Setting up an SSL secured Webserver with CentOS

http://wiki.centos.org/HowTos/Https

How to Disable SELinux

Temporarily switch off enforcement
You can switch the system into permissive mode with the following command:

echo 0 >/selinux/enforce

more info:
 http://www.crypt.gen.nz/selinux/disable_selinux.html#DIS2

Finding out largest tables on MySQL Server

http://www.mysqlperformanceblog.com/2008/02/04/finding-out-largest-tables-on-mysql-server/

SELECT CONCAT(table_schema, '.', table_name),CONCAT(ROUND(table_rows / 1000000, 2),

       'M')rows,CONCAT(ROUND(data_length / ( 1024 * 1024 * 1024 ), 2),'G')DATA,

       CONCAT(ROUND(index_length / ( 1024 * 1024 * 1024 ), 2), 'G')idx,

       CONCAT(ROUND(( data_length + index_length ) / ( 1024 * 1024 * 1024 ), 2), 'G')

       total_size,ROUND(index_length / data_length, 2)idxfrac
FROM   information_schema.TABLES
ORDER  BY data_length + index_length DESC
LIMIT  10;

vi  / vim graphical cheat sheet

How to remove GPT partitions

http://d52floats.blogspot.com/2012/07/removing-gpt-information-from-drive.html

Linux disable screen blanking i.e. preventing screen going blank

 http://www.cyberciti.biz/tips/linux-disable-screen-blanking-screen-going-blank.html

Ping sweep with nmap

From nmap man

 " -sP (Ping Scan)
              This option tells Nmap to only perform a ping scan (host discovery), then print out the available hosts that responded to the scan. No further testing (such as port scanning or OS detection) is performed. This is one step more intrusive than the list scan, and can often be used for the same purposes. It allows light reconnaissance of a target network without attracting much attention. Knowing how many hosts are up is more valuable to attackers than the list provided by list scan of every single IP and host name.

              Systems administrators often find this option valuable as well. It can easily be used to count available machines on a network or monitor server availability. This is often called a ping sweep, and is more reliable than pinging the broadcast address because many hosts do not reply to broadcast queries.

              The -sP option sends an ICMP echo request and a TCP packet to port 80 by default. When executed by an unprivileged user, a SYN packet is sent (using a connect() call) to port 80 on the target. When a privileged user tries to scan targets on a local ethernet network, ARP requests (-PR) are used unless --send-ip was specified. The -sP option can be combined with any of the discovery probe types (the -P* options, excluding -P0) for greater flexibility. If any of those probe type and port number options are used, the default probes (ACK and echo request) are overridden. When strict firewalls are in place between the source host running Nmap and the target network, using those advanced techniques is recommended. Otherwise hosts could be missed when the firewall drops probes or their responses."

nmap -sP 192.168.*.*

Linux LVM: Recovering a lost volume.

This is one of the best "How To" to recover an lost LVM, it works forme me ;)

.."NOTE: Do not attempt these steps unless you have a firm understanding of UNIX / LINUX.  The concepts here are relatively advanced."....

The Perfect Server - CentOS 5.7
http://www.howtoforge.com/perfect-server-centos-5.7-x86_64-ispconfig-2

"This tutorial shows how to set up a CentOS 5.7 server (x86_64) that offers all services needed by ISPs and web hosters: Apache web server (SSL-capable), Postfix mail server with SMTP-AUTH and TLS, BIND DNS server, Proftpd FTP server, MySQL server, Dovecot POP3/IMAP, Quota, Firewall, etc."

Linux Fundamentals, Part 1 

DIY: Destroy data on drives via a Linux live distro

http://www.techrepublic.com/blog/doityourself-it-guy/diy-destroy-data-on-drives-via-a-linux-live-distro/835

How to lock down Linux

"Any operating system can be cracked if you don’t adequately protect it. Yes, even Linux. Here are some security basics on how to protect your Linux systems."

Dig Howto

Instead using nslookup use dig,  in RHEL distro, dig is part of bind-utils package.
http://www.madboa.com/geek/dig/

How to SMTP Auth in Sendmail (CentOS)

By default sendmail-cf  is not installed in CentOS:

yum install sendmail-cf

Then edit /etc/mail/sendmail.mc and add this:

TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl

compile the new configuration:

make -C /etc/mail/

saslauthd must by running:

/etc/init.d/saslauthd start 

and make it available on startup:

chkconfig  saslauthd on

then restart sendmail:

/etc/init.d/sendmail restart

and it's ready to use
For a powerful mail server, you can combine this configuration with MailScanner, clamav and grey-list.

Risk Management Strategy for the Provide Domain Name Resolution Services Critical Function

http://www.dhs.gov/xlibrary/assets/it-sector-risk-management-strategy-domain-name-resolution-services-june2011.pdf

Unix file compression utilities

to compress and zip:

tar -czvf archive.tgz files/

 more info

http://www.fluidthoughts.com/howto/tar-gzip/

Virtualization in Linux, KVM way by IBM

Well documented information at:
http://publib.boulder.ibm.com/infocenter/lnxinfo/v3r0m0/index.jsp?topic=/liaat/liaatkvm.htm&sf1617284=1

vi intro -- the cheat sheet method by Daniel Robbins

vi,  useful  cheat sheet
http://www.ibm.com/developerworks/linux/tutorials/l-vi/

How to add rpmforge repo to CentOS 5.5

x86_64 version

 wget http://dag.wieers.com/rpm/packages/rpmforge-release/rpmforge-release-0.3.6-1.el5.rf.x86_64.rpm

rpm -ivh rpmforge-release-0.3.6-1.el5.rf.x86_64.rpm

You can disable the rpmforge repo in /etc/yum.repos.d/rpmforge.repo
and changed enabled = 1 to enabled = 0

Source

http://blog.bloke.com/2010/05/enable-rpmforge-for-centos-5-5-for-subversion-1-6/

Updating time on Linux

First install NTP
yum install ntp
 then update by a remote NTP server
ntpdate my.server.xx

or set manually
date mmddHHMM[YYyy]