how to assignig ip on linux

Assigning IP Address on Linux:

To check IP address:

# ifconfig              >> to see all interfaces

# ifconfig eth0      >> to see specific interface

Required File to Edit:
#vi  /etc/sysconfig/network-scripts/ifcfg-eth0   >> edit ifcfg-eth0 file to add IP detail
#Vi  etc/resolv.conf  >> to add NameServer or dns
# vi /etc/sysconfig/network  >> add GATEWAY & Hostname etc
#vi /etc/hosts    >> To Name Resolv

 

To up/down interfaces:

# ifconfig eth0 up       >> to up eth0

#ifconfig eth0 down  >> to down eth0

Assigning IP Address Temporary on interface: (After restarting this IP address will gone)

# ifconfig eth0 172.16.2.21 netmask 255.255.255.0 up  >> set IP on eth0 interface

# route add default gw 172.16.2.1 eth0  >> set getaway on eth0 interface

Assigning IP Address Permanently on interface:  (For this situation you have to edit mamually and also using netconfig command)

Using netconfig command:

# netconfig   >>(Press Enter Key, Now you get an interface, where you configure IP address). Then

# service network restart (Press Enter Key, that will done)

(N.B. As soon as possible i provide more details screen shot)

Manually Assigning IP address:

# cat /etc/sysconfig/network-scripts/ifcfg-eth0   >> just view the configuration file

#  vi  /etc/sysconfig/network-scripts/ifcfg-eth0   >> edit ifcfg-eth0 file to add IP detail

 

To add default gateway (location - /etc/sysconfig/network)

# vi /etc/sysconfig/network  >> add GATEWAY

To Add NameServer ( /etc/resolv.conf)

Vi  etc/resolv.conf  >> to add NameServer

# services network restart  >> run this command to enable changes .

Now you see the change of "ifcfg-eth0" file. # cat /etc/sysconfig/network-scripts/ifcfg-eth0

 Add Virtual interface address permanently:

#  vi  /etc/sysconfig/network-scripts/ifcfg-eth0:1      >> to create new virtual interface and assign IP

check out the created virtual interface

# services network restart  >> run this command to enable changes .

# cat   /etc/sysconfig/network-scripts/ifcfg-eth0:1      >> to view interface

Some other Ping commands:
#ping 4.2.2.2 -s 2048   >> to ping load
#ping 4.2.2.2 -c 5        >> number of time to ping
#ping 172.168.1.0 -b  >> Broadcast ping 

How to reset centos password

CentOS Password Resetting (GRUB):

 

Step 1: The first step is to reboot your Server/PC

Step 2:  At during rebooting, you see the following screen. Press any key to hold booting

 

Step 3:  After pressing key, you get the screen. (Cause I have GRUB Password)

  Step 4: Now you press “P” for entering GRUB Password

 

Step 5: After entering GRUB Password, you get the screen, now you press “e” for edit

 Step 6: You get 3 options. You select “Kernel /vmlinez” line and press “e” again.

Step 7: you get the screen…

Step 8: On the screen you type “single” keyword with “Space” (Make sure the space before “single” keyword), don’t wary see the screen….

Step 9:  After typing “Single” keyword, you press Enter. Then you get the screen again. Now you press “b” to boot the system into single user mode.

Step 10: After complete booting you get the screen. Now you can able to change the password.

Step 11: On the screen you just type “password” keyword and press enter to type your new password.

Step 12: After changing password you just type “reboot” to reboot your system. You can login with your system with new password. .  I hope that will be fine….