CloudFormation - A Sample

I'm not sure I like AWS CloudFormation (CF). Beside the obvious lock-in I currently would rather use TerraForm or similar to describe what infrastructure I want. However CF will always have the most complete features especially for new AWS services, so it's probably good to know. And one day you'd possibly have to modify a CF configuration file, so it's a really good thing to know if you work with AWS.

Anyway, my observations:

  1. I do not recommend to use JSON for CF. Use YAML. It's much shorter and much easier to read. I usually like JSON, but here it's outclassed by YAML.
  2. As a PowerUser, to use CF you need some extra permissions:
    1. iam:CreateInstanceProfile
    2. iam:DeleteInstanceProfile
    3. iam:PassRole
    4. iam:DeleteRole
    5. iam:AddRoleToInstanceProfile
    6. iam:RemoveRoleFromInstanceProfile

Here are the command lines to use:

aws cloudformation create-stack --template-body file://OneEC2AndDNS.yaml --stack-name OneEC2 \
--parameters ParameterKey=InstanceType,ParameterValue=t2.nano --capabilities CAPABILITY_IAM

To see what was created (takes about 4 min 20 sec):

aws cloudformation describe-stacks --stack-name=OneEC2-6

gives you this output (some data replaced by X):

aws cloudformation describe-stacks --stack-name=OneEC2-6
    "Stacks": [
            "StackId": "arn:aws:cloudformation:ap-northeast-1:XXXXXXXXXXXX:stack/OneEC2-6/XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX", 
            "Description": "Build EC2 instance with current AWS Linux and create a DNS entry in", 
            "Parameters": [
                    "ParameterValue": "", 
                    "ParameterKey": "HostedZone"
                    "ParameterValue": "t2.nano", 
                    "ParameterKey": "InstanceType"
            "Tags": [], 
            "Outputs": [
                    "Description": "Fully qualified domain name", 
                    "OutputKey": "DomainName", 
                    "OutputValue": ""
            "CreationTime": "2018-03-11T12:57:50.851Z", 
            "Capabilities": [
            "StackName": "OneEC2-6", 
            "NotificationARNs": [], 
            "StackStatus": "CREATE_COMPLETE", 
            "DisableRollback": false, 
            "RollbackConfiguration": {}

And to delete it all (takes about 3 min 30 sec):

aws cloudformation delete-stack --stack-name=OneEC2-6

Moving Containers from CA to TK

From CA to TK

Moving Docker container is supposed to be easy, but when doing a move, why not clean up, modernize and improve? Which of course makes such a move as difficult as any non-Docker move.

I moved several containers/services by literally copying the directory with the docker-compose.yml file in it.  That same directory has all the mount points for the Docker images, so moving is as simple as

On the old VM:

ssh OLD_HOST 'tar cf - DIR_NAME' | tar xfv -

which, if you got the permissions, works like a charm. If you don't have the permissions to tar up the old directory (e.g. root owned files which are only root-readable, e.g. private keys). If you don have the permissions, then execute this (the tar as well as the un-tar) as root.

Then a

docker-compose up -d

and all is running now and will continue to run in case of a reboot.


For mail I wanted to go away from the home-made postfix-dovecot container I created a long time ago: with the constant thread of security issues, maintenance and updates are getting mandatory. Also I had no spam filter included which back then was less of a problem than it is now. So I was looking for a simpler to maintain mail solution. I would not have minded to pay for a commercial one. Most commercial email hosting companies are totally oversized for my needs though, but at the same time I have to host 2 or 3 DNS domains which often is not part of the smallest offering.

My requirements were modest:

  1. 2 or 3 DNS domains to host, with proper MX records
  2. IMAP4 and SMTP
  3. web mailer frontend for those times I cannot use my phone
  4. TLS everywhere with no certificate warnings (e.g. self-signed certificates) for SMTP, IMAP4 and webmail
  5. 2 users minimum, unlikely ever more than 5
  6. Aliases from the usual suspects (info, postmaster)
  7. Some anti-spam solution

In the end I decided to do self-hosting again, if only to not forget how this all works. Here is the docker-compose.yml file:

version: '3'

    image: analogic/
      - /home/USER_NAME/mymailserver/data:/data
      - /etc/localtime:/etc/localtime:ro
      - "25:25"
      - "8080:80"
      - "110:110"
      - "143:143"
      - "8443:443"
      - "465:465"
      - "587:587"
      - "993:993"
      - "995:995"
    restart: always

You will have to configure the users and domains once incl. uploading the certificate (one certificate with two alternative names for 2 DNS domains). Also DKIM records (handled by, SPF (manual) and updating the MX records. It worked flawlessly!

Updating the Let's Encrypt certificate is not difficult: since all files are in the /data directory, updating those from outside the container is simple. It does need a restart of the container though.

One issue though:

As you can see, quite a lot of memory is used: 27.6% of a 2 GB RAM VM. The small VM I started with had only 1 GB RAM, and while all was running, it was very low on free memory and had to use swap. That's the only drawback of this Docker image: you cannot turn off ClamAV. However maybe that's ok since viruses and malware are a real problem and this helps to contain it.


AWS Snippets

Find Latest AMI

Find latest Amazon Linux 2 image in us-east-1:

aws --region=us-east-1 ec2 describe-images --owners amazon --filters \
'Name=name,Values=amzn2-ami-hvm-*-x86_64-gp2' \
'Name=state,Values=available' | \
jq -r '.Images | sort_by(.CreationDate) | last(.[]).ImageId'

To verify or generally check out an AMI:

aws --region=us-east-1 ec2 describe-images --image-ids ami-XXXXXXX | jq .

Find latest Amazon Linux 2 images in all regions

regions==$(aws ec2 describe-regions --query 'Regions[].{Name:RegionName}' --output=text | sort)
for i in $regions ; do
  echo -n "$i "
  aws --region=$i ec2 describe-images --owners amazon \
  --filters 'Name=name,Values=amzn2-ami-hvm-*-x86_64-gp2' 'Name=state,Values=available' | \
  jq -r '.Images | sort_by(.CreationDate) | last(.[]).ImageId'

List all Regions

aws ec2 describe-regions --query 'Regions[].{Name:RegionName}' --output=text | sort
# same as
aws ec2 describe-regions | jq -r '.Regions | sort_by(.RegionName) | .[].RegionName'

See also for some more examples using NodeJS instead of the AWS CLI.


Static WDS on Mikrotik's RouterOS

Mikrotik's RouterOS and WDS

WDS is a bit of a mystery: when it works, it's great, especially in fully automatic meshed mode: add a node, extend your network. So much the theory. But when it won't work, it's causing trouble. Then it's time to take out the big guns: static WDS connections.

As so often, it's easy to do once you know how to do it:

1. For the WLAN interface to use, set WDS mode to static:

2. Define a static WDS connection. Needs to be done on both sides. You'll need to add the WLAN MAC address of the counterpart (remote) WDS endpoint:

Done. It should connect now and be used.


Comparing JPEG, x265, AV1 and RAW

Here a nice link where you can compare visually the differences in JPEG, x265, AV1 and RAW image format: