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QC crates.io

Introduction

nss-docker-ng is a NSS plugin for finding Docker containers by their ID or name.

The container names are searched in a virtual domain name .docker.

Install it, then try:

$ docker run --name my-app -d hashicorp/http-echo -listen=:80 -text="✅ it works!"
04e8b7ccf6215a17064ec0d15d4235d5c62c461bc26a681c8ee64344bb0dc2df

$ getent hosts my-app.docker
172.17.0.4      my-app.docker 04e8b7ccf621.docker

$ curl http://my-app.docker
✅ it works!

$ ping my-app.docker
PING test.docker (172.17.0.4) 56(84) bytes of data.
64 bytes from 172.17.0.4: icmp_seq=1 ttl=64 time=0.171 ms

$ docker stop my-app

Subdomain / wildcard behavior

You can have nss-docker-ng respond to all subdomains for a container by setting the label .com.github.petski.nss-docker-ng.container-subdomains-allowed to true, True or 1.

$ docker run --name my-app-with-subdomains -d --label=".com.github.petski.nss-docker-ng.container-subdomains-allowed=true" hashicorp/http-echo -listen=:80 -text="✅ it works!"
670b3dc0aa2761d0fa150180e1cc1769d5e7e5a3332c12562197c7a782ed8a94

$ getent hosts my-app-with-subdomains.docker
172.29.0.2      my-app-with-subdomains.docker 670b3dc0aa27.docker

$ getent hosts foo.my-app-with-subdomains.docker
172.29.0.2      my-app-with-subdomains.docker 670b3dc0aa27.docker foo.my-app-with-subdomains.docker

$ docker stop my-app-with_subdomains

Installation instructions

Binary install

DESTDIR="/usr/local/lib/nss-docker-ng/" && \
 sudo --preserve-env=DESTDIR install -m 0755 -d "$DESTDIR" && \
 curl -sL 'https://github.com/petski/nss-docker-ng/releases/latest/download/libnss_docker_ng.so' -o - | sudo --preserve-env=DESTDIR tee "${DESTDIR}/libnss_docker_ng.so" > /dev/null && \
 echo "${DESTDIR}" | sudo tee /etc/ld.so.conf.d/nss-docker-ng.conf > /dev/null && \
 sudo /sbin/ldconfig

Then, add the docker_ng service to the hosts:-line in /etc/nsswitch.conf. For example: hosts: files docker_ng dns

Ubuntu 22.04 "jammy" and higher

sudo add-apt-repository ppa:petski/ubuntu/nss-docker-ng && \
 sudo apt install nss-docker-ng

From source

You'll need at least git, cargo and patchelf.

git clone https://github.com/petski/nss-docker-ng.git
cd nss-docker-ng
cargo build --release && \
 patchelf --set-soname libnss_docker_ng.so.2 target/release/libnss_docker_ng.so && \
 DESTDIR="/usr/local/lib/nss-docker-ng/" && \
 sudo --preserve-env=DESTDIR install -m 0755 -d "$DESTDIR" && \
 sudo --preserve-env=DESTDIR install -m 0644 target/release/libnss_docker_ng.so "${DESTDIR}/libnss_docker_ng.so" && \
 echo "${DESTDIR}" | sudo tee /etc/ld.so.conf.d/nss-docker-ng.conf > /dev/null && \
 sudo /sbin/ldconfig

Then, add the docker_ng service to the hosts:-line in /etc/nsswitch.conf. For example: hosts: files docker_ng dns

Contributions

Contributions are welcome! Nothing to contribute, but you do appreciate this software? Please star ⭐ this repo.

Development

cargo build && \
 patchelf --set-soname libnss_docker_ng.so.2 target/debug/libnss_docker_ng.so && \
 DESTDIR="/usr/local/lib/nss-docker-ng/" && \
 sudo --preserve-env=DESTDIR install -m 0755 -d "$DESTDIR" && \
 sudo --preserve-env=DESTDIR install -m 0644 target/debug/libnss_docker_ng.so "${DESTDIR}/libnss_docker_ng.so" && \
 echo "${DESTDIR}" | sudo tee /etc/ld.so.conf.d/nss-docker-ng.conf > /dev/null && \
 sudo /sbin/ldconfig

getent hosts not-existing-container.docker
# Failed to inspect container 'not-existing-container': error 404 Not Found - No such container: not-existing-container

Comparison

There are other options to achieve this feature. I'm comparing them HERE.

Useful links