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man pages section 4: Device and Network Interfaces

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Updated: Thursday, June 13, 2019
 
 

ramdisk(4D)

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(8)) or during normal system operation (see ramdiskadm(8) 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.conf

Driver configuration file. (Do not alter).

/kernel/drv/sparcv9/ramdisk

64-bit driver

Attributes

See attributes(7) for descriptions of the following attribute:

ATTRIBUTE TYPE
ATTRIBUTE VALUE
Interface Stability
Committed

See Also

dkio(4I), driver.conf(5), filesystem(7), fsck(8), fstyp(8), mount(8), newfs(8), ramdiskadm(8)

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.