How to display physical memory details in Linux

Knowing the physical memory details of your Linux system can help you monitor memory usage, troubleshoot performance issues, or plan for hardware upgrades. Linux provides various commands to check the total memory, available memory, and other detailed information about the system's physical memory.

Different tools are available to view these details, each offering specific information about the system’s memory. These tools include basic commands like free and top for general memory status and more advanced ones like dmidecode to display hardware-level information about installed memory modules. These commands are accessible directly from the terminal and do not require any special configuration.

This article outlines several commands to help you display and analyze the physical memory details on a Linux system. These commands provide information such as total memory size, memory type, speed, and usage statistics.

1. Open the terminal on your Linux system.
2. Check the total and available memory using the free command.

   $ free -h
                 total        used        free      shared  buff/cache   available
   Mem:          15Gi       2.3Gi       9.6Gi       221Mi       3.3Gi        12Gi
   Swap:        2.0Gi          0B       2.0Gi

   This command shows the total, used, and available memory in human-readable format (MB or GB).

3. Use the top command to display real-time memory usage.

   $ top
   top - 10:20:34 up  1:15,  2 users,  load average: 0.32, 0.44, 0.55
   Tasks: 199 total,   1 running, 198 sleeping,   0 stopped,   0 zombie
   %Cpu(s):  3.2 us,  1.3 sy,  0.0 ni, 94.5 id,  0.7 wa,  0.1 hi,  0.1 si,  0.0 st
   MiB Mem :  15712.0 total,  2350.5 used,  9847.2 free,   223.1 shared,  3514.3 buff/cache
   MiB Swap:  2048.0 total,     0.0 used,  2048.0 free

   Press `q` to exit the top command. This tool also displays the running processes and how much memory each process is consuming.

4. View detailed hardware information about the installed memory using dmidecode.

   $ sudo dmidecode --type memory
   Memory Device
       Size: 8192 MB
       Form Factor: DIMM
       Type: DDR4
       Speed: 3200 MHz
       Manufacturer: Samsung
       Serial Number: 1234567890
       Part Number: ABCD1234XYZ
       ...

   The dmidecode command provides in-depth details about each memory module, such as size, speed, manufacturer, and type (e.g., DDR4, DDR5).

5. Display memory information from the proc file system.

   $ cat /proc/meminfo
   MemTotal:       15712000 kB
   MemFree:        10035200 kB
   MemAvailable:   12567000 kB
   Buffers:          512000 kB
   Cached:          3000000 kB
   SwapTotal:      2048000 kB
   SwapFree:       2048000 kB

   This command shows raw data about memory usage and allocation directly from the kernel.

6. Use the vmstat command to display memory statistics.

   $ vmstat -s
        15712000 K total memory
         2350500 K used memory
         9847200 K active memory
          512000 K buffer memory
         2048000 K total swap
               0 K used swap

   The vmstat command provides detailed statistics about system memory usage, including free memory, used memory, and memory buffers.

7. Get a summary of memory usage and other system resources using the htop command.

   $ htop
   Mem[|||||    2.34G/15.7G]
   Swp[          0K/2.0G]

   If htop is not installed, use your package manager to install it:

   $ sudo apt install htop #Ubuntu
   $ sudo yum install htop #CentOS