Apa bedane antara ENTRYPOINT lan CMD?

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Accepted Answer

**ENTRYPOINT** lan **CMD** loro-lorone nggandeng apa sing mlaku nalika container miwiti, nanging padha gawe peran beda lan obah ing cara-cara khusus. Mangerteni bedane (lan loro bentuke — exec vs shell) penting kanggo nulis Dockerfile sing tumindak bener.

## CMD — perintah default (bisa diganti)

```dockerfile
CMD ["node", "server.js"]
# → the DEFAULT command when the container starts
# → but it's REPLACED if you pass a command at run time:
#   docker run myapp echo hello   → runs "echo hello" INSTEAD of node server.js
```

`CMD` nyedhiyakake **perintah default**, kang **diganti kanthi lengkap** dening perintah apa wae sing diwenehi ing `docker run`.

## ENTRYPOINT — executable tetep

```dockerfile
ENTRYPOINT ["node", "server.js"]
# → ALWAYS runs; run-time arguments are APPENDED (not replacing it):
#   docker run myapp --port 8080   → runs "node server.js --port 8080"
# → makes the container behave like a specific executable
```

`ENTRYPOINT` nyetakake **executable tetep** kang tansah mlaku; argument run-time **ditambahake** minangka argumenten-e tinimbang ngganteni.

## Nggunaake loro-lorone (pola umum)

```dockerfile
ENTRYPOINT ["node", "server.js"]   # the fixed command
CMD ["--port", "3000"]              # DEFAULT arguments (overridable)
# docker run myapp                  → node server.js --port 3000 (defaults)
# docker run myapp --port 8080      → node server.js --port 8080 (CMD overridden)
→ ENTRYPOINT = the command; CMD = default arguments you can override. A clean pattern.
```

## Bentuk exec vs bentuk shell

```text
EXEC form  → CMD ["node", "server.js"]  (JSON array) — PREFERRED:
  runs the executable DIRECTLY (PID 1) → receives signals (SIGTERM) → graceful shutdown
SHELL form → CMD node server.js  → runs via /bin/sh -c → the shell is PID 1,
  the app may NOT receive signals properly (shutdown issues) → avoid for the main process
```

## Apa sing penting

Mangerteni bedane ENTRYPOINT lan CMD penting kanggo **nulis Dockerfile kang tumindak bener**, dadi pengetahuan praktis kang berharga lan topik kang asring mbingungake.

Bedane ing tumindak penting: **CMD** nyedhiyakake perintah default kang **diganti kanthi lengkap** dening perintah apa wae kang dikirimi menyang `docker run`, dene **ENTRYPOINT** nyetakake executable tetep kang tansah mlaku kanthi argument run-time **ditambahake** — tumindak beda-beda kang nyukupi carane container nanggapi argument run-time.

Mangerteni **pola umum nggunaake loro-lorone** (`ENTRYPOINT` minangka perintah lan `CMD` minangka argument default kang bisa diganti) minangka pendekatan bersih lan idiomatis kang ndadekake container tumindak kaya executable kang bisa dikonfigurasi — teknik kang wis-wis digunakake sing patut dimangerteni.

Sang penting, mangerteni **bentuk exec vs bentuk shell** penting kanggo kaengganan: **bentuk exec** (array JSON, conto: `CMD ["node", "server.js"]`) luwih milih amarga mlaku executable-e **langsung minangka PID 1**, dadi **nampa sinyal kaya SIGTERM** kanthi bener, ngaktifake **pamungkas kang arum** — dene **bentuk shell** (`CMD node server.js`) mlaku liwat shell kang dadi PID 1, asring ndadekake aplikasi **ora nampa sinyal pamungkas kanthi bener** (ndadekake pamungkas sing ora arum, ilang pakaryan sing isih mlayu, utawa pamungkas kang alon).

Masalah penanganan-sinyal/pamungkas-arum iki masalah nyata lan halus kang disirnakake bentuk exec.

Amarga nggandeng apa kang mlaku nalika container miwiti minangka kasunyatan kanggo saben Dockerfile, lan amarga bedane ENTRYPOINT/CMD (lan keprihatinan sinyal bentuk-exec-vs-shell) langsung ngaruhi tumindake container lan kaengganan (panganan argument, pamungkas arum), mangerteni ENTRYPOINT vs CMD — peran-e, carane obah, lan praktik bentuk-exec-kanggo-sinyal kang penting — pengetahuan Docker kang berharga, praktis-relevan, topik kang asring salah mangerteni ngendi mangerteni bedane nyegah gangguan tumindak lan pamungkas kang nyata.