Small Docker Notes
Note - vm and container is used below interchangeably.
Contents
Installation and Verification
# install Docker $ curl -fsSL https://get.docker.com/ | sh # add your-user to docker group to be able to run docker as non-root $ usermod -aG docker your-user # you'll need to log out and in after this, or run all docker commands as root # verify the installation $ docker run hello-world # this should download image from docker hub, and print "Hello from Docker." message
As a rule of thumb: `docker` is the "super-system" used to manage docker containers (and more). `docker-compose` does the same tasks as docker, but only on containers defined in docker-compose.yml file in current directory. So, `docker ps -a` will list all containers, `docker-compose ps` will list info about all containers from local docker-compose.yml file.
If something goes wrong, check
$ docker-compose logs
or
$ docker logs container-id
Stack in Separate Containers
Let's create few containers to hold different parts of the stack:
- nginx
- php-fpm
- mysql
- data volume for mysql
- kyoto tycoon with python
- data volume for kyoto tycoon
First, create config file for docker compose, called docker-compose.yml .
nginx:
# based on latest nginx image
image: nginx:latest
ports:
# map vm's port 80 to local port 8080
- 8080:80
Now we have defined our first image, let's get it running:
$ docker-compose up -d
# you should be able to reach the nginx on localhost:8080 now;
# you can always check running containers, incl. ports map, with
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
e795e45c3e6b nginx:latest "nginx -g 'daemon off" 24 hours ago Up 24 hours 443/tcp, 0.0.0.0:8080->80/tcp dockertut_nginx_1
# using container ID or name from `docker ps`, you can get lots of useful info with
$ docker inspect {container-id|name}
Adding php-fpm
Let's now add VM for php-fpm, and edit the docker-compose.yml like this:
nginx:
build:
# don't use image, build based on ./docker/nginx/Dockerfile
./docker/nginx/
ports:
# vm's port 80 will be available as 8080 on localhost
- 8080:80
links:
# has access to 'php' vm
- php
volumes:
# mount current directory as /var/www/html inside the container
- .:/var/www/html
php:
image: php:5.5-fpm
expose:
# expose port 9000 only to other vm's, not host machine like the 'ports' command
- 9000
volumes:
- .:/var/www/html
Now the nginx image is based on Dockerfile in ./docker/nginx/ folder, which should look like this:
FROM nginx:latest COPY ./default.conf /etc/nginx/conf.d/default.conf
See official Dockerfile reference for details.
This will build vm from nginx:latest image, and copy ./docker/nginx/default.conf to /etc/nginx/conf.d/ in the vm. Create this file with the following content:
server {
listen 80 default_server;
root /var/www/html;
index index.html index.php;
charset utf-8;
location / {
try_files $uri $uri/ /index.php?$query_string;
}
location = /favicon.ico { access_log off; log_not_found off; }
location = /robots.txt { access_log off; log_not_found off; }
access_log off;
error_log /var/log/nginx/error.log error;
sendfile off;
client_max_body_size 100m;
location ~ \.php$ {
fastcgi_split_path_info ^(.+\.php)(/.+)$;
fastcgi_pass php:9000;
fastcgi_index index.php;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_intercept_errors off;
fastcgi_buffer_size 16k;
fastcgi_buffers 4 16k;
}
location ~ /\.ht {
deny all;
}
}
Note that root /var/www/html; will actually use the mount of our local directory.
Also note fastcgi_pass php:9000; that uses the link created using links: key in the docker-compose.yml.
Now, let's just add index.php in the root folder (where docker-compose.yml resides):
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Hello World!</title>
</head>
<body>
<?php echo "this is php!"; ?>
</body>
</html>
Let's start the images; this time, php image should be pulled as well:
$ docker-compose up -d Pulling php (php:5.5-fpm)... 5.5-fpm: Pulling from library/php efd26ecc9548: Already exists <-- the nginx image, already pulled a3ed95caeb02: Download complete ...
If you get "Service 'nginx' needs to be built, but --no-build was passed." message, run `docker-compose build` and again `docker-compose up -d`. Verify all is OK and started:
$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES fd04b796e34f dockertut_nginx "nginx -g 'daemon off" 4 seconds ago Up 4 seconds 443/tcp, 0.0.0.0:8080->80/tcp dockertut_nginx_1 402fb35b762e php:5.5-fpm "php-fpm" 5 seconds ago Up 4 seconds 9000/tcp dockertut_php_1
Note that nginx's image name has changed, since we have built a new one.
Now, when you open localhost:8080, you should get "this is php!" message. Open the index.php file, and edit it; the change should be immediately reflected. Sweet!
Data Volumes
Both the nginx and php vm's now use local folder through the volumes directive.
Better yet is to have a separate container; we'll build this container based on some image we're already using (to avoid having yet another image downloaded), but it won't be running - it'll just sit there, collecting data. Change docker-compose.yml like this:
nginx:
build:
./docker/nginx/
ports:
- 8080:80
links:
- php
volumes_from:
- app
php:
image: php:5.5-fpm
expose:
- 9000
volumes_from:
- app
app:
# it's good practice to "reuse" some image, not to have yet another one pulled
image: php:5.5-fpm
volumes:
- .:/var/www/html
# container won't run - it'll execute `true` and sit there, collecting data
command: "true"
Let's check all is OK:
$ docker-compose up -d Creating dockertut_app_1... Recreating dockertut_php_1... Recreating dockertut_nginx_1... # list all containers (note that 'app' container is not listed in `ps`, since it's not running): $ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES af0110364abf dockertut_nginx "nginx -g 'daemon off" 2 minutes ago Up 2 minutes 443/tcp, 0.0.0.0:8080->80/tcp dockertut_nginx_1 94a1c3d317dd php:5.5-fpm "php-fpm" 2 minutes ago Up 2 minutes 9000/tcp dockertut_php_1 861cca283ceb php:5.5-fpm "true" 2 minutes ago Exited (0) 2 minutes ago dockertut_app_1
and check that localhost:8080 is still responding.
Adding MySQL
Update the 'php' section:
php:
build:
./docker/php/
expose:
- 9000
links:
- mysql
volumes_from:
- app
And add the following:
mysql:
image: mysql:latest
volumes_from:
- mysqldata
# set environment variables
environment:
MYSQL_ROOT_PASSWORD: secret
MYSQL_DATABASE: test
MYSQL_USER: test
MYSQL_PASSWORD: test
mysqldata:
image: mysql:latest
volumes:
# the /var/lib/mysql will be present in container, and "somewhere" on host
- /var/lib/mysql
command: "true"
And, create ./docker/php/Dockerfile:
FROM php:5.5-fpm RUN docker-php-ext-install pdo_mysql
Now we're all set to `docker-compose build` and `docker-compose up -d`. Let's check what containers we have now:
$ docker ps -a CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES e43265be9680 dockertut_nginx "nginx -g 'daemon off" 16 seconds ago Up 14 seconds 443/tcp, 0.0.0.0:8080->80/tcp dockertut_nginx_1 48cd3b544fb1 dockertut_php "php-fpm" 19 seconds ago Up 17 seconds 9000/tcp dockertut_php_1 0e4f40d9ae8b mysql:latest "docker-entrypoint.sh" 21 seconds ago Up 20 seconds 3306/tcp dockertut_mysql_1 963440e29d89 mysql:latest "docker-entrypoint.sh" 22 seconds ago Exited (0) 20 seconds ago dockertut_mysqldata_1 1458644df104 php:5.5-fpm "true" 4 minutes ago Exited (0) 4 minutes ago dockertut_app_1
Now that all is set up, we can check where did docker mount the folder on host, that is seen as /var/lib/mysql in mysqldata instance:
$ docker inspect dockertut_mysqldata_1
...
"Mounts": [
{
"Name": "d1352deaff99b25ee68bc53c07150b12b5eb7028b6182f1c97f71f7e21c8ee1d",
"Source": "/var/lib/docker/volumes/d1352deaff99b25ee68bc53c07150b12b5eb7028b6182f1c97f71f7e21c8ee1d/_data",
"Destination": "/var/lib/mysql",
...
The Source is the folder on host that docker mounted as Destination in VM.
If you want all volumes removed when deleting docker container, use
$ docker rm -v container-id
Otherwise, the volumes will stay on your disk, taking up space.
You can also list all volumes registered by docker:
$ docker volume ls
and use this to remove all "dangling" volumes:
$ docker volume rm $(docker volume ls -qf dangling=true)
Let's check if mysql is up and running, through terminal. You can open interactive terminal in image like this:
$ docker exec -it dockertut_mysql_1 /bin/bash root@0e4f40d9ae8b:/# mysql -u root -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. ... mysql> _
Neat, huh? The -i means to run interactive command, -t to run in terminal.
Manage Docker as non-root User
By creating docker group, and adding users to it, you may select users that can manage docker daemon and processes:
$ sudo groupadd docker $ sudo usermod -aG docker $USER
Afterwards, restart your machine (or, log out and in, and stop and start the docker daemon), and you should be able to control docker without the need for sudo.
