On Tue, Mar 13, 2018 at 11:29 AM, Miroslav Lichvar <mlich...@redhat.com> wrote:
> On Tue, Mar 13, 2018 at 10:45:56AM +0100, Christian Ehrhardt wrote: > > In unprivileged containers even after e8096330 "sys_linux: don't keep > > CAP_SYS_TIME with -x option" default installations > > will still run without an explicit -x being set and therefore fail by > > missing CAP_SYS_TIME. > > > > In some use cases users want the NTP server service to "just work" which > > in a non-CAP_SYS_TIME environment means that chrony has to fall back. > > As I said in the previous mail, they can use -x to have an NTP server > that always "works". We seem to agree that neither -x or -X should be > a default. In what configuration it would be useful to enable -X but > not -x? > The important part is the lack of knowledge of the target systems capabilities. They are: - not detectable by some install paths, for example - install in VM with behavior A onto phys disk but reboot host into said disk - installing on a remote disk mounted chroot, which might be totally different when this runs. - ... - Several tools/configs might add/remove capabilities from a system later on in the lifecycle - Some move machines between places with different capabilities - ... The TL;DR of the "motivation" is: the inability to decide if using "-x" is right or not (at any time). With just "-x" available this leads to one of the following: A) So if one sets "-x" it will NEVER sync the clock even if the system would be capable to do so. B) if one does not set "-x" it will fail to start (even the server portion of chronyd) in some environments The addition of the new "-X" provides a new case C) set -X which will sync the clock if it runs (currently) in an environment able to do so BTW - in case it might be better to discuss interactive - I'm "cpaelzer" on freednode IRC. If there is a common place chrony matters are usually discussed (other than the ML) that would be nice to know - I haven't found a hint about it on the web page. I appreciate the effort you put into the patch, but without a use case > it seems to me like an unnecessary complication of the code and > another trap for the user to fall in. > > > By that a user will get an NTP server working independent to the > > environment, that will control the local time if it is able to do so. > > > > This is not set as default as the fallback is considered a loss of time > > control that users should opt-in, but the new config allows an admin and > > setup tools to opt into -x like behavior without loosing the feature to > > control time when running in an environment that is able to do so. > > They either need the clock to be controlled by chronyd or they don't. > If they don't, I think they can always use -x. > > I have some comments about the patch, but I think we should make this > clear first. > > -- > Miroslav Lichvar > > -- > To unsubscribe email chrony-dev-requ...@chrony.tuxfamily.org with > "unsubscribe" in the subject. > For help email chrony-dev-requ...@chrony.tuxfamily.org with "help" in the > subject. > Trouble? Email listmas...@chrony.tuxfamily.org. > > -- Christian Ehrhardt Software Engineer, Ubuntu Server Canonical Ltd
