Category Archives: DevOps

Docker Debian locales installation

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Problem

You want to install some default locales in a Docker image, and the suggestion is to use locale-gen to do so, but it does not work as expected.

Solution

In order to be able to use the locale-gen and install the locales you need you will have to uncomment the ones needed from /etc/locale.gen first and then use the locale-gen. Example below:

## Set up locales
## Uncomment the ones we need as locale-gen does not work without that
RUN sed -i '/en_US.UTF-8/s/^#//' /etc/locale.gen
RUN sed -i '/de_DE.UTF-8/s/^#//' /etc/locale.gen
## Now install them and set the default one
RUN locale-gen
ENV LANG en_US.UTF-8
ENV LANGUAGE en_US:en
ENV LC_ALL en_US.UTF-8

Dockercloud-agent error: …Error creating default \”bridge\” network:…

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Problem

When trying to use the dockercloud-agent with docker you have the following error in the /var/log/dockercloud/agent.log

level=fatal msg="Error starting daemon: Error initializing network controller: Error creating default \"bridge\" network: cannot create network xxx... (docker0): conflicts with network yyy.... (docker0): networks have same bridge name"

Solution

If you remove the file var/lib/docker/network/files/local-kv.db as suggested here, then if you look again at the log files, it should be a message that the docker daemon has been started:

016/11/17 10:30:28 Respawning docker daemon
2016/11/17 10:30:28 Starting docker daemon: [/usr/bin/docker daemon -H unix:///var/run/docker.sock -H tcp://0.0.0.0:2375 --userland-proxy=false --tlscert /etc/dockercloud/agent/cert.pem --tlskey /etc/dockercloud/agent/key.pem --tlscacert /etc/dockercloud/agent/ca.pem --tlsverify]
2016/11/17 10:30:28 Docker daemon (PID:4036) has been started

Clearing unused (dangling) docker volumes

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Problem

After you start using and building Docker images, there is a case that there is a lot of space used even after deleting images and containers (a few GB maybe).

Solution

To clean out the volumes that are no longer used (ie dangling) use the following:

sudo docker volume ls -qf dangling=true | xargs -r sudo docker volume rm

Error response from daemon: conflict: unable to delete xxx (must be forced) – image is referenced in one or more repositories

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Problem

Trying to remove some unused docker images that you no longer use with docker rmi image_id you get the following error message:

Error response from daemon: conflict: unable to delete 75d009de0479 (must be forced) - image is referenced in one or more repositories

Solution

Use the following to delete multiple images (ie ubuntu):

docker images ubuntu | tail -n +2 | awk '{ print $1 ":" $2 }' | xargs sudo docker rmi

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Stopping a blocking query in postgresql

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Problem

You run a query in PostgreSQL that takes a lot of time to finish (maybe because of an error) and you want to stop/kill it as it is blocking other queries in db.

Solution

You will need to find the pid for the query, either by using a GUI program like Pgadmin or by issuing the following to an SQL prompt:

select * from pg_stat_activity

make a note of the pid of the query that you want to stop/kill and issue the following:

select pg_cancel_backend(pid)

Remove terminated/unused docker containers from your system

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Problem

After playing around with docker containers for some time the terminated/unused ones are still hanging around your system, and prevent you from using a new container with the same name as any of the previous ones with the error:

Error response from daemon: Conflict. The name "container_name" is already in use by container 61f023f06a98. You have to remove (or rename) that container to be able to reuse that name.

Solution

You can remove all the containers by using the following:

docker rm $(docker ps -aq)

SSL received a record that exceeded the maximum permissible length.

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Problem

You want to install rbenv, but when you are trying to clone the code with: 

git clone https://github.com/rbenv/rbenv.git ~/.rbenv

you get the following error:

fatal: unable to access 'https://github.com/rbenv/rbenv.git/': SSL received a record that exceeded the maximum permissible length.

Solution

If you are behind a proxy server make sure that you add your proxy server details in your ~/.bash_profile and source the file afterwards.

So first add the details of your proxy like:

export http_proxy=http://xxx.xxx.xxx.xxx:8080
export https_proxy=https://xxx.xxx.xxx.xxx:8080

And finally source the file before running the installation again:

source ~/.bash_profile