So I wasn't 100% sure which forum to go to for this question and came here as my system has crashed several times in the last couple of weeks and always has happened whilst i am using my web browser (chromium) --- could be a coincidence

I predominantly always have a browser window open on something so again not sure if this is the cause

So to my actual question, where should I be looking to best diagnose and solve why the system is crashing?

I have tried looking over multiple log files but nothing in particular has lept out at me as a cause

Any suggestions greatly appreciated

Have you checked your RAM?

Seems to be ok after running 2 different tests

You wouldn't happen to be on web sites that use adobe flashplayer?

At times ... I have also noted that shockwave crashes in the browser seem to be quite frequent too?

Any suggestions? Is there a known issue of late?

I has just recently update to newer version of flash player that so far seems to fix some of the crashes I was getting.

If it's hardware, most likely causes would be bad ram, power supply, or overheating. There are several apps to chose from for monitoring your heat sensors. Wouldn't hurt to install one and set some alerts to trigger when temps get high. Also, clean out the innards of your system (get rid of dust, etc.) and remove any unneeded hardware cards. Give things a look-over checking for any obvious damage - popped open capacitors, melted/burned resistors, etc. Those are not so common a cause for spontaneous crashes, but still worth a look.

If it's software, it's hard to predict what it might be. If you can't determine some repeatable sequence of events that lead to the crash, things can be tough to diagnose.

When it crashes, does power stay on and the system reboot (assuming you have it set to do that)? Or is it an unexpected total "lights out" crash where everything just goes immediately dead? If it's the "lights out" variety, I would more suspect hardware.

You could try to exercise your system to see if you can trigger a reboot. Start up a lot of things and try to overwhelm your memory ("overwhelm" is a bad choice of words, but you get the picture). Transcode some video or something else that is CPU-intensive to try to raise the temperature level.

@colorpurple21859

Currently running latest Arch version of flash:
Is there something more recent than that?

@haertig.

As far as the crash goes, the screen freezes and the mouse and keyboard are unresponsive and if there is a sound playing at the time then the last note is held playing through my speakers.
I have 'exercised' the machine as suggested with the following:

1. transcoded 4 movies at the same time
2. extracted eight 5 - 11GB rar files using a single call to p7zip for each at the same time
3. played a movie
4. had someone else watching a movie via ps3media server

All of the above were happening at the same time and the system seemed happy most of the time ... no crash

can you try to log in from another host? Do you have something strange in /var/log? (kernel panic or kernel module segfault or ???)

That sounds like a software problem, not hardware or overheating. This description is bringing back memories from way back when when I still used Windows. It used to do this a lot. I haven't experienced this bad behavior in Linux myself, but obviously it can happen - you're seeing it!

When it locks up like this, can you open a new console window? <ctrl><alt><F1> If so, your system hasn't "crashed", rather, some app is misbehaving.

If you can indeed open this new console window, login as root and start killing processes that are running with the hung user's userid. Start killing application processes first, before advancing to windows manager processes, etc. The first thing I would try to kill would be the web browser. See if things improve in the hung console window as you go about your process killing. As a final blow, you can try killing everything running as the hung userid, including the window manager, and restart the window manager up again after the kill.

You can get back to the hung console with <ctrl><alt><F8> usually. It may not be <F8> on your computer, but that's what it is on my system.

@pan64 - Unfortunately I don't currently have another machine in the house so a bit stuck there. I have looked through a large portion of the log files and have not seen any specific kernel issues.

@haertig - as mentioned, the keyboard is unresponsive as trying top go to a console was one of my first ideas

I do believe the issue is somehow linked to the browser so I will try another for a while and see how that goes. If it were the browser, would there be any where I could look, log wise or other,
to see what is happening at that point?

Oh yeah, I forgot that little detail. Oops!

In your case I think the kernel is frozen, so you have no chance to check what's going on. You may try to create a file and write some info (timestamp, hw temperature) into it time by time and you will see if it still works after the crash.
Also you may try even a smartphone to log in and check if it can alive that crash.
If not you should need to identify the kernel module (I think that will be the video driver). You can try to replace it.

Have you checked your hdd's smart info?

So I am almost positive it is either Chromium or flash as my computer stayed up for days until I was playing a game on FB which uses flash.

Would there be any record to prove my assumption?
Also is it likely that an application would lock up everything in such a way?

An app may not lock up anything but itself, but obviously there are bugs. Most likely memory leaks and/or memory corruption (= data was overwritten). The kernel (os) will take care about all the apps, therefore apps cannot damage other apps. The only exception is the kernel itself. The kernel serves all the apps but it has its own memory and it can be corrupted by the loaded modules. You need to try different drivers and/or different FB.