'\" te
.\" Copyright (c) 2003, Sun Microsystems, Inc.
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH RAMDISK 4D "Mar 04, 2003"
.SH NAME
ramdisk \- RAM disk device driver
.SH SYNOPSIS
.LP
.nf
\fBramdisk@0:\fR\fIdiskname\fR
.fi

.SH DESCRIPTION
.sp
.LP
The \fBramdisk\fR driver supports numerous ramdisk devices that are created by
the system during the boot  process (see \fBboot\fR(8)) or during normal
system operation (see \fBramdiskadm\fR(8) for more information).
.SH DEVICE SPECIAL FILES
.sp
.LP
Each ramdisk can be accessed either as a block device or as a raw device. When
accessed as a block device, the normal buffering          mechanism is used
when reading from and writing to the device, without regard to physical disk
records. Accessing the ramdisk as a raw device enables direct transmission
between the disk and the read or write buffer. A single read or write call
usually results in a single  I/O operation, meaning that raw I/O is more
efficient when many bytes are  transmitted. You can find block files names in
\fB/dev/ramdisk\fR. Raw file names are found in \fB/dev/rramdisk\fR.
.sp
.LP
There are no alignment or length restrictions on I/O requests to either block
or character devices.
.SH ERRORS
.sp
.ne 2
.na
\fB\fBEFAULT\fR\fR
.ad
.RS 10n
The argument features a bad address.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
Invalid argument. EIO. An I/O error occurred.
.RE

.sp
.ne 2
.na
\fB\fBEPERM\fR\fR
.ad
.RS 10n
Cannot create or delete a ramdisk without write permission on
\fB/dev/ramdiskctl\fR.
.RE

.sp
.ne 2
.na
\fB\fBENOTTY\fR\fR
.ad
.RS 10n
The device does not support the requested ioctl function.
.RE

.sp
.ne 2
.na
\fB\fBENXIO\fR\fR
.ad
.RS 10n
The device did not exist during opening.
.RE

.sp
.ne 2
.na
\fB\fBEBUSY\fR\fR
.ad
.RS 10n
Cannot exclusively open \fB/dev/ramdiskctl\fR. One or more ramdisks are still
open.
.RE

.sp
.ne 2
.na
\fB\fBEEXIST\fR\fR
.ad
.RS 10n
A ramdisk with the indicated name already exists.
.RE

.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
Cannot allocate resource for ramdisk. Try again later.
.RE

.SH FILES
.sp
.ne 2
.na
\fB\fB/dev/ramdisk/diskname\fR\fR
.ad
.sp .6
.RS 4n
Block device for ramdisk named \fIdiskname\fR.
.RE

.sp
.ne 2
.na
\fB\fB/dev/rramdisk/diskname\fR\fR
.ad
.sp .6
.RS 4n
Raw device for ramdisk name \fIdiskname\fR
.RE

.sp
.ne 2
.na
\fB\fB/kernel/drv/ramdisk\fR\fR
.ad
.sp .6
.RS 4n
32-bit driver
.RE

.sp
.ne 2
.na
\fB\fB/kernel/drv/ramdisk.conf\fR\fR
.ad
.sp .6
.RS 4n
Driver configuration file. (Do not alter).
.RE

.sp
.ne 2
.na
\fB\fB/kernel/drv/sparcv9/ramdisk\fR\fR
.ad
.sp .6
.RS 4n
64-bit driver
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attribute:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Evolving
.TE

.SH SEE ALSO
.sp
.LP
.BR dkio (4I),
.BR driver.conf (5),
.BR filesystem (7),
.BR fsck (8),
.BR fstyp (8),
.BR mount (8),
.BR newfs (8),
.BR ramdiskadm (8)
.SH NOTES
.sp
.LP
The percentage of available physical memory that can be allocated to ramdisks
is constrained by the variable \fBrd_percent_physmem\fR. You can tune the
\fBrd_percent_physmem\fR variable in \fB/etc/system\fR. By default, the
percentage of available physical memory that can be allocated to ramdisks is
fixed at 25%.
.sp
.LP
A ramdisk may not be the best possible use of system memory. Accordingly, use
ramdisks only when absolutely necessary.