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Re: jails

From: Jeremy Chadwick (koitsuFreeBSD.org)
Date: Tue Sep 09 2008 - 11:46:08 CDT

On Tue, Sep 09, 2008 at 08:45:33AM -0700, gahn wrote:
> Hello:
> I don't know what you were referring to. but the date and time of the machine was set correctly.
> #date Tue Sep 9 11:40:04 EDT 2008
> best

Is your system clock skewing a lot? Are you running ntpd? (I hope
you're not using ntpdate from a cronjob, that would pretty much
guarantee what you're seeing.)

You can't easily tell clock skew with userland utilities, but the
result often manifests itself in the way you're seeing. I can provide
some advice on how to use ntpd/ntpq/ntpdc if need be.

If you're not using ntpd, you should be! Here's a decent/proper
ntp.conf (you should visit the use.html document and pick servers that
are appropriate for your region). Do not add "iburst" to all of the
servers; just the first one.

# north-america.pool.ntp.org
# http://www.pool.ntp.org/use.html
# maxpoll 9 is used to work around PLL/FLL flipping, which
# happens at exactly 1024 seconds (the default maxpoll value).
# Another FreeBSD member recommended using 9 instead.
# http://lists.freebsd.org/pipermail/freebsd-stable/2006-December/031512.html
server 0.north-america.pool.ntp.org maxpoll 9 iburst
server 1.north-america.pool.ntp.org maxpoll 9
server 2.north-america.pool.ntp.org maxpoll 9

# Default: ignore all ntp queries from all other hosts. Packets
# to/from "server" lines are still respected.
restrict default noquery nomodify nopeer

# Allow queries to/from localhost, used for ntpdc and other utils
# Allow queries to/from the local private network (read-only)
restrict mask
restrict mask nomodify nopeer notrap

After, run "ntpdate <server>", where server is the first server in your
list. ntpdate should update the clock for you, and provide you an idea
of just how skewed it was compared to the remote NTP server's clock.

Then you can run ntpd safely. Just place the below into /etc/rc.conf
and run /etc/rc.d/ntpd start. (ntpd_sync_on_start is primarily for
when you reboot the box; don't let the name mislead you)


Hope this helps, or at least educates.

| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |

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