Learn more about How To Check Memory Usage In Linux ;
Overview Of Linux
Linux is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged in a Linux distribution. Linux is the best-known and most-used open source operating system. As an operating system, Linux is software that sits underneath all of the other software on a computer, receiving requests from those programs and relaying these requests to the computer’s hardware.
What Is Meant By Memory Usage In Linux ?
The Memory Usage window displays the amount of memory available on your system, as well as the memory currently in use by all applications, including Windows itself.Memory utilization is calculated using the “free” command. The output of this command varies according to the Linux distribution used. Case 1: Memory Utilized = ( (Total – Free Memory) / Total * 100 ).
How To Check Memory Usage In Linux using the GUI
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:
- Navigate to Show Applications.
- Enter System Monitor in the search bar and access the application.
- Select the Resources tab.
- A graphical overview of your memory consumption in real time, including historical information is displayed.
Commands to Check Memory Use in Linux
cat Command to Show Linux Memory Information
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.
free Command to Display the Amount of Physical and Swap Memory
Typing free in 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 kibibytes |
| -m | output in mebibytes |
| -g | output in gibibytes |
| -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 |
vmstat Command to Report Virtual Memory Statistics
The vmstat command 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.
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