I am pretty sure /etc/hosts (i.e. an explicitly configured, local,
trusted database) should be useful for overriding the automatic
myhostname logic.
resolved's internal logic handles it that way and hence we should
suggest it in the NSS fallback line, too.
Let's also bring the factory file back into sync with what the docs say.
And update the prose a bit too, to actually match what we recommend.
Now that we make the user/group name resolving available via userdb and
thus nss-systemd, we do not need the UID/GID resolving support in
nss-mymachines anymore. Let's drop it hence.
We keep the module around, since besides UID/GID resolving it also does
hostname resolving, which we care about. (One of those days we should
replace that by some Varlink logic between
nss-resolve/systemd-resolved.service too)
The hooks are kept in the NSS module, but they do not resolve anything
anymore, in order to keep compat at a maximum.
It's not that I think that "hostname" is vastly superior to "host name". Quite
the opposite — the difference is small, and in some context the two-word version
does fit better. But in the tree, there are ~200 occurrences of the first, and
>1600 of the other, and consistent spelling is more important than any particular
spelling choice.
The text in the man page provides the justification why I think this is
generally the right thing. An additional reason is that with the previous
commit (to move resolved earlier), since resolved internally implements the
same rules that nss-myhostname does, we'd have this strange inversion where
the priority of external configuration would be different in the "resolve"
path and in the fallback path.
The "include" files had type "book" for some raeason. I don't think this
is meaningful. Let's just use the same everywhere.
$ perl -i -0pe 's^..DOCTYPE (book|refentry) PUBLIC "-//OASIS//DTD DocBook XML V4.[25]//EN"\s+"http^<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"\n "http^gms' man/*.xml
No need to waste space, and uniformity is good.
$ perl -i -0pe 's|\n+<!--\s*SPDX-License-Identifier: LGPL-2.1..\s*-->|\n<!-- SPDX-License-Identifier: LGPL-2.1+ -->|gms' man/*.xml
This adds -Dnss-resolve= and -Dnss-mymachines= meson options.
By using this option, e.g., resolved can be built without nss-resolve.
When no nss modules are built, then test-nss is neither built.
Also, This changes the option name -Dmyhostname= to -Dnss-myhostname=
for consistency to other nss related options.
Closes#9596.
Docbook styles required those to be present, even though the templates that we
use did not show those names anywhere. But something changed semi-recently (I
would suspect docbook templates, but there was only a minor version bump in
recent years, and the changelog does not suggest anything related), and builds
now work without those entries. Let's drop this dead weight.
Tested with F26-F29, debian unstable.
$ perl -i -0pe 's/\s*<authorgroup>.*<.authorgroup>//gms' man/*xml
These lines are generally out-of-date, incomplete and unnecessary. With
SPDX and git repository much more accurate and fine grained information
about licensing and authorship is available, hence let's drop the
per-file copyright notice. Of course, removing copyright lines of others
is problematic, hence this commit only removes my own lines and leaves
all others untouched. It might be nicer if sooner or later those could
go away too, making git the only and accurate source of authorship
information.
This part of the copyright blurb stems from the GPL use recommendations:
https://www.gnu.org/licenses/gpl-howto.en.html
The concept appears to originate in times where version control was per
file, instead of per tree, and was a way to glue the files together.
Ultimately, we nowadays don't live in that world anymore, and this
information is entirely useless anyway, as people are very welcome to
copy these files into any projects they like, and they shouldn't have to
change bits that are part of our copyright header for that.
hence, let's just get rid of this old cruft, and shorten our codebase a
bit.
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.
I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
The configuration option was called -Dresolve, but the internal define
was …RESOLVED. This options governs more than just resolved itself, so
let's settle on the version without "d".
This unifies the suggested nsswitch.conf configuration for our four NSS modules to this:
hosts: files mymachines resolve [!UNAVAIL=return] dns myhostname
Note that this restores "myhostname" to the suggested configuration of
nss-resolve for the time being, undoing 4484e1792b.
"myhostname" should probably be dropped eventually, but when we do this we
should do it in full, and not only drop it from the suggested nsswitch.conf
for one of the modules, but also drop it in source and stop referring to it
altogether.
Note that nss-resolve doesn't replace nss-myhostname in full: the former only
works if D-Bus/resolved is available for resolving the local hostname, the
latter works in all cases even if D-Bus or resolved are not in operation, hence
there's some value in keeping the line as it is right now. Note that neither
dns nor myhostname are considered at all with the above configuration unless
the resolve module actually returns UNAVAIL. Thus, even though handling of
local hostname resolving is implemented twice this way it is only executed once
for each lookup.
It needs to be possible to tell apart "the nss-resolve module does not exist"
(which can happen when running foreign-architecture programs) from "the queried
DNS name failed DNSSEC validation" or other errors. So return NOTFOUND for these
cases too, and only keep UNAVAIL for the cases where we cannot handle the given
address family.
This makes it possible to configure a fallback to "dns" without breaking
DNSSEC, with "resolve [!UNAVAIL=return] dns". Add this to the manpage.
This does not change behaviour if resolved is not running, as that already
falls back to the "dns" glibc module.
Fixes#4157
So far we recommended placing "nss-mymachines" after "nss-resolve" in the order
of preference in /etc/nsswitch.conf. This change reverse this order.
Rationale: single-label names are resolved via LLMNR by resolved, which has to
time out if no peer by that name exists. By placing "nss-mymachines" first
(which always responds immediately) we avoid running into this timeout for most
containers. Both modules should return the same data if LLMNR is used by the
container anyway.
While we are at it, improve the man pages of the three NSS modules in other
ways a bit.
Show the same recommended example file in all three man pages, just
highlight the different, relevant parts.
This should be less confusing for users, and clarify what we actually
recommend how /etc/nsswitch.conf is set up.
Lennart Poettering