Using the free Command
The free command is used to display the amount of free and used memory in the system.
It's useful for monitoring memory usage and managing system resources.
Basic Usage
To display memory usage, use free :
Example
free -k
total used free shared buff/cache available
Mem: 8176588 1376568 5869188 146532 1051172 6352280
Swap: 2097148 0 2097148Options
The free command has options to change how it works:
- -h - Show memory in human-readable format (e.g., KB, MB, GB)
- -b - Show memory in bytes
- -k - Show memory in kilobytes (KB)
- -m - Show memory in megabytes (MB)
- -g - Show memory in gigabytes (GB)
- -s [interval] - Continuously display memory usage at specified intervals
- -t - Display total memory
Show Memory in Human-Readable Format
The -h option allows you to show memory in a human-readable format, such as KB, MB, or GB.
Without this option, memory is displayed in kilobytes by default.
Example: Show Memory in Human-Readable Format
free -h
total used free shared buff/cache available
Mem: 7.8G 1.3G 5.6G 142M 1.0G 6.1G
Swap: 2.0G 0B 2.0GShow Memory in Bytes
The -b option allows you to show memory in bytes, providing a more precise measurement.
Without this option, memory is displayed in kilobytes by default.
Example: Show Memory in Bytes
free -b
total used free shared buff/cache available
Mem: 8374145024 1409286144 6008344576 149946368 1076512768 6563766272
Swap: 2147479552 0 2147479552Show Memory in Kilobytes
The -k option allows you to show memory in kilobytes.
This is the default behavior of the free command.
Example: Show Memory in Kilobytes
free -k
total used free shared buff/cache available
Mem: 8176588 1376568 5869188 146532 1051172 6352280
Swap: 2097148 0 2097148Show Memory in Megabytes
The -m option allows you to show memory in megabytes, which can be easier to read for larger memory sizes.
Without this option, memory is displayed in kilobytes by default.
Example: Show Memory in Megabytes
free -m
total used free shared buff/cache available
Mem: 7985 1344 5730 143 1026 6199
Swap: 2047 0 2047Show Memory in Gigabytes
The -g option allows you to show memory in gigabytes, which is useful for systems with large amounts of memory.
Without this option, memory is displayed in kilobytes by default.
Example: Show Memory in Gigabytes
free -g
total used free shared buff/cache available
Mem: 7 1 5 0 1 6
Swap: 1 0 1Continuously Display Memory Usage
The -s option allows you to continuously display memory usage at specified intervals. This is useful for monitoring memory usage over time.
Example: Continuously Display Memory Usage
free -s 5This command will update the memory usage every 5 seconds.
Display Total Memory
The -t option includes a line showing the total memory (used + free) for both RAM and swap. This provides a quick overview of total memory resources.
Example: Display Total Memory
free -t
total used free shared buff/cache available
Mem: 8176588 1376568 5869188 146532 1051172 6352280
Swap: 2097148 0 2097148
Total: 10273736 1376568 7966336