---
name: "umass"
section: "4freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/umass/4freebsd"
---

# umass(4freebsd)

USB Mass Storage Devices driver

## NAME

**umass** – USB Mass Storage Devices driver

## SYNOPSIS

To compile this driver into the kernel, place the following line in your kernel configuration file:

**device scbus** **device usb** **device umass**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
umass_load="YES"
```

## DESCRIPTION

The **umass** driver provides support for Mass Storage devices that attach to the USB port.

To use the **umass** driver, [usb(4)](/usb/4.md) and one of [uhci(4)](/uhci/4.md) or [ohci(4)](/ohci/4.md) or [ehci(4)](/ehci/4.md) or [xhci(4)](/xhci/4.md) must be configured in the kernel. Additionally, since **umass** uses the SCSI subsystem and sometimes acts as a SCSI device, it requires [da(4)](/da/4.md) and [scbus(4)](/scbus/4.md) to be included in the kernel.

## EXAMPLES

```
device umass
device scbus
device da
device pass
```

Add the **umass** driver to the kernel.

```
camcontrol rescan 0:0:0
camcontrol rescan 0:0:1
camcontrol rescan 0:0:2
camcontrol rescan 0:0:3
```

Rescan all slots on a multi-slot flash reader, where the slots map to separate LUNs on a single SCSI ID. Typically only the first slot will be enabled at boot time. This assumes that the flash reader is the first SCSI bus in the system and has 4 slots.

## SEE ALSO

[cfumass(4)](/cfumass/4.md), [ehci(4)](/ehci/4.md), [ohci(4)](/ohci/4.md), [uhci(4)](/uhci/4.md), [usb(4)](/usb/4.md), [xhci(4)](/xhci/4.md), [camcontrol(8)](/camcontrol/8.md)

## 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*⟩.