Got a Nice post by Mr. Rvkumar on his blog, posting it here.. So the Admins can read and take benefit of it.

• Linux Get Memory Slot Info
• Linux Print Memory Info

• First check the actual memory Info from the either “top” or “free -m” command.
• Check the “dmidecode” output for the DIMM slot and each RAM size

FREE COMMAND OUTPUT

Dmidecode shows the number of slots available for the controller. There are up to 4 DMI types, 2 can be memory arrays, and 2 can be specific slots. 2 are less common. The information in dmidecode/inxi is extremely unreliable when it comes to the array data, but the actual slot data is generally very reliable. @azorius (and probably unimplemented) means the bios/chipset can handle 4 slots, but the board manufacturer decided not to include 2 of the possible slots the bios can support in the physical realm that is the actual MB. Since dmidecode talks to the bios, rather than the actual physical screws,bolts and glue, it only knows what's in the dmi table - which is that it can handle 4 slots, but for.

So the below command shows that we have around 2GB of memory installed in the system.
[root@bravo]# free -m
total used free shared buffers cached
Mem: 2026 1585 440 0 222 551
-/+ buffers/cache: 811 1215
Swap: 4094 0 4094
TOP COMMAND OUTPUT
Let’s verify our understanding of memory available using the TOP command which also shows that we have approx 2GB memory approx.
[root@bravo]# top
top – 13:18:56 up 216 days, 4:12, 3 users, load average: 0.14, 0.11, 0.09
Tasks: 199 total, 1 running, 198 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.8% us, 1.4% sy, 0.0% ni, 97.4% id, 0.3% wa, 0.0% hi, 0.0% si
Mem: 2074900k total, 1623648k used, 451252k free, 227816k buffers
Swap: 4192924k total, 296k used, 4192628k free, 565160k cached
DMIDECODE COMMAND
Run the DMIDECODE command and look for the data where the word “Physical Memory Array” starts and go through each line to get detailed information. In some new systems you can also use the command dmidecode –s memory and dmidecode –t 17 , where “s” means string and “t” means type. Let’s just use dmidecode here for now.
Summary of the memory data
——————————————————————————————-
Maximum memory that the ON BOARD memoryslots can accept is= 8GB
Type of memory = DDR
Error Correction Type: Single-bit ECC
Size of each DIMM = 1024 MB (1GB)
DIMM Speed = 333 MHz (3.0 ns)
Number of DIMM slots = Total4 DIMM slots and only 2 DIMM slots are filled with 1GB memory each
Note: where ever the Memory module is not installed the “Size” would show as “Size: No Module Installed”
——————————————————————————————-
[root@bravo]# dmidecode more
So here is the summary of the Info that we are looking from the Important Information we have from the dmidecode data
Handle 0×1000
DMI type 16, 15 bytes.
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: Single-bit ECC
Maximum Capacity: 8 GB
Error Information Handle: Not Provided
Number Of Devices: 4
Handle 0×1100
DMI type 17, 23 bytes.
Memory Device
Array Handle: 0×1000
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: 1
Locator: DIMM 01
Bank Locator: Not Specified
Type: DDR
Type Detail: Synchronous
Speed: 333 MHz (3.0 ns)
Handle 0×1101
DMI type 17, 23 bytes.
Memory Device
Array Handle: 0×1000
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: 1024 MB
Form Factor: DIMM
Set: 1
Locator: DIMM 02
Bank Locator: Not Specified
Type: DDR
Type Detail: Synchronous
Speed: 333 MHz (3.0 ns)
Handle 0×1102
DMI type 17, 23 bytes.
Memory Device
Array Handle: 0×1000
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: No Module Installed
Form Factor: DIMM
Set: 2
Locator: DIMM 03
Bank Locator: Not Specified
Type: DDR
Type Detail: Synchronous
Speed: 333 MHz (3.0 ns)
Handle 0×1103
DMI type 17, 23 bytes.
Memory Device
Array Handle: 0×1000
Error Information Handle: Not Provided
Total Width: 72 bits
Data Width: 64 bits
Size: No Module Installed
Form Factor: DIMM
Set: 2
Locator: DIMM 04
Bank Locator: Not Specified
Type: DDR
Type Detail: Synchronous
Speed: 333 MHz (3.0 ns)
So here is my learning for the day. So I am signing of for the day looking forward to learn something new tomorrow. Infact there are couple of things that I have learnt today and I would try to either share it today or tomorrow in my new post.
Also, one thing that I started believing these days is that there is no job which is small or waste of time. We just have to look at the learning that we can grab from it. I am sure every job teaches us something might not be technical always but I am sure we would have some thing to learn from it directly or in directly.

It is essential that your Linux system runs at an optimal level. A few simple terminal commands provide access to all relevant information and help you monitor memory statistics.

In this tutorial, learn five powerful commands to check memory usage in Linux.

We also provide detailed explanations of what they do and more importantly, how to interpret the results. The commands will work with nearly all Linux distributions. In this instance, the commands and the results are presented using Ubuntu 18.04

• Access to a command line / terminal
• User with sudo privileges
• The apt package manager

Entering cat /proc/meminfo in your terminal opens the /proc/meminfo file.

This is a virtual file that reports the amount of available and used memory. It contains real-time information about the system’s memory usage as well as the buffers and shared memory used by the kernel. The output might differ slightly based on the architecture and operating system in question.

This is an example of what the /proc/meminfo file looks like in Ubuntu 18.04:

The terminal displays the information in kilobytes.

Typing freein your command terminal provides the following result:

The data represents the used/available memory and the swap memory figures in kilobytes.

total	Total installed memory
used	Memory currently in use by running processes (used= total – free – buff/cache)
free	Unused memory (free= total – used – buff/cache)
shared	Memory shared by multiple processes
buffers	Memory reserved by the OS to allocate as buffers when process need them
cached	Recently used files stored in RAM
buff/cache	Buffers + Cache
available	Estimation of how much memory is available for starting new applications, without swapping.

Compared to the /proc/meminfo file, the free command provides less information. However, it is easier to understand. The key figure being the available value as it displays how much memory is still available for running new applications.

The free command has multiple options to format the output so that it better matches your requirements. The table below lists the most useful variations of the free command.

Options	Result
-b	output in bytes
– k	output in kilobytes
– m	output in megabytes
– g	output in gigabytes
– l	detailed low and high memory statistics
– o	old format (no -/+buffers/cache line)
– t	total for RAM + swap
– s	update every [delay] seconds
– c	update [count] times

Note: As with most commands, entering man free displays an overview of all variations and descriptions of the results.

The vmstatcommand is a useful tool that reports virtual memory statistics.

vmstat provides general information about processes, memory, paging, block IO, traps, and CPU activity.

The detailed description listed below provides an explanation for each value in case you need assistance in analyzing the results.

• Procs
  • r: number of processes waiting for run time.
  • b: number of processes in uninterruptible sleep.
• Memory
  • swpd: amount of virtual memory used.
  • free: amount of idle memory.
  • buff: the amount of memory used as buffers.
  • cache: amount of memory used as cache.
• Swap
  • si: memory swapped in from disk (/s).
  • so: memory swapped to disk (/s).
• IO
  • bi: Blocks received from a block device (blocks/s).
  • bo: Blocks sent to a block device (blocks/s).
• System
  • in: number of interrupts per second, including the clock.
  • cs: number of context switches per second.
• CPU – These are percentages of total CPU time.
  • us: Time spent running non-kernel code. (user time, including nice time)
  • sy: Time spent running kernel code. (system time)
  • id: Time spent idle. Before Linux 2.5.41, this includes IO-wait time.
  • wa: Time spent waiting for IO. Before Linux 2.5.41, included in idle.
  • st: Time stolen from a virtual machine. Before Linux 2.6.11, unknown.

The top command is useful to check memory and CPU usage per process. It displays information about:

• uptime
• average load
• tasks running
• number of users logged in
• number of CPUs/CPU utilization
• memory/swap system processes

The data is continuously updated, which allows you to follow the processes in real-time.

Aside from providing you with essential memory information, the top command provides a limited interactive interface. It is possible to manipulate and configure operations by using command-line options.

The man top command provides a comprehensive list of all available variations.

The information the htop command provides is similar to the top command. However, the real advantage to the htop command is its user-friendly environment and improved controls.

The command uses color for its output, provides full command lines for processes, as well as the option to scroll both vertically and horizontally.

The following output appears:

• 1. The top segment provides summary information and contains graphic meters and text counters.
  2. The lower section structures the detailed data, per process. This allows you to perform actions on individual processes with ease.
  3. The shortcuts listed at the bottom of the screen will enable you to manipulate and customize the processes quickly and without the need to type specific commands.

Note: If you run into “Command ‘htop’ not found” message when trying to run the htop command, you will need to install the htop function first:

Linux Get Memory Slot Info

As an alternative, use the command below:

Linux Print Memory Info

Using a graphical interface for server administration is not common practice. However, certain data sets are much clearer, with a visual representation of memory usage.

To access the System Monitor:

1. Navigate to Show Applications.
2. Enter System Monitor in the search bar and access the application.
3. Select the Resources tab.
4. A graphical overview of your memory consumption in real time, including historical information is displayed.

This guide provided several options to check memory usage on your Linux system. We learned that a single command provides an abundance of valuable data for future analysis. Learning to interpret the information correctly is critical.

Now you can administer your server more efficiently.

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