CLI Basics for Node

Q: jq not installed on minimal container?

Run from bastion or debug pod with jq. Alternatively node -e parse JSON, but jq is faster for ops.

10 examples for curl, jq, ss, and log tailing on Linux servers running Node.js APIs - 7 basic and 3 intermediate.

Prerequisites

SSH access to a staging or production VM/container host (read-only role for juniors).
curl, jq, and ss installed (default on most Linux images).
Know your service port (3000 default) and health route (/health).

Basic Examples

1. Health Check with curl

curl -sf http://localhost:3000/health
curl -sf http://localhost:3000/ready

-s silent, -f fail on HTTP 4xx/5xx (non-zero exit)
Use in load balancer probes and deploy smoke scripts
ready should fail when Postgres/Redis unreachable

# With timing for latency triage
curl -sf -w "time_total=%{time_total}\n" -o /dev/null http://localhost:3000/health

2. POST JSON to an API

curl -sf -X POST http://localhost:3000/orders \
  -H "Content-Type: application/json" \
  -H "x-request-id: cli-smoke-$(date +%s)" \
  -d '{"customerId":"550e8400-e29b-41d4-a716-446655440000","items":[{"sku":"550e8400-e29b-41d4-a716-446655440001","quantity":1}]}'

Always send x-request-id for log correlation
Pipe through jq for readable output: | jq .

3. Filter JSON Logs with jq

# Last 100 error lines from container stdout
kubectl logs deploy/orders-api --tail=500 | jq -c 'select(.level=="error")' | tail -20
 
# Trace one request
kubectl logs deploy/orders-api --since=10m | jq -c 'select(.requestId=="abc-123")'

Pino logs are one JSON object per line - perfect for jq
select(.statusCode >= 500) for HTTP errors in request_complete events

Related: pino - log field conventions

4. List Listening Ports with ss

ss -tlnp | grep node
ss -tlnp 'sport = :3000'

ss replaces deprecated netstat on modern Linux
Confirm Node bound 0.0.0.0:3000, not 127.0.0.1 only in containers
Check TIME-WAIT accumulation under load: ss -s

5. Tail systemd Journal for Node Service

sudo journalctl -u orders-api -f --since "15 min ago"
sudo journalctl -u orders-api -p err --since today

-f follow live logs on VMs without Kubernetes
Pair with systemctl status orders-api for restart loops

6. Follow Docker Container Logs

docker logs -f --tail 200 orders-api
docker logs orders-api 2>&1 | jq -c 'select(.level=="error")' | tail -10

Node apps log to stdout - Docker captures it
Do not docker exec to read log files that do not exist

7. DNS and Upstream Check from Server

curl -sf https://api.stripe.com/v1/charges -H "Authorization: Bearer sk_test_xxx" -o /dev/null -w "%{http_code}\n"
getent hosts postgres.internal

Distinguish app bug vs network/DNS failure during incidents
Run from same network namespace as the app pod when possible

Intermediate Examples

8. Smoke Script in Repo

#!/usr/bin/env bash
set -euo pipefail
BASE_URL="${BASE_URL:-http://localhost:3000}"
 
curl -sf "$BASE_URL/health" | jq -e '.status == "ok"'
curl -sf "$BASE_URL/ready" | jq -e '.status == "ok"'
echo "smoke OK"

Commit to bin/smoke.sh; run post-deploy in CI or SSH
set -euo pipefail fails fast on first error

Related: Linux CLI Best Practices - script hygiene

9. Compare Response Headers (Caching, Auth)

curl -sI http://localhost:3000/orders/1 | grep -iE 'cache-control|x-request-id|content-type'

-I HEAD request for metadata only
Verify CDN/cache headers on GET routes

10. Load Spot-Check with curl Loop

for i in $(seq 1 20); do
  curl -sf -o /dev/null -w "%{http_code} %{time_total}\n" http://localhost:3000/health
done

Quick manual check before declaring incident resolved
For real load tests use k6 or autocannon, not bash loops in production

FAQs

jq not installed on minimal container?

Run from bastion or debug pod with jq. Alternatively node -e parse JSON, but jq is faster for ops.

curl works locally but not from laptop to prod?

Expected - production is behind VPN or private network. SSH to bastion or kubectl port-forward first.

Process Inspection - top, lsof
Linux CLI Best Practices - portable summary
Incident Triage Skill - incident commands

Node.js Learn Guides - Official learning path.
DigitalOcean Node.js Tutorials - Production-oriented how-tos.
NodeSchool - Free interactive workshoppers.
Node.js the Right Way - Server-side JavaScript fundamentals.
Get Programming with Node.js - Introductory programming with Node.js.

Stack versions: This page was written for Node.js 24.18.0 (Active LTS), npm 10+, TypeScript 5.6+, Express 5, Fastify 5, and NestJS 11.

Prerequisites

SSH access to a staging or production VM/container host (read-only role for juniors).
curl, jq, and ss installed (default on most Linux images).
Know your service port (3000 default) and health route (/health).

Basic Examples

1. Health Check with curl

curl -sf http://localhost:3000/health
curl -sf http://localhost:3000/ready

-s silent, -f fail on HTTP 4xx/5xx (non-zero exit)
Use in load balancer probes and deploy smoke scripts
ready should fail when Postgres/Redis unreachable

# With timing for latency triage
curl -sf -w "time_total=%{time_total}\n" -o /dev/null http://localhost:3000/health

2. POST JSON to an API

curl -sf -X POST http://localhost:3000/orders \
  -H "Content-Type: application/json" \
  -H "x-request-id: cli-smoke-$(date +%s)" \
  -d '{"customerId":"550e8400-e29b-41d4-a716-446655440000","items":[{"sku":"550e8400-e29b-41d4-a716-446655440001","quantity":1}]}'

Always send x-request-id for log correlation
Pipe through jq for readable output: | jq .

3. Filter JSON Logs with jq

# Last 100 error lines from container stdout
kubectl logs deploy/orders-api --tail=500 | jq -c 'select(.level=="error")' | tail -20
 
# Trace one request
kubectl logs deploy/orders-api --since=10m | jq -c 'select(.requestId=="abc-123")'

Pino logs are one JSON object per line - perfect for jq
select(.statusCode >= 500) for HTTP errors in request_complete events

Related: pino - log field conventions

4. List Listening Ports with ss

ss -tlnp | grep node
ss -tlnp 'sport = :3000'

ss replaces deprecated netstat on modern Linux
Confirm Node bound 0.0.0.0:3000, not 127.0.0.1 only in containers
Check TIME-WAIT accumulation under load: ss -s

5. Tail systemd Journal for Node Service

sudo journalctl -u orders-api -f --since "15 min ago"
sudo journalctl -u orders-api -p err --since today

-f follow live logs on VMs without Kubernetes
Pair with systemctl status orders-api for restart loops

6. Follow Docker Container Logs

docker logs -f --tail 200 orders-api
docker logs orders-api 2>&1 | jq -c 'select(.level=="error")' | tail -10

Node apps log to stdout - Docker captures it
Do not docker exec to read log files that do not exist

7. DNS and Upstream Check from Server

curl -sf https://api.stripe.com/v1/charges -H "Authorization: Bearer sk_test_xxx" -o /dev/null -w "%{http_code}\n"
getent hosts postgres.internal

Distinguish app bug vs network/DNS failure during incidents
Run from same network namespace as the app pod when possible

Intermediate Examples

8. Smoke Script in Repo

#!/usr/bin/env bash
set -euo pipefail
BASE_URL="${BASE_URL:-http://localhost:3000}"
 
curl -sf "$BASE_URL/health" | jq -e '.status == "ok"'
curl -sf "$BASE_URL/ready" | jq -e '.status == "ok"'
echo "smoke OK"

Commit to bin/smoke.sh; run post-deploy in CI or SSH
set -euo pipefail fails fast on first error

Related: Linux CLI Best Practices - script hygiene

9. Compare Response Headers (Caching, Auth)

curl -sI http://localhost:3000/orders/1 | grep -iE 'cache-control|x-request-id|content-type'

-I HEAD request for metadata only
Verify CDN/cache headers on GET routes

10. Load Spot-Check with curl Loop

for i in $(seq 1 20); do
  curl -sf -o /dev/null -w "%{http_code} %{time_total}\n" http://localhost:3000/health
done

Quick manual check before declaring incident resolved
For real load tests use k6 or autocannon, not bash loops in production

FAQs

jq not installed on minimal container?

Run from bastion or debug pod with jq. Alternatively node -e parse JSON, but jq is faster for ops.

curl works locally but not from laptop to prod?

Expected - production is behind VPN or private network. SSH to bastion or kubectl port-forward first.

Process Inspection - top, lsof
Linux CLI Best Practices - portable summary
Incident Triage Skill - incident commands

Node.js Learn Guides - Official learning path.
DigitalOcean Node.js Tutorials - Production-oriented how-tos.
NodeSchool - Free interactive workshoppers.
Node.js the Right Way - Server-side JavaScript fundamentals.
Get Programming with Node.js - Introductory programming with Node.js.

Stack versions: This page was written for Node.js 24.18.0 (Active LTS), npm 10+, TypeScript 5.6+, Express 5, Fastify 5, and NestJS 11.

CLI Basics for Node

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CLI Basics for Node