mjhjmtu

we have linux machine with 32G

we capture the mem as the follwing

mem=` cat /proc/meminfo | grep MemTotal | awk 'print $2' `
echo $mem
32767184

and now we convert it to GIGA

mem_in_giga=` echo $(( $mem / 1024 / 1024)) `
echo $mem_in_giga
31

but from results we get 31 and not 32G

the same story with free command

free -g
 total used free shared buff/cache available
Mem: 31 9 17 0 4 20
Swap: 7 0 7

so how to get the 32G by any command solution?

MemTotal shows

Total usable RAM (i.e., physical RAM minus a few reserved bits and the kernel binary
code).

You can’t use that to determine the exact installed memory, except by using heuristics...

To determine the actual installed memory, you should use lshw or dmidecode which will show the size of the installed modules; e.g. from lshw:

 *-memory
 description: System Memory
 physical id: 4c
 slot: System board or motherboard
 size: 32GiB
 capabilities: ecc
 configuration: errordetection=ecc

or in more compact form (lshw -class memory -short):

H/W path Device Class Description
=========================================================
/0/0 memory 64KiB BIOS
/0/47/48 memory 256KiB L1 cache
/0/47/49 memory 1MiB L2 cache
/0/47/4a memory 8MiB L3 cache
/0/4c memory 32GiB System Memory
/0/4c/0 memory 8GiB DIMM DDR3 Synchronous 1600 MHz (0.6 ns)
/0/4c/1 memory 8GiB DIMM DDR3 Synchronous 1600 MHz (0.6 ns)
/0/4c/2 memory 8GiB DIMM DDR3 Synchronous 1600 MHz (0.6 ns)
/0/4c/3 memory 8GiB DIMM DDR3 Synchronous 1600 MHz (0.6 ns)