[GH-ISSUE #627] Bug: DPS is not working for Alpine containers #207

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opened 2026-02-26 04:34:23 +03:00 by kerem · 3 comments

kerem commented

2026-02-26 04:34:23 +03:00

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Originally created by @cmiguelcabral on GitHub (Aug 13, 2025).
Original GitHub issue: https://github.com/mageddo/dns-proxy-server/issues/627

What is Happening

DPS is not working for Alpine containers.
The comment # dps-entry creates the problem.
nslookup: bad address '172.18.0.4 # dps-entry

Changing the resolv.conf manually to:

# dps-entry
nameserver 172.18.0.4

Solves the problem. But it gets changed again automatically to nameserver 172.18.0.4 # dps-entry
The problem is having the comment on the same line as the IP.

Please describe how to reproduce the issue with a MRE - Minimal Reproducible Example.

Start some container that uses alpine as base image with the resolv.conf mounted
docker exec to that container
Try nslookup to resolve some other container

What is Expected

It should return the IP address of the container, but instead I receive this:
nslookup: bad address '172.18.0.4 # dps-entry

Specs

Docker Version: 28.3.3
DPS Version: 3.32.5-snapshot-aarch64
Attach DPS Log file: N/A
OS: Fedora 42 and Debian Bullseye (On host)

Originally created by @cmiguelcabral on GitHub (Aug 13, 2025). Original GitHub issue: https://github.com/mageddo/dns-proxy-server/issues/627 ## What is Happening DPS is not working for Alpine containers. The comment `# dps-entry` creates the problem. `nslookup: bad address '172.18.0.4 # dps-entry` Changing the `resolv.conf` manually to: ```` # dps-entry nameserver 172.18.0.4 ```` Solves the problem. But it gets changed again automatically to `nameserver 172.18.0.4 # dps-entry` The problem is having the comment on the same line as the IP. Please describe how to reproduce the issue with a [MRE - Minimal Reproducible Example][1]. - Start some container that uses `alpine` as base image with the `resolv.conf` mounted - `docker exec` to that container - Try `nslookup` to resolve some other container ## What is Expected It should return the IP address of the container, but instead I receive this: `nslookup: bad address '172.18.0.4 # dps-entry` ## Specs * Docker Version: `28.3.3` * DPS Version: `3.32.5-snapshot-aarch64` * Attach DPS Log file: N/A * OS: Fedora 42 and Debian Bullseye (On host) [1]: https://en.wikipedia.org/wiki/Minimal_reproducible_example

kerem closed this issue

2026-02-26 04:34:23 +03:00

kerem commented

2026-02-26 04:34:24 +03:00

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@cmiguelcabral commented on GitHub (Aug 14, 2025):

I suggest doing it like Ansible does. Adding a BEGIN in the line before and an END in the line after the nameserver.

# BEGIN dps-entries
nameserver 172.18.0.4
# END dps-entries

This can also open the door to having multiple instances running.

@cmiguelcabral commented on GitHub (Aug 14, 2025): I suggest doing it like Ansible does. Adding a `BEGIN` in the line before and an `END` in the line after the `nameserver`. ```` # BEGIN dps-entries nameserver 172.18.0.4 # END dps-entries ```` This can also open the door to having multiple instances running.

kerem commented

2026-02-26 04:34:24 +03:00

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@mageddo commented on GitHub (Dec 17, 2025):

Hey, better late than never. Really nice suggestion, I adopted that, released version 5.1.x, hope it will conciliate and adjust old changed files. I would appreciate feedback. Thanks in advance.

Example:

cat /etc/resolv.conf

# BEGIN dps-entries
nameserver 192.168.0.227
# END dps-entries

# BEGIN dps-comments
# nameserver 127.0.0.53
# END dps-comments

@mageddo commented on GitHub (Dec 17, 2025): Hey, better late than never. Really nice suggestion, I adopted that, released version [5.1.x][1], hope it will conciliate and adjust old changed files. I would appreciate feedback. Thanks in advance. Example: cat /etc/resolv.conf ``` # BEGIN dps-entries nameserver 192.168.0.227 # END dps-entries # BEGIN dps-comments # nameserver 127.0.0.53 # END dps-comments ``` [1]: https://github.com/mageddo/dns-proxy-server/releases/tag/5.1.2-snapshot

kerem commented

2026-02-26 04:34:24 +03:00

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@cmiguelcabral commented on GitHub (Dec 18, 2025):

Awesome!
Thank you

@cmiguelcabral commented on GitHub (Dec 18, 2025): Awesome! Thank you