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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   normal   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. Access-
     ing 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.conf
         Driver configuration file. (Do not alter).


     /kernel/drv/sparcv9/ramdisk
         64-bit driver

Attributes
     See attributes(5) for descriptions of the  following  attri-
     bute:



     tab() box; cw(2.75i) |cw(2.75i) lw(2.75i) |lw(2.75i)  ATTRI-
     BUTE TYPEATTRIBUTE VALUE _ Interface StabilityCommitted

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.
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