[OmniOS-discuss] Swap and dump

[Dan McDonald]

> On Aug 15, 2015, at 2:57 PM, Olaf Marzocchi <lists at marzocchi.net> wrote:
> 
> Hello,
> over two years ago I installed my OmniOS server and after the install I found a 16 GB dump dataset and a 4 GB swap dataset. I have 32 GB RAM. My root disk is 30 GB, you can feel my pain :)
> 
> I don't remember ever changing them, but now I was investigating the matter after for the second time in two years the automatic updates (that I set) filled the root disk, and I found:
> 
>      Dump content: kernel pages
>       Dump device: none (dumps disabled)
> Savecore directory: /var/crash/OmniOS-Xeon
>  Savecore enabled: yes
>   Save compressed: on
> 
> Dumps are disabled. Do I need that dataset anymore?

If you don't want your kernel panics to dump core, you may certainly destroy your 16GB dump dataset.

If it disappeared, perhaps you renamed your rpool, or for some obscure reason the system could find the dump device originally configured. If the system cannot find your dump device, even once, your dumps are disabled.

> I don't understand (from the man page) how savecores can be working, when they are taken at the reboot after a crash and when they rely on a dump, that is not being taken.

Some people use swap for their dump device, but I don't see that enabled in your output either.

> I reduced the dump dataset to 8 GB that should be enough for the kernel pages, but if I really don't need one to get the savecores (not that I ever had crashes in the last 18 months anyway) I will remove it altogether.
> 
> Could you clarify me how this works and at what time the dumps got disabled automatically?

I'm guessing you modified something, even temporarily, such that the system couldn't find the configured dump device and it therefore disappeared.

You may remove the dump dataset if you wish.  You understand the risk (kernel panic means you won't get a kernel dump).

Dan