How to check the System Information about Memory usage on Linux ?

Описание: How to check the System Information about Memory usage on Linux ?
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Memory
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1. free
free displays the total amount of free and used physical and swap memory in the system, as well as the buffers and caches used by the kernel. The information is gathered by parsing /proc/meminfo.

free
free -b Memory in Bytes
free -k Memory in KiloBytes(default)
free -m Memory in Megabytes
free -g Memory in Gigabytes
free -h Human readable format
free -w Wide format
free -c Count, used with -s (secs)
Example "free -c 2 -s 5"

free -l Low and High Stats
free -t Memory info with Total

How to create a Huge file and check the Cache
WARNING : The Filesystem will get full.
nohup dd if=/dev/zero of=test9 bs=10k &

2. cat /proc/meminfo

3. vmstat (virtual memory stats)
vmstat -a Display in/active Memory
vmstat -s Memory Statistics
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