dumpdev default

Ken Smith kensmith at buffalo.edu
Tue Jan 17 15:07:35 UTC 2012

On Tue, 2012-01-17 at 18:37 +1100, Aristedes Maniatis wrote:
> The manual states that dumpdev "AUTO is the default as of FreeBSD
> 6.0" [1]
> However:
> # uname -a
> FreeBSD xxxxxx 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Tue Jan  3 07:46:30
> UTC 2012     root at farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC
> amd64
> # grep dumpdev /etc/defaults/rc.conf
> dumpdev="NO"		# Device to crashdump to (device name, AUTO, or NO).
> savecore_flags=""	# Used if dumpdev is enabled above, and present.
> It looks like NO is still the default. Is there a reason why this
> should not be turned on even for production machines? I haven't read
> about any side effects, but it seems to be off by default for some
> reason.
> Please cc me on any responses since I'm not currently subscribed.
> Cheers
> Ari

If you use bsdinstall(8) to install a machine from scratch it explicitly
asks you about whether you want crash dumps enabled or not.

As long as you're aware that the crash dumps are happening and know that
you might need to clean up after them (remove stuff from /var, etc)
there are no dangers.  You just need to make sure wherever the crash
dumps will wind up going (/var by default) has enough space to handle
both the crash dumps and anything else the machines need to do.  We
currently have no provision for preventing crash dumps from filling up
the target partition.

I keep advocating for the conservative side of this issue, preferring
that crash dumps be an opt-in setting until we have infrastructure in
place to prevent them from filling the target partition.  I still
picture there being people out there who don't know what crash dumps
are, wouldn't know they might need to clean up after them, and may
be negatively impacted if the target partition wound up full without
them knowing why.

                                                Ken Smith
- From there to here, from here to      |       kensmith at buffalo.edu
  there, funny things are everywhere.   |
                      - Theodor Geisel  |
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