How can I find out the total physical memory RAM of my linux box suitable to be parsed by a shell script

Question

I m typing a shell script to find out the total physical memory in some RHEL linux boxes   First of all I want to stress that I m interested in the total physical memory recognized by kernel  not just the available memory  Therefore  please  avoid answers suggesting to read  proc meminfo or to use the free  top or sar commands -- In all these cases  their  total memory  values mean  available memory  ones   The first thought was to read the boot kernel messages   Memory  61861540k 63438844k available  2577k kernel code  1042516k reserved  1305k data  212k init    But in some linux boxes  due to the use of EMC2 s PowerPath software and its flooding boot messages in the kernel startup  that useful boot kernel message is not available  not even in the  var log dmesg file   The second option was the dmidecode command  I m warned against the possible mismatch of kernel recognized RAM and real RAM due to the limitations of some older kernels and architectures   The option --memory simplifies the script but I realized that older releases of that command has no --memory option   My last chance was the getconf command  It reports the memory page size  but not the total number of physical pages -- the  PHYS PAGES system variable seems to be the available physical pages  not the total physical pages      getconf -a   grep PAGES PAGESIZE                           4096  AVPHYS PAGES                      1049978  PHYS PAGES                        15466409   My question  Is there another way to get the total amount of physical memory  suitable to be parsed by a shell script

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In Linux Kernel  present pages are physical pages of RAM which kernel can see  Literally  present pages is total size of RAM in 4KB unit  grep present  proc zoneinfo   awk   sum   2 END print sum 4  quot KB quot     The  MemTotal  form  proc meminfo is the total size of memory managed by buddy system And we can also compute it like this  grep managed  proc zoneinfo   awk   sum   2 END print sum 4  quot KB quot

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cat  proc meminfo   grep MemTotal or free gives you the exact amount of RAM your server has  This is not  available memory    I guess your issue comes up when you have a VM and you would like to calculate the full amount of memory hosted by the hypervisor but you will have to log into the hypervisor in that case   cat  proc meminfo   grep MemTotal   is equivalent to    getconf -a   grep PAGES   awk  BEGIN  total   1   if  NR    1    NR    3  total    NF  END  print total   1024  kB

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Total memory in Mb   x   awk   MemTotal   print  2    proc meminfo  echo    x 1024     or   x   awk   MemTotal   print  2    proc meminfo    echo    x 1024

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free -h   awk   Mem      print  2       This will provide you with the total memory in your system in human readable format and automatically scale to the appropriate unit   e g  bytes  KB  MB  or GB

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If you re interested in the physical RAM  use the command dmidecode  It gives you a lot more information than just that  but depending on your use case  you might also want to know if the 8G in the system come from 2x4GB sticks or 4x2GB sticks

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Total online memory  Calculate the total online memory using the sys-fs   totalmem 0  for mem in  sys devices system memory memory   do         cat   mem  online       1            amp  amp  totalmem    totalmem    0x  cat  sys devices system memory block size bytes       done   one-line code totalmem 0  for mem in  sys devices system memory memory   do       cat   mem  online       1      amp  amp  totalmem    totalmem    0x  cat  sys devices system memory block size bytes       done  echo   totalmem  bytes echo    totalmem 1024  3   GB   Example output for 4 GB system   4294967296 bytes 4 GB   Explanation      sys devices system memory block size bytes   Number of bytes in a memory block  hex value   Using 0x in front of the value makes sure it s properly handled during the calculation       sys devices system memory memory    Iterating over all available memory blocks to verify they are online and add the calculated block size to totalmem if they are            cat   mem  online       1      amp  amp    You can change or remove this if you prefer another memory state

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One more useful command  vmstat -s   grep memory sample output on my machine is       2050060 K total memory   1092992 K used memory    743072 K active memory    177084 K inactive memory    957068 K free memory    385388 K buffer memory   another useful command to get memory information is  free sample output is                  total       used       free     shared    buffers     cached Mem        2050060    1093324     956736        108     385392     386812 -   buffers cache      321120    1728940 Swap       2095100       2732    2092368   One observation here is that  the command free gives information about swap space also  The following link may be useful for you  http   www linuxnix com find-ram-details-in-linuxunix

User · Answer

Have you tried cat  proc meminfo  You can then awk or grep out what you want  MemTotal e g   awk   MemTotal   print  2    proc meminfo   or  cat  proc meminfo   grep MemTotal

User · Answer

Add the last 2 entries of  proc meminfo  they give you the exact memory present on the host   Example   DirectMap4k        10240 kB DirectMap2M      4184064 kB   10240   4184064   4194304 kB   4096 MB

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I know this question was asked a long time ago  but I wanted to provide another way to do this that I found useful for an issue I just worked on  lshw -c memory  lshw  lshw is a small tool to extract detailed information on the hardware configuration of the machine  It can report exact memory configuration  firmware version  mainboard configuration  CPU version and speed  cache configuration  bus speed  etc  on DMI-capable x86 or IA-64 systems and on some PowerPC machines  PowerMac G4 is known to work

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These are the ways    1   proc meminfo  MemTotal  8152200 kB  MemFree  760808 kB   You can write a code or script to parse it   2  Use sysconf by using below macros  sysconf   SC PHYS PAGES    sysconf   SC PAGESIZE    3  By using sysinfo system call  int sysinfo struct sysinfo  info    struct sysinfo                      unsigned long totalram     Total memory size to use        unsigned long freeram       Available memory size

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dmidecode -t 17   grep  Size    Adding all above values displayed after  Size    will give exact total physical size of all RAM sticks in server

User · Answer

I find htop a useful tool       sudo apt-get install htop    and then     free -m   will give the information you need

[linux] How can I find out the total physical memory (RAM) of my linux box suitable to be parsed by a shell script?

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