On Tuesday, July 28, 2020 5:11:31 AM MST Lennart Poettering wrote: > On Mo, 27.07.20 09:20, Neal Gompa (ngomp...@gmail.com) wrote: > > > > That *is* what will happen. In this scenario, systemd-resolved creates > > a file in /run that is populated with the required information for > > applications to request name resolution from resolved through the > > standard DNS protocol. The /etc/resolv.conf file becomes a symlink to > > the file in /run so that the file in /etc is stable and regenerating > > the file in /run won't cause issues for package management. This > > system has been in use *already* for a while now in other > > distributions (see Debian and resolvconf(8), which systemd-resolved > > replaced in Ubuntu). > > > > > > > > The only thing this mechanism breaks is applications trying to *write* > > to the resolv.conf file, because systemd-resolved will just blow away > > those changes right after. If you want to modify DNS settings, you > > need to configure systemd-resolved itself, either through > > NetworkManager (as we will recommend) or directly through > > systemd-resolved's configuration interface (if not using NetworkManager). > > > That's not quit true: if you replace th /etc/resolv.conf symlink with > a file of your own choosing, then resolved will not muck around with > that, and not modify it anymore. instead, it will start to *read* it > and use the data. i.e. depending on symlinks vs. file it either > provides or consumes the data in it. > > Thus admin-provided configuration in /etc/resolv.conf takes precedence > over the stuff systemd-resolved puts there, as long as the admin > properly replaces the symlink. If the admin doesn't replace the > symlink and writes to it naively, i.e. where it points then it will > make changes to files in /run/systemd/ (because that's where the > symlink points to), i.e. files clearly owned by systemd, and > systemd-resolved will brutally overwrite them whenever it feels the > need to.
To prevent brutally overwriting configuration, it would be best not to replace /etc/resolv.conf with a symlink on upgrade, ignoring user configuration, but to do so on all new installs. -- John M. Harris, Jr. _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org
