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Way back in the when I first started using Docker in earnest, I wrote about my web hosting stack. Recently, this has undergone an upgrade as I’m working on a new website which will be served from the same server. I took the opportunity to split the system up into multiple docker-compose projects, which makes deployment of further sites much easier. It allows me to manage the common containers from one docker-compose project and then each of the sites from their own project. This will be of further use in future as I move towards deploying these with Ansible.
The Approach
My basic approach here is to move my two common containers (my Traefik container and SMTP forwarder) into their own project. This project will create a couple of networks for interfacing to the containers from other projects. To create these networks I add the following to my common project docker-compose.yml:
Here I create two networks as per normal. The key is to give them a proper name, rather than the auto generated one that would be assigned by Docker. This will enable us to address them easily from our other projects. We then assign these to our common containers:
services:
traefik:
image: traefik:2.1
command:
...
volumes:
...
ports:
- "80:80"
- "443:443"
- "127.0.0.1:8080:8080"
networks:
gateway:
aliases:
# add hostnames you might want to refer to this container by
- example.com
restart: always
postfix:
image: boky/postfix
ports:
...
environment:
...
volumes:
...
networks:
smtp:
aliases:
- postfix
restart: always
Here I simply assign the relevant network to each container. The aliases section allows other containers on these networks to find our common containers by whatever name we specify. In the case of the postfix container this is to connect via SMTP. For the traefik container, adding hostnames which internal apps my need to refer to can help (for example with the WordPress loopback test).
External Projects
With this in place, the other applications can be moved out into their own projects. For each one we need to access the gateway and smtp networks in order to have access to our common services. These are accessed as external networks via the docker-compose.yaml file for our project:
Here I add my varnish cache, as per my previous article. The key thing here is to specify the label traefik.docker.network=gateway to allow Traefik to reliably discover the container. We then also make sure the container is added to the gateway network. I’ve also added a WordPress container, which is on the smtp network. This will allow sending of email from WordPress via the SMTP forwarder.
Conclusion
This is a pretty simple approach for better management of my increasingly complex web stack. As I mentioned earlier that the next step will be to deploy these projects via Ansible. In this case the common containers will become part of a role which can be used across my infrastructure.
The splitting out of the apps into their own projects has enabled me to duplicate my current WordPress+Varnish+Mariadb setup for the new site I’m working on. There will be more info to come about that site as soon as I am ready to share!
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In my previous article on the Traccar GPS tracking software, I lamented the state of my broken internal HTTPS/TLS setup. I’ve known that using DNS validation for Let’s Encrypt was the way to fix this for some time. However, that required me to migrate my DNS to another provider, because my provider (Namecheap) only allow API access if you have a large enough account. Since I wrote that article, I’ve been investigating this further and have found my solution in the form of Linode‘s Domains Service. As I’m already using Linode for hosting my cloud servers (including this website) this is the perfect option for me.
The application which prompted me getting this sorted was bitwarden_rs, which I really didn’t want to run over plain HTTP and also didn’t want to expose to the outside world. I’d recommend the excellent Self Hosted Home article on this as a getting started point if you’d like to deploy it.
Migrating my DNS to Linode
For a job that I wasn’t looking forward to, this migration couldn’t have gone better. The main issue I encountered was that I wasn’t able to import my records over directly from Namecheap, but I think that’s a problem at their end rather than Linode’s. I ended up copying over the records one by one, which was easier than I expected since I didn’t have as many records as I thought.
One other minor issue that I ran into was the SOA email address that I had to add. Weirdly I never had to specify this with Namecheap. The problem stemmed from the fact that Linode will not allow you to use an address from the same domain for this. I contacted Linode support about this because it seemed contrary to their docs. They responded incredibly quickly (time measured in minutes, over a weekend too) and said that is so you can be notified about problems with your domain. This makes sense, but it is a little annoying. In the end I created another third party (gmail, boo!) address for this and forwarded it back to my main self hosted account. I also added it as a secondary account on my phone, just in case.
Getting an API Token
In order to perform the DNS-01 certificate validation with Linode, your client software needs to create a temporary DNS record. This requires an API token to authenticate to the Linode Domains API. This token can be created from the Linode Manager. The only permission required is read/write access to the Domains service, as per the screenshot below:
Required Linode API token permissions
Setting Up Traefik
I wanted to use Traefik as my reverse proxy for this, given my previous success with it. This was massively complicated by the fact that Traefik 2.0 was released just a few days ago. This release introduces a lot of changes both in concepts and configuration, which make Traefik significantly more complex. I was able to work through these changes, but it took me a while to work it all out!
The Traefik Dashboard has changed quite a bit
The Traefik setup I ended up with was as follows (in docker-compose.yml):
Obviously, you need to insert your email address and Linode API token in the relevant places. Make sure not to include quotes around the API token, since these will be passed into the container and make the token invalid. This appears to be some weird and surprising behaviour in docker-compose.
This configuration sets up Traefik with a DNS challenge certificate resolver called mydnschallenge. This needs to be specified in the configuration for each service that you want to use it with. This is done by adding following labels to your service in docker-compose.yml:
These labels first enable Traefik for the container in question. Then we add a new router called myservice and specify that it should be attached to the websecure entrypoint at the hostname given. We then add our mydnschallenge as the TLS certificate resolver. Finally, I specify the backend port on which this service listens – this isn’t required if it just listens on port 80.
With this in place you should be able to successfully get a certificate and then access your service over HTTPS. For me this took a few minutes the first time for the DNS to refresh, but this won’t be an issue for future renewals.
HTTP to HTTPS Redirects with Traefik 2.0
So far our service is available only via HTTPS. If you’ve followed the above configuration for Traefik then it is also listening on port 80 for plain HTTP. However, you will receive a 404 error if you try to access your service via HTTP. What we want to do is the traditional redirect from HTTP to HTTPS.
This turns out to be a little more complex in Traefik 2.0 than in previous versions and requires a little understanding of some new concepts. Traefik 2.0 introduces the concept of middlewares, which can operate on a request as it passes between the router and the backend service. One such middleware is the redirectscheme, which will do exactly what we need. Adding the following labels to your service container will do the trick:
Here we create the middleware myservice_redirect before adding another router (myservice_insecure). This router is attached to the web entrypoint at our hostname, making it available on port 80. Finally we add the myservice_redirect middleware to our new router and we are done! It’s pretty simple when you understand it the concepts.
The Traefik dashboard shows a nice pipeline of how your request gets routed
Conclusion
This solves the problem of internal HTTPS perfectly for me! I’m looking forward to migrating other internal services over to this arrangement. Of course, the configuration presented here only works with Traefik and not other software such as Nginx or Mosquitto. There are other options here which support the Linode API for DNS validation. However, since Traefik 2.0 supports arbitrary TCP services I think I’m going to give that a try for my MQTT server. It’s one less piece of software to maintain!
I’m really happy with how my DNS migration went and how well this all works with the Linode Domains service. It’s nice to discover another aspect to a service that I’ve been using for so long.
I hope you find this setup useful, or perhaps you’ve already solved this problem in a different way. Please feel free to let me know in the feedback channels.
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I’ve been following and using Docker since it’s early days. I think 0.6 was one of the first releases I tried. That said, I’ve never actually had that much luck getting it deployed on meaningful parts of my infrastructure. Usually, I would start some new deployment of something with the intention of using Docker. Then I’d hit some issue which made it difficult (or at least more difficult than it should be). Either that, or I’d run some Docker containers as a testing deployment for a while and then pull them down. It’s safe to say my road to Docker has been long, winding and full of potholes!
Recently, I’ve been giving my infrastructure choices more thought. My main goals are that I want to reduce maintenance and keep the high level of separation and security I have between my different services. As detailed in my last post on my self hosting setup, I’ve been using LXD fairly successfully. The problem with this is really that LXD containers are more like virtual machines. Each container is a little Linux system which needs to be kept up to date, monitored and generally looked after. When you have one container per service this becomes a chore. In actuality I don’t have one LXD container per service. Instead I group dependent services such as databases with their parent. However, I’ve still ended up with quite a few containers.
Decisions, decisions…
I really like the separation I’m able to have by keeping my LXD containers on separate VLANs. Docker does support this via macvlan, but the last time I played with it I had to manually assign IPs to each container. It looks like Docker will now do this automatically. However, it allocates from it’s own IP pool and won’t use your DHCP server. This means I can’t assign IPs from my Pfsense firewall. Also having one public (LAN) IP per Docker service kinda sucks and I also don’t want to rely on just one project for the security of my system.
Additionally, I have the need to run at least one VM anyway for my virtualised Pfsense firewall. This brings me to the idea of running Docker inside VMs. Each VM can be assigned to the relevant VLAN interface and get it’s IP from DHCP. I also get the benefit of two levels of isolation using different technologies. I haven’t yet decided on whether to use Proxmox or Ubuntu Server+Libvirt+Cockpit for the host systems. Hopefully this will be the subject of a future post.
On To Today
All the above is pretty much background, because I actually don’t want to talk about my locally hosted stuff today. Instead I’m going to talk about my stuff in the cloud – specifically the hosting for this site.
I’ve used Linode since around 2011 when I set up my self hosted mail server. Since this time, I’ve hosted this site on a fairly standard LAMP setup on that same server. The mail server install is now getting on a bit, but being CentOS based it’s all still supported for updates until next year. However, in preparation for re-building the mail server I decided to move the web stuff out onto another server and run it in Docker. This basically gives me the same setup of Docker-on-VM as I have on my local infrastructure. Just the hypervisor UI differs – it’s all KVM underneath.
Since I was moving the site to a new server, I also decided to move closer to my audience. According to my Matomo statistics this is predominantly US based. To this end I span up a new $5 Linode (Nanode), running Ubuntu 18.04 in their New Jersey datacenter. This should also be pretty fast for European visitors (to be honest it’s lightning fast even from NZ).
Getting Going
After doing some pretty standard first 10 minutes on a server stuff, I set about installing Docker. Instead of installing via my usual method of adding the APT repository I decided to see how installing from a Snap would work in production:
$ sudo snap install docker
A few seconds later Docker was installed. However, I ran into a wrinkle when trying to add myself to the Docker group. Basically, it wouldn’t allow me to run Docker commands without root access (still). The solution is to add the Docker group before installing the Snap, so I removed it, added the group and reinstalled. So full instructions for installing Docker via Snap should more accurately be:
I’d resolved to install the blog inside the official WordPress container and connect use mariadb for the database. Since I was moving my install over, it was slightly more complex than it would be for a clean install, but this article put me on the right track.
The main issue I encountered didn’t happen until I had the site running and was trying to get HTTPS running. Due to Let’s Encrypt’s HTTP verification this had to be done after the DNS settings were updated i.e. the site was live. This issue manifested as WordPress serving HTTP URLs for all links and embedded content. This leads to mixed content warnings/blocks in Firefox and Chrome. The issue seems to be common to any setup where HTTPS is handled by a reverse proxy. Basically, in this setup WordPress isn’t aware that it should be using HTTPS and needs to be told. Adding the following to wp-config.php fixes the problem:
$_SERVER['HTTPS']='on';
I decided to use Traefik as my reverse proxy, which I’m quite pleased with. The automated service discovery is pretty awesome and will really come into it’s own on my other self hosted infrastructure. I also whacked a Varnish cache (from this Docker image) in between. So far I haven’t done much with Varnish, but it’s there for when I get time to tweak it.
Moving Matomo
I also moved my Matomo Analytics instance to the new server using the official Docker image. This gave me much less trouble than WordPress since I just allowed it to use the embedded Matomo version with my configuration file and database from the old install.
I connected Matomo up directly to my Traefik instance, without running it through Varnish, to avoid any potential issues with the cache interfering with my statistics. Traefik just worked with this setup, which was pretty refreshing.
My Traefik Dashboard
PSA: Docker will Ignore Your Firewall!
Along the way, I ran into another issue. Before I changed the DNS settings to make the site live, I was binding Traefik to port 8080 and accessing it via an SSH tunnel for making changes in WordPress. Since I had configured UFW to block everything (except SSH) when I set up the server, I thought this was a nice secure setup for debugging.
I was wrong.
I only noticed something was off because I happened to have the log output from Traefik open and saw random IPs in the logs. Luckily, the only virtual host I had configured at that point was localhost:8080 so all the unwanted visitors got 404 responses. Needless to say I pulled down all the containers until I could work out what was going on.
This appears to be a known interaction between Docker and any firewall utility (including both UFW and Firewalld). The issue is inherent in the way that Docker uses iptables to route traffic to your containers. Basically, the port forwarding rules go in the NAT chain in iptables. This means incoming traffic is re-routed before it hits the INPUT chain containing the rules from UFW/Firewalld.
I tried the fix suggested – disabling iptables support in Docker, but this completely broke inter-container connectivity (unsurprising, when you think about it). My solution for now is just to be really careful when binding ports. Make sure that any ports you don’t want to give access to the outside world are bound only to 127.0.0.1. There is also the DOCKER-USER iptables chain if you need more flexibility, but it means you need to use raw iptables rules.
This issue is a major security flaw and needs to be given more attention. Breaking administrator expectations of security like this is going to lead to loads of services being exposed to the big bad Internet that really shouldn’t be!
My Full Web Stack
Below is the docker-compose.yml file for my full web stack. I store any secret variables in an env.sh file which I source before running my docker-compose commands.
This is all pretty much as described, however there are two notable points:
I went for separate mariadb containers for the databases for WordPress and Matomo. This is because the official mariadb container only supports creation of one database/user via environment variables. I’m not super happy with this arrangement, but it is working well and doesn’t seem to use too much memory.
The aliases portion under the network configuration for the Traefik container allow the other containers to route internal requests back to themselves. This helps with things such as the loopback check in WordPress, which will otherwise fail.
That’s pretty much all there is to it!
Conclusion
Overall, I’m really happy with the way this migration has worked out. I’ve even been able to downgrade the Linode plan for the original server to the $5/month plan, since it now has less load. This means I’m paying the same as I was for the single server for two servers, although with half the RAM each. I think I paid an extra $2-3 during the migration period, since that took me a while to compete. Even that isn’t too bad.
I’ve already started on further Docker migrations on some of the infrastructure I have on my home servers. These should be the subject of further posts.
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