1.\" Copyright (c) 1996 2.\" Mike Pritchard <mpp@FreeBSD.org>. All rights reserved. 3.\" 4.\" Copyright (c) 1992, 1993, 1994 5.\" The Regents of the University of California. All rights reserved. 6.\" All rights reserved. 7.\" 8.\" This code is derived from software donated to Berkeley by 9.\" Jan-Simon Pendry. 10.\" 11.\" Redistribution and use in source and binary forms, with or without 12.\" modification, are permitted provided that the following conditions 13.\" are met: 14.\" 1. Redistributions of source code must retain the above copyright 15.\" notice, this list of conditions and the following disclaimer. 16.\" 2. Redistributions in binary form must reproduce the above copyright 17.\" notice, this list of conditions and the following disclaimer in the 18.\" documentation and/or other materials provided with the distribution. 19.\" 3. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.Dd June 30, 2022 36.Dt DEVFS 4 37.Os 38.Sh NAME 39.Nm devfs 40.Nd device file system 41.Sh SYNOPSIS 42.Bd -literal 43devfs /dev devfs rw 0 0 44.Ed 45.Sh DESCRIPTION 46The device file system, or 47.Nm , 48provides access to kernel's device 49namespace in the global file system namespace. 50The conventional mount point is 51.Pa /dev . 52.Pp 53The file system includes several directories, links, symbolic links 54and devices, some of which can also be written. 55In a chroot'ed 56environment, 57.Xr devfs 8 58can be used to create a new 59.Pa /dev 60mount point. 61.Pp 62The 63.Xr mknod 8 64tool can be used to recover deleted device entries under 65.Nm . 66.Pp 67The 68.Xr fdescfs 4 69filesystem is an alternate means for populating 70.Pa /dev/fd . 71The character devices that both 72.Nm 73and 74.Xr fdescfs 4 75present in 76.Pa /dev/fd 77correspond to the open file descriptors of the process 78accessing the directory. 79.Nm 80only creates files for the standard file descriptors 81.Pa 0 , 82.Pa 1 83and 84.Pa 2 . 85.Xr fdescfs 4 86creates files for all open descriptors. 87.Pp 88The options are as follows: 89.Bl -tag -width indent 90.It Fl o Ar options 91Use the specified mount 92.Ar options , 93as described in 94.Xr mount 8 . 95The following devfs file system-specific options are available: 96.Bl -tag -width indent 97.It Cm ruleset Ns No = Ns Ar ruleset 98Set ruleset number 99.Ar ruleset 100as the current ruleset for the mount-point and apply all its rules. 101If the ruleset number 102.Ar ruleset 103does not exist, an empty ruleset with the number 104.Ar ruleset 105is created. 106See 107.Xr devfs 8 108for more information on working with devfs rulesets. 109.El 110.El 111.Sh FILES 112.Bl -tag -width /dev/XXXX -compact 113.It Pa /dev 114The normal 115.Nm 116mount point. 117.El 118.Sh EXAMPLES 119To mount a 120.Nm 121volume located on 122.Pa /mychroot/dev : 123.Pp 124.Dl "mount -t devfs devfs /mychroot/dev" 125.Sh SEE ALSO 126.Xr fdescfs 4 , 127.Xr devfs 8 , 128.Xr mount 8 , 129.Xr make_dev 9 130.Sh HISTORY 131The 132.Nm 133file system first appeared in 134.Fx 2.0 . 135It became the preferred method for accessing devices in 136.Fx 5.0 137and the only method in 138.Fx 6.0 . 139The 140.Nm 141manual page first appeared in 142.Fx 2.2 . 143.Sh AUTHORS 144The 145.Nm 146manual page was written by 147.An Mike Pritchard Aq Mt mpp@FreeBSD.org . 148