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UMASS(4) Kernel Interfaces Manual UMASS(4) NAME umass -- USB Mass Storage Devices driver SYNOPSIS device da device scbus device pass device usb device umass In loader.conf(5): umass_load DESCRIPTION The umass driver provides support for Mass Storage devices that attach to the USB interface. If the appropriate hardware is detected, the driver will be loaded au- tomatically by devmatch(8). To load the driver manually at boot time, use the umass_load command at the loader(8) prompt, or add it to loader.conf(5). To use the driver in a custom kernel, usb(4) and at least one of uhci(4), ohci(4), ehci(4), or xhci(4) must be configured in the kernel. Additionally, since umass uses the SCSI subsystem and sometimes acts as a SCSI device, it requires da(4) and scbus(4) to be included in the kernel. HARDWARE The umass driver supports USB Mass Storage devices such as: • USB thumb drives • USB hard disk drives • USB floppy drives The umass driver tries its best to avoid issues with the drives, not all issues can be handled automatically, so quirks may be necessary. See the USB Mass Sotrage quirks section of usb_quirk(4) for quirks for the drives. The add_dev_quirk_vplh and add_quirk commands of usbconfig(8) can manage these dynamically. Quirks can be specified via tuables, as described in usb_quirk(4). EXAMPLES Rescan all slots on a multi-slot flash reader, where the slots map to separate LUNs on a single SCSI ID: camcontrol rescan 0:0:0 camcontrol rescan 0:0:1 camcontrol rescan 0:0:2 camcontrol rescan 0:0:3 Typically only the first slot will be enabled at boot time. This as- sumes that the flash reader is the first SCSI bus in the system and has 4 slots. SEE ALSO cfumass(4), ehci(4), ohci(4), uhci(4), usb(4), usb_quirk(4), xhci(4), camcontrol(8), usbconfig(8). HISTORY The umass driver appeared in FreeBSD 4.3. AUTHORS The umass driver was written by MAEKAWA Masahide <bishop@rr.iij4u.or.jp> and Nick Hibma <n_hibma@FreeBSD.org>. This manual page was written by Nick Hibma <n_hibma@FreeBSD.org>. FreeBSD 16.0 CURRENT November 28, 2025 UMASS(4)
NAME | SYNOPSIS | DESCRIPTION | HARDWARE | EXAMPLES | SEE ALSO | HISTORY | AUTHORS
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