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/.