I'm running a project in a container on my machine. this project needs to list other containers on machine. previously this project was on machine (not on a container in machine) and it was possible to do that. but now it's in one of those containers. I want to know is it possible to create an access for this type of jobs (listing containers, stop/start/... them or any other works on other containers or the host machine)?
if it's true, how can it be possible?
You can use so-called docker-in-docker technique. But before starting with it, you are obligated to read the post:
http://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/
which is the best explanation of pros and cons.
All you have is to export /var/run/docker.sock to your container and setup docker-cli inside the container. It will give you docker access inside container, at the same time you will be adressing your host's docker engine.
Related
We're running Docker on Digital Ocean App Engine, and can't pass flags (e.g. --cpus) to docker run.
We can't use docker-compose either.
Is it possible to set an environment variable (ARG? ENV?), e.g. $CPUS=blah) in a way that can be picked up by the Docker instance?
Stated differently, are there internal environment variables that correspond to specific flags, that can be set from with a Dockerfile / environment itself?
As we can see in the very first steps of official documentation of Docker (this link):
Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security allow you to run many containers simultaneously on a given host. Containers are lightweight and contain everything needed to run the application, so you do not need to rely on what is currently installed on the host. You can easily share containers while you work, and be sure that everyone you share with gets the same container that works in the same way.
The main concept of Docker is to isolate each container from the other container, environment variables and anything that relates to the them. So the only thing we can access and modify them is what that reside outside of the container like:
exposing ports
exposing volumes
map container port to the host port
map container volume to the host volume and vice-versa
...
Okay so in Vagrant/VVV you can assign different hostnames to your different projects so when you go to http://myproject-1.dev your website shows up.
This is very convenient if you are working on dozens of projects at the same time, As far as I know such thing is not possible in docker (it can't touch hosts file), My question is, is there something similar we can do in Docker? Some automated tool maybe?
Using docker for windows.
Hostnames can map many containers together. In docker compose, there's a hostname option. But that's only within the Docker network bridge, not available to the host
Docker isn't a VM (although it runs within one in Windows).
You can edit your hosts file to have the HyperVisor available, but you're supposed to have the host ports forwarded into the container.
Use localhost, not any hostname.
If you prefer your Vagrant patterns, continue using it, but provision Docker containers from it, or use Docker Machine
Docker has great documentation on linking containers - allowing one container to make use of the other container's environment variables.
However, how would one go about exposing command line aliases (and their respective programs) of the host machine to the Docker container?
Or, perhaps the better way to go about this is to simply configure the Docker container to build from an image that has these aliases / "dotfiles" built in?
I don't think that you approach to docker as you should. A docker container's purpose is to run a network application and expose it to outside world.
If you need aliases for your application running inside a container, then you have to build an image first, that contains the whole environment your app needs...
Or specify them in the Dockerfile, while building your image.
I created a customize Docker image based on ubuntu 14.04 with the Sensu-Client package inside.
Everything's went fine but now I'm wondering how can I trigger the checks to run from the hosts machine.
For example, I want to be able to check the processes that are running on the host machine and not only the ones running inside the container.
Thanks
It depends on what checks you want to run. A lot of system-level checks work fine if you run sensu container with --net=host and --privileged flags.
--net=host not just allows you to see the same hostname and IP as host system, but also all the tcp connections and interface metric will match for container and host.
--privileged gives container full access to system metrics like hdd, memory, cpu.
Tricky thing is checking external process metrics, as docker isolates it even from privileged container, but you can share host's root filesystem as docker volume ( -v /:/host) and patch check to use chroot or use /host/proc instead of /proc.
Long story short, some checks will just work, for others you need to patch or develop your own way, but sensu in docker is one possible way.
an unprivileged docker container cannot check processes outside of it's container because docker uses kernel namespaces to isolate it from all other processes running on the host. This is by design: docker security documentation
If you would like to run a super privileged docker container that has this namespace disabled you can run:
docker run -it --rm --privileged --pid=host alpine /bin/sh
Doing so removes an important security layer that docker provides and should be avoided if possible. Once in the container, try running ps auxf and you will see all processes on the host.
I don't think this is possible right now.
If the processes in the host instance are running inside docker, you can mount the socket and get the status from the sensu container
Add a sensu-client to the host machine? You might want to split it out so you have granulation between problems in the containers VS problems with your hosts
Else - You would have to set up some way to report from the inside - Either using something low level (system calls etc) or set up something from outside to catch the the calls and report back status.
HTHs
Most if not all sensu plugins hardcode the path to the proc files. One option is to mount the host proc files to a different path inside of the docker container and modify the sensu plugins to support this other location.
This is my base docker container that supports modifying the sensu plugins proc file location.
https://github.com/sstarcher/docker-sensu
I'm running Jenkins inside a Docker container. I wonder if it's ok for the Jenkins container to also be a Docker host? What I'm thinking about is to start a new docker container for each integration test build from inside Jenkins (to start databases, message brokers etc). The containers should thus be shutdown after the integration tests are completed. Is there a reason to avoid running docker containers from inside another docker container in this way?
Running Docker inside Docker (a.k.a. dind), while possible, should be avoided, if at all possible. (Source provided below.) Instead, you want to set up a way for your main container to produce and communicate with sibling containers.
Jérôme Petazzoni — the author of the feature that made it possible for Docker to run inside a Docker container — actually wrote a blog post saying not to do it. The use case he describes matches the OP's exact use case of a CI Docker container that needs to run jobs inside other Docker containers.
Petazzoni lists two reasons why dind is troublesome:
It does not cooperate well with Linux Security Modules (LSM).
It creates a mismatch in file systems that creates problems for the containers created inside parent containers.
From that blog post, he describes the following alternative,
[The] simplest way is to just expose the Docker socket to your CI container, by bind-mounting it with the -v flag.
Simply put, when you start your CI container (Jenkins or other), instead of hacking something together with Docker-in-Docker, start it with:
docker run -v /var/run/docker.sock:/var/run/docker.sock ...
Now this container will have access to the Docker socket, and will therefore be able to start containers. Except that instead of starting "child" containers, it will start "sibling" containers.
I answered a similar question before on how to run a Docker container inside Docker.
To run docker inside docker is definitely possible. The main thing is that you run the outer container with extra privileges (starting with --privileged=true) and then install docker in that container.
Check this blog post for more info: Docker-in-Docker.
One potential use case for this is described in this entry. The blog describes how to build docker containers within a Jenkins docker container.
However, Docker inside Docker it is not the recommended approach to solve this type of problems. Instead, the recommended approach is to create "sibling" containers as described in this post
So, running Docker inside Docker was by many considered as a good type of solution for this type of problems. Now, the trend is to use "sibling" containers instead. See the answer by #predmijat on this page for more info.
It's OK to run Docker-in-Docker (DinD) and in fact Docker (the company) has an official DinD image for this.
The caveat however is that it requires a privileged container, which depending on your security needs may not be a viable alternative.
The alternative solution of running Docker using sibling containers (aka Docker-out-of-Docker or DooD) does not require a privileged container, but has a few drawbacks that stem from the fact that you are launching the container from within a context that is different from that one in which it's running (i.e., you launch the container from within a container, yet it's running at the host's level, not inside the container).
I wrote a blog describing the pros/cons of DinD vs DooD here.
Having said this, Nestybox (a startup I just founded) is working on a solution that runs true Docker-in-Docker securely (without using privileged containers). You can check it out at www.nestybox.com.
Yes, we can run docker in docker, we'll need to attach the unix socket /var/run/docker.sock on which the docker daemon listens by default as volume to the parent docker using -v /var/run/docker.sock:/var/run/docker.sock.
Sometimes, permissions issues may arise for docker daemon socket for which you can write sudo chmod 757 /var/run/docker.sock.
And also it would require to run the docker in privileged mode, so the commands would be:
sudo chmod 757 /var/run/docker.sock
docker run --privileged=true -v /var/run/docker.sock:/var/run/docker.sock -it ...
I was trying my best to run containers within containers just like you for the past few days. Wasted many hours. So far most of the people advise me to do stuff like using the docker's DIND image which is not applicable for my case, as I need the main container to be Ubuntu OS, or to run some privilege command and map the daemon socket into container. (Which never ever works for me)
The solution I found was to use Nestybox on my Ubuntu 20.04 system and it works best. Its also extremely simple to execute, provided your local system is ubuntu (which they support best), as the container runtime are specifically deigned for such application. It also has the most flexible options. The free edition of Nestybox is perhaps the best method as of Nov 2022. Highly recommends you to try it without bothering all the tedious setup other people suggest. They have many pre-constructed solutions to address such specific needs with a simple command line.
The Nestybox provide special runtime environment for newly created docker container, they also provides some ubuntu/common OS images with docker and systemd in built.
Their goal is to make the main container function exactly the same as a virtual machine securely. You can literally ssh into your ubuntu main container as well without the ability to access anything in the main machine. From your main container you may create all kinds of containers like a normal local system does. That systemd is very important for you to setup docker conveniently inside the container.
One simple common command to execute sysbox:
dock run --runtime=sysbox-runc -it any_image
If you think thats what you are looking for, you can find out more at their github:
https://github.com/nestybox/sysbox
Quicklink to instruction on how to deploy a simple sysbox runtime environment container: https://github.com/nestybox/sysbox/blob/master/docs/quickstart/README.md