About Crontab file

crontab -l -r -e

-l list the current contab file

-r removes entry

-e edit the crontab file

Fileds of crontab file

Minute [ 0-59]

Hour [0-23]

Day of Month [1-31]

Month [1-12]

Day of Week [0-6] 0-Sunday

Download Linux Ebooks RedHat Fedora

Addison Wesley - A Practical Guide to Red Hat Linux 8 (2002).chm
Apress - Beginning Fedora, From Novice to Professional (2007).pdf
Hungry Minds - Red Hat Linux Security and Optimization (2002).pdf
Hungry Minds - RedHat Linux Networking and System Administration (2002).pdf
McGraw Hill - Red Hat Linux Pocket Administrator (2003).pdf
McGraw-Hill - Fedora 7 and Red Hat Enterprise Linux, The Complete Reference (2007).pdf
McGraw-Hill - Red Hat, The Complete Reference Enterprise Linux & Fedora Edition (2004).chm
McGraw-Hill - RHCE Red Hat Certified Engineer Linux Study Guide 5th Edition (2007).chm
O'Reilly - Fedora Linux (2006).chm
O'Reilly - Learning Red Hat Enterprise Linux & Fedora 4th Edition (2004).chm
O'Reilly - Learning RedHat Linux 3rd Edition (2003).chm
Prentice Hall - A Practical Guide to Red Hat Linux 3rd Edition (2006).chm
Que - Red Hat Linux Fedora 3 Unleashed (2004).chm
Red Hat - Red Hat Linux 9, Red Hat Linux Customization Guid (2003).pdf
Red Hat - Red Hat Linux 9, Red Hat Linux Getting Started Guide (2003).pdf
Red Hat - Red Hat Linux 9, Red Hat Linux Security Guide (2002).pdf
Red Hat - Red Hat Linux 9, Red Hat Linux x86 Installation Guide (2003).pdf
RedHat Cluster Manager.pdf
Sams - Fedora 7 Unleashed (2008).pdf
Sams - Fedora Unleashed 2008 Edition (2008).pdf
Sams - Red Hat Enterprise Linux 5 Administration Unleashed (2007).pdf
Sams - Red Hat Fedora Core 6 Unleashed (2007).pdf
Sams - Red Hat Linux Unleashed 2nd Edition (1998).pdf
Sams - Teach Yourself Red Hat Fedora 4 Linux All in One (2005).chm
Sams - Teach Yourself Red Hat Linux Fedora in 24 Hours (2004).pdf
Wiley - Fedora 10 and Red Hat Enterprise Linux Bible (2009).pdf
Wiley - Fedora 8 and Red Hat Enterprise Linux Bible (2008).pdf
Wiley - Fedora Linux Toolbox (2008).pdf
Wiley - Red Hat Enterprise Linux 4 For Dummies (2005).pdf
Wiley - Red Hat Fedora Linux 2 All-in-One Desk Reference For Dummies (2004).pdf
Wiley - Red Hat Fedora Linux 3 Bible (2005).chm
Wiley - Red Hat Linux Bible (2003).chm
Wrox - Beginning Fedora 2 (2004).chm
Wrox - Beginning Red Hat Linux 9 (2003).chm
Wrox - Beginning Red Hat Linux 9 (2003).pdf


Apache configuration httpd.conf

3 main sections of httpd.conf

Main server configuration ( host-specific server directives)

Global environment ( the location of configuration files )

Virtual hosts (Server values specific to virtual hosts)

Global environment

ServerType ( run under inetd daemon or standalone service)
ServerRoot ( identifies server root , for security resons you need to ensure that root has exclusive write access to the server root directory tree and its contents and ordinary users cant make modifications )

Timeout 300 (default is 300 ie 5mins) ( sets time period for which apache waits during certain operations are performed before it sends or recieves a timeout signal )

StartServers ( number of services you want to run on startup)

Main server configuration

it contains directives for main server. the values of these directives are also used as default values for virtual hosts unless virtual hosts section of the file specifes diffrent values

it contains configrations related to

User and Group
ServerAdmin email@address.com ( mails if any notifications of server problems to this id)
ServerName www.validhostname.com:80 (address to which sites clients will connect, so give valid DNS name.)
DocumentRoot "/var/www/html" (content will be in this directory we can use symbolic links if space is less)
ScriptAlias /cgi-bin/ "/var/www/cgi-bin/"

It is important to keep all the CGI scripts and executable files in single direcotry "cgi-bin" to avoid security risks
or if you want to give access to some executables then keep them in another directory.Also keep cgi-bin directory
outside /var/www/html
create different CGI direcotries for diffrent virtualhosts we can do it by setting User and Group

User apache
Group apache

when apache starts or get initiated it starts as root to configure itself but later it forks into child and run as
specified user and group as running as root causes security risks.

ps -aux | grep httpd

(display httpd processes currently running )

Listen 80 ( portnumber to listen to default is 80)

if you want to change port chage port higher than 1023 as below 1024 are reserverd for root's use

most commonly used options for httpd are

-d serverroot (sets the location of the server root overrieds ServerRoot in httpd.conf)
-f config ( carryout commands in configurations at startup)

-h display summary of possible commands
-L provides directive list and possible argeuments and locations where each directive is valid
-t run syntax tests on configuration files returns 0 if acceptable
-x instructs httpd to run in single-process mode genrally used for internal debugging.
-s verify the virtual host configuration

Virtual hosts

it enables to setup virtual host containers to enable multiple-server capability
without vritual hosting you need to run two seperate web servers listening on diffrent IP addresses, and
have a unique network interface bound to each address.
Virtual hosting enables you to host both sites on one computer with the same IP address.

Creating and Managing Virtual Networks Part 1

We start with

1) Identifying the compents of virtual Netwoks

2) creating virtual switches and virtual Switch port groups

3) managing NIC teams

4)managinv Virtual LANs (VLANs)

5)configuring virtual switch security policies


it resides in vmkernel , it manages traffic between virtual machines


Its on virtual switch (logical object).

it provies services for Service console,Vmkernel and hosted virtual machines

i) service console port : It is configured with an IP address to allow access to service console at that respective address.(vswif)

ii)VMkernel port: it is configured with IP address to allow access to VMotion,
iscsi storage or NAS/NFS storage access,

this is referred as (vmknic)

iii)VM port group:it is switch to switch connection which allows VMs to access physical networks