Friday 8 March 2019

Introduction to Docker

Docker is a platform which allows an application and all its dependencies to be packed in an image, shipped within this monolithic bundle and then deployed on any other machine with no fear that some dependency would be missing or not compatible with the new host. Running version of the image is called a container.

Here are some terms:

  •  may be local or remote

  • process which runs on a host

Docker runs processes in isolated containers.

Lifecycle of Docker Container

Image Source and Credits:


Docker images can consist of multiple layers. Layers can be reused by images. If a layer is downloaded as part of imageA and it is also part of imageB then when we pull/download imageB, this layer will not be downloaded again but will be reused.
  • image ID is a SHA256 digest covering the image’s configuration and layers. 

Benefits of containerisation

  • Standardized application packaging - no matter of the application's source language or framework, Docker images are created and applications packed in the same way
  • Multiplatform support - Docker image can be run on any OS, on a local machine or in the cloud
  • Containers are light-weight and isolated from each other
    • Applications running in Virtual Machines run on the following stack: Hardware - host OS - hypervisor - guest OS - software - application while those running in Docker run on: host OS - Docker Engine - Container - application. In case of VMs application can't utilize hardware to the full due to the fact that two OSes needs to run, on on top of another. 
    • Docker images are also isolated, it is possible to use multiple containers in parallel; if one container has a failure, it will not affect other containers 

Docker Architecture

Docker installation on a local machine comprises of two components:
  • client - we issue commands (e.g. docker images, docker container ls, ...) to it and it forwards them to daemon
  • daemon 
    • pulls/pushes images from/to image registry/repositories
    • manages local images
    • manages local containers 


Multi-stage build

This is one of the use cases which shows benefits of multi-staged build:
Docker container running golang http.Client getting error `certificate signed by unknown authority`

If we already have app binary built and can simply copy it onto an image but still have to add certificates, Dockerfile can look like:

FROM golang:alpine as build
RUN apk --no-cache add ca-certificates

FROM scratch
COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
COPY ./bin/my_app /my_app
CMD ["/my_app"]
If we set working directory in the image created at first stage, it will remain set to the same path in the following images:

FROM python:3-alpine as base

# Required for installing psycopg2 (see
RUN apk update && apk add --no-cache postgresql-dev python3-dev gcc musl-dev

ENV appDir /usr/local/src/python-demo
WORKDIR ${appDir}

COPY ./requirements.txt ./
RUN pip install -r requirements.txt

FROM base
COPY . .
COPY src/ ./src
RUN pwd // /usr/local/src/python-demo
CMD [ "python", "./" ]


FROM scratch

If we use FROM scratch then we can't use/execute bash/sh terminal if we attach to the container from the outside. The lightest image which provides bash terminal is alpine:

FROM alpine

alpine contains /bin/sh so we can use it via

$ docker exec -it <container_name> sh

Attaching to a docker container with base image scratch?

Why we needed to run apk add ca-certificates?
Install Certificates in Alpine Image to establish Secured Communication (SSL/TLS)



  • added manually in the same directory where Dockerfile resides
  • a newline-separated list of patterns that define a set of files and/or directories that should be ignored by ADD and COPY commands in Dockerfile
  • should contain any directory/file present in the same directory as .dockerfile but which should not be in the newly built image e.g. application's output directory (present on the dev machine and populated during testing) which can be large in size. This can cause sending unnecessary files to Docker daemon and long times for building an image:
$ docker build -t my_image .
Sending build context to Docker daemon  20.66GB

.dockerignore Example:

# comment

# ignore all .md files apart from

Can dockerfile be put in .dockerignore?



$ docker run --rm -i hadolint/hadolint < Dockerfile
Unable to find image 'hadolint/hadolint:latest' locally
latest: Pulling from hadolint/hadolint
447f1c00f9d8: Pull complete 
Digest: sha256:6e67b08b2f9b3cf57616cfc92adb8864b74b02f079d70eabc944b29f05aff5f9
Status: Downloaded newer image for hadolint/hadolint:latest
/dev/stdin:27 DL3025 Use arguments JSON notation for CMD and ENTRYPOINT arguments

Docker CLI Commands

$ docker --help

Usage: docker [OPTIONS] COMMAND

A self-sufficient runtime for containers

      --config string      Location of client config files (default "/home/bojan/.docker")
  -D, --debug              Enable debug mode
  -H, --host list          Daemon socket(s) to connect to
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
      --tls                Use TLS; implied by --tlsverify
      --tlscacert string   Trust certs signed only by this CA (default "/home/bojan/.docker/ca.pem")
      --tlscert string     Path to TLS certificate file (default "/home/bojan/.docker/cert.pem")
      --tlskey string      Path to TLS key file (default "/home/bojan/.docker/key.pem")
      --tlsverify          Use TLS and verify the remote
  -v, --version            Print version information and quit

Management Commands:
  builder     Manage builds
  config      Manage Docker configs
  container   Manage containers
  engine      Manage the docker engine
  image       Manage images
  network     Manage networks
  node        Manage Swarm nodes
  plugin      Manage plugins
  secret      Manage Docker secrets
  service     Manage services
  stack       Manage Docker stacks
  swarm       Manage Swarm
  system      Manage Docker
  trust       Manage trust on Docker images
  volume      Manage volumes

  attach      Attach local standard input, output, and error streams to a running container
  build       Build an image from a Dockerfile
  commit      Create a new image from a container's changes
  cp          Copy files/folders between a container and the local filesystem
  create      Create a new container
  diff        Inspect changes to files or directories on a container's filesystem
  events      Get real time events from the server
  exec        Run a command in a running container
  export      Export a container's filesystem as a tar archive
  history     Show the history of an image
  images      List images
  import      Import the contents from a tarball to create a filesystem image
  info        Display system-wide information
  inspect     Return low-level information on Docker objects
  kill        Kill one or more running containers
  load        Load an image from a tar archive or STDIN
  login       Log in to a Docker registry
  logout      Log out from a Docker registry
  logs        Fetch the logs of a container
  pause       Pause all processes within one or more containers
  port        List port mappings or a specific mapping for the container
  ps          List containers
  pull        Pull an image or a repository from a registry
  push        Push an image or a repository to a registry
  rename      Rename a container
  restart     Restart one or more containers
  rm          Remove one or more containers
  rmi         Remove one or more images
  run         Run a command in a new container
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  search      Search the Docker Hub for images
  start       Start one or more stopped containers
  stats       Display a live stream of container(s) resource usage statistics
  stop        Stop one or more running containers
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
  top         Display the running processes of a container
  unpause     Unpause all processes within one or more containers
  update      Update configuration of one or more containers
  version     Show the Docker version information
  wait        Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

Since version 1.13, Docker command-line has the following syntax:

docker <object> <command> <options>

In this syntax:
  • <object> indicates the type of Docker object you'll be manipulating. This can be a container, image, network or volume object.
  • <command> indicates the task to be carried out by the daemon, that is the run command.
  • <options> can be any valid parameter that can override the default behavior of the command, like the --publish option for port mapping.

Builds an image from a Dockerfile. 

$ docker build --help
Usage: docker build [OPTIONS] PATH | URL | -
Build an image from a Dockerfile

--add-host list Add a custom host-to-IP mapping (host:ip)
--build-arg list Set build-time variables
--cache-from strings Images to consider as cache sources
--cgroup-parent string Optional parent cgroup for the container
--compress Compress the build context using gzip
--cpu-period int Limit the CPU CFS (Completely Fair Scheduler) period
--cpu-quota int Limit the CPU CFS (Completely Fair Scheduler) quota
-c, --cpu-shares int CPU shares (relative weight)
--cpuset-cpus string CPUs in which to allow execution (0-3, 0,1)
--cpuset-mems string MEMs in which to allow execution (0-3, 0,1)
--disable-content-trust Skip image verification (default true)
-f, --file string Name of the Dockerfile (Default is 'PATH/Dockerfile')
--force-rm Always remove intermediate containers
--iidfile string Write the image ID to the file
--isolation string Container isolation technology
--label list Set metadata for an image
-m, --memory bytes Memory limit
--memory-swap bytes Swap limit equal to memory plus swap: '-1' to enable unlimited swap
--network string Set the networking mode for the RUN instructions during build (default "default")
--no-cache Do not use cache when building the image
--pull Always attempt to pull a newer version of the image
-q, --quiet Suppress the build output and print image ID on success
--rm Remove intermediate containers after a successful build (default true)
--security-opt strings Security options
--shm-size bytes Size of /dev/shm
-t, --tag list Name and optionally a tag in the 'name:tag' format
--target string Set the target build stage to build.
--ulimit ulimit Ulimit options (default [])

The PATH specifies where to find the files for the “context” of the build on the Docker daemon.

Example (has to be run in a directory which contains Dockerfile):

$ docker build -t <my username>/<my-app-name> .

Example of how to build and run a Docker image:

$ docker build -t jsonschema2db . && docker run jsonschema2db

If Docker has to fetch some resources from remote host whose domain name can't be resolved from within Docker native network but can from your local/dev host network use --network host:

$ docker build --network host -t my-image . 

--pull instructs docker to pull the latest version of any base image(s) instead of reusing whatever you already have tagged locally. From
Take for instance an image based on a moving tag (such as ubuntu:bionic). Upstream makes changes and rebuilds this periodically but you might have a months old image locally. Docker will happily build against the old base. --pull will pull as a side effect so you build against the latest base image.

It's usually a best practice to use it to get upstream security fixes as soon as possible (instead of using stale, potentially vulnerable images). Though you have to trade off breaking changes (and if you use immutable tags then it doesn't make a difference). 

--no-cache forces rebuilding of layers already available. 
In normal use you shouldn’t need --no-cache. If the base image is updated (and --pull gets a new version) that automatically invalidates the cache; similarly if you COPY different code that will invalidate the cache. The only thing this will usually affect is if you’re doing something like apt-get install of a network-hosted package, in which case --no-cache will cause it to check for a newer version even if the base image hasn’t updated.

--build-arg arg=value - used to pass to Dockerfile an argument from command line. arg needs to be defined in Dockerfile via ARG command:

ARG arg[=default_value] 

If arg is http_proxy or https_proxy there is no need to define these arguments as they are defined by default (predefined args).


docker container

Used for managing containers.

docker create

$ docker create --help

Usage: docker create [OPTIONS] IMAGE [COMMAND] [ARG...]

Create a new container

      --add-host list                  Add a custom host-to-IP mapping (host:ip)
  -a, --attach list                    Attach to STDIN, STDOUT or STDERR
      --blkio-weight uint16            Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0)
      --blkio-weight-device list       Block IO weight (relative device weight) (default [])
      --cap-add list                   Add Linux capabilities
      --cap-drop list                  Drop Linux capabilities
      --cgroup-parent string           Optional parent cgroup for the container
      --cidfile string                 Write the container ID to the file
      --cpu-period int                 Limit CPU CFS (Completely Fair Scheduler) period
      --cpu-quota int                  Limit CPU CFS (Completely Fair Scheduler) quota
      --cpu-rt-period int              Limit CPU real-time period in microseconds
      --cpu-rt-runtime int             Limit CPU real-time runtime in microseconds
  -c, --cpu-shares int                 CPU shares (relative weight)
      --cpus decimal                   Number of CPUs
      --cpuset-cpus string             CPUs in which to allow execution (0-3, 0,1)
      --cpuset-mems string             MEMs in which to allow execution (0-3, 0,1)
      --device list                    Add a host device to the container
      --device-cgroup-rule list        Add a rule to the cgroup allowed devices list
      --device-read-bps list           Limit read rate (bytes per second) from a device (default [])
      --device-read-iops list          Limit read rate (IO per second) from a device (default [])
      --device-write-bps list          Limit write rate (bytes per second) to a device (default [])
      --device-write-iops list         Limit write rate (IO per second) to a device (default [])
      --disable-content-trust          Skip image verification (default true)
      --dns list                       Set custom DNS servers
      --dns-option list                Set DNS options
      --dns-search list                Set custom DNS search domains
      --entrypoint string              Overwrite the default ENTRYPOINT of the image
  -e, --env list                       Set environment variables
      --env-file list                  Read in a file of environment variables
      --expose list                    Expose a port or a range of ports
      --group-add list                 Add additional groups to join
      --health-cmd string              Command to run to check health
      --health-interval duration       Time between running the check (ms|s|m|h) (default 0s)
      --health-retries int             Consecutive failures needed to report unhealthy
      --health-start-period duration   Start period for the container to initialize before starting health-retries countdown (ms|s|m|h) (default 0s)
      --health-timeout duration        Maximum time to allow one check to run (ms|s|m|h) (default 0s)
      --help                           Print usage

-h, --hostname string                
Container host name

      --init                           Run an init inside the container that forwards signals and reaps processes
  -i, --interactive                    Keep STDIN open even if not attached
      --ip string                      IPv4 address (e.g.,
      --ip6 string                     IPv6 address (e.g., 2001:db8::33)
      --ipc string                     IPC mode to use
      --isolation string               Container isolation technology
      --kernel-memory bytes            Kernel memory limit
  -l, --label list                     Set meta data on a container
      --label-file list                Read in a line delimited file of labels
      --link list                      Add link to another container
      --link-local-ip list             Container IPv4/IPv6 link-local addresses
      --log-driver string              Logging driver for the container
      --log-opt list                   Log driver options
      --mac-address string             Container MAC address (e.g., 92:d0:c6:0a:29:33)
  -m, --memory bytes                   Memory limit
      --memory-reservation bytes       Memory soft limit
      --memory-swap bytes              Swap limit equal to memory plus swap: '-1' to enable unlimited swap
      --memory-swappiness int          Tune container memory swappiness (0 to 100) (default -1)
      --mount mount                    Attach a filesystem mount to the container
      --name string                    Assign a name to the container
      --network string                 Connect a container to a network (default "default")
      --network-alias list             Add network-scoped alias for the container
      --no-healthcheck                 Disable any container-specified HEALTHCHECK
      --oom-kill-disable               Disable OOM Killer
      --oom-score-adj int              Tune host's OOM preferences (-1000 to 1000)
      --pid string                     PID namespace to use
      --pids-limit int                 Tune container pids limit (set -1 for unlimited)
      --privileged                     Give extended privileges to this container
  -p, --publish list                   Publish a container's port(s) to the host
  -P, --publish-all                    Publish all exposed ports to random ports
      --read-only                      Mount the container's root filesystem as read only
      --restart string                 Restart policy to apply when a container exits (default "no")
      --rm                             Automatically remove the container when it exits
      --runtime string                 Runtime to use for this container
      --security-opt list              Security Options
      --shm-size bytes                 Size of /dev/shm
      --stop-signal string             Signal to stop a container (default "SIGTERM")
      --stop-timeout int               Timeout (in seconds) to stop a container
      --storage-opt list               Storage driver options for the container
      --sysctl map                     Sysctl options (default map[])
      --tmpfs list                     Mount a tmpfs directory
  -t, --tty                            Allocate a pseudo-TTY
      --ulimit ulimit                  Ulimit options (default [])
  -u, --user string                    Username or UID (format: <name|uid>[:<group|gid>])
      --userns string                  User namespace to use
      --uts string                     UTS namespace to use
  -v, --volume list                    Bind mount a volume
      --volume-driver string           Optional volume driver for the container
      --volumes-from list              Mount volumes from the specified container(s)
  -w, --workdir string                 Working directory inside the container


$ docker create \
-e DB_HOST= \
-e DB_PORT=5432 \
-e DB_NAME=test_db \
-e DB_USER=postgres \
-e DB_PASSWORD=postgres \
-e OUTPUT_DIR=./data-vol \
--rm \
-it \
--mount type=bind,src="$(pwd)/data-vol",target=/data-vol \
--network=bridge \
--name my_app_test_container \ 

If environment variable contains a question mark character which we want to preserve, this string has to be enclosed in single quotation mark.

Example: If we have:

docker run \
--rm \
-e NODE_ENV=dev \
-e API_QUERY_TEMPLATE=?post_type={post_type}&json=1&count=1000 \
-e PGHOST=postgres \
-e PGDATABASE=test_dev \
-e PGUSER=postgres \
-e PGPASSWORD=postgres \
-v "$(pwd)/${SCHEMAS_DIR}":/usr/local/my-app/${SCHEMAS_DIR} \
--name my-app \
--network myappnet \
--user $(id -u):$(id -g) \

it would fail with error:

-e: not found

Because docker run would interpret/expand ? as wildcard (?). Fix is to enclose env var value in single quotes:

docker run \
-e API_QUERY_TEMPLATE='?post_type={post_type}&json=1&count=1000' \

shell - How to escape "!" and "&" in docker's environment varibles - Super User

docker exec

To execute a command inside a running container, use docker exec. For example, we can run a bash terminal as:

$ docker exec -it my-postgres bash

-i // keeps stdin opened
-t // allocates pseudo TTY

In this terminal we can run usual Linux commands as we were inside the container:

root@a4a7486fea59:/# ls
bin  boot  dev docker-entrypoint-initdb.d  etc  home  lib  lib64  media mnt  opt  proc root  run  sbin  srv  sys  tmp usr  var
root@a4a7486fea59:/# pwd

not able to use docker exec shell 
Try the alpine tag of image:

$ docker run --name gorush -d appleboy/gorush:alpine
$ docker exec -ti gorush /bin/sh

docker inspect

$ docker inspect --help

Usage: docker inspect [OPTIONS] NAME|ID [NAME|ID...]

Return low-level information on Docker objects

  -f, --format string   Format the output using the given Go template
  -s, --size            Display total file sizes if the type is container
      --type string     Return JSON for specified type


How to find mounting points of a (stopped) container? E.g. find local directory that is mounted as a volume on some container.

$ docker inspect -f {{.Mounts}} my_container
[{bind  /home/bojan/tmp/data-vol /data-vol   true rprivate}]

What to Inspect When You're Inspecting

docker logs

Exploring Docker commands: docker logs | My Public Notepad

docker network

$ docker network --help

Usage: docker network COMMAND

Manage networks

  connect     Connect a container to a network
  create      Create a network
  disconnect  Disconnect a container from a network
  inspect     Display detailed information on one or more networks
  ls          List networks
  prune       Remove all unused networks
  rm          Remove one or more networks

Run 'docker network COMMAND --help' for more information on a command.

List all networks:

$ docker network ls
NETWORK ID          NAME                             DRIVER              SCOPE
110d23a9b23f        bridge                           bridge              local
b32aba0ecc85        my_app1       bridge              local
5a91d6b95b25        my_app2   bridge              local
7422e6165f7a        my_app3                     bridge              local
b2977102daa4        my_app4_test-network                bridge              local
e829cad5a344        host                             host                local
6b0d605ed4a5        none                             null                local

Connect a container to the network (of some other container):

$ docker network connect --help

Usage: docker network connect [OPTIONS] NETWORK CONTAINER

Connect a container to a network

      --alias strings           Add network-scoped alias for the container
      --ip string               IPv4 address (e.g.,
      --ip6 string              IPv6 address (e.g., 2001:db8::33)
      --link list               Add link to another container
      --link-local-ip strings   Add a link-local address for the container

Use case example:

Running Postgres DB in one container (based on postgres image; container runs in its own network) and connecting to it via pgAdmin which runs in another container (based on dpage/pgadmin4 image).

docker container ls shows that my_app_db_1 is up and running with port mapping as>5432/tcp. This container runs Postgres DB.

To find the name of the network this container is connected to use docker inspect <container_name> and in the output json look for "NetworkSettings" > "Networks". There should be a network name like "my_app_default".

Let's inspect that network:

$ docker network inspect my_app_default
        "Name": "my_app_default",
        "Id": "5a91d6b95b25fdd6d24e921e1ccdb69f24ae4b1c509188ccfc087acd330375ca",
        "Created": "2019-06-05T10:19:11.576495786+01:00",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                    "Subnet": "",
                    "Gateway": ""
        "Internal": false,
        "Attachable": true,
        "Ingress": false,
        "ConfigFrom": {
            "Network": ""
        "ConfigOnly": false,
        "Containers": {
            "9ae5dfe822348906d2bdf2b55314a323f7ba03360eb2edf8e5d7d42afca40e34": {
                "Name": "my_app_service",
                "EndpointID": "a5230696caabc7d230df8f589066b8028c3b03493a2f05ed0dc5e224944952fc",
                "MacAddress": "02:42:ac:13:00:03",
                "IPv4Address": "",
                "IPv6Address": ""
            "e52e5d6de6b6a062d2cbfaf921f3365f20db0208511a906cab6143528a14ee6d": {
                "Name": "my_app_db_1",
                "EndpointID": "bbe87692635abe7cd45a3980d0982ca1dbc6c9a5718a267935659cfb036b2da1",
                "MacAddress": "02:42:ac:13:00:02",
                "IPv4Address": "",
                "IPv6Address": ""
        "Options": {},
        "Labels": {
            "": "default",
            "com.docker.compose.project": "my_app",
            "com.docker.compose.version": "1.23.2"

my_app_db_1 is the name of the container which is running db service (Postgres) as I specified in docker-compose.yml.

Now, I want to run pgAdmin DB client (which is also a web server...) from its own container, based on dpage/pgadmin4 image:

$ docker run -p 5051:5051 -d -e "" -e "PGADMIN_DEFAULT_PASSWORD=postgres" -e "PGADMIN_LISTEN_PORT=5051" --name pgadmin dpage/pgadmin4

We can use docker container ls to verify that this container is now up and running, with port mappings as 80/tcp, 443/tcp,>5051/tcp. We can now open in browser on the local host the address http://localhost:5051/ which should open pgAdmin login page. If we try to add DB server with IP address (as listed in the postgres container network spec above), connecting to it will fail as pgAdmin runs in its own network. We need to connect pgadmin container to my_app_default network:

$ docker network connect my_app_default pgadmin

We can now use address to connect to DB from pgAdmin web app.

If we again inspect my_app_default network we can verify that there is one more container attached to it: pgadmin.

To avoid issuing two commands, we can specify network container shall connect to in docker run command:

$ docker run -p 5051:5051 -d -e "" -e "PGADMIN_DEFAULT_PASSWORD=postgres" -e "PGADMIN_LISTEN_PORT=5051" --network=my_app_default --name pgadmin dpage/pgadmin4

Creating a network:

$ docker network create --help

Usage: docker network create [OPTIONS] NETWORK

Create a network

      --attachable           Enable manual container attachment
      --aux-address map      Auxiliary IPv4 or IPv6 addresses used by Network driver (default map[])
      --config-from string   The network from which copying the configuration
      --config-only          Create a configuration only network
  -d, --driver string        Driver to manage the Network (default "bridge")
      --gateway strings      IPv4 or IPv6 Gateway for the master subnet
      --ingress              Create swarm routing-mesh network
      --internal             Restrict external access to the network
      --ip-range strings     Allocate container ip from a sub-range
      --ipam-driver string   IP Address Management Driver (default "default")
      --ipam-opt map         Set IPAM driver specific options (default map[])
      --ipv6                 Enable IPv6 networking
      --label list           Set metadata on a network
  -o, --opt map              Set driver specific options (default map[])
      --scope string         Control the network's scope
      --subnet strings       Subnet in CIDR format that represents a network segment


Create a network:

$ docker network create --subnet= --gateway=  mynet123

Attach container to that network and assign a static IP address to it:

$ docker run --net mynet123 --ip -it ubuntu bash

Destroying a network

$ docker network rm mynet123


docker ps

To list all running containers use docker ps:

$ docker ps
CONTAINER ID  IMAGE   COMMAND         CREATED     STATUS      PORTS                      NAMES
b9f263f2b517 postgres "some.command…" 9 hours ago Up 5 hours>5432/tcp  my_project_postgres_1

If no containers are running:

$ sudo docker ps
CONTAINER ID    IMAGE           COMMAND         CREATED         STATUS          PORTS               NAMES

To list all containers, use docker ps -a.

docker pull

docker pull pulls an image from the repository.


$ docker pull <image_name>:<tag_name>

If no tag is provided, Docker Engine uses the :latest tag as a default.

Apart from pulling some image for the first time, this command is used to pull a new version of the existing image. [Update a docker container to the latest version]

In my case, I have been running pgAdmin4 from within a container but after some time I started getting a popup on pgAdmin4 main web page that I am using the old version of it. My course of actions was:

$ docker images | grep pgadmin
dpage/pgadmin4                  latest               c32b95c07a00        5 weeks ago         237MB

$ docker pull dpage/pgadmin4
Using default tag: latest
latest: Pulling from dpage/pgadmin4
e7c96db7181b: Already exists 
44bc3cf004be: Already exists 
aa774cf9fd8b: Pull complete 
660e231737f7: Pull complete 
Digest: sha256:2c46b3e631f33434246a2a51134e3a43951b00c5639f7fc158b4b973879f9ea3
Status: Downloaded newer image for dpage/pgadmin4:latest

How to upgrade docker container after its image changed

docker run

Exploring Docker commands: docker run | My Public Notepad

docker search 

Search for images available at Docker Hub.

 % docker search mysql
NAME                            DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED
mysql                           MySQL is a widely used, open-source relation…   13600     [OK]       
mariadb                         MariaDB Server is a high performing open sou…   5188      [OK]       
phpmyadmin                      phpMyAdmin - A web interface for MySQL and M…   707       [OK]       
percona                         Percona Server is a fork of the MySQL relati…   597       [OK]       
bitnami/mysql                   Bitnami MySQL Docker Image                      80                   [OK]
databack/mysql-backup           Back up mysql databases to... anywhere!         77                   
linuxserver/mysql-workbench                                                     45                   
ubuntu/mysql                    MySQL open source fast, stable, multi-thread…   40                   
linuxserver/mysql               A Mysql container, brought to you by LinuxSe…   37                   
circleci/mysql                  MySQL is a widely used, open-source relation…   28                   
google/mysql                    MySQL server for Google Compute Engine          22                   [OK]

docker start

To start a container use docker start. In the following example container name is my-postgres:

$ docker start my-postgres 

docker stop

To stop running one or more containers use docker stop:

$ docker stop my_service_postgres_1 my-other-app

docker image

Exploring Docker commands: docker image | My Public Notepad

docker images

Exploring Docker commands: docker images | My Public Notepad

docker volume 

$ docker volume

Usage:  docker volume COMMAND

Manage volumes

  create      Create a volume
  inspect     Display detailed information on one or more volumes
  ls          List volumes
  prune       Remove all unused local volumes
  rm          Remove one or more volumes

Run 'docker volume COMMAND --help' for more information on a command.


docker volume ls 

$ docker volume ls --help

Usage:  docker volume ls [OPTIONS]

List volumes

  ls, list

  -f, --filter filter   Provide filter values (e.g. 'dangling=true')
      --format string   Pretty-print volumes using a Go template
  -q, --quiet           Only display volume names


$ docker volume ls
local               1a2a9d0f43ce94ad1e176f9bb318f46829fcd34354d4d648d70434efa0f43f60
local               1a66b905bcd4be936b8df26cacf018d7f863e758773a11be5faf9d9949311eb0
local               1c6af16b8d8b1041ad3a46e3910bde9121b64cfae65f8299cedd81793d8fce37

$ docker volume ls -q


docker volume rm

$ docker volume rm --help

Usage:  docker volume rm [OPTIONS] VOLUME [VOLUME...]

Remove one or more volumes

  rm, remove


$ docker volume rm hello

  -f, --force   Force the removal of one or more volumes

To remover all volumes:

$ docker volume rm $(docker volume ls -q)



Lifecycle of Docker Container
Hey Docker! Why do you hate Windows so much?
Exploring Docker container's file system

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