watchdogd_flags followed by panic watchdog timeout, after reboot my rc.conf disappear

[Dmitry Pryanishnikov]

Hello!

On Sat, 2 Sep 2006, Daniel Dvo??k wrote:
> I saved my rc.conf without any doubt.

  I believe you, really ;)

> Answear: Because rc.conf had 0 Bytes !!!
>
> -rw-r--r--  1 root  wheel      6174 Sep  1 XX:XX rc.conf , I do not remember
> time of last modification of file.
>
> So the content of rc.conf was completly gone !!!

  Yes, because by default "/" is mounted in the following fashion:

              noasync
                      Metadata I/O should be done synchronously, while data I/O
                      should be done asynchronously.  This is the default.
-----------------------------------------------------^^^^^^^^^^^^^^^^^^^^

So yes, /etc/rc.conf will become empty if you're just edited it, and then,
e.g., power disappears. It's a dangerous situation, because box becomes
unreachable via network. To guard against it, you can just mount "/"
using synchronous mode:

              sync    All I/O to the file system should be done synchronously.

I've just modified my test machine's configuration in this way:

/dev/ad0s3a	/	ufs	rw,sync		1	1

and done several times "edit /etc/rc.conf" -> "power off/on" sequence
(no RESET key on box). The rc.conf is intact (while w/o "sync" it became empty 
after my second attempt). Note that this will further decrease FS performance 
for "/" (I always follow old good RELENG_4 advise NOT to turn softupdates on 
for "/" also). That's why /tmp and /var are separate partiotions (or just 
symlinks to SU-enabled /usr) in my typical setup.

> And please explain me somebody, how I lost the content of rc.conf file. :-O

  I hope I've just managed to do that ;)

> P.S.: I am not currently subscribed in the freebsd-stable mailling list, so
> use my e-mail address. I am ok with freebsd-current mailling list.

  I think my recipe would be more useful in -stable list (which IMHO is
"a must" for reading by the production machines admins), that's why I'm 
sending to the -stable also.

Sincerely, Dmitry
-- 
Atlantis ISP, System Administrator
e-mail:  dmitry at atlantis.dp.ua
nic-hdl: LYNX-RIPE