Hunt the RAM hog in 3 commands

Hunt the RAM hog in 3 commands
Box at 95% memory and you don't know why. My triage order:
— free -h first — if buff/cache is high that's FINE, Linux uses free RAM as cache, ignore it
— Real offenders: ps aux --sort=-%mem | head -5
— Per-process truth (shared memory counted once): smem -tk -c 'name pss' | sort -k2 -h | tail
— MySQL usually wins. Drop innodb_buffer_pool_size to 128M on a tiny box and reclaim 300MB instantly
Know your real headroom before you upsize the plan. Try it tonight.