Practical use of sysctl

Beepie

I got a general question about sysctl. I understand how I can view and change kernel parameters but I'm struggling to think of parameters I might want to tweak. The video in chapter 25 shows how to change kernel.pid_max but that doesn't seem particularly useful (on my Fedora PC it's set to 4194304, which seems more than enough).

I looked into kernel.ctrl-alt-del and kernel.hostname. On my system kernel.ctl-alt-del is set to 0, which means the Ctrl-Alt-Del behaviour is managed by the init system. Changing the value to 1 didn't change its behaviour.

Next, I permanently changed my system's hostname by adding a file under /etc/sysctl.d/. This worked, and I was very proud of myself. However, when I cat /etc/hostname I am still seeing the old hostname. That makes me wonder why I would want change the hostname via sysctl. Simply updating /etc/hostname seems the right way to do this.

In short, I'm looking for some practical examples. Do any of you use sysctl to tweak settings?

coop

There are many parameters that include memory management and also networking properties. Take a look in /proc/sys/vm and /proc/sys/net/ipv4 for example. On my system there are over 900 entries in /proc/sys

Beepie

Thanks for the quick response. I think you are the gentleman in the video? (I'm sure I've seen the user name coop in one of the videos).

I've dived into /proc/sys/vm/swappiness and it's al starting to sink in now, so thanks again for your reply.

coop

yes that's me. I'm a little older than the avatar image here