Several methods to check available memory size in Linux

As Linux users, especially administrators, we need to check how much memory resources the system uses and how many memory resources are free. Since the most important thing is to check the memory resources on the server, it is best to learn the relevant commands that can help us with server management.

This article explains the use of the following 5 commands to check available memory:

1, free command

2, vmstat command

3, /proc/ meminfo command

4, top command

5, htop command

By using these commands, you can always ensure that there are enough memory resources for running on the server. process. For example, if you're running a web server, you can make sure that missing resources don't slow down your site, or that it doesn't stop functioning entirely.

We ran the commands and procedures mentioned in this article on a CentOS 7.5 system, as well as on Ubuntu Linux.

To view memory usage, we use the Linux command line, terminal application. You can open the terminal via the system Dash.

Method 1: free command

Since the free command is the most widely used and undoubtedly the most useful, we will mention its usage first. This command is used to check information about system RAM usage. Here is the command you would enter in the terminal:

available column represents available memory.

The used column in the Swap entry is 51, which means it uses 51M and the free part is 1996M.

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Method 2: vmstat command

To view memory statistics through the vmstat command Information, you can use it in the following ways:

s tag provides detailed statistics about memory usage.

You can view Free Memory and Free Swap Memory entries in the output, indicating the available memory in the system.

Method 3: /proc/meminfo command

The following command extracts memory-related information from the /proc file system. These files contain dynamic information about the system and kernel, rather than real system files.

This is the command used to print memory information:

The output of this command is similar to the vmstat command. You can easily view free memory in MemFree results and available swap memory in SwapFree results.

Method 4: top command

The top command is used to print the CPU and memory usage of the system. You can use this command as follows:

In the header of the output you can see the KiB Mem and Kib Swap entries through which you can check the used and available memory resources.

Method 5: htop command

Just like the top command, the htop command also analyzes your CPU and memory usage in detail. If htop is not installed on your system, you can first update the abt repository to install it under Ubuntu by running the following command:

$ sudo apt-get update

Then enter the following command

$ sudo apt install htop

Use the following command to install under CentOS:

[linuxidc@localhost ~]$ sudo yum install htop

After installing htop, you can simply use the following command to print the required information:

[linuxidc@localhost ~]$ htop

Mem in title (Memory aka RAM) and Swp (Swap) entries represent used and total memory, through which the free memory available on the system can be calculated.

Using the commands we mentioned in this article, you can monitor the system process memory situation. You can not use the GUI at all and still check memory usage on your personal computers and servers.

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