NVME-DISCOVERD(8) NVMe Manual NVME-DISCOVERD(8) NAME nvme-discoverd - NVMe-oF discovery and connectivity daemon SYNOPSIS nvme-discoverd [--config=] [--nvme-path=] [--debug] [--help] DESCRIPTION nvme-discoverd is a persistent daemon that connects the host's desired NVMe-oF controllers and keeps them connected. It reads three sources to build its set of desired connections: the NBFT ACPI table (boot-time controllers), the shared NVMe-oF fabrics configuration (nvme-fabrics.conf(5)), and the Discovery Log Pages of any Discovery Controllers it connects to (including FC targets found via FC kickstart). It never disconnects a live controller in response to a discovery change; the only disconnects it causes are a side effect of stopping its own systemd units, at shutdown or on request. At shutdown, a unit is stopped only after the file systems mounted with the _netdev option are unmounted. A file system on an NVMe-oF namespace must use _netdev in fstab(5). Without it, the controller can be disconnected while the file system is still mounted. Every connection attempt is delegated to nvme connect, which runs inside a systemd transient unit instead of writing directly to /dev/nvme-fabrics. As a result, a stuck connect attempt never blocks the daemon's event loop. Each unit is named after a hash of the controller's transport identity. Failed connections retry with exponential backoff. Discovery Controllers from NBFT or the fabrics config represent explicit intent, so they always retry forever. A Discovery Controller found only through a referral or FC kickstart is different: it gives up after dc-giveup-timeout (default 72hours) of unbroken failure and is dropped from tracking. A TLS connection needs tlshd(8) from ktls-utils. Enable it with systemctl enable --now tlshd. When both are enabled, nvme-discoverd starts after tlshd. Before connecting or reconnecting anything, nvme-discoverd checks the system-wide exclusion list. It also registers ownership of every controller it connects (--owner discoverd, or --owner nbft for an NBFT-sourced controller) in the NVMe-oF ownership registry. See nvme-registry-list(1) and nvme-exclusion-add(1). A Discovery Controller that has no owner, for example one connected with nvme discover --persistent, is not tracked. When its discovery log changes, or when it reconnects, nvme-discoverd runs nvme connect-all for it in a transient unit, as the legacy udev rules do. The connections it makes have no owner, and nvme disconnect-all removes them. Events from a Discovery Controller with another owner are ignored. nvme-discoverd is still experimental. It is meant to replace the older udev-rule/systemd-unit autoconnect mechanism. By default, the legacy mechanism is built only when nvme-discoverd is not. Building with -Dnvmf-autoconnect=enabled installs both. The legacy udev rules are active as soon as they are installed. nvme-discoverd runs only when the administrator enables it with systemctl enable --now nvme-discoverd. While nvme-discoverd is active, nvmf-autoconnect.service and the FC kickstart skip their connect step. OPTIONS -c , --config= Path to the daemon's own configuration file. Default: /usr/local/etc/nvme/nvme-discoverd.conf; see CONFIGURATION below. A missing file is not an error -- every knob keeps its default. --nvme-path= Absolute or relative path to the nvme binary that transient connection units exec. Default: /usr/local/sbin/nvme. Mainly useful for running nvme-discoverd against a locally built nvme instead of the installed one. -d, --debug Enable debug-level logging for both nvme-discoverd and the libnvme calls it makes, overriding the configured debug-level. -h, --help Print usage and exit. CONFIGURATION nvme-discoverd.conf holds the daemon's own knobs, in a [Global] section and a [Discovery] section: [Global] nbft = true debug-level = info [Discovery] epcsd-poll-interval-minutes = 15 fc-kickstart-interval-minutes = 0 dc-giveup-timeout = 72hours zeroconf = false nbft (boolean, default true) adopts and connects controllers listed in the NBFT ACPI table. debug-level (err, warn, info, or debug; default info) sets the log threshold; --debug on the command line overrides it. epcsd-poll-interval-minutes (default 15, minimum 1) sets how often, in minutes, to reconnect and re-check a DC whose effective EPCSD (Explicit Persistent Connection Support for Discovery) is 0. Such a DC is disconnected between checks. fc-kickstart-interval-minutes (default 0) re-issues FC kickstart every N minutes; 0 = only at startup and on every FC controller drop. dc-giveup-timeout (default 72hours) is the give-up horizon described above. It takes a systemd time span ("72hours", "3 days 5 hours") or a unit-less value in seconds; "infinity" = never give up, 0 = give up on the first failure. A DC connects with a keep-alive timeout of 30 seconds, or with its configured keep-alive-tmo (see nvme-fabrics.conf(5)). A DC configured with persistent = no connects with none. zeroconf (boolean, default false) connects to and manages Discovery Controllers found through mDNS (TP8009). It requires systemd-resolved v258 or later with mDNS enabled (MulticastDNS=yes), and an nvme-discoverd built with mDNS support. It is re-read on SIGHUP. The connections nvme-discoverd manages come entirely from the shared fabrics configuration, not from this file: which Discovery Controllers and subsystems to connect, host identity, per-connection parameters. See nvme-fabrics.conf(5). SIGNALS SIGHUP Reload both nvme-discoverd.conf and the shared fabrics configuration. Newly desired connections are started; nothing already connected is ever disconnected by a reload. If the fabrics configuration fails to reload (e.g. a syntax error), the previous one is kept and the failure is logged. SIGTERM, SIGINT Shut down gracefully. FILES /usr/local/etc/nvme/nvme-discoverd.conf The daemon's own configuration; see CONFIGURATION. /usr/local/etc/nvme/nvme-discoverd.conf.sample A commented example of nvme-discoverd.conf with every knob at its default. It is not read; copy it to nvme-discoverd.conf to change a setting. /usr/local/etc/nvme/nvme-fabrics.conf, /usr/local/etc/nvme/nvme-fabrics.conf.d/*.conf The connections nvme-discoverd manages; see nvme-fabrics.conf(5). /run/nvme/discoverd/ Runtime state linking each connected controller to the systemd transient unit that owns it. Does not survive a reboot. SEE ALSO nvme-fabrics.conf(5) tlshd(8) nvme-connect(1) nvme-registry-list(1) nvme-exclusion-add(1) NVME Part of the nvme-user suite NVMe 10/30/2026 NVME-DISCOVERD(8)