Category Archives: docker

migrate local docker images to a remote docker host

A. New remote host
– install docker
– setup simple configuration to let docker daemon be accessible from other machines:
Edit /etc/default/docker, and add following line

DOCKER_OPTS=”-H tcp://0.0.0.0:2375″

– restart docker daemon

sudo service docker restart

IMPORTANT:
With systemd systems (trusty and vivid), we must add new file :
/etc/systemd/system/docker.service.d/docker.conf
with following content:

[Service]
EnvironmentFile=-/etc/default/docker
ExecStart=
ExecStart=/usr/bin/docker -d $DOCKER_OPTS

And then restart socker.

Now, when trying :

docker ps

we’ll got error:

Get http:///var/run/docker.sock/v1.19/containers/json: dial unix /var/run/docker.sock: no such file or directory. Are you trying to connect to a TLS-enabled daemon without TLS?

That’s because docker client try to connect to file socket by default. So, from now, we must specify which host to connect to when running docker client. Like so :

docker -H localhost:2375 ps
# or
docker -H 127.0.0.1:2375 ps
# or
simply docker -H :2375 ps

Ok, but it’s annoying to specify the host all the time !
So, the solution is to define an environment variable DOCKER_HOST:

export DOCKER_HOST=0.0.0.0:2375

then we can just run :

docker ps

B. Local host

We must set environment variable DOCKER_HOST like following (assume host machien ip is 192.168.33.10)

export DOCKER_HOST=192.168.33.10:2375

C. transfer images from local docker host to remote docker host
Now, to move all local images to the new docker host, we have to make it in three steps :
1. under local machine: export images as tar files

docker -H “” save -o /tmp/myimage.tar myimage

2. transfer tar files from local machine to the remote one (with scp for example)

scp /tmp/myimage.tar user@192.168.33.10:/tmp/

3. under remote machine: load images

docker load -i /tmp/myimage.tar

Hope this help

access to a dockerized apache from local mochine

Get ubuntu

docker pull ubuntu:vivid

Start ubuntu container

docker run -ti ubuntu:vivid /bin/bash

Install apache

root@54a954be4ca3:/# apt-get install apache2

Type CTRL+P then CTRL+Q : this will exit the shell without killing the process
Now in the local machine, check out the container name

docker ps

Save the container with its apache installed (suppose your container name is happy_pasteur)

docker commit -a “witr ” -m “install apache2” happy_pasteur witr/myapache

Stop the container

docker stop happy_pasteur

Start apache in new container “myapache” and bind ports

docker run -d -p 9999:80 witr/myapache /usr/sbin/apache2ctl -D FOREGROUND

Finally browse http://localhost:9999