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DNS resolution issue in Alpine Linux (2021)

christoph.luppri.ch

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Re: DNS resolution issue in Alpine Linux (2021)

#31

Post by encryptluks2 »

qbasic_forever wrote: post #27
blueflow wrote: post #10

Earlier quoted context omitted.

"you're on your own" is like, the expected thing when you are doing something different. Still, Alpine is on top of everyone else when it comes to Docker Images sizes. Thats why it will stick.

If you care about image size you need to switch to a distroless image base. It's incredibly easy nowadays with multi-stage builds. IMHO people use alpine not because they seek it out but because they're reading old guides and advice that hasn't been updated with the times. Blindly switching to alpine to save space is opening yourself up to exactly these sorts of musl-libc quirks and issues--you better have solid test…

There are a lot of tools that simply can't run distroless and adding in all the requirements is often tedious with little reward.

Re: DNS resolution issue in Alpine Linux (2021)

#32

Post by encryptluks2 »

traceroute66 wrote: post #15
blueflow wrote: post #10

Earlier quoted context omitted.

"you're on your own" is like, the expected thing when you are doing something different. Still, Alpine is on top of everyone else when it comes to Docker Images sizes. Thats why it will stick.

> "you're on your own" is like, the expected thing when you are doing something different. Indeed. And that's fine. As long as you're willing to support that difference. But the "Alpine compiling XYZ against musl" thing is/was just being done blindly by Alpine (i.e. load X into auto-build and let it rip). Sure it compiled without errors. But it never ran properly.

I've rarely had issues and if I do there is a process to report them to get them fixed. Not yet mad and act like the entire distro is worthless because I can't be bothered with reporting an issue for something that is already free. I've had less issues with Alpine than I've had with software on Windows.

Re: DNS resolution issue in Alpine Linux (2021)

#33

Post by blueflow »

sciurus wrote: post #29
blueflow wrote: post #10

Earlier quoted context omitted.

"you're on your own" is like, the expected thing when you are doing something different. Still, Alpine is on top of everyone else when it comes to Docker Images sizes. Thats why it will stick.

Are they still on to of everyone else in a meaningful way, though? There was discussion yesterday [0] that pointed out that there are 29MB Debian [1] and Ubuntu [2] images. [0] https://news.ycombinator.com/item?id=30633670 [1] https://hub.docker.com/layers/debian/library/debian/stable-s... [2] https://ubuntu.com/blog/minimal-ubuntu-released

I run Alpine Linux from a 512 MB CF card, so yes.

Re: DNS resolution issue in Alpine Linux (2021)

#34

Post by blueflow »

tptacek wrote: post #19
blueflow wrote: post #11

Earlier quoted context omitted.

Its okay to ignore "modern" features if they create bad edge cases.

This feature is from 1986.

So are absolute domain names, but everyone is using relative domain specifications now, omitting the final dot.

HTTP Transfer-Encoding also got specified, and then collectively mis-implemented.

That its in the standard for decades doesnt mean it will be good when used.

Re: DNS resolution issue in Alpine Linux (2021)

#35

Post by johnklos »

There are two problems here:

• musl should support EDNS and DNS over TCP/IP without issues

• People should be smart enough to use DNS services that don't have stupid edge cases

For the latter, if you use Google for resolving DNS, you get what you deserve. Run your own resolver if DNS resolution matters.

Re: DNS resolution issue in Alpine Linux (2021)

#36

Post by charcircuit »

blueflow wrote: post #34
tptacek wrote: post #19

Earlier quoted context omitted.

This feature is from 1986.

So are absolute domain names, but everyone is using relative domain specifications now, omitting the final dot. HTTP Transfer-Encoding also got specified, and then collectively mis-implemented. That its in the standard for decades doesnt mean it will be good when used.

I can use absolute domain names just fine in the software I use.

Re: DNS resolution issue in Alpine Linux (2021)

#37

Post by jve »

Few days ago, I spent quite a few hours trying to make `apk update` work for alpine on WSL2 on Windows. It didn't want to resolve dl-cdn.alpinelinux.org within alpine. Did resolve on host ubuntu.

1. WFH from VPN, firstly I had to lower mtu from 1500 to 1392 (My VPN specific issue) https://github.com/microsoft/WSL/issues/4698

2. Next, I had to run some powershell script that updates /etc/resolv.conf to use my VPN DNS (WSL specific stuff) https://github.com/microsoft/WSL/issues/1350

3. And I still don't know if apk works properly. Kind of works in Docker build, but I have a feeling something not quite right.

See this example. Why does it "hang"? Docker command not exiting

  docker run -it alpine:3.15 apk update
  fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/APKINDEX.tar.gz
Now, doing it within container itself, works:

  docker run -it alpine:3.15 sh
  / # apk update
  fetch https://dl-cdn.alpinelinux.org/alpine/v3.15/main/x86_64/APKINDEX.tar.gz
  fetch https://dl- 
  cdn.alpinelinux.org/alpine/v3.15/community/x86_64/APKINDEX.tar.gz
  v3.15.0-342-g4fee739486 [https://dl-cdn.alpinelinux.org/alpine/v3.15/main]
  v3.15.0-340-g4ed6115e99 [https://dl-cdn.alpinelinux.org/alpine/v3.15/community]
  OK: 15859 distinct packages available
  / # exit
Can someone shed some light?

Re: DNS resolution issue in Alpine Linux (2021)

#38

Post by tptacek »

blueflow wrote: post #34
tptacek wrote: post #19

Earlier quoted context omitted.

This feature is from 1986.

So are absolute domain names, but everyone is using relative domain specifications now, omitting the final dot. HTTP Transfer-Encoding also got specified, and then collectively mis-implemented. That its in the standard for decades doesnt mean it will be good when used.

This doesn't make sense as an argument. Without TCP DNS, you're stuck with an untenably low limit for how much data can fit in a DNS response. Not having TCP DNS breaks DNS. It's not an aesthetic argument.

Re: DNS resolution issue in Alpine Linux (2021)

#39

Post by infogulch »

rascul wrote: post #21
nwmcsween wrote: post #17

Earlier quoted context omitted.

There isn't anything weird, I went on #musl asked the question, the functionality is desired but it should be worked with the community to ensure correctness.

The functionality was explicitly not added by the developer. > My choice not to do TCP in musl's stub resolver was based on an interpretation that truncated results are not just acceptable but better ux - not only do you save major round-trip delays to DNS but you also get a reasonable upper bound on # of addrs in result. https://twitter.com/RichFelker/status/994629795551031296 Maybe he is willing to consider it now,…

It's not a bug, it's a feature! You're welcome. (tm)

Re: DNS resolution issue in Alpine Linux (2021)

#40

Post by dividedbyzero »

blueflow wrote: post #33
sciurus wrote: post #29

Earlier quoted context omitted.

Are they still on to of everyone else in a meaningful way, though? There was discussion yesterday [0] that pointed out that there are 29MB Debian [1] and Ubuntu [2] images. [0] https://news.ycombinator.com/item?id=30633670 [1] https://hub.docker.com/layers/debian/library/debian/stable-s... [2] https://ubuntu.com/blog/minimal-ubuntu-released

I run Alpine Linux from a 512 MB CF card, so yes.

What do you use this for?
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