Chapter 4: Linux Ops Refresh for DevOps
4.8 Quick extras — uptime, memory, who am I
Handy one-liners you will see in runbooks:
uptime # how long the VM ran; load averages
free -h # memory (human units)
whoami # current user
id # user + groups
uname -a # kernel / OS hint
Why load and memory. High load with a healthy app process can mean CPU saturation. Low free memory with heavy swap can make the API crawl. You do not need to tune kernels here — you need to notice the symptom and say it clearly.
| Symptom | Possible next look |
|---|---|
systemctl failed |
journalctl -u … |
Port missing in ss |
Start service / wrong listen port in app config |
| Disk 100% | Clear old logs/images carefully; find large files with guidance |
| Localhost OK, internet not | Security Group / OS firewall (AWS networking habits) |