Summary
A practical reference covering four methods for monitoring memory usage on Linux systems: the free command, interactive process viewers (htop/top/btop++), the /proc/meminfo virtual file, and GUI system monitors. Each method is explained with what it displays and when to use it, making this a quick-reference guide for sysadmins and DevOps engineers diagnosing memory issues.
一篇實用的 Linux 記憶體監控參考指南，涵蓋四種方法：free 指令、互動式程序查看器（htop/top/btop++）、/proc/meminfo 虛擬檔案，以及 GUI 系統監控器。適合系統管理員和 DevOps 工程師快速診斷記憶體問題。
Key Points
free -h: shows total/used/free/buff-cache/available in human-readable format;available≠free(buff/cache is reclaimable)buff/cacheis not wasted memory — it can be reclaimed by applications at any timehtop/top/btop++: real-time per-process%MEMcolumn plus system summary header/proc/meminfo: the raw source file that all other tools (free,htop,ps) read from; parseable in shell scripts- GUI system monitor (GNOME): useful for historical visualization of memory trends, though rare in production sysadmin workflows
Insights
- The
availablecolumn infreeis more useful thanfreefor capacity planning — it accounts for reclaimable cache, which is the actual headroom for new processes /proc/meminfobeing the authoritative source means all other tools are just formatted views of the same data; scripting against it directly removes tool dependencies- This article pairs directly with the DevOps 6-month roadmap in this vault: Linux Month 1 covers exactly these diagnostic skills — knowing where memory lives is foundational before debugging process crashes
Connections
Raw Excerpt
The simplest method to check RAM memory use is to display the contents of the /proc/meminfo virtual file. This file is utilized by the free, htop, top, ps, and other system information commands.