Atop - see what is going on in your Linux system

[viking60]

There are a few monitoring tools like htop glances etc. Atop is a "competitor" to Glances and can give a lot of information about your system.
Glances looks better, but Atop has some powerful features that can come in handy.

Atop is an ASCII full-screen performance monitor that is capable of reporting the activity of all processes (even if processes have finished during the interval), daily logging of system and process activity for long-term analysis, highlighting overloaded system resources by using colors, etc. At regular intervals, it shows system-level activity related to the CPU, memory, swap, disks (including LVM) and network layers, and for every process (and thread) it shows e.g. the CPU utilization, memory growth, disk utilization, priority, username, state, and exit code.

I installed atop from the repos and started it in a terminal with

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atop

no surprise there. I could have started atop with several switches but I can simply enther the switch while atop is running to alter the given information.

So while atop is running I can enter "m" to see the memory used by active processes or press "d" to check out the disk.
Here is a list over some letters you can press to get different info:

http://www.atoptool.nl/screenshots.php

That is pretty much how Glances does it too. What I often need is to see how much memory or cpu a particular program is using.
How much memory is Chromium using? Is python2 a resource hog? etc
So to check out Chromium I simply pressed P (remember <shift> as in capital P) on a running atop.
And this nice prompt turned up:

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Process-name as regular expression (enter=no specific name):

so here I entered "chromium"
Now I only get live data regarding chromium.

I can use all the switches listed in the link above only on chromium - so to check out memory; I simply press "m" - and it will only show the memory chromium uses.
If I press "v" it gives miscellaneous info about chromium.
If I press "g" it goes back to the default (generic) info - about chromium.

Every switch I type gives info about Chromium - only.

So how do I get away from Chromium and back to checking all processes again?

Just press P again and hit <ENTER>

So by using this; I found out that Atop uses less resources than Glances - less memory and less CPU.
Nice...
I have only scratched the surface here but if you want to dive in deeper - check out the man page