The free(1) <https://linux.die.net/man/1/free> command shows you system memory usage. E.g. on my laptop a few seconds ago: ldo(a)theodora:~> free total used free shared buff/cache available Mem: 7922644 1210968 3137520 135964 3574156 6265612 Swap: 8388604 24912 8363692 But there’s something not quite right about that “total” number. The machine has 8GiB of RAM, which should show as 8388608KiB. What happened to the remaining 465964KiB? That is taken up by the kernel. But where can you find a figure for this amount? Where can you make up a total that adds up to 8388608KiB? Seems there is no such place, at least not one accessible to non-privileged software. free(1) gets its info from /proc/meminfo, which is where the kernel reports it. But there is no place in this file (or anywhere else that I know of) that the kernel calculates its own memory usage. However, there is a privileged tool, dmidecode(8) <https://linux.die.net/man/8/dmidecode>, which can get information direct from the “DMI” (aka “SMBIOS”) table. In particular, the command dmidecode -t 17 on the laptop reports two “Memory Device” entries (slots for RAM DIMMs?), one of which says “Size: No Module Installed” while the other has “Size: 8192 MB” (which obviously means 8192MiB). So you have to take the total from here as your actual physical RAM, and subtract the amount shown by free(1) (or read from /proc/meminfo) to get the kernel RAM usage.