Problem
When trying to configure nullmailer you may end up with many test emails that end up in the queue, that you don’t want to keep trying to send, but to delete them.
Solution
Clear the nullmailer queue by running:
rm /var/spool/nullmailer/queue/*
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
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
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
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.
sudo docker ps -a | grep 'Exited' | tail -n +1 | awk '{ print $1 }' | xargs sudo docker rm
Problem
You would like to know the IP for a running Docker container.
Solution
Run the following two commands (taken from here
docker ps docker inspect container_name | grep IPAddress
Problem
When doing a query in MySQL you would like to display the results vertically instead of horizontally as they are much more readable.
Solution
Terminate the query with \G instead of a semicolon (MySQL documentation):
SELECT * FROM users\G
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
Mentioned here
Problem
You would like start a phoenix application in a port different from the default 4000, by using something similar to the rails:
rails s -p 4001
Solutin
You will need to change the config/dev.exs file to include the following:
http: [port: System.get_env("PORT") || 4000],
and then start the server with:
PORT=4002 mix phoenix.server
Taken from the answer here
Problem
You would like to add a routing rspec test in your rails application that tests for a nested route.
So while you have something like the following in your config/routes.rb file:
namespace :admin do
resources :users do
resources :audits, only: [:index]
end
end
you want to add the following test for your route:
expect(get: '/admin/users/:user_id/audits').to route_to(controller: 'admin/audits', action: 'index')
but you are getting an error like the following:
The recognized options <{"controller"=>"admin/audits", "action"=>"index", "user_id"=>":user_id"}> did not match <{"controller"=>"admin/audits", "action"=>"index"}>, difference:.
--- expected
+++ actual
@@ -1 +1 @@
-{"controller"=>"admin/audits", "action"=>"index"}
+{"controller"=>"admin/audits", "action"=>"index", "user_id"=>":user_id"}
Solution
You will need to change your rspec to the following using any number for the user_id:
expect(get: '/admin/users/42/audits').to route_to(controller: 'admin/audits', action: 'index', user_id: '42')
Solution adapted from here