Tuesday, 3 February 2009

Useful Unix commands - part 1

CPU Usage
The prstat command displays information about active processes on the system and resource consumption. By default, prstat displays information about all processes sorted by CPU usage.

The prstat -s cpu -n 5 command is used to list the five processes that are consuming the most CPU resources. The -s cpu flag tells prstat to sort the output by CPU usage (This is a default flag set, so can be skipped). The -n 5 flag tells prstat to restrict the output to the top five processes.

Adding the -a option to any prstat command will identify how many processes each user is using, what percent of the CPUs, and how much memory, they are using on a system

prstat -a 

The ps command displays information about currently running processes. Pipe the output to search for specific processes

 ps -ef  | grep java

/usr/ucb/ps -auxwww | grep {pid}

This command gives the complete classpath and start parameters of the process mentioned in pid

Example:

/usr/ucb/ps -auxwww | grep 19138 


user 19138 0.4 2.31272184732136 ? S Jun 01 342:11 /resolve/j2sdk1.4.2_03/bin/java -Xmx1024m -Xms1024m -XX:NewSize=341m -XX:MaxNewSize=341m -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90 -XX:+DisableExplicitGC -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime -Xloggc:/resolve/CPEE3112/composer/log/pa3.gc -Drmiport=61050 -Dg2config.home=/resolve/CPEE3112/composer/conf -Dg2config.baseipport=61020 -Dg2config.instance=Engine14 -Dg2.processid=3 -cp /resolve/lib/any_custom_libs.jar:/resolve/lib/G2.jar:/resolve/lib/oracle_10_2_0_1_0jdbc.jar com.xyz.platform.Main -recover &





prstat -L -p {pid}

The above cmd gives the summary of lightweight processes which make up the process. More is at an example I gave here

The top command provides an overview of CPU and memory utilization, and a list of the top consumers of CPU, it updates it's display every few seconds so you can monitor continuously. Use http://www.groupsys.com/top/display/ to view details of the stats shown


top

sar -s


Memory Usage
vmstat 5 vmstat reports virtual memory statistics regarding kernel, thread, virtual memory, and disk, trap, and CPU activity. vmstat also helps calculate the average page scan rate.


Below is the vmstat output


vmstat 5



kthr memory page disk faults cpu

r b w swap free re mf pi p fr de sr s0 s1 s2 s3 in sy cs us sy id

0 0 0 11456 4120 1 41 19 1 3 0 2 0 4 0 0 48 112 130 4 14 82

0 0 1 10132 4280 0 4 44 0 0 0 0 0 23 0 0 211 230 144 3 35 62

0 0 1 10132 4616 0 0 20 0 0 0 0 0 19 0 0 150 172 146 3 33 64

0 0 1 10132 5292 0 0 9 0 0 0 0 0 21 0 0 165 105 130 1 21 78

Note: The first line of vmstat shows a cumulative value and must be ignored. sr is the pages scanned by clock algorithm.




On Unix, to find out how much RAM is present on a machine, use

prtconf grep 'Memory size:'


On Linux, the same is done using

free -m


Disk Space

df -ek

du -h