RAID 5 Configuration in RHEL5.3

Step 1: Create 3 partitions by using #fdisk /dev/sda (say /dev/sda6, /dev/sda7, /dev/sda8) and change the system id as fd (Linux raid autodetect)
Step 2: #partprobe or #reboot -f
Step 3: #mdadm -C /dev/md0 -l 5 -n 3 /dev/sda6 /dev/sda7 /dev/sda8
            #mkfs.ext3 /dev/md0
Step 4: #mkdir /raid5
            mount in /etc/fstab (/dev/md0  /raid5 ext3 defaults 0 0) (add an entry in /etc/fstab)
            #mount -a
Step 5: #mdadm --detail /dev/md0 (viewing the raid device)
            #cat /proc/mdstat (viewing the raid device configuration)
Step 6: #mdadm -f /dev/md0 /dev/sda8 (disabling device from the existing RAID)
           #mdadm -a /dev/md0 /dev/sda9 (adding a new device in the existing RAID)
           #mdadm -r /dev/md0 /dev/sda8 (for removing a device from the existing RAID)

HTTP or Apache Server with Authentication

Step1: Install rpms
#rpm -ivh http*
          or
#yum install http*

Step2: Setting up the configuration file
#vim /etc/httpd/conf/httpd.conf
ESC+shift+g

<Directory "/var/www/html/test"> create index.html file in this location
AuthType Basic
AuthName "password protected"
AuthUserFile  /etc/httpd/testpass
Require user pna
<Directory>

Step3:
#htpasswd -c /etc/httpd/testpass pna
  give the password two times
#service httpd restart
#chkconfig httpd on

Step4:
#elinks http://192.168.0.254/test (it will ask for username and password for accessing the website.)

Swap file creation & Swap partition creation

Step:1 Adding virtual memory (adding swap file)

#dd if=/dev/zero of=/var/local/swapfile bs=1k count=1M (creating a file)
#mkswap /var/local/swapfile

Step:2 add an entry to /etc/fstab

/var/local/swapfile    swap    swap    defaults    0 0

Step:3 enabling the swap partitions

#swapon -a (enabling all swap partitions)
#swapon -s (showing all swap partitions)

 Creating swap partition
 
1.create a partition (eg:/dev/sda6)
2.#mkswap -L swap2 /dev/sda6 (creating a partition and label as swap2)

add an entry to /etc/fstab
LABEL=swap2    swap    swap    defaults    0 0
save and quit /etc/fstab

#swapon -a (enabling all swap partitions.)
#swapon -s (showing all swap partitions)

DHCP is working good in RHEL6

Server Configuration:
Step1: install the following rpm

rpm -ivh dhcp-4.1.1-12.P1.el6.i686.rpm

Step 2:  cp /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample /etc/dhcp/dhcpd.conf
Step 3:  change the range of ip address as per your wish.
Step 4:  service dhcpd restart
Step 5:  chkconfig dhcpd on

Client Configuration:
Step 1: dhclient
Step 2: check the following file
            /etc/resolv.conf


Sample file: Copy and paste the specified location /etc/dhcp/dhcpd.conf and get the dhcp service

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "jetking.com";
option domain-name-servers ns1.example.org, ns2.example.org;

default-lease-time 600;
max-lease-time 7200;

# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.

subnet 192.168.0.0 netmask 255.255.255.0 {
 range 192.168.0.1 192.168.0.10;
}

# This is a very basic subnet declaration.

subnet 10.254.239.0 netmask 255.255.255.224 {
  range 10.254.239.10 10.254.239.20;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

subnet 10.254.239.32 netmask 255.255.255.224 {
  range dynamic-bootp 10.254.239.40 10.254.239.60;
  option broadcast-address 10.254.239.31;
  option routers rtr-239-32-1.example.org;
}

# A slightly different configuration for an internal subnet.
subnet 10.5.5.0 netmask 255.255.255.224 {
  range 10.5.5.26 10.5.5.30;
  option domain-name-servers ns1.internal.example.org;
  option domain-name "internal.example.org";
  option routers 10.5.5.1;
  option broadcast-address 10.5.5.31;
  default-lease-time 600;
  max-lease-time 7200;
}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

host passacaglia {
  hardware ethernet 0:0:c0:5d:bd:95;
  filename "vmunix.passacaglia";
  server-name "toccata.fugue.com";
}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
host fantasia {
  hardware ethernet 08:00:07:26:c0:a5;
  fixed-address fantasia.fugue.com;
}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

class "foo" {
  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

shared-network 224-29 {
  subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
  }
  subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
  }
  pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
  }
  pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
  }
}