Linux and UNIX Man Pages

Linux & Unix Commands - Search Man Pages

mem(4) [debian man page]

MEM(4)							     Linux Programmer's Manual							    MEM(4)

NAME
mem, kmem, port - system memory, kernel memory and system ports DESCRIPTION
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 FILES
/dev/mem /dev/kmem /dev/port SEE ALSO
chown(1), mknod(1), ioperm(2) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 1992-11-21 MEM(4)

Check Out this Related Man Page

MEM(4)							     Linux Programmer's Manual							    MEM(4)

NAME
mem, kmem, port - system memory, kernel memory and system ports DESCRIPTION
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 FILES
/dev/mem /dev/kmem /dev/port SEE ALSO
chown(1), mknod(1), ioperm(2) COLOPHON
This page is part of release 3.25 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 1992-11-21 MEM(4)
Man Page

15 More Discussions You Might Find Interesting

1. Programming

Physical Memory

Hi, My problem is next.... How can I work with physical memory in the Unix FreeBSD 2.2 or hight? What is the "mem" & "kmem" drivers? P.S./ writing device driver for UNIX FreeBSD 2.2 :D (2 Replies)
Discussion started by: Alex_T
2 Replies

2. UNIX for Advanced & Expert Users

Not using more than 8G of memory

I have a Sun V880/ Solaris 8/ 16 G of memory We previously had 8 G of mem. Started getting fork errors. Thought problem was becauseit was low on memory. Upgrade to 16 G of mem. Still, box is getting fork errors. Not seem to be using over 7 G of memory. We think it's the PeopleSoft and... (10 Replies)
Discussion started by: greddy09sc
10 Replies

3. SCO

how can I get the system information such as cup,memory,ports etc?

In the sco unix ,how can i get the system information ? such as cpu,memory,interrupter,io ports etc look forword to quick replay (2 Replies)
Discussion started by: fresh
2 Replies

4. UNIX for Advanced & Expert Users

Q1 :/dev/null Q2 -A

Hi, Q1-What does nroff -ms > /dev/null Q2- What does mean -A under STAT column : ps aux |head -20 UTIL PID %CPU %MEM SZ RSS TTY STAT STIME TIME COMMAND root 516 93,0 0,0 12 12 - A 04 nov 3906:51 wait Thank you. (4 Replies)
Discussion started by: big123456
4 Replies

5. Shell Programming and Scripting

Converting a decimal into integer

Hi all, I'm trying to convert a decimal number into an integer number; I'm doing this: n=`echo |awk '{ print "'"$mem"'"*10}'` where the variable mem is equal to 3.7 I'd like to obtain 37, but the expression above gives me 30. Help please!!!! thx a lot (4 Replies)
Discussion started by: idro
4 Replies

6. HP-UX

How to find CPU Speed of HP UX

Need to find the CPU speed of HP UX for a non root login. echo "itick_per_usec/D" | adb /stand/vmunix /dev/mem | tail -1 will give the following for non root users ERROR: cannot open `/dev/mem', errno = 13, Permission denied (2 Replies)
Discussion started by: surajb
2 Replies

7. Solaris

File permission on : kmem file

Hello , I want to check the file permissions of /dev/kmem . I am getting 2 kind of file perms... so which permission i have to consider.. here is 2 case .. 1. ls -al /dev/kmem lrwxrwxrwx 1 root other 27 Sep 8 2008 /dev/kmem -> ../devices/pseudo/mm@0:kmem 2. ... (4 Replies)
Discussion started by: avklinux
4 Replies

8. Shell Programming and Scripting

How to add text to a field within a csv file

I have a csv file which has three columns mem no. name surname 1234 John Smith 12345 John Doe I want to change the mem no. to add TF to the mem no. field i.e. mem no. name surname 1234TF John Smith 12345TF John Doe How do you do this for all records in the file? (3 Replies)
Discussion started by: Pablo_beezo
3 Replies

9. Fedora

Piping output of "top" to a text file

I would like to pipe "top -n" to a text file, but I get an error: top: cannot open /dev/kmem kvm_open: Permission denied I am a non-root user. If I could find a way to get this type of output: "Memory: 2048M real, 1516M free, 4099M swap free" into a text file, I could further automate... (13 Replies)
Discussion started by: safraser
13 Replies

10. Shell Programming and Scripting

What is max MEM% in top command?

HI, When i use the top command in Linux I get the below values. PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND What is the maximum MEM% that will occur. I got once 303% . Is it possible to get such a high value. Regards, Ahamed. (2 Replies)
Discussion started by: ahamed
2 Replies

11. UNIX for Dummies Questions & Answers

Kernel/ user space and high/ low mem

Need some clarification on this.... 1. how are kernel/ user spaces and high/low memory related? 2. What do they all mean when i have the kernel command line as: "console=ttyS0,115200 root=/dev/sda2 rw mem=exactmap memmap=1M@0 memmap=96M@1M irqpoll" or 2. what do mem and memmap mean in... (3 Replies)
Discussion started by: dragonpoint
3 Replies

12. Emergency UNIX and Linux Support

Can top show more than 100% in %MEM?

Can the %MEM value for a process show more than 100% in top output?Is this ever possible? (5 Replies)
Discussion started by: proactiveaditya
5 Replies

13. Programming

Write to a specific memory space.

Hello all. I need a simple way to write to a specific memory space (/dev/mem). In a bash script if possible. (I am using dd to read the changes) Thanks in advace. (4 Replies)
Discussion started by: King_Richee
4 Replies

14. Solaris

Physical and Free mem on TOP command

Hi, When I run the free command on solaris, I get the following: "Memory: 60G phys mem, 69G free mem" Q: how cna the free mem be higher then the physical mem?:confused: Amit (3 Replies)
Discussion started by: amitlib
3 Replies

15. Solaris

Lifecycle patching

I am trying to understand how people manage lifecycle patching these days. I am not a sysadmin (I am a DB Architect) and what I am being told is that if there is any lag between patching a dev server and a prod server that we will liley get new patches in prod that have not had any soak time in... (9 Replies)
Discussion started by: mse
9 Replies

Featured Tech Videos