Hi, I am not very much familiar with linux. I know installation, basic services & configuration, but not done the troubleshooting part. Can someone tell me the basic steps to troubleshoot the slowness of a linux system? I tried a few commands like top, vmstat, iostat, sysstat etc. Is there anything else that i shall look into? Please advise.

If it is only a web oriented program that seems slow to start up, one thing to consider is to disable ipv6. Sometimes a dns lookup is tried using it resulting in a delay until it times out.

Please fill in your user info like distribution and such.

In relation to what's said already, "slowness" is not easy to deal with if it's not expressed in values (in other words: perception of speed). In my opinion the best way to start is to set up baseline data like you did with your SAR tools (or Atop or Dstat or Collectl) running for at least 24 hours. This way, if you tweaked things, you'll have objective numbers to compare against. List your hardware, distribution, kernel, any sysctls or other tweaks you already tried (for most of that I still use ServDoc. OK, it's old but it doesn't need to be installed and can output text, HTML, etc.). Data and information together can also help when comparing with other peoples benchmarks, say if you expected higher disk throughput, or directly pinpoint bottlenecks like low RAM, swap usage, wrong scheduler, et cetera. You might also want to search LQ for threads about performance tuning or performance issues, we've got quite some threads. Any questions, just ask.

Can you be more specific about what is slow? Disk I/O , booting, video, communication??? It is difficult to help with very little information.

Just in general i like to remove all unnecessary services, most people tend to think oh yeah thats great at the time of install and never use it = )

Regards
JKZfixme

Basically, you're on the right way. You need to find the process(-es) which consumes a lot of resource such as memory or CPU or disk.
If there are no "crocodiles", try to switch off some unused services and applettes.
Another way is to rebuild the kernel, but it's already the topic of the book, but not the forum post

Also, look in your logs. A hardware problem such as a hard drive going bad could cause slowdowns as well.