linux man page for ramdisk

ramdisk(7D)							      Devices							       ramdisk(7D)

NAME
       ramdisk - RAM disk device driver

SYNOPSIS
       ramdisk@0:diskname

DESCRIPTION
       The  ramdisk driver supports numerous ramdisk devices that are created by the system during the boot  process (see boot(1M)) or during nor-
       mal system operation (see ramdiskadm(1M) for more information).

DEVICE SPECIAL FILES
       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 /dev/ramdisk. Raw
       file names are found in /dev/rramdisk.

       There are no alignment or length restrictions on I/O requests to either block or character devices.

ERRORS
       EFAULT	       The argument features a bad address.

       EINVAL	       Invalid argument. EIO. An I/O error occurred.

       EPERM	       Cannot create or delete a ramdisk without write permission on /dev/ramdiskctl.

       ENOTTY	       The device does not support the requested ioctl function.

       ENXIO	       The device did not exist during opening.

       EBUSY	       Cannot exclusively open /dev/ramdiskctl. One or more ramdisks are still open.

       EEXIST	       A ramdisk with the indicated name already exists.

       EAGAIN	       Cannot allocate resource for ramdisk. Try again later.

FILES
       /dev/ramdisk/diskname

	   Block device for ramdisk named diskname.

       /dev/rramdisk/diskname

	   Raw device for ramdisk name diskname

       /kernel/drv/ramdisk

	   32-bit driver

       /kernel/drv/ramdisk.conf

	   Driver configuration file. (Do not alter).

       /kernel/drv/sparcv9/ramdisk

	   64-bit driver

ATTRIBUTES
       See attributes(5) for descriptions of the following attribute:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       ramdiskadm(1M), fsck(1M), fstyp(1M), mount(1M), newfs(1M), driver.conf(4), filesystem(5), dkio(7I)

NOTES
       The percentage of available physical memory that can be allocated to ramdisks is constrained by the variable rd_percent_physmem.   You  can
       tune  the  rd_percent_physmem  variable	in  /etc/system.  By default, the percentage of available physical memory that can be allocated to
       ramdisks is fixed at 25%.

       A ramdisk may not be the best possible use of system memory. Accordingly, use ramdisks only when absolutely necessary.

SunOS 5.10							    04 Mar 2003 						       ramdisk(7D)