On 10/19/15 17:18, Christoph R. Murauer wrote: > Hello ! ... > If I follow the FAQ, then core dumps should not work. I could resize swap > and /var to have the same (or bigger size) as the physical RAM which is > also no problem. My question - or better the things I don't understand (I > found no informations and also had no panic message till now) are, which > size had a core dump and, will core dumps work, if swap (on /var is enough > place to copy the core dump file from swap to /var/crash after a reboot) > is smaller then the physical RAM ? My question is meaned, that swap is > only used for core dumps - nothing more.
The core dumps in question here are for when the OS panics. Core dumps can be used by developers to look at what went wrong, but in order to do so, you may need everything that was in RAM at the time of the panic. So...the kernel can dump to swap (whatever was in swap wasn't in RAM, thus wasn't part of what caused the panic). On next boot, savecore will find the dump in swap, and save it to /var. So that means swap has to be at least the size of RAM and you have to have AT LEAST that much space FREE on your /var partition. Your 256G SSD just got ~70G smaller. Ouch. ... or ... you can look at the big picture and realize... 1) you probably aren't a developer. 2) you probably haven't seen a core dump. 3) you probably wouldn't know what to do with the core dump. 4) if you got a core dump and wanted to send it to a developer, a 32G core dump would probably create a lot of problems for everyone. 5) that's a freaking big chunk of your SSD devoted to stuff you are unlikely to ever do anything with! and thus, I'll suggest you just don't worry about it. IF you manage to find a way to panic your machine, drop the memory waaaay down to 2G or so, reproduce it and worry about a 2G core dump. And -- even if you do have a system panic, very often developers can make sense out of what went wrong from the output of the debugger's trace and ps commands, rather than having to dig through an entire core dump. This is always what they ask for FIRST. Nick.
