GCE – SSH Directly Into Your Docker Container

google_cloud_plattform

In this article, I am going to change the SSH port from 22 to 52241 and create a new firewall rule in VPC. Please do your own research and make sure you understand the impact, especially on a production environment.

When you deploy a new docker container on GCE, you can SSH into the host machine ( VM ). This is simply because the IP address is pointing to the host machine. But what about the docker container that runs on it? In this case, you must use docker exec or the gcloud command-line tool in order to get access to the container, which can be pretty time consuming over time.

I am working on a project where I need direct access to my alpine docker container on port 22 or any other port. As you can see in the below output, no ports are exposed for my container.

This is mainly because the docker container shares the network with the host. Source

Containerized VMs launch containers with the network set to host mode. A container shares the host network stack, and all interfaces from the host are available to the container.

This is very convenient because it allows you to access your docker container from pretty much any port. However, only a few ports are actually open and configured in the VPC Network > Firewall settings for security reasons. For the SSH connection I decided to open a custom port 52241. You can do this in your GCP Console under VPC Network > Firewall or with the following gcloud command-line tool.

Once completed, here is how the new firewall rule looks like in the console. If you scroll down, you will also see all affected instances.

GCP Custom Firewall

Before you can SSH into your container on port 52241 you must change the port in the sshd configuration /etc/ssh/sshd_config within your container or container image. Not on the VM.

You may have to restart your ssh service before you can use the new port. Once this is done, you can SSH into your docker container.

Notice: Use of undefined constant T_CURLY_OPEN – assumed ‘T_CURLY_OPEN’ in /var/www/src/setup/src/ Magento/Setup/Module/ Di/Code/Reader/FileClassScanner.php on line 72

Today I finally had some time to cleaned up my Dockerfile for Magento 2. I am using Alpine Linux for most of my Magento 2 projects which usually includes NGINX, PHP-FPM and MariaDB.

While testing my updated Dockerfile I came across the following PHP notice which prevented the deployment scripts from finishing the Magento 2 setup.

The problem was simply a missing PHP extension php7.1-tokenizer which has resolved the issue after re-creating the container with –build.

 

Nginx Docker Container and getpwnam(“www-data”) problem

I am using nginx:1.10.1-alpine to run Nginx as a docker container. Today I have replaced the Nginx container and always got the status Restarting (1) Less than a second ago after starting the container.

With the command docker logs nginx I got the following error logs.

The error message basically means that the user www-data which I have defined in /etc/nginx/nginx.conf doesn’t exists in /etc/passwd. That makes sense, because nginx:1.10.1-alpine comes with a minimal setup. I my case I need the user www-data for other linked php-fpm containers. To fix the problem I just added the missing user during the container build.

Voilà.

Nginx and Cached CSS / JS files

Yesterday I had a pretty hard time with cached CSS / JS files on my developer environment. I supposed to review layout changes, but I always got the old CSS files. I have spent about 2 hours to find the reason. At the end the solution was to turn off the syscall sendfile in my virtual host configuration.

If you use Nginx as a reverse proxy to serve pages from an application server, you can leave sendfile turned off.

 

Reload Nginx Inside Docker Container

I am using docker for Nginx which is running with multiple virtual hosts. Sometimes I have to reload my updated nginx configurations, but I don’t want restart the container each time. Here is how you can reload your nginx without any downtime and without interrupting any connections.

1. Find your container name

Use docker ps to find your nginx container.

2. Reload Nginx

With docker exec -it {container_name} {command} you can directly access your container and execute commands. In my case the name of the container is nginx-server.