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docker-hosts-updater

Automatic update /etc/hosts on start/stop containers by labels.

Requirements

  • Native linux
    This tool has no effect on macOS or windows, because docker on these OS run in VM and you can't directly access from host to each container via ip. Yet you can pass traffic through loadbalancer, see section above.

Usage

Start up docker-hosts-updater:

$ docker run -d --restart=always \
    --name docker-hosts-updater \
    -v /var/run/docker.sock:/var/run/docker.sock \
    -v /etc/hosts:/opt/hosts \
    grachevko/docker-hosts-updater

Start containers with label ru.grachevko.dhu option

% docker run -d --label ru.grachevko.dhu=nginx.local nginx

Try to ping from host

% ping nginx.local

Default hosts

By default adding records with container name and container hostname. To disable it you can use environments CONTAINER_HOSTNAME_DISABLED and CONTAINER_NAME_DISABLED:

$ docker run -d --restart=always \
    --name docker-hosts-updater \
    -v /var/run/docker.sock:/var/run/docker.sock \
    -v /etc/hosts:/opt/hosts \
    -e CONTAINER_HOSTNAME_DISABLED=false \
    -e CONTAINER_NAME_DISABLED=false \
    grachevko/docker-hosts-updater

Multiple Hosts

You can add multiple hosts, just separate them by semicolon:

$ docker run --label ru.grachevko.dhu="nginx.local;nginx.ru" nginx
$ ping nginx.local
$ ping nginx.ru

Subdomains

Add subdomains by using pattern {www,api}.nginx.local:

$ docker run -d --label ru.grachevko.dhu="{www,api}.nginx.local" nginx
$ ping nginx.local
$ ping www.nginx.local
$ ping api.nginx.local

Priority

If you want to run two containers with same hosts and want one override another, just add priority after colon:

$ docker run -d --label ru.grachevko.dhu="nginx.local" nginx
$ docker run -d --label ru.grachevko.dhu="nginx.local:10" nginx
$ ping nginx.local

Container with greater priority will be used. Default priority 0. If priority is the same then early created container will be used.

Load Balancer

In order to pass the traffic through the loadbalancer you should define container's name or valid IPv4. Just add one more colon and container name after it.

$ docker run -d --name lb nginx
$ docker run -d --label ru.grachevko.dhu="nginx1.local:0:lb" nginx
$ docker run -d --label ru.grachevko.dhu="nginx2.local:0:127.0.0.1" nginx
$ ping nginx1.local // ip of lb
$ ping nginx2.local // ip of lb

Keep in mind, loadbalancer container must have fixed name.