1. What is difference between SAN and NAS?
Storage area network (SAN) is  a high-speed special-purpose network storage and connected in a fabric, so that there can be easy access to storage from many different servers
SAN support for backup and restore, disk mirroring, data migration from one storage device to another device.

Network attached storage (NAS) is a dedicated hard disk storage device and its a own network address and provides file-based data storage services to other devices on the network.
The file access is redirected using a remote protocol such as CIFS or NFS to another device.

2. Network Interface bounding in Linux?
Linux kernel features that can allows combine multiple network interface(eth0, eth1) into a single virtual link like as bound0,

3. How do I find out runlevel of Unix or Linux system?
#  runlevel
#  who -r

4. What are the command to find HBA port number and WWN in Solaris?
#  luxadm -e port    

#  fcinfo hba-port
#  fcinfo hba-port | grep WWN

5. ipv4 is how many bits addressing system?
IPv4 IP address are 32 bit numbers so total of 4 bytes here. There are  Each and every binary numbers are separated by the dot.

6. When do you use protrob command?
If You don't like to reboot the Linux system after making any changes in partition table or created new partition , just use partprobe. Command should able to create a new file system.

7. what is an Inode?
Inode is  an index node. It's a data structure that stores the following information about a file, the inode contains information
about the file-size,
Timestamps for fiel creation, file access and modification time
User ID, Group ID, device ID
the inode contains pointers to the data blocks of the file.
access privileges for owner, group and others.
link counter to determine the number of hard links

8. How do you remove RPM Package?
Find rpm package name use  -qa and remove that package use -e
#  rpm -qa | grep packagename
#  rpm -e packagename

9. How to check all open ports on linux machine and block unsed ports?
#  netstat -tulpn
#  netstat -anp

10. how can you make an user to nologin without locking the account for the user?
You can use the -M option will not created home directory
#  useradd -M username

then lock the account to prevent logging in:
#  usermod -L username
You can  edit a line in /etc/passwd file  and made changes below line to that user's shell to
# vi /etc/passwd
/bin/false (For ubuntu)
/bin/nologin (For Redhat,CentOS)

Interview Questions-1
Interview Questions-2
Interview Questions-3