OS Security

Here are some links I've used many times to secure and harden my servers. They're for CentOS v.5.7.

-Hardening procedures.-
http://wiki.centos.org/HowTos/OS_Protection

-Default services-
http://www.cyberciti.biz/faq/linux-default-services-which-are-enabled-at-boot/

-Iptables-
http://wiki.centos.org/HowTos/Network/IPTables

Django

Getting started with Django is easy.

Install it.
Learn it.
Build an app.
Read the FAQs.

Grub

Getting locked out of Linux is not fun. Getting back in can be a chore, sometimes. Luckily, I know the basics but needed a little help. Finding this link did the trick on one of my Ubuntu 10.10 servers. I didn't have to resort to the install dvd.

http://www.botskool.com/geeks/how-recover-your-ubuntu-1004-password

Python

Here are Python websites I find very useful. They contain very good explanations and examples of all things Python.

Python for SysAdmins-
http://www.ibm.com/developerworks/aix/library/au-python/

Ebooks-
http://www.djangobook.com/en/2.0/chapter01/
http://www.swaroopch.com/notes/Python_en:Table_of_Contents


Python Tutorial-
http://zetcode.com/
http://python.org


Django tutorials-
http://lightbird.net/dbe/


Python gtk tutorial-
http://pygtk.org/pygtk2tutorial/ch-GettingStarted.html#sec-HelloWorld
www.pygtk.org/tutorial.html
www.pygtk.org/pygtk2tutorial/ch-GettingStarted.html

Nagios

One way to create a custom Nagios service check on CentOS-

1) Create new script file in /etc/nagios/scripts. It will contains a shell command to check if a specific script is running on a remote host. It should look like this-

#!/bin/sh
#
#2012Feb11
#
/usr/bin/ssh -p 1132 user@10.99.20.15 'if ! pgrep -f '/[r]oot/scripts/cfg/scriptssh.cfg.server01'; then echo 'Process not running!'; exit 1; fi'

2) Add new code block to /etc/nagios/servers/main.server.cfg. It will contain-

define service{
use generic-service
host_name some.server
service_description process check
is_volatile 0
check_period 24x7
max_check_attempts 4
normal_check_interval 5
retry_check_interval 1
contact_groups admins
notification_interval 960
notification_period 24x7
check_command process_check
}

3) Add new code block to /etc/nagios/objects/command.cfg. It will contain-

# 'check_processes' command definition
define command{
command_name process.check
command_line /etc/nagios/scripts/./process.check.sh
}

4)Reload Nagios-

nagios -v /etc/nagios/nagios.cfg
->Fix any errors. If none, then continue.
nagios service reload

Pgrep

Here's a one liner that gets a pid off a remote host and returns it to Nagios. This one took a little effort. Running pgrep across ssh returns two pids, the target pid and the pid of the pgrep search. These were undesireable results because I didn't want the pgrep pid. To simulate grep's -v switch I chose to use brackets, [ ]. This worked perfectly. Here's the code-

ssh -p 4231 user@10.98.34.199 'if ! pgrep -f '/[h]ome/user/diamonds.cfg.server'; then echo 'Diamond not running!'; exit 1; fi'