Docker – Debian – Kernel panick – Automatic restart

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Problem

You have a remote server (Debian) running some Docker containers and you want to make sure that they all restart in the event of a kernel panick.

solution

  • Add an automatic restart after a kernel panick by running:

  • Emulate a kernel panick by running the following (SysRq more info here :

  • Check that the containers have restarted again with docker ps (NOTE: the containers should have been enabled to autorestart)

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:

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

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:

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:

Removing Docker containers that have exited

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Problem

You would like to clear Docker containers that have been exited and not cleared properly.

Solution

Run the following to find out the containers that have exited and remove them.

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:

Solution

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

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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:

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