Docker Cheatsheet
If you can’t find what you are looking for try my other sources:
Index:
Docker
Manipulating Output
Filter and specify the name that you are interested in:
$ docker ps -f name=my-hostname-service
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
edb30579c208 ruanbekker/hostname:latest "/app" About a minute ago Up About a minute 0.0.0.0:42177->8080/tcp my-hostname-service-1234
Only output the ID:
$ docker ps -f name=my-hostname-service --format ''
edb30579c208
or:
$ docker ps -f name=my-hostname-service -q
edb30579c208
If you have more than one container with the same prefix, but you are only interested in the most recent one:
$ docker ps -f name=my-hostname-service -ql
edb30579c208
ID, string characters and Name:
$ docker ps -f name=my-hostname-service --format ' -> '
edb30579c208 -> my-hostname-service-1234
Chaining them to exec into the container:
$ docker exec -it $(docker ps -f name=my-hostname-service -ql) sh
More examples:
- https://docs.docker.com/engine/reference/commandline/ps/
Template Variables
For Docker:
$ docker run -it --log-driver json-file --log-opt tag="||||" alpine echo hi
hi
Get the logfile:
$ docker inspect $(docker ps -l) | jq '.[].LogPath'
/var/lib/docker/containers/b8e6523c8741d33f778a4f899dc04dab912472cedfba5ab71119a8c9ab1555a8/b8e6523c8741d33f778a4f899dc04dab912472cedfba5ab71119a8c9ab1555a8-json.log
View the content:
$ cat /var/lib/docker/containers/b8e6523c8741d33f778a4f899dc04dab912472cedfba5ab71119a8c9ab1555a8/b8e6523c8741d33f778a4f899dc04dab912472cedfba5ab71119a8c9ab1555a8-json.log
{"log":"hi\r\n","stream":"stdout","attrs":{"tag":"alpine|festive_bell|sha256:e7d92cdc71feacf90708cb59182d0df1b911f8ae022d29e8e95d75ca6a99776a|b8e6523c8741d33f778a4f899dc04dab912472cedfba5ab71119a8c9ab1555a8|b8e6523c8741"},"time":"2020-07-07T12:35:12.3938298Z"}
- https://docs.docker.com/config/formatting/
For Swarm:
- https://forums.docker.com/t/example-usage-of-docker-swarm-template-placeholders/73859
Get a container to report the host’s hostname:
version: '3.7'
services:
telegraf:
..
hostname: ""
For Docker Swarm:
Service Name:
docker service create \
--env "SERVICE_NAME=" \
--name helloworld \
alpine /bin/sh -c 'echo $SERVICE_NAME'
docker service create \
--name=coordinator \
--env "SERVICE_NAME=" \
arangodb/arangodb /bin/sh -c 'arangod --server.authentication=false --server.endpoint tcp://0.0.0.0:8529 --cluster.my-address tcp://${SERVICE_NAME}:8529 --cluster.my-local-info ${SERVICE_NAME} --cluster.my-role COORDINATOR --cluster.agency-endpoint tcp://agency:8529 --log.file /var/log/arangodb3/arangod.log'
Task Slot:
docker service create --name mariadb-cluster \
--network default \
--replicas=1 \
--mount type=volume,src=mariadb-cluster."",dst=/var/lib/mysql \
--env DB_SERVICE_NAME=mariadb-cluster \
toughiq/mariadb-cluster:10.2
Others:
Docker Service PS
$ docker service ps api --format ' '
api.1 Running about an hour ago
Inspect the Service:
$ docker service inspect my-service
[
{
"ID": "abcdef",
"Version": {
"Index": 123
},
"CreatedAt": "2018-05-30T00:00:00.452848973Z",
"UpdatedAt": "2018-05-30T00:00:00.457986437Z",
"Spec": {
"Name": "my-service",
"TaskTemplate": {
"ContainerSpec": {
...
"LogDriver": {
"Name": "sumologic",
"Options": {
"sumo-compress": "false",
"sumo-sending-frequency": "500ms",
"sumo-url": "https://endpoint.sumologic.com/receiver/..."
}
...
Inspect the LogDriver:
$ docker service inspect my-service --format=''
{sumologic map[sumo-compress:false sumo-sending-frequency:500ms sumo-url:https://endpointsumologic.com/receiver/...]}
Getting only the sumo-url value:
$ docker service inspect my-service -f ''
https://endpoint.sumologic.com/receiver/...
Getting the Swarm Service and Task Name by inspecting the container:
$ docker inspect abc123def --format ''
my-app-ui.1.209jdwldi38jd
$ docker inspect abc123def --format ''
2093123jahas3d3
$ docker inspect abc123def --format ''
my-app-ui
Permissions
Copy as User:
FROM python:2.7
RUN pip install Flask==0.11.1
RUN useradd -ms /bin/bash admin
COPY --chown=admin:admin app /app
WORKDIR /app
USER admin
CMD ["python", "app.py"]
Update
Service Update
Add a constraint to move to a worker node:
$ docker service update --constraint-add 'node.role==worker' my-service-name
Docker Compose
Docker Compose Build
In our Dockerfile we can specify:
ARG APP_VERSION=1
ENV APP_VERSION=$APP_VERSION
Then we can set or overwrite the value by using build arguments:
services:
my-app:
build:
context: .
dockerfile: test/Dockerfile
args:
APP_VERSION: 1.1
Docker Compose Healthchecks
To see how to use health checks for dependencies / conditions, look at the gist below:
services:
php:
build:
context: .
dockerfile: tests/Docker/Dockerfile-PHP
args:
version: cli
depends_on:
couchbase:
condition: service_healthy
Credit to:
HTTP Healthcheck:
version: '2.1'
services:
depends_on:
couchbase:
condition: service_healthy
http-service:
image: nginx
healthcheck:
test: ["CMD", "curl", "-f", "http://localhost:80/"]
interval: 1s
timeout: 3s
retries: 60
MySQL Healthcheck:
mysql:
image: mysql
environment:
- MYSQL_ALLOW_EMPTY_PASSWORD=yes
- MYSQL_ROOT_PASSWORD=
- MYSQL_DATABASE=test
healthcheck:
test: ["CMD", "mysql" ,"-h", "mysql", "-P", "3306", "-u", "root", "-e", "SELECT 1", "test"]
interval: 1s
timeout: 3s
retries: 30
Postgres Healthcheck:
postgresql:
image: postgres
environment:
- POSTGRES_PASSWORD=
- POSTGRES_DB=test
healthcheck:
test: ["CMD", "pg_isready"]
interval: 1s
timeout: 3s
retries: 30
Redis Healthcheck:
redis:
image: redis
healthcheck:
test: ["CMD", "redis-cli", "ping"]
interval: 1s
timeout: 3s
retries: 30
Docker in Docker Healthcheck:
docker:
image: docker:19.03.12-dind
container_name: docker
privileged: true
environment:
DOCKER_HOST: tcp://docker:2375/
DOCKER_DRIVER: overlay2
DOCKER_TLS_CERTDIR: ""
networks:
- docker
healthcheck:
test: ["CMD", "docker" ,"ps"]
interval: 5s
timeout: 3s
retries: 30
Docker Compose Logging
JSON File Logging:
service:
myservice:
logging:
driver: "json-file"
options:
max-size: "1m"
Loki Logging:
service:
myservice:
logging:
driver: loki
options:
loki-url: http://192.168.0.2:3100/loki/api/v1/push
loki-external-labels: job=dockerlogs
Docker Compose Depends On
Depends-On Defaults, which will be wait for the database to start, before starting the web container:
version: "3.8"
services:
web:
build: .
depends_on:
- db
db:
image: postgres
Depends-On Types, where you can specify if it should wait for the service to start or to be healthy before starting the web container:
version: "3.8"
services:
web:
build: .
depends_on:
db:
condition: service_healthy
redis:
condition: service_started
redis:
image: redis
db:
image: postgres
healthcheck:
test: "exit 0"
Different types of depends on:
condition: service_started
condition: service_healthy
condition: service_completed_successfully