Q. I am new to Linux. What tools or commands are recommended to troubleshoot performance related problems?
A. Following are the basic or essential tools that every Linux or UNIX system admin should be aware of:
a) top
b) sar
c) vmstat
d) iostat
e) free
top command
The top program provides a dynamic real-time view of a running system. It can display system summary information as well as a list of tasks currently being managed by the Linux kernel. Type the top command:
$ top
sar command
The sar command is performance monitoring tool. It can find out what Linux is doing all the time. It can generate report and email them to sys admin. In order to use sar you need to install sysstat package. sar displays performance data for:
- CPU and Queue,
- Disk I/O
- Swap and Memory
- CPU interrupts, Networking and much more
vmstat command
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity. See the detailed article “How do I find out Linux Resource utilization to detect system bottlenecks?”
iostat command
The iostat command is used for monitoring system input/output device loading by observing the time the devices are active in relation to their average transfer rates i.e. it is useful to monitor disk throughput. See the detailed article: “How do I find out Linux CPU utilization?”
free command
The free command displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel. See the detailed article: “Linux check memory usage”
Read the man pages of all of these tools. Always remember, you need to spend some time using these tools, and then only you will be able to understand the output of these commands.
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cool stuff
usefull, nice.
one link does it all! check out http://collectl.sourceforge.net/ for all your performance monitoring needs.
-mark
Hmm… many of these worked, except for sar. It keeps telling me:
Cannot open /var/log/sysstat/sa15: No such file or directory
I wonder what the problem is.
However, some of those other utilities are new to me. It’s nice to learn of them.
These tools seem to be find for looking at the overall performance of a server, but is there a tool that can be used to see specifically at a certain process and measure the impact of that process on the system?
sar 1 5
I had the same problem with
$ sar. On a CentOS box, install sysstat using$ yum install sysstatif you are missing sar altogether. Then let it run a couple of cron jobs (sa1 and sa2 – sa1 runs every 10 mins, sa2 runs close to midnight). If you can’t wait till midnight then run$ /usr/lib64/sa/sa2 -Abut be prepared to see limited informationQ. Lets say you have a remote machine on which your server application runs. The remote server is linux based. Mention what all steps you would do to IDENTIFY and SOLVE each of the following two problems:
1. The server is not reachable
2. The server is running slow
Found a cool little ruby script that can be used to send a HTML email of these stats from your server via cron. https://raw.github.com/watsonian/server-status-report/master/status.rb
You can read about setting it up here: http://wiki.dreamhost.com/PS_Server_Status_Script
My problem was that our VPS was showing intermittent memory issues. The hosting company automatically reboots the server but doesn’t provide any stats on what might be causing the problem. Logging in after the server is rebooted and not having sar access, left you with no way to tell what was causing the problem. Logging all the output of the above commands in a cron job just didn’t sound right to me. So I thought I’d try this ruby script.
Setup a little cron job and Bam, we have stats…
Jw
Thanks So Much…
Above written or given info are very helpfulll for all,,,
Keep it up this good work ….all
Thank you, Can you post some more useful commands which are used to troubleshoot disk issues in Linux.