port (4)

mem is a character device file that is an image of the main memory of the computer. It may be used, for example, to examine (and even patch) the system.

Byte addresses in mem are interpreted as physical memory addresses. References to nonexistent locations cause errors to be returned.

Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.

It is typically created by:

mknod -m 660 /dev/mem c 1 1

chown root:kmem /dev/mem

The file kmem is the same as mem, except that the kernel virtual memory rather than physical memory is accessed.

It is typically created by:

mknod -m 640 /dev/kmem c 1 2

chown root:kmem /dev/kmem

port is similar to mem, but the I/O ports are accessed.

It is typically created by:

mknod -m 660 /dev/port c 1 4

chown root:mem /dev/port

/dev/mem

/dev/kmem

/dev/port

chown(1), mknod(1), ioperm(2)

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