unix/linux System Admin Interview Questions And Answers 3

Q: - What "neat" command will do?

neat command provides Graphical interface to change network settings for network devices.


Q: - Which protocol is required to allow local printing and print sharing?

Internet Printing Protocol (IPP) is required to allow local printing and print sharing.

Q: - What is CUPS?

CUPS stands for "Common UNIX Printing System". CUPS is a open source printing system developed by Apple Inc. CUPS uses the Internet Printing Protocol (IPP) to allow local printing and print sharing.

Q: -What is the location of log files for CUPS?

The log files for the CUPS printing system are located in the /var/log/cups/ directory.

Q: - What is YUM?

YUM stands for Yellow dog Updater, Modified because it is based on YUP, the Yellow dog Updater. Where does the name Yellow dog come from? Yellow Dog is a version of Linux for the Power Architecture hardware and is RPM-based, just like Red Hat Enterprise Linux and Fedora. YUP, and later YUM, were written by the Linux community as a way to maintain an RPM-based system.

Q: - What are the advantages of YUM?

- Automatic resolution of software dependencies.
- Multiple software locations at one time.
- Ability to specify particular software versions or architectures.

Q: - How you will install software by YUM?

yum install <pkgname>

Q: - Which option is required to assume the answer "yes" to any questions asked during installation of package dependencies for YUM?

The "-y" option is used to assume the answer "yes".

For Example

yum -y install squid

Q: - How to remove a software by YUM?

yum remove <pkgname>

Q: - How Many Run Levels present in Linux?

There are 7 run levels, with each having its own properties.

-   0: Halt the system
-   1: Single-user mode
-   2: Not used
-   3: Multi-user mode with text login
-   4: Not used
-   5: Multi-user mode with graphical login
-   6: Reboot

Q: - Which configuration file is required to change the Run Level of Server or system?

/etc/inittab

To change the default run level, modify this line.

id:5:initdefault:

Q: - Explain architectures required for RPMs?

noarch Architecture-independent, can run on any architecture

i386   Generic build for a 32-bit x86 system

i586   Sometimes used when building kernels for older x86 processors
Intel® Pentium ® II, Intel Pentium III, Intel Pentium 4, AMD Athlon, and

i686   AMD Duron systems (Most RPMs for these architectures are built using the i386 architecture, with the kernel for these architectures being built with the
i686 for optimal performance.)

x86_64 64-bit processors such as AMD Athlon64, AMD Opteron, and Intel EM64T

ia64   Intel® Itanium

ppc    32-bit IBM® POWER, IBM eServer„ pSeries®, and IBM eServer iSeries

s390x  64-bit IBM eServer System z

Q: - How to install Linux software’s by RPM?

rpm -ivh test-1.0-1.i386.rpm

test  ######################### [100%]

Q: - If a file associated with test-1.0-1.i386.rpm deleted, than How we will recover that file?

We can reinstall this rpm again.

Q: - If you are getting error "package is already installed" but you have to install package any how. what option you will use?

rpm -ivh test-1.0-1.i386.rpm

Preparing... ########################################### [100%] package test-1.0-1 is already installed

In this case you can use "--replacepkgs" option.

rpm -ivh –replacepkgs   test-1.0-1.i386.rpm

Q: - Which options are required to upgrade a RPM?

Upgrading a package is similar to installing one. Type the following command at a shell prompt:

rpm -Uvh test-2.0-1.i386.rpm

Q: - In which directory RPM database stored?

/var/lib/rpm

Q: - Explain the command "rpm -qa"?

It will queries all currently installed packages.

Q: - Explain the command "rpm -qf "?

it queries the RPM database for which package owns <filename>. When specifying a file, specify the absolute path of the file.

Q: - How to verify all installed packages?

rpm -Va

Q: - How to verify the signature of an rpm?

rpm -K test-1.0-1.i386.rpm

Q: - How to list PCI Devices on your server or System?

use "lspci" command.

Q: - What is the role of "Kudzu"?

Kudzu is used to Detect new Hardware

Q: - What happens when you add a new device after installation?

The Kudzu program runs each time the system boots and performs a hardware probe. If new hardware is found, Kudzu attempts to map it to a kernel module. If successful, the information is saved, and the device is configured.

Q: - How to Enable ACLs for /home partition?
Add following entry in /etc/fstab

LABEL=/home    /home       ext3        acl      1  2

Now remount /home partition with acl option.

mount -t ext3 -o acl /dev/sda3  /home

Q: - How to View ACLs for a file(test_file)?

getfacl test_file

Q: - How to remove an ACL?

setfacl --remove-all <file-name>

Q: - What is the difference between pop3 and imap protocols ?
POP3 (Post Office Protocol) is the most commonly used internet mail protocol.It works on 110 port. It is easy to configure and use. With a POP account you download the mail to your local computer and keep it there. Most of the time it gets deleted off of the mail server after being downloaded. One disadvantage of POP is that once you download it to your computer you won't be able to check your mail from a different computer since it will already be downloaded onto your own computer. It tends to be slower than IMAP as well.

IMAP (Internet Message Access Protocol) uses a method where all the mailboxes and messages are maintained on the server. Therefore you can access your e-mail from any location with an internet connection. IMAP is faster than POP because the mail client reads all of the message headers without having to download the entire message. IMAP is also supported in a variety of clients just like POP. One thing to keep in mind is the amount of disk space allocated to your mail on the server may not be enough to hold all of your mail.IMAP supports the folder synchronization option e.g if you create any folder  on the client m/c in outlook(mail client) then that folder will automatically created on the mailserver for the account 

POP works best when you are using only a single computer, since you don’t have to worry about checking your e-mail from multiple locations. Plus it is faster as well.

IMAP would suit you better if you need to check your e-mail from multiple locations if you travel a lot. To use IMAP your ISP/mail provider must offer that type of account.

Q: - How to Disable a User Account in Linux ?

#   passwd <username> -l

   This might be useful in the situation where you don’t want to permanently remove the user, but you just want it disabled and no longer able to use the system. The user will still receive emails for example, but he will not be able to login and check them out.

To re-enable the account ,just use below command

# passwd <username> -u

Q: - How to detect CPU architecture/bitmode (32-bit or 64-bit) for Linux ?
# cat /proc/cpuinfo | grep flags

you will find one of them with name "tm(transparent mode)" or
"rm(real mode)" or "lm(long mode)"

1. rm tells ,it is a 16 bit processor
2. tm tells, it is a 32 bit processor
3. lm tells, it is a 64 bit processor

Q: - What is the difference between SSH and Telnet ?

The Primary difference between SSH and Telnet is of security i.e in ssh data transfer between the systems is in encrypted form so it is difficult for the hackers to understand what is going on network.

 In Telnet data transfer between the systems is in plain text. 

SSH uses a public key for authentication while Telnet does not use any authentication.

Due to the security measures that were necessary for SSH to be used in public networks, each packet contains less data to make room for the data of the security mechanisms. In order to transmit the same amount of data, you would need to take-up a lot more bandwidth. This is called overhead..

SSH adds a bit more overhead to the bandwidth compared to Telnet.

Q: - What is difference between AT and CRON? 

Cron command is used to schedule the task daily at the same time repeatedly ,

at command is used to schedule the task only once i.e to run only one time.

Q: - What is network bonding in Linux and steps to configure network bonding ?
 Network interface card (NIC) bonding (also referred to as NIC teaming) is the bonding together of two or more physical NICs so that they appear as one logical device. This allows for improvement in network performance by increasing the link speed beyond the limits of one single NIC and increasing the redundancy for higher availability. For example, you can use two 1-gigabit NICs bonded together to establish a 2-gigabit connection to a central file server.

When bonded together, two or more physical NICs can be assigned one IP address. And they will represent the same MAC address. If one of the NICs fails, the IP address remains accessible because it is bound to the local NIC rather than to a single physical NIC.
Steps to configure :

Step #1: Create a bond0 configuration file

Red Hat Linux stores network configuration in /etc/sysconfig/network-scripts/ directory. First, you need to create bond0 config file:

# vi /etc/sysconfig/network-scripts/ifcfg-bond0

Append following lines to it:

DEVICE=bond0
IPADDR=192.168.1.20
NETWORK=192.168.1.0
NETMASK=255.255.255.0
USERCTL=no
BOOTPROTO=none
ONBOOT=yes

Replace above IP address with your actual IP address. Save file and exit to shell prompt.

Step #2: Modify eth0 and eth1 config files:

Open both configuration using vi text editor and make sure file read as follows for eth0 interface
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
Modify/append directive as follows:
DEVICE=eth0
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

Open eth1 configuration file using vi text editor:

# vi /etc/sysconfig/network-scripts/ifcfg-eth1Make sure file read as follows for eth1 interface:

DEVICE=eth1
USERCTL=no
ONBOOT=yes
MASTER=bond0
SLAVE=yes
BOOTPROTO=none

Save file and exit to shell prompt.

Step # 3: Load bond driver/module

Make sure bonding module is loaded when the channel-bonding interface (bond0) is brought up. You need to modify kernel modules configuration file:

# vi /etc/modprobe.conf
Append following two lines:

alias bond0 bonding
options bond0 mode=balance-alb miimon=100

Step # 4: Test configuration

First, load the bonding module:
# modprobe bonding
Restart networking service in order to bring up bond0 interface:
# service network restart

Verify everything is working:
# less /proc/net/bonding/bond0Output:

Bonding Mode: load balancing (round-robin)

MII Status: up
 MII Polling Interval (ms): 0
 Up Delay (ms): 0
 Down Delay (ms): 0


 Slave Interface: eth0
 MII Status: up
 Link Failure Count: 0
 Permanent HW addr: 00:0c:29:c6:be:59

Slave Interface: eth1
 MII Status: up
 Link Failure Count: 0
 Permanent HW addr: 00:0c:29:c6:be:6