free

See how much memory is used and free

What it does

free -h shows memory and swap: the total, used, free and available. The column that matters is available: how much memory programs can get right now.

A small number under free is no reason to panic: Linux uses spare memory as a disk cache (buff/cache) and gives it back as soon as it is needed. But if available is nearly gone and swap is busy, the server slows down.

Syntax

free -h

Examples

• See how much memory is used and available

  free -h

  same as: free --human

  • free — memory and swap
  • -h — in readable units

Related commands

• top — Watch the system load and processes live
• df — See how much disk space there is
• ps — List processes

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