set attr allow_any_host=1

* Create a new namespace.  If you do not specify a namespace ID the fist
unused one will be used:
...> cd /subsystems/testnqn/namespaces
...> create 1
...> cd 1
...> set device path=/dev/nvme0n1
...> enable

Note that in the above setup the 'device_nguid' attribute
does not have to be set for correct NVMe Target functionality (but
to correctly match a namespace to the exact device upon
clear and restore operations, it is advised to set the
'device_nguid' parameter).

* Create a loopback port that can be used with nvme-loop module
on the same physical machine...
...> cd /ports/
...> create 1
...> cd 1/
...> set addr trtype=loop
...> cd subsystems/
...> create testnqn

* or create an RDMA (IB, RoCE, iWarp) port using IPv4 addressing. 4420 is the
IANA assigned default port for NVMe over Fabrics using RDMA:
...> cd /ports/
...> create 2
...> cd 2/
...> set addr trtype=rdma
...> set addr adrfam=ipv4
...> set addr traddr=
...> set addr trsvcid=4420
...> cd subsystems/
...> create testnqn

* or create an FC port. traddr is the WWNN/WWPN of the FC port.
...> cd /ports/
...> create 3
...> cd 3/
...> set addr trtype=fc
...> set addr adrfam=fc
...> set addr traddr=nn-0x1000000044001123:pn-0x2000000055001123
...> set addr trsvcid=none
...> cd subsystems/
...> create testnqn

* Saving the NVMe Target configuration:
...> saveconfig test.json

* Loading an NVMe Target configuration:
  ./nvmetcli restore test.json

* Clearing a current NVMe Target configuration:
  ./nvmetcli clear

nvmetcli has the ability to start and stop the NVMe Target configuration
on boot and shutdown through the *systemctl* Linux utility via a .service file.
nvmetcli package comes with *nvmet.service* which when installed, it can 
automatically restore the default, saved NVMe Target configuration from
*/etc/nvmet/config.json*.  *nvmet.service* can be installed in directories
such as */lib/systemd/system*.

To explicitly enable the service, type:
  systemctl enable nvmet

To explicitly disable the service, type:
  systemctl disable nvmet

See also systemctl(1).

This man page was written by[Jay Freyensee]. nvmetcli was
originally written by[Christoph Hellwig].

Please send patches and bug reports to
for review and acceptance.

nvmetcli is licensed under the *Apache License, Version 2.0*. Software
distributed under this license is distributed on an "AS IS" BASIS, WITHOUT
WARRANTIES OR CONDITIONS OF ANY KIND, either expressed or implied.