1. What is vnc?

vnc or virtual network computing is a way computing remote
computer in linux world.when you connect a vnc client to a
remote computer using vnc server we an take the full acces
of that client computer.
to check installed or not
rpm -qa | grep vnc
configuration file
vi /etc/sysconfig/vncservers

2. What is the Difference between su and su- ?

there is little difference in both of these commends...

su --> just switch you to user mode (root) but didn't provide the complete user environment

su - ---> provide you the complete user environment and also direct jump to user home directory.

3. How to shuffle the GRUB booting from one Disk to other?

grub> map (hd0) (hd1)
grub> map (hd1) (hd0)

4. How to hide the partition in GRUB booting?

grub> unhide (hd0,0)
grub> hide (hd0,1)
grub> rootnovery (hd0,0)
grub> chainloader +1
grub> makeactive
grub> boot

5. What is chainloading?

The chainloading technique tells GRUB to read +n sectors from
the start of the partition. Usually n = 1. The chainloading
command may specify also a file name: chainloader +1 read 1
sector from start of the partition
chainloader /boot/chain.os2 load a file

6. How to restart apache server with out shatdown?

whenever you want restart Apache web server without shutdown
Apache web server that time you use the commands service
httpd reload ,if you type the commands service httpd restart
that time frist shut down the service then startup the
service but if you type commands service httpd reload, only
read the configuration file and startup the service

7. How to give acl permission in numerical mode on linux?

By using chmod command
for example chmod 777 <file name>
its for full permissionof the file

read =4
write =2

user group other
7 7 7
4+2+1 4+2+1 4+2+1

r+w+e r+w+e r+w+e

other example

we give permission to user to full and give group and other
to only read and execute than

chmod 755 <file name>

8. What is the command to check wwn # in linux?

Emulex HBA Adaptor.

Find the WWPN.
Confirm if the HBA is Emulex.
# lspci
0e:00.0 Fibre Channel: Emulex Corporation Zephyr LightPulse
Fibre Channel Host Adapter (rev 02)
17:00.0 Fibre Channel: Emulex Corporation Zephyr LightPulse
Fibre Channel Host Adapter (rev 02)

# cd /sys/class/fc_host/
# ls -l
total 0
drwxr-xr-x 3 root root 0 Oct 14 20:57 host0
drwxr-xr-x 3 root root 0 Oct 14 20:57 host1
# cat port_name

9. How to root mirror in Linux? How to replace mirrored hdd in case of failure?

we need to create raid level 1 in linux. and create a
backup of data.