doc/md/docker/docker-101.md

   1 ## Basics
   2 Install [Docker](https://www.docker.com/), by following the instructions relevant
   3 to your OS / distribution, and start the service.
   4
   5 ### Search an image on [DockerHub](https://hub.docker.com/)
   6
   7 ```bash
   8 $ docker search debian
   9
  10 NAME            DESCRIPTION                                     STARS   OFFICIAL   AUTOMATED
  11 ubuntu          Ubuntu is a Debian-based Linux operating s...   2065    [OK]
  12 debian          Debian is a Linux distribution that's comp...   603     [OK]
  13 google/debian                                                   47                 [OK]
  14 ```
  15
  16 ### Show available tags for a repository
  17 ```bash
  18 $ curl https://index.docker.io/v1/repositories/debian/tags | python -m json.tool
  19
  20 % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
  21 Dload  Upload   Total   Spent    Left  Speed
  22 100  1283    0  1283    0     0    433      0 --:--:--  0:00:02 --:--:--   433
  23 ```
  24
  25 Sample output:
  26 ```json
  27 [
  28     {
  29         "layer": "85a02782",
  30         "name": "stretch"
  31     },
  32     {
  33         "layer": "59abecbc",
  34         "name": "testing"
  35     },
  36     {
  37         "layer": "bf0fd686",
  38         "name": "unstable"
  39     },
  40     {
  41         "layer": "60c52dbe",
  42         "name": "wheezy"
  43     },
  44     {
  45         "layer": "c5b806fe",
  46         "name": "wheezy-backports"
  47     }
  48 ]
  49
  50 ```
  51
  52 ### Pull an image from DockerHub
  53 ```bash
  54 $ docker pull repository[:tag]
  55
  56 $ docker pull debian:wheezy
  57 wheezy: Pulling from debian
  58 4c8cbfd2973e: Pull complete
  59 60c52dbe9d91: Pull complete
  60 Digest: sha256:c584131da2ac1948aa3e66468a4424b6aea2f33acba7cec0b631bdb56254c4fe
  61 Status: Downloaded newer image for debian:wheezy
  62 ```
  63
  64 Docker re-uses layers already downloaded. In other words if you have images based on Alpine or some Ubuntu version for example, those can share disk space.
  65
  66 ### Start a container
  67 A container is an instance created from an image, that can be run and that keeps running until its main process exits. Or until the user stops the container.
  68
  69 The simplest way to start a container from image is ``docker run``. It also pulls the image for you if it is not locally available. For more advanced use, refer to ``docker create``.
  70
  71 Stopped containers are not destroyed, unless you specify ``--rm``. To view all created, running and stopped containers, enter:
  72 ```bash
  73 $ docker ps -a
  74 ```
  75
  76 Some containers may be designed or configured to be restarted, others are not. Also remember both network ports and volumes of a container are created on start, and not editable later.
  77
  78 ### Access a running container
  79 A running container is accessible using ``docker exec``, or ``docker copy``. You can use ``exec`` to start a root shell in the Shaarli container:
  80 ```bash
  81 $ docker exec -ti <container-name-or-id> bash
  82 ```
  83 Note the names and ID's of containers are listed in ``docker ps``. You can even type only one or two letters of the ID, given they are unique.
  84
  85 Access can also be through one or more network ports, or disk volumes. Both are specified on and fixed on ``docker create`` or ``run``.
  86
  87 You can view the console output of the main container process too:
  88 ```bash
  89 $ docker logs -f <container-name-or-id>
  90 ```
  91
  92 ### Docker disk use
  93 Trying out different images can fill some gigabytes of disk quickly. Besides images, the docker volumes usually take up most disk space.
  94
  95 If you care only about trying out docker and not about what is running or saved, the following commands should help you out quickly if you run low on disk space:
  96
  97 ```bash
  98 $ docker rmi -f $(docker images -aq) # remove or mark all images for disposal
  99 $ docker volume rm $(docker volume ls -q) # remove all volumes
 100 ```
 101
 102 ### Systemd config
 103 Systemd is the process manager of choice on Debian-based distributions. Once you have a ``docker`` service installed, you can use the following steps to set up Shaarli to run on system start.
 104
 105 ```bash
 106 systemctl enable /etc/systemd/system/docker.shaarli.service
 107 systemctl start docker.shaarli
 108 systemctl status docker.*
 109 journalctl -f # inspect system log if needed
 110 ```
 111
 112 You will need sudo or a root terminal to perform some or all of the steps above. Here are the contents for the service file:
 113 ```
 114 [Unit]
 115 Description=Shaarli Bookmark Manager Container
 116 After=docker.service
 117 Requires=docker.service
 118
 119
 120 [Service]
 121 Restart=always
 122
 123 # Put any environment you want in an included file, like $host- or $domainname in this example
 124 EnvironmentFile=/etc/sysconfig/box-environment
 125
 126 # It's just an example..
 127 ExecStart=/usr/bin/docker run \
 128   -p 28010:80 \
 129   --name ${hostname}-shaarli \
 130   --hostname shaarli.${domainname} \
 131   -v /srv/docker-volumes-local/shaarli-data:/var/www/shaarli/data:rw \
 132   -v /etc/localtime:/etc/localtime:ro \
 133   shaarli/shaarli:latest
 134
 135 ExecStop=/usr/bin/docker rm -f ${hostname}-shaarli
 136
 137
 138 [Install]
 139 WantedBy=multi-user.target
 140 ```