Allow Docker Container Access to Host's Postgres Database on linux (ubuntu)

access_postgresql_with_docker.md

You have to do 2 things in order to allow your container to access your host's postgresql database

1. Make your postgresql listen to an external ip address
2. Let this client ip (your docker container) access your postgresql database with a given user

Obs: By "Host" here I mean "the server where docker is running on".

Make your postgresql listen to an external ip address

Find your postgresql.conf (in case you don't know where it is)

$ sudo find / -type f -name postgresql.conf # => /etc/postgresql/9.5/main/postgresql.conf

Change postgresql.conf to allow external access

$ sudo atom /etc/postgresql/9.5/main/postgresql.conf # or the path you found before

Look for the line: #listen_addresses = 'localhost' # what IP address(es) to listen on;

Uncomment and set the external ip adress that'll be trying to access your DB. If you don't know it, or want to free all ips to access it (not that safe), set it to '*':

listen_addresses = '*' # what IP address(es) to listen on;

Restart postgres

$ /etc/init.d/postgresql restart

You can check if this worked out with this command:

$ netstat -nlt

It will output something like this:

Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:5432            0.0.0.0:*               LISTEN 

See that it has the address 0.0.0.0 on port 5432.

Let your container access your postgresql database with a given user

Find your pg_hba.conf

$ sudo find / -type f -name pg_hba.conf # => /etc/postgresql/9.5/main/pg_hba.conf

Change pg_hba.conf to allow access to your database

$ sudo atom /etc/postgresql/9.5/main/pg_hba.conf # or the path you found before

# This file controls: which hosts are allowed to connect, how clients
# are authenticated, which PostgreSQL user names they can use, which
# databases they can access.  Records take one of these forms:
#
host my_database_name my_database_user 172.17.0.0/16 trust # Allowing docker container connections to host db
#
# local      DATABASE  USER  METHOD  [OPTIONS]
# host       DATABASE  USER  ADDRESS  METHOD  [OPTIONS]
# hostssl    DATABASE  USER  ADDRESS  METHOD  [OPTIONS]
# hostnossl  DATABASE  USER  ADDRESS  METHOD  [OPTIONS]

Restart postgres and test your connection

$ psql my_database_name my_database_user -h <host-ip-address>

References:

https://stackoverflow.com/questions/31249112/allow-docker-container-to-connect-to-a-local-host-postgres-database

https://www.thegeekstuff.com/2014/02/enable-remote-postgresql-connection/

In my case, sharing host network using --net=host will lead to port conflicts.
This solution works fine. Thank you!

Be aware that trust means "you can login as any user without a password via this connection". So any container you run will be able to access your database. See https://www.postgresql.org/docs/9.1/auth-methods.html#AUTH-TRUST

Maybe you want to replace trust by md5 or password and provide your container with the password.

thanks a lot, I've been looking for this solution

Be aware that trust means "you can login as any user without a password via this connection". So any container you run will be able to access your database. See https://www.postgresql.org/docs/9.1/auth-methods.html#AUTH-TRUST

Maybe you want to replace trust by md5 or password and provide your container with the password.

this very helpful!

For reasons I don't know, my docker container was assigned a 172.18.x.x address, so you might need to replace 172.17.0.0/16 with 172.0.0.0/8.

172.0.0.0/8

*172.16.0.0/12

listen_addresses = '*'
holly mother.... DO NOT USE '*' for security reasons! It allows to connect to your db from anywhere

listen_addresses = '*'
holly mother.... DO NOT USE '*' for security reasons! It allows to connect to your db from anywhere

... unless you have a firewall in place

listen_addresses = '*'
holly mother.... DO NOT USE '*' for security reasons! It allows to connect to your db from anywhere

... unless you have a firewall in place

Tell it to mongodb users :D

This solution works, thanks. Gracias, Excelente artículo

For reasons I don't know, my docker container was assigned a 172.18.x.x address, so you might need to replace 172.17.0.0/16 with 172.0.0.0/8.

It really depends on your app and what docker decides the IP will be set as.

Thank you!

You don't have to (and probably shouldn't) use listen_addresses = '*'. Here's what I did instead.

First, I've used ip addr to determine docker network address:

...
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    ...
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
    ...

In my case it's 172.17.0.1/16, so I use this one in my postgresql.conf:

listen_addresses = 'localhost,172.17.0.1'

And then I've set the following in pg_hba.conf:

host    all             all             172.17.0.0/16           md5

What happens here: I've allowed Docker subnet (172.17.0.0/16) to connect all databases (first all) from all users (second all) using md5 method which is defined in official PostgreSQL docs as:

Perform SCRAM-SHA-256 or MD5 authentication to verify the user's password.

That allows me to login from my Docker container to local PostgreSQL instance using login and password. You can adapt it to your case, but I hope the general idea is clear.

Thanks!

thanks!

Thanks!!

Thanks🥰