I'm on windows 10 with docker version 1.9.1 using docker toolbox
I wanted to put up a quick postgres container, something I've done before with a dockerfile I had laying around.
FROM postgres
ADD create-db.sql /tmp/
ADD drop_create_table.sql /tmp/
ADD db.sql /tmp/
ADD create-db.sh /docker-entrypoint-initdb.d/
It's pretty simple.
and when i run the resulting image. it starts fine.
However at the end it says:
...
server started ALTER ROLE
/docker-entrypoint-sh: running
/docker-entrypoint-initdb.d/create-db.sh :No such file or directory
If I try to do docker run -it <imagename> //bin/bash I can see that the file is indeed there:
root#xxxx:/docker-entrypoint-initdb.d# ls
create-db.sh
but whenever I run it it tells me it's not.
The container promptly stops when it doesn't find the file, so I can't try to ssh into the running container.
Related
I'm trying to docker-containerize PostgreSQL server and this container will have many other applications as well. The need is that, PostgreSQL server data should be mapped to the host volume so that when container is stopped, we won't lose the data. Also that, the next time when we start the container, the same directory can be mapped again and postgres can use the old data. Below is the DOCKERFILE. Note that I'm using ubuntu 22.04 on the host.
FROM ubuntu:22.04
ENV DEBIAN_FRONTEND noninteractive
RUN apt install -y postgresql
ENTRYPOINT ["tail", "-f", "/dev/null"]
Docker image is built using the command
docker build -t pg_test .
and the container is run using the command
docker run --name test -v /home/me/data:/var/lib/postgresql/14/main pg_test
'/home/me/data' is the host directory which is empty where I want to map the postgres server data. '/var/lib/postgresql/14/main' is the directory inside the docker container where the postgres is supposed to store the data.
Once the docker container starts, I enter the docker container using the command
docker exec -it test bash
and once I'm inside, I'm trying to start the PostgreSQL service. But PostgreSQL fails to start as there is no data in '/var/lib/postgresql/14/main' directory. I understand that since I have mapped an empty host directory to '/var/lib/postgresql/14/main' directory, postgres doesn't have the files required to start.
I understand that I'm doing it the wrong way, but I couldn't find a way around it. Can anyone please help me to do this the right way, if there is one?
Any help would be appreciable.
You should use the postgres docker image, it will set up the db for you when you start the container, you can find instructions on https://hub.docker.com/_/postgres
If you must use a custom image, you will need to initialize the db yourself, usually by running initdb or whatever your system provides.
But really you should use the appropriate docker image, and if you need more services you start them in their own container and connect them to the postgres one
I'm very new to using docker and I've created a postgres container using
docker run --name mytrainingdb -e POSTGRES_PASSWORD=mysecretpassword -d postgres. Then I connected to it with docker exec -it <container-id> bash and then psql.
Then I stop the container.
My query is, what do I do reconnect to the same database? I tried to run same docker run command, but it says the name 'mytrainingdb' is used, which means it is trying to create it afresh, which is not what I want. Hope my expectation is right, as in when I restart my laptop or resume work I can just restart the same container and my data/config would be preserved?
The documentation also mentions that we can link a host directory to volume of pg container to have the stored data accessible to us, but I'm ok with docker managing my storage for that database.
You will have error when you try to re-run the same command, because docker is trying to create a new container with same name as the previous one "mytrainingdb". If you close docker and reopen it you will still find your container , but its not running , you can start it again with docker start mytrainingdb or you can remove it with docker rm mytrainingdb .
However , dont restart docker because you want to create a new container with the same name! If you want to start a new container with the same name and your container is still running you can first stop it with docker stop mytrainingdb and docker rm mytrainingdb or you can just do docker rm -f mytrainingdb (this will remove you running container with force ) and then create a new container..
As for the volumes ,you just created one by default which is named is kind of hash , and its found at volumes/var/lib/docker/volumes/ .Because generally containers such PostgreSQL, or databases in general persists volumes. The volume gets created when running the container and is handy to save persistent data, whether you start the container with -v or not.
The volume you talked about in your question , is called mounted volume , is when you basically just bind a certain directory or file from the host (outside) to inside the container
docker run -v /hostdir:/containerdir in your case docker run -v /hostdir:/var/lib/postgresql/data
If you restart docker or your computer running containers won't be automatically restarted. You can start your container again with docker start mytrainingdb (related question), then connect with your docker exec command.
(one tip: instead of running bash, then psql, you can directly run psql, e.g. docker exec -it mytrainingdb psql --user postgres)
Your understanding of data persistence is correct, docker will manage the data and it will still be around.
From the postgres image documentation
There are several ways to store data used by applications that run in Docker containers. We encourage users of the postgres images to familiarize themselves with the options available, including:
Let Docker manage the storage of your database data by writing the database files to disk on the host system using its own internal volume management. This is the default and is easy and fairly transparent to the user. The downside is that the files may be hard to locate for tools and applications that run directly on the host system, i.e. outside containers.
You can add --rm argument so that whenever you stop the container manually, or container stops for any reasons (his task is done or it fails), it will remove that container.
In your case, you can use this:
docker run --name mytrainingdb --rm -e POSTGRES_PASSWORD=mysecretpassword -d postgres
I am using the "plain" postgresql:alpine docker image, but have to schedule a database backup daily. I think this is a pretty common task.
I created a script backupand stored in the container in /etc/periodic/15min, and made it executable:
bash-4.4# ls -l /etc/periodic/15min/
total 4
-rwxr-xr-x 1 root root 95 Mar 2 15:44 backup
I tried executing it manually, that works fine.
My problem is getting crond to run automatically.
If I exec docker exec my-postgresql-container crond, the deamon is started and cron works, but I would like to embed this into my Dockerfile
FROM postgres:alpine
# my backup script, MUST NOT have .sh extension
COPY backup.sh /etc/periodic/15min/backup
RUN chmod a+x /etc/periodic/15min/backup
RUN crond # <- doesn't work
I have no idea how to rewrite or overwrite the commands in the official image. For update reasons I also would like to stay on these images, if possible.
Note: This option if you would like to use the same container with multiple service
Install Supervisord which will makes you able to run crond and postgresql. The Dockerfile will be as the following:
FROM postgres:alpine
RUN apk add --no-cache supervisor
RUN mkdir /etc/supervisor.d
COPY postgres_cron.ini /etc/supervisor.d/postgres_cron.ini
ENTRYPOINT ["/usr/bin/supervisord", "-c", "/etc/supervisord.conf"]
And postgres_cron.ini will be as the following:
[supervisord]
logfile=/var/log/supervisord.log ; (main log file;default $CWD/supervisord.log)
loglevel=info ; (log level;default info; others: debug,warn,trace)
nodaemon=true ; (start in foreground if true;default false)
[program:postgres]
command=/usr/local/bin/docker-entrypoint.sh postgres
autostart=true
autorestart=true
[program:cron]
command =/usr/sbin/crond -f
autostart=true
autorestart=true
Then you can start the docker build process and run a container from your new image. Feel free to modify the Dockerfile or postgres_cron.ini as needed
I had the exact same problem a few month ago. The key aspect is that a container can have only one main process defined by the ENTRYPOINT and/or CMD in your Dockerfile.
You cannot just swap out postgres with crond otherwise your database isn't running. It is generally recommended to separate areas of concern by using one service per container.
With that in mind either use a separate container which runs nothing but crond and thus Docker can both track its lifecycle, and restart it when/if it fails, the machine restarts, etc.
Or run the jobs via cron on your host using docker exec.
The third and in my opinion best (but also advanced) solution is pg_cron. It is an postgres extension and therefore runs the jobs in the same database container. Your challenge would be to adapt the configuration and installation of it.
The easy part should be the
postgresql.conf:
# add to postgresql.conf:
shared_preload_libraries = 'pg_cron'
cron.database_name = 'postgres'
Next, you need to add the pg_cron extension to your image by adjusting the Dockerfile, which you can derive from the official alpine postgres image. The installation of it is described here.
I wish to store my persists data in my local D:\dockerData\postgres9.6. Below is my docker command
docker pull postgres
docker run -d -v /d/dockerData/postgres9.6:/var/lib/postgresql/data -p 5432:5432 postgres
It successful create a container and I can use pgAdmin to access and create database.
But I found out that there is no file in my D:\dockerData\postgres9.6. I exec bash into the container, there is at least 20+ files inside /var/lib/postgresql/data.
Anyone can point out which part goes wrong?
It depends what kind of Docker you are using on Windows:
Docker Toolbox with VirtualBox: only C:\Users\mylogin is shared by default. D:\ is not mounted.
Docker for Windows with HyperV: only C:\ is mounted by default. Make sure D:\ is a shared drive: see image
Previously, to access a file in a running dokku instance I would run:
docker ps to get the container ID followed by
ls /var/lib/docker/aufs/diff/<container-id>/app/...
note: I'm just using 'ls' as an example command. I ultimately want to reference a particular file.
This must have changed, as the container ID is no longer accessible via this path. There are loads of dirs in that folder, but none that match any of the running containers.
It seems like mounting a volume for the entire container would be overkill in this scenario. I know I can access the file system using dokku run project-name ls, and also docker exec <container-id> ls, but neither of those will satisfy my use case.
To explain a bit more fully, in my dokku project, I have some .sql files that I'm using to bootstrap my postgres DB. These files get pushed up via git push with the rest of the project.
I'm hoping to use the postgres dokku plugin to run the following:
dokku postgres:connect db-name < file-name.sql
This is what I had previously been doing using:
dokku postgres:connect db-name < /var/lib/docker/aufs/diff/<container-id>/app/file-name.sql but that no longer works.
Any thoughts on this? Am I going about this all wrong?
Thanks very much for any thoughts.
Here's an example:
dokku apps:list
=====> My Apps
DummyApp
dokku enter DummyApp
Enter bash to the DummyApp container.
Never rely on the /var/lib/docker file system paths as most of the data stored there is dependent on the storage driver currently in use so it is subject to change.
cat the file from an existing container
docker exec <container> cat file.sql | dokku postgres:connect db-name
cat the file from an image
docker run --rm <image> cat file.sql | dokku postgres:connect db-name
Copy file from an existing container
docker cp <container>:file.sql file.sql
dokku postgres:connect db-name < file.sql