HOWTO

Use the following option to check out how network (NFS) shares are performing on your sever

[code]iostat -n 2[/code]

The -n option tells iostat to just show the network shares

2 tells iostat to refresh the stats every 2 seconds

Want your terminal to look like this? 

In addition to the coolness, factor it also helps you do (monitor) multiple things at  a time. In this screenshot

• I am checking the resource utilization on my web server
• Tailing the web server logs to look for errors
• have a small console for me to run any commands

You can achieve this by using the nifty screen utility. Screen allows you to multiplex between multiple consoles.  So you can open one terminal and have multiple consoles on it. The commands for using screen are a bit hard to get used to. Here are the shortcuts I used to achieve the screen above

1. Install the screen package
2. Create a new screen session by running[code] screen [/code]
3. Add a new screen console by executing[code] ctrl + a [/code]

   [code]c[/code]

4. Split the screen by executing[code]ctrl + a [/code]

   [code] Shift + s [/code]

5. Name the different consoled by executing[code]ctrl + a[/code]

   [code]Shift + a[/code]

As you might have figured out by now, “ctrl + a” puts you into screen command mode. You can get a list of all available options by executing

[code]ctrl +a[/code]

[code]?[/code]

Here’s a quick reference guide that has more details http://aperiodic.net/screen/quick_reference 

Have fun multitasking 🙂

For my own notes.. if you are using grep to parse through the contents of a file and want to see the preceding or proceeding content than the line that matched your query, you can use the following options

preceding content [code]grep -B NUMBER_OF_LINES_TO_DISPLAY query filename[/code]

for example, if I was searching for kudithipudi in a file names access.log and want to see 2 lines prior to the match, I would use [code]grep -B 2 kudithipudi access.log[/code]

proceeding content[code]grep -A NUMBER_OF_LINES_TO_DISPLAY query filename[/code]

for example, if I was searching for kudithipudi in a file names access.log and want to see 2 lines after the match, I would use [code]grep -A 2 kudithipudi access.log[/code]

preceding and proceeding content[code]grep -C NUMBER_OF_LINES_TO_DISPLAY query filename[/code]

for example, if I was searching for kudithipudi in a file names access.log and want to see 2 lines before and after the match, I would use [code]grep -C 2 kudithipudi access.log[/code]

puppet, is a configuration management framework that can be used to perform several different things to validate/configure your infrastructure. We have been using puppet for sometime at my work and have just started moving into some of the advanced uses of the tool.

One of the features offered by puppet is the capability to use templates to configure different servers.

For example, say you want to configure an application on server ABCD, XYZ and 123. And the configuration file for all these servers is the same, other than the hostname of the server. The configuration file has to reside in /opt/application/config.conf . The config.xml file looks like this

[code]

db.name=blah
db.user=blahblah
db.hostname=XYZ
log.level=ERROR
log.location=/var/log/application

[/code]

Here is how you can do it in puppet.

Define a module which uses a template and then configure the template to put the host specific entry in the template. Let’s name our module test_config

• Create the module

• cd $PUPPET_HOME/modules
• mkdir test_config/{files,manifests,templates}
• Create the template
• cd templates
• vi config.conf.template and add the following to the file[code]db.name=blah
  db.user=blahblah
  db.hostname=<%= fqdn %>
  log.level=ERROR
  log.location=/var/log/application [/code]
• note : see how I replaced the hostname XYZ, which was specific to one server with <%= fqdn %>. This is one of the “facts” provided by puppet. you can get a list of all the facts by running facter on any of the puppet clients.
• Configure the module to use the template. In this case, we want the module to place the file config.conf in /opt/application
• cd manifests
• vi init.pp and add the following to the file[code]class test_config {
  file { "/opt/application/config.conf":
  ensure => present,
  owner => appuser,
  group => appuser,
  mode => 755,
  content => template("test_config/config.conf.template"),
  }
  }[/code]
• note : There are several other options you can use for the class file.. I just gave an example of some of the common ones. Like setting the owner, group and the rights.
• Finally configure the clients to use the module. In the individual node config files, include the module you just created. Here is how the config for node ABCD would look like[code]node ABCD {
  include test_config
  }[/code]

The next time the puppet client runs on host ABCD, it would create the file /opt/application/config.conf with the right hostname in the config file.