11-27-2001
The -k lists everything in the kernel's internal data structures. The -u lists usable entries.
Yes, when you limit things to disks, they are the same. But compare "ioscan -ufn" and "ioscan -kfn". With the -k, you will see entries for cpu and memory. There are no drivers for cpus and memory (/dev/mem is a psuedo driver). We also have some UNCLAIMED entries on our -k listing since we have some hardware connected that doesn't have a driver. Until a driver claims them, those devices are also unusable.
So the -u and -k are indeed different. But "-kC disk" and "-uC disk" are indeed redundant. By the time the kernel knows an entry is a disk, it must also be usable. "Usable" in this context means the kernel can attempt an open on the device, not that the device is working properly.
I'm not absolutely certain that it is impossible to create an unusable disk entry in the kernel, but there is no documented way to do so. But if /etc/ioconfig is badly garbled, maybe ioinit could do it at boot time. Also ioscan, insf, rmsf,...etc all work by opening /dev/config and sending undocumented ioclt's to it. I'm not sure how much checking is done so maybe a program could open /dev/config and fiddle with it.
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LEARN ABOUT LINUX
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)