Bruce Dubbs wrote: > I believe there was some discussion of setting the system clock via > udev a while back, but I can't find the thread right now.
http://wiki.linuxfromscratch.org/lfs/changeset/8902 is the actual change. You could probably find that though. :-) I'm not sure where the thread was either. Anyway... > I had a short email conversation with the util-linux-ng maintainer > about putting /etc/adjtime in /var/lib like is done in LFS. He asked > about the timing of mounting partitions (S40mountfs for us) and > running hwclock (S25setclock for us). Well, S20udev now... but yeah. :-) > We modify the code to make the default location of adjtime to be > /var/lib, but we don't warn about making /var a separate partition. > If that is done, hwclock will not be able to save it's drift > adjustment parameters. It may be a non issue for us because I > haven't heard anyone complain and the error message should be in the > logs. The error message might be in the logs -- if /var/log was mounted and sysklogd was running. :-P (Or if hwclock printed out whatever error message it generates today. I haven't seen this though, and my /var is a separate partition to prevent logs from filling the rootfs. I don't know if udevd will log that output if it exists...) That being said, I use NTP, so if the lack of drift-records are actually hurting me (and hwclock is silently failing to record drift), that's why I never noticed. > If we use udev to set the clock, we may get into a race problem with > certain configurations. I doubt it'll be a race; that's what the udevsettle is supposed to prevent. (...Not that it's a perfect solution either; I still add a "sleep 5 ; udevsettle" onto the end of that script because otherwise it misses various USB devices. But it shouldn't miss the RTC.) setclock will always fail to read/write adjtime when run before mountfs, so it's probably much more likely that it just fails when run from udev rules. > I don't know if this is worth spending a lot of time, but I'd like to > see a system that can have / mounted read only. Then you're going to *NEED* the adjtime file somewhere other than the rootfs... :-) > The problem areas during boot are /etc/mtab, /etc/blkid.tab, and > /etc/adjtime. With the move of libblkid and libuuid to > util-linux-ng, the first two are being addressed in the relatively > near future, Mmm? Did mount stop writing to /etc/mtab or something? That needs to be writable no matter which blkid / uuid library you use. Unless you don't mind having "-o user" broken (I don't, but others probably do); then you can symlink it to /proc/mounts. blkid.tab may not be required anymore, though. I don't know the status of that. > but we should get adjtime right for any reasonable configuration. A warning in the book regarding /var might be in order. Mentioning that NTP probably doesn't require the adjtime file at all (depending on whether the user wants a more-accurate clock before NTP starts) may be a good idea as well.
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