The Sisyphean Task of DNS Client Config on Linux
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The Sisyphean Task of DNS Client Config on Linux
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Re: The Sisyphean Task of DNS Client Config on Linux
#2The most interesting takeaway from this article is that, according to people who actually do the work, NetworkManager and systemd-resolved do get things right.
Re: The Sisyphean Task of DNS Client Config on Linux
#3The most interesting takeaway from this article is that, according to people who actually do the work, NetworkManager and systemd-resolved do get things right.
one reason resolv.conf is/was so sticky is that gethostbyname (and friends) is a libc thing and pretty low-level
Re: The Sisyphean Task of DNS Client Config on Linux
#4Where does /etc/nsswitch.conf factor in? I don't see it mentioned.
Re: The Sisyphean Task of DNS Client Config on Linux
#5The most interesting takeaway from this article is that, according to people who actually do the work, NetworkManager and systemd-resolved do get things right.
one reason resolv.conf is/was so sticky is that gethostbyname (and friends) is a libc thing and pretty low-level
Problem is, modern browsers do things differently yet again. So the insanity continues, just on different levels.
Re: The Sisyphean Task of DNS Client Config on Linux
#6Where does /etc/nsswitch.conf factor in? I don't see it mentioned.
It’s probably omitted as nsswitch doesn’t affect DNS client configuration.
It affects which sources are consulted to lookup a name (including maybe asking DNS), but it doesn’t configure things like which DNS servers to ask or what options to set.
> The Name Service Switch (NSS) configuration file, /etc/nsswitch.conf, is used by the GNU C Library and certain other applications to determine the sources from which to obtain name-service information in a range of categories, and in what order.
Re: The Sisyphean Task of DNS Client Config on Linux
#7If you are just trying to use curl or some other straightforward small application - this is enough. But running Kubernetes, docker, or some other container system? This mess is much more deep...
For example: there are known issues with systemd-resolved & Kubernetes (at least on Ubuntu that defaults to systemd-resolved) https://kubernetes.io/docs/tasks/administer-cluster/dns-debu...
Re: The Sisyphean Task of DNS Client Config on Linux
#8I recommend the series "Anatomy of a Linux DNS lookup"[0].
Everything you never wanted to know.
https://zwischenzugs.com/2018/06/08/anatomy-of-a-linux-dns-l...
Re: The Sisyphean Task of DNS Client Config on Linux
#9Where does /etc/nsswitch.conf factor in? I don't see it mentioned.
nsswitch.conf tells it whether to consult `/etc/hosts` (`hosts: files`), `/etc/resolv.conf` (`hosts: dns`), or systemd-resolved (`hosts: resolve`); and if multiple of those, in what order (`hosts: first second third...`).
Re: The Sisyphean Task of DNS Client Config on Linux
#10Where does /etc/nsswitch.conf factor in? I don't see it mentioned.
It’s probably omitted as nsswitch doesn’t affect DNS client configuration. It affects which sources are consulted to lookup a name (including maybe asking DNS), but it doesn’t configure things like which DNS servers to ask or what options to set. > The Name Service Switch (NSS) configuration file, /etc/nsswitch.conf, is used by the GNU C Library and certain other applications to determine the sources from which to ob…
nsswitch.conf is what tells it whether to use the traditional nss_dns (the thing that looks at /etc/resolv.conf), or whether to use the newer nss_resolve (the thing that talks to systemd-resolved).
So yeah, if the article is contrasting resolv.conf vs systemd-resolved, nsswitch.conf is how you select which of those approaches is used.