stafd

nvme-stas 1.0

## Name

stafd — STorage Appliance Finder

## Synopsis

`stafd` [OPTIONS...]

## Description

stafd is a system daemon that can be used to automatically locate and connect to NVMe-oF Discovery Controllers using mDNS service discovery. It can also be manually configured with stafd.conf(5) to connect to Discovery Controllers that cannot be located using mDNS.

## Options

The following options are understood:

`-h`, `--help`

  Print the help text and exit.

`--version`

  Print the version string and exit.

`-fFILE`, `--conf-file=FILE`

  Specify a different configuration file than stafd.conf(5) (default: `/etc/stas/stafd.conf`).

`-s`, `--syslog`

  Send messages to syslog instead of stdout. Use this when running stafd as a daemon. (default: "`false`").

`--tron`

  Trace ON. (default: "`false`")

`--idl=FILE`

  Print D-Bus IDL to FILE and exit.

## Exit status

On success, 0 is returned, a non-zero failure code otherwise.

## Daemonization

stafd is managed by `systemd`. The following operations are supported:

Table 1.

Command | Description
--- | ---
    $ systemctl start stafd
| Start daemon.
    $ systemctl stop stafd
| Stop daemon. The `SIGTERM` signal is used to tell the daemon to stop.
    $ systemctl restart stafd
| Effectively a `stop` + `start`.
    $ systemctl reload stafd
| Reload configuration. This is done in real time without restarting the daemon. The `SIGHUP` signal is used to tell the daemon to reload its configuration file. Note that configuration parameters that affect connections (e.g. `kato`), will not apply to existing connections. Only connections established after the configuration was changed will utilize the new configuration parameters.

## Design

stafd use the `GLib` main loop. The `GLib` Python module provides several low-level building blocks that stafd requires. In addition, many Python modules "play nice" with `GLib` such as `dasbus` (D-Bus package) and `pyudev` (UDev package). `GLib` also provides additional components such as timers, signal handlers, and much more.

stafd connects to the `avahi-daemon` using D-Bus. The `avahi-daemon`, or simply Avahi, is an mDNS discovery service used for zero-configuration networking (zeroconf). stafd registers with Avahi to automatically locate Central Discovery Controllers (CDC) and Direct Discovery Controllers (DDC). When Avahi finds Discovery Controllers (DC), it notifies stafd which connects to the DC with the help of the `libnvme` library. Once a connection to a DC is established, stafd can retrieve the discovery log pages from that DC and cache them in memory.

## Configuration

stafd can automatically locate discovery controllers (DC) with the help of Avahi and connect to them. However, stafd can also operate in a non-automatic mode based on manually entered configuration. In other words, DCs can be entered in a configuration named `/etc/stas/stafd.conf`. This configuration file also provides additional parameters, such as log-level attributes used for debugging purposes.

## D-Bus API

The interface to stafd is D-Bus. This allows other programs, such as stafctl, to communicate with stafd. The D-Bus address is `org.nvmexpress.staf`.

## See Also

stafd.conf(5), stafd.service(8), stafctl(1), org.nvmexpress.staf(5).