dumpdev default

[Aristedes Maniatis]

On 18/01/12 2:07 AM, Ken Smith wrote:
> 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.
>

Thanks Ken. That is very clear. If you have time, please update the documentation with that answer too since others are likely to be confused by what I found there which is incorrect and incomplete.

Also, for ZFS users, I assume that the first swap disk will be default? So this is another consideration when sizing up swap partitions as compared to the size of memory installed.


Thanks

Ari


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Aristedes Maniatis
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