Monitoring Linux Disk load

Using iostat you can monitor disk load on a specific device.

iostat -dx {device name} 2 10

Examples:
iostat -dx /dev/sdc 2 10

The 2 is the interval and the 10 is the number of iterations. So you will see stats every 2 seconds for 10 iterations.

du command

I was finally able to harness the power of the du command. The -s flag has a cryptic definition in the man page (nothing new for man there). But using the -s flag allows you to summarize the file size for directories.


This command will give you a summary of the directory sizes in root. You can of course target down to other folders like so

Update 8/17/2015

Often I need to sort the output by size. Here you go.

Deleting files older than X on Linux

The following is handy if you need to delete files older than X on a Linux server. I like to run the find command first before actually moving or deleting the files. Just to make sure the files I want to remove are returned from the find command.

find /fullpath -mtime +4 -ls

The -ls flag will list out the details of the file so you can verify that the mtime parameter returns the right files.

find /fullpath -mtime +4 -ls -exec mv {} /destination ;

After you verify that the find command returns the files you want then you are ready to use the -exec flag on the find command to actually execute the move/delete. I also like to use full path here on the find command, just to make sure I move the right files.

makewhatis

So that took longer than it should. There is a command called whatis that gives you a single line description of a command:

whatis grep

grep (1) - print lines matching a pattern
grep (1p) - search a file for a pattern
grep (rpm) - The GNU versions of grep pattern matching utilities

A nice little tool to use. I just installed CentOS 5 in a VM and noticed that all my whatis commands were returning nothing appopriate…I quickly found the makewhatis command on some articles but could not locate it for CentOS 5 at first. Finally found the location:

/usr/sbin/makewhatis

This command builds the database and now my whatis commands are working.

Using PS to find resource intensive processes

#Top (X) Memory Consumers
#just change the head command to see more, this will show you top 10 

ps -auxf | sort -nr -k 4 | head -10

#Top (X) CPU Consumers
#just change the head command to see more, this will show you top 10

ps -auxf | sort -nr -k 3 | head -10

Linux uptime and version info

#uptime:

uptime

output: current time, how long system has been running, how many users are logged in, system load averages for past 1, 5, and 15 minutes

#Version info

uname -a
cat /etc/redhat-release
cat /etc/issue

df output format CSV

# File size on your drives in CSV format
# no header on the DF command, append the date to each row
# good for throwin in Excel and doing some trending.

df -Pk | awk '{print $1,$2,$3,$4,$5,$6,strftime("%Y-%m-%d")}' OFS="," | sed -e 1d