• Container with alpine failing to execute a file with not found

  3 min read

  
  

  While building a container using alpine as a base image we can get a not found error while trying to execute a file that doesn't make much sense:

  $ docker run -it test /usr/local/bin/example-app
  exec /usr/local/bin/example-app: no such file or directory
  

  14/11/2022

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• How docker generates container's names

  2 min read

  
  

  Everytime you create a container using docker, if not already set using --name, docker chooses a name for you: you can expect two words with a underscore:

  $ docker run --rm -d alpine sleep 24h
  38c4cc4e87762fc113ef174e9a4989e13d21037678abd3fe73840b825f14c7bf
  $ docker ps
  CONTAINER ID   IMAGE                          COMMAND                  CREATED         STATUS                PORTS                    NAMES
  38c4cc4e8776   alpine                         "sleep 24h"              5 seconds ago   Up 3 seconds                                   romantic_shtern
  

  For this example it was chosen romantic_shtern, but it can use a great variety of words:

  $ docker ps --all | grep -v "Up" | awk '{ print $NF }'
  NAMES
  mystifying_poitras
  suspicious_shtern
  focused_chatelet
  keen_mendel
  happy_jackson
  xenodochial_margulis
  kind_blackburn
  gallant_pascal
  trusting_thompson
  (...)
  

  So, how does Docker generate names for it's containers?

  01/08/2022

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• Docker: Using the host's network

  2 min read

  If we use the --net=host option with docker to create a new container, it will share it's network namespace with the host machine. It's main advantage is that it will provide higher performance (it will be close to bare metal speed); however, we might get port conflicts.

  24/02/2022

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• How to build a multi architecture container using rootless nerdctl

  3 min read

  
  

  One of the great things about using nerdctl is that it does not try to include everything you might need. This means that if you try to build a container using nerdctl you'll realize you still need to install the buildkit (unless you have installed the "nerdctl-full" version)

  Moreover it's something you don't actually need to have installed locally:

  $ nerdctl build --help | grep buildkit
  Build an image from a Dockerfile. Needs buildkitd to be running.
        --buildkit-host string     BuildKit address [$BUILDKIT_HOST] (default "unix:///run/user/1000/buildkit/buildkitd.sock")
  

  09/02/2022

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• Running rootless containers with nerdctl

  6 min read

  
  

  It's no secret that docker comes stuffed with many options that many of us don't need. This is why on servers we can find containerd instead of a fully featured docker. Despite that, the real deal breaker is that whatever we are running, we are going to do it with root privileges. We can check this by running the following container:

  $ docker run -v /etc:/itc -it --rm alpine sleep 24
  

  And then looking for the process on the host

  $ ps auxf
  
  root        1307  0.0  0.1 2084820 46676 ?       Ssl  11:36   0:04 /usr/bin/containerd
  root       66978  0.0  0.0 709860  6120 ?        Sl   05:12   0:00  \_ containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/50cf9789d0e68949d1cf79462956bde98b46a4616e8
  b81977d8c89d2af9c34e7 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
  root       66996  2.0  0.0   1588     4 pts/0    Ss+  05:12   0:00      \_ sleep 24
  

  Is it possible to run rootless containers? Is there an alternative to docker?

  08/02/2022

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