Keeping /etc/localtime up-to-date

[Olivier Smedts]

2011/3/29 Devin Teske <dteske at vicor.com>:
> On Mon, 2011-03-28 at 16:52 -0400, dieterbsd at engineer.com wrote:
>> >>> And while I (think I) recall that the equivalent of /etc/localtime
>> >>> was implemented in some version of SunOS many years ago as a
>> symlink,
>> >>> I believe that approach could be problematic for FreeBSD, as it
>> >>> could impose some unintended requirements on some of the start-up
>> >>> scripts.
>> >>
>> >> I have been running FreeBSD and NetBSD with /etc/localtime being
>> >> a symlink for years and have not seen any problems as a result.
>> >
>> > The one (and only) problem that I've seen from using a symlink for
>> > /etc/localtime is that -- since the /usr partition is not mounted
>> > early-on -- boot messages get logged in GMT offset until /usr is
>> mounted.
>> >
>> > However, some simply ignore this.
>>
>> What boot messages are these?
>
> The messages generated during boot -- see /var/log/messages.
>
>
>> grep 2011 /var/run/dmesg.boot
>
> Those aren't the boot messages I'm referring to (and by convention, I
> would call those the "kernel boot messages" as only the kernel messages
> are found there).
>
>> Copyright (c) 1992-2011 The FreeBSD Project.
>> FreeBSD 8.2-RELEASE #9: Sun Mar  6 18:47:36 pst 2011
>
> Huh? Please help me understand why you'd grep for "2011" in the context
> of this topic (timezone differences).
>
> Here's an impirical test:
> 1. Put your BIOS into GMT
> 2. Make /etc/localtime a symbolic link
> to /usr/share/zoneinfo/America/Los_Angeles
> 3. Reboot
>
> In our experience, the "Regents of the University of California" message
> is logged to /var/log/messages in GMT and subsequent messages (produced
> after /usr is mounted) are logged in the desired timezone.
>
> NOTE: This assumes that "/" and "/usr" are separate partitions.

Not for me (BIOS clock set to UTC) :
% uname -a
FreeBSD q.gid0.org 9.0-CURRENT FreeBSD 9.0-CURRENT #0 r220114: Mon Mar
28 23:42:11 CEST 2011     root at q.gid0.org:/usr/obj/usr/src/sys/QUAD
amd64
% date
mar 29 mar 2011 00:41:41 CEST
% uptime
 0:41  up 30 mins, 3 users, load averages: 0,06 0,06 0,07
% ls -l /etc/localtime
lrwxr-xr-x  1 root  wheel  32 29 jui  2008 /etc/localtime@ ->
/usr/share/zoneinfo/Europe/Paris
% mount
tank/freebsd on / (zfs, local, noatime, nfsv4acls)
[...]
tank/freebsd/usr on /usr (zfs, local, noatime, nfsv4acls)
[...]
% grep -i regents /var/log/messages
Mar 29 00:12:08 q kernel: The Regents of the University of California.
All rights reserved.
% tail -n 1 /var/log/messages
Mar 29 00:12:08 q kernel: kbd0 at ukbd0

I don't think this content is added to /var/log/messages during boot,
because the kernel doesn't have access to the log file (and if /usr is
not mounted, neither is /var). I thought the kernel messages were
saved in memory (system message buffer), and only after boot (and
filesystems mounted, and syslogd started) were they dumped to a file.


-- 
Olivier Smedts                                                 _
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