Linux Survival Basics
Read-onlyCheck Memory Pressure Quickly
A VPS feels slow, and people often restart daemons before checking whether memory pressure is the cause.
Command
free -hBefore you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not use it to identify which process is responsible; follow up with ps, top, or systemd-cgtop.
Expected output
A memory table with total, used, free, buff/cache, and available columns.
System impact
Read-only. Nothing changes. free prints total, used, free, shared, buff/cache, and available memory.
Recovery / rollback: no state is changed.
When to use it
Use during slowdowns, deploy validation, memory alerts, or before resizing a VPS.
When not to use it
Do not use it to identify which process is responsible; follow up with ps, top, or systemd-cgtop.
next steps
Related commands
Check Memory Pressure with free
Linux memory numbers look scary until you know which column matters.
free -h
Spot OOM Kills in the Kernel Journal
Exit code 137 often means the kernel has something to say.
journalctl -k --since "2 hours ago" --no-pager -o short-iso | grep -Ei 'out of memory|oom|killed process'
Find the Processes Eating Memory
Memory pressure can look like a slow app, a stuck deploy, or random crashes.
ps -eo pid,ppid,stat,pcpu,pmem,rss,comm,args --sort=-pmem | head -n 10
Snapshot Container CPU and Memory
Get Docker resource usage once, without leaving a live dashboard running.
docker stats --no-stream --format 'table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}\t{{.BlockIO}}'
Find the Processes Using Memory
The server felt slow. Memory pressure was the first thing to rule out.
ps -eo pid,comm,%mem,%cpu --sort=-%mem | head
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.