docker.notes.md

gistfile1.txt

# Docker-notes


# Test docker installation
docker ps

# and run a test container 
docker run hello-world

# and stop it with 
# docker stop hello-world

# See docker images
docker images

# See running docker procs
docker ps

# See all docker procs
docker ps -a

# Delete exited containers 
docker rm $(docker ps -a -q -f status=exited) 
# or 
docker container prune

# Run command on a docker container
docker run spapas/foodrec ls

# Add -it for interactive and pseudo tty:
docker run -it spapas/foodrec bash

# Docker run server
docker run -d -P --name static-site prakhar1989/static-site

# --name: Give a name to the container
# -d: Detach from terminal
# -P: Export ports randomly. Use docker port static-site

# Dockerfile
# We start with specifying our base image. Use the FROM keyword to do that -

FROM python:3
# The next step usually is to write the commands of copying the files and installing the dependencies. 
# First, we set a working directory and then copy all the files for our app.

# set a directory for the app
WORKDIR /usr/src/app

# copy all the files to the container
COPY . .
# Now, that we have the files, we can install the dependencies.

# install dependencies
RUN pip install --no-cache-dir -r requirements.txt
# set env vars
ENV DJANGO_SETTINGS_MODULE=foodrec.settings.prod
# The next thing we need to specify is the port number that needs to be exposed. 
# Since our flask app is running on port 5000, that's what we'll indicate.

EXPOSE 5000
# The last step is to write the command for running the application, 
# which is simply - python ./app.py. We use the CMD command to do that -

CMD ["python", "./app.py"]
# The primary purpose of CMD is to tell the container which command it should run when it is started.

# Build an image
# Use

docker build -t spapas/foodrec .
# and then

docker run -p 8888:8000 spapas/foodrec
# (expose container port 5000 to local 8888)

# Volumes and bind mounts
# Volumes
# Volumes are the preferred mechanism for persisting data generated by and used by Docker containers. 
# While bind mounts are dependent on the directory structure and OS of the host machine, volumes are 
# completely managed by Docker: https://docs.docker.com/storage/volumes/

C:\progr\py3\foodrec\foodrec>docker run -it --mount source=testvol,target=/bar  spapas/foodrec ls -l /bar
total 0

 C:\progr\py3\foodrec\foodrec>docker run -it --mount source=testvol,target=/bar  spapas/foodrec bash
root@3f6fa9a1d3f6:/app# ls -l /bar
total 0
root@3f6fa9a1d3f6:/app# cd /bar
root@3f6fa9a1d3f6:/bar# ls -l
total 0
root@3f6fa9a1d3f6:/bar# echo x > y
root@3f6fa9a1d3f6:/bar# ls -l
total 4
-rw-r--r-- 1 root root 2 Nov 15 10:09 y
root@3f6fa9a1d3f6:/bar# exit

C:\progr\py3\foodrec\foodrec>docker run -it --mount source=testvol,target=/bar  spapas/foodrec ls -l /bar
total 4
-rw-r--r-- 1 root root 2 Nov 15 10:09 y

# File is saved. If you don't use a volume on the other hand:

(venv) C:\progr\py3\foodrec\foodrec>docker run -it --mount source=testvol,target=/bar  spapas/foodrec bash
root@26120bfba417:/app# cd /
root@26120bfba417:/# mkdir foo
root@26120bfba417:/# cd foo
root@26120bfba417:/foo# ls
root@26120bfba417:/foo# echo z > b
root@26120bfba417:/foo# exit

(venv) C:\progr\py3\foodrec\foodrec>docker run -it --mount source=testvol,target=/bar  spapas/foodrec ls -l /foo
ls: cannot access '/foo': No such file or directory
# the file is lost !


# Inspect a volume:

# docker volume inspect testvol
[
    {
        "CreatedAt": "2021-11-15T10:09:25Z",
        "Driver": "local",
        "Labels": null,
        "Mountpoint": "/var/lib/docker/volumes/testvol/_data",
        "Name": "testvol",
        "Options": null,
        "Scope": "local"
    }
]
# And the actual volume data is saved at: \\wsl$\docker-desktop-data\version-pack-data\community\docker\volumes (on windows)

# Bind mounts
# https://docs.docker.com/storage/bind-mounts/

# Mount a local folder to docker:

C:\progr\py3\foodrec\foodrec>dir foo
 Volume in drive C is Windows
 Volume Serial Number is 10D2-719C

 Directory of C:\progr\py3\foodrec\foodrec\foo

15/11/2021  12:03    <DIR>          .
15/11/2021  12:03    <DIR>          ..
15/11/2021  12:03                 0 zz.txt
               1 File(s)              0 bytes

# docker run -it --mount type=bind,source=c:/progr/py3/foodrec/foodrec/foo,target=/bar  spapas/foodrec ls -l /bar
total 0
-rwxrwxrwx 1 root root 0 Nov 15 10:03 zz.txt