NAME

       mem, kmem, port - system memory, kernel memory and system ports

DESCRIPTION

       /dev/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  /dev/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.

       Since  Linux  2.6.26,  and  depending  on the architecture, the CONFIG_STRICT_DEVMEM kernel configuration
       option limits the areas which can be accessed through this file.  For example: on x86, RAM access is  not
       allowed but accessing memory-mapped PCI regions is.

       It is typically created by:

           mknod -m 660 /dev/mem c 1 1
           chown root:kmem /dev/mem

       The  file  /dev/kmem  is the same as /dev/mem, except that the kernel virtual memory rather than physical
       memory is accessed.  Since Linux 2.6.26, this  file  is  available  only  if  the  CONFIG_DEVKMEM  kernel
       configuration option is enabled.

       It is typically created by:

           mknod -m 640 /dev/kmem c 1 2
           chown root:kmem /dev/kmem

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

       It is typically created by:

           mknod -m 660 /dev/port c 1 4
           chown root:kmem /dev/port

FILES

       /dev/mem
       /dev/kmem
       /dev/port

SEE ALSO

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

COLOPHON

       This  page  is  part  of  release  5.10  of  the  Linux man-pages project.  A description of the project,
       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.

Linux                                              2015-01-02                                             MEM(4)