System Admin Questions

Q: - How are devices represented in UNIX?
All devices are represented by files called special files that are located in /dev directory.

Q: - What is 'inode'?
All UNIX files have its description stored in a structure called 'inode'. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as files and have an associated inode.

Q: - What are the process states in Unix?
As a process executes it changes state according to its circumstances. Unix processes have the following states:

Running : The process is either running or it is ready to run .
Waiting : The process is waiting for an event or for a resource.
Stopped : The process has been stopped, usually by receiving a signal.
Zombie : The process is dead but have not been removed from the process table.

Q: - What command should you use to check the number of files and disk space used and each user's defined quotas?
 repquota

Q: - What command is used to remove the password assigned to a group?
gpasswd –r

Q: - What can you type at a command line to determine which shell you are using?
echo $SHELL

Q: - Write a command to find all of the files which have been accessed within the last 30 days.
find / -type f -atime -30 > filename.txt

Q: - What is a zombie?
Zombie is a process state when the child dies before the parent process. In this case the structural information of the process is still in the process table.

Q: - What daemon is responsible for tracking events on your system?
syslogd

Q: - What do you mean a File System?
File System is a method to store and organize files and directories on disk. A file system can have different formats called file system types. These formats determine how the information is stored as files and directories.

Q: - What does /boot directory contains?
The /boot/ directory contains static files required to boot the system, such as the Linux kernel, boot loader configuration files. These files are essential for the system to boot properly.

Q: - If some one deletes /boot directory from your server, than what will happen?
In that case your server will be in unbootable state. Your Server can’t boot without /boot directory because this directory contains all bootable files

Q: - What does /dev directory contain?
The /dev directory contains all device files that are attached to system or virtual device files that are provided by the kernel.

Q: - What is the role of udev daemon?
The udev demon used to create and remove all these device nodes or files in /dev/ directory.

Q: - What kind of files or nodes /dev/ directory contains and how do I access or see device files?
Block Device Files:-

Block device files talks to devices block by block [1 block at a time (1 block = 512 bytes to 32KB)].
Examples: - USB disk, CDROM, Hard Disk
# ls /dev/sd*

brw-rw----	1 root	root	8,	0 Mar 15  2009 sda
brw-rw----	1 root	root	8,	1 Mar 15  2009 sda1
brw-rw----	1 root	root	8,	2 Mar 15  2009 sda2
brw-rw----	1 root	root	8,	3 Mar 15  2009 sda3
brw-rw----	1 root	root	8,	4 Mar 15  2009 sda4
brw-rw----	1 root	root	8,	16 Mar 15  2009 sdb

Character Device Files:-
Character device files talk to devices character by character.
Examples: - Virtual terminals, terminals, serial modems, random numbers
#ls /dev/tty*

crw-rw----	1 root	root	4,	64 Mar 15  2009 ttyS0
crw-rw----	1 root	root	4,	65 Mar 15  2009 ttyS1
crw-rw----	1 root	root	4,	66 Mar 15  2009 ttyS2
crw-rw----	1 root	root	4,	67 Mar 15  2009 ttyS3

Q: - Tell me the name of device file for PS/2 mouse connection.
/dev/psaux

Q: - Tell me the name of device file for parallel port (Printers).
/dev/lp0

Q: - What does /etc/X11/ directory contains?
The /etc/X11/ directory is for X Window System configuration files, such as xorg.conf.

Q: - What does /etc/skell directory contains?
The /etc/skel directory contains files and directories that are automatically copied over to a new user's home directory when such user is created by the useradd or adduser command. 

Q: - Rembember some Port no?

samba                                     139                  

samba-swat                             901

ftp                                           20 & 21

ssh                                           22

telnet                                       23

nfs                                           2049   

dns                                          53

squid                                       3128   

http                                          80

https                                        443

pop3                                        110

smtp                                        25

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Networking Questions2

What is router?

Router is a device that is used to connect two different networks.

How will you configure ADS?

Start ==> Run ==> DCPROMO
Or
Start==> Configure your server ==> add/Remove a Role

What is ADS?

A central component of the Windows platform, Active Directory service provides the means to manage the identities and relationships that make up network environments.

What if this wizard (ADS) is not running?

Check the network cable it should be plugged
Check root partition it should be in NTFS
Check IP of server it should be configured statically

How will you add a client to server? /
How’s the client join a domain?
What are the client configurations?

On Server
Configure ADS (for example it’s configured with xyz.com)
On Client
Log in form local administrator account
My Computer ==> Properties ==> Computer Name ==> Change
==>Domain ==>xyz.com ==> username Administrator (of xyz.com)
Password xxxxxxxxxxx (of admin of xyz.com)
Welcome to xyz.com ==> Restart the computer

Does it necessary to use administrator account to configure the client?

Not every time but you are required a properly configured user account in domain controller security policy.

ISO stand for?

International standard organization

OSI stand for?

Open System Interconnection

What is full form DHCP and how will you configure it?

Dynamic host configuration protocol
To configure it on Server
Configure your server ==>Add/Remove a role ==>DHCP server ==>complete the wizard
Start ==> Administrative tools ==> DHCP ==>New scope ==> Wizard
Now authorized this server and do activate it
On client
Local area network ==> tcp/ip ==> obtain ip automatically
Obtain DNS automatically

Which OSI layer does IP belong?

P belongs to the Network Layer (layer 3) in the OSI model.

What is a subnet mask?

Subnet mask is a 4 byte (32 bit) number used to identify the sub-network ID and the host ID from an IP address. All the hosts in a sub-network will have the same subnet mask. E.g. 255.255.255.0, 255.255.127.0, 255.255.0.0

Why do we do networking?

For data sharing
To accumulate hardware resource

What are the benefits of networking?

There are lots of advantages from build up a network, but the three big facts are-
File Sharing
From sharing files you can view, modify, and copy files stored on a different computer on the network just as easily as if they were stored on your computer.
Resource Sharing
Resources such as printers, fax machines, Storage Devices (HDD, FDD and CD Drives), Webcam, Scanners, Modem and many more devices can be shared.
Program Sharing
Just as you can share files on a network, you can often also share program on a network. For example, if you have the right type of software license, you can have a shared copy of Microsoft Office, or some other program, and keep it on the network server, from where it is also run

What is network?

A network is basically all of the components (hardware and software) involved in connecting computers across small and large distances.

What is networking?

A process that is describes how the network will connect.

What is meshing?

Meshing generically describes how devices are connected together. It is also the part of topology. There are two types of meshed topologies: partial and full.
In a partially meshed environment , every device is not connected to every other device.
In a fully meshed environment, every device is connected to every other device.
Wireless is the good example of meshing. Wan ( internet is also a good example of meshing where a computer have connectivity with all internet network.)

 
Describe Various Network Type

Local Area Networks Local area networks (LANs) are used to connect networking devices that are in a very close geographic area, such as a floor of a building, a building itself, or a campus environment.

Wide Area Networks Wide area networks (WANs) are used to connect LANs together. Typically, WANs are used when the LANs that must be connected are separated by a large distance.

Metropolitan Area Networks A metropolitan area network (MAN) is a hybrid between a LAN and a WAN.

Content Networks Content networks (CNs) were developed to ease users’ access to Internet resources. Companies deploy basically two types of CNs:
1.Caching downloaded Internet information
2.Distributing Internet traffic loads across multiple servers

Storage Area Networks Storage area networks (SANs) provide a high-speed infrastructure to move data between storage devices and file servers.
Advantage
Performance is fast.
Availability is high because of the redundancy features available.
Distances can span up to 10 kilometers.
Management is easy because of the centralization of data resources.
Overhead is low (uses a thin protocol).
Disadvantage of SANs is their cost.

Intranet An intranet is basically a network that is local to a company. In other words, users from within this company can find all of their resources without having to go outside of the company. An intranet can include LANs, private WANs and MANs,

Extranet An extranet is an extended intranet, where certain internal services are made available to known external users or external business partners at remote locations.

Internet An internet is used when unknown external users need to access internal resources in your network. In other words, your company might have a web site that sells various products, and you want any external user to be able to access this service.

VPN A virtual private network (VPN) is a special type of secured network. A VPN is used to provide a secure connection across a public network, such as an internet. Extranets typically use a VPN to provide a secure connection between a company and its known external users or offices. Authentication is provided to validate the identities of the two peers. Confidentiality provides encryption of the data to keep it private from prying eyes. Integrity is used to ensure that the data sent between the two devices or sites has not been tampered with.

Networking Questions1

How will you register and activate windows?

If you have not activated windows XP, you can do so at any time by clicking the windows Activation icon in the system tray to initiate activation. Once you have activated windows XP, this icon disappears from the system tray.
For registration
Start ==> Run ==> regwiz /r

Where do we use cross and standard cable?

Computer to computer ==> cross
Switch/hub to switch/hub ==>cross
Computer to switch/hub ==>standard

How many pins do serial ports have?

In computer it’s known as com port and could be available in 9pin or 25 pin. On router it have 60 pins.

How will check ip address on 98?

Start ==> Run ==> command ==> winipcfg

How will you make partition after installing windows?

My computer ==> right click ==> manage ==> disk management ==>
select free space ==> right click ==> New partition

What is IP?

It’s a unique 32 bits software address of a node in a network.

What is private IP?

Three ranges of IP addresses have been reserved for private address and they are not valid for use on the Internet. If you want to access internet with these address you must have to use proxy server or NAT server (on normal cases the role of proxy server is played by your ISP.).If you do decide to implement a private IP address range, you can use IP addresses from any of the following classes:
Class A      10.0.0.0    10.255.255.255
Class B       172.16.0.0     172.31.255.255
Class C       192.168.0.0     192.168.255.255

What is public IP address?

A public IP address is an address leased from an ISP that allows or enables direct Internet communication.

What’s the benefit of subnetting?

Reduce the size of the routing tables.
Reduce network traffic. Broadcast traffic can be isolated within a single logical network.
Provide a way to secure network traffic by isolating it from the rest of the network.

What are the differences between static ip addressing and dynamic ip addressing?

With static IP addressing, a computer (or other device) is configured to always use the same IP address. With dynamic addressing, the IP address can change periodically and is managed by a centralized network service

What is APIPA?

Automatic private IP addressing (APIPA) is a feature mainly found in Microsoft operating systems. APIPA enables clients to still communicate with other computers on the same network segment until an IP address can be obtained from a DHCP server, allowing the machine to fully participate on the network. The range of these IP address are the 169.254.0.1 to 169.254.255.254 with a default Class B subnet mask of 255.255.0.0.

What are the LMHOSTS files?

The LMHOSTS file is a static method of resolving NetBIOS names to IP addresses in the same way that the HOSTS file is a static method of resolving domain names into IP addresses. An LMHOSTS file is a text file that maps NetBIOS names to IP addresses; it must be manually configured and updated.

What is DHCP scope?

A scope is a range, or pool, of IP addresses that can be leased to DHCP clients on a given subnet.

What is FQDN?

An FQDN contains (fully qualified domain name) both the hostname and a domain name. It uniquely identifies a host within a DNS hierarchy

What is the DNS forwarder?

DNS servers often must communicate with DNS servers outside of the local network. A forwarder is an entry that is used when a DNS server receives DNS queries that it cannot resolve locally. It then forwards those requests to external DNS servers for resolution.

Which command will you use to find out the name of the pc in networks?

NSLOOKUP [192.168.0.1]
[Ip of target computer]

How will enable sound service in 2003?

By default this service remain disable to enable this service
Start ==> administrative tools ==> service ==> windows audio ==> start up type ==> automatic

How will enable CD burning service in 2003?

By default this service remain disable to enable this service
Start ==> administrative tools ==> service ==> IMAPI CD burning com service ==> start up type ==> automatic

Networking Questions

What are the difference between hub and switch?

Hub is  layer 1 device. It out the signal from all of its port except the one from where its insert. It’s unable to find the collision. Its based to work on single collision and single broadcast domain.
Switch is layer 2 device. It maintains CAM table that store the MAC address of devices attached on its port. CAM table is used to make the forwarding decision. It works on each port collision and single broadcast domain. 

What is layer?

Layer is  fully logical partition of protocol data unit process. Layer defines how information travel form one computer to all over the network.

What is TCP/IP?

It’s  a combination of two protocols TCP and IP. It’s use for reliable data transfer.

What full form of TCP/IP?

Transmission Control Protocol/Internet Protol

What is operating system?

An operating system is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. It provides a platform to application software.

What is the full form of .co.in, .com?

• COM - ".com" stands for "commercial".
• NET - ".net" stands for "network"
• ORG - ".org" stands for "organization"
• INFO - ".info" stands for "information"
• BIZ - ".biz" stands for "business".
• IN - 'IN' stands for India. The 'IN' is a 2-letter country code for India.

What is ring topology?

In a ring topology, device one connects to device two, device two connects to device three, and so on to the last device, which connects back to device one.

Which cable is used in LAN?

Generally we used coaxial and Twisted pair media is used in LAN networking.

What are Difference between STP and UTP?

STP cable is mostly used by IBM; it has an extra cover over each pair.
UTP cable is used in star topology. It has a single cover over all pair.

What is IEEE?

The Institute of Electrical and Electronics Engineers or IEEE (read eye-triple-e) is an international non-profit, professional organization for the advancement of technology related to electricity. It has the most members of any technical professional organization in the world, with more than 365,000 members in around 150 countries.

What is 802.3?

IEEE 802.3 is a collection of IEEE standards defining the physical layer and the media access control (MAC) of the data link layer of wired Ethernet. Physical connections are made between nodes and infrastructure devices hubs, switches and routers by various types of copper or fiber cable.

What is the full form of ping?

PING stand for Packet Internet Grouper 

What is MAC address?

It is the 48 bit hardware address of LAN card. MAC address is usually stored in ROM on the network adapter card and it is unique.

What are the minimum requirements for xp installation?

64MB RAM
1.5GB free HDD space
233MHz minimum processor.

What are 10Base2, 10Base5 and 10BaseT Ethernet LANs?

10Base2— An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with a contiguous cable segment length of 100 meters and a maximum of 2 segments.
10Base5—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling, with 5 continuous segments not exceeding 100 meters per segment.
10BaseT—An Ethernet term meaning a maximum transfer rate of 10 Megabits per second that uses baseband signaling and twisted pair cabling.

What is the difference between an unspecified passive open and a fully specified passive open?

An unspecified passive open has the server waiting for a connection request from a client.
A fully specified passive open has the server waiting for a connection from a specific client.

Explain the function of Transmission Control Block?

A TCB is a complex data structure that contains a considerable amount of information about each connection.

What is a Management Information Base (MIB)?

A Management Information Base is part of every SNMP-managed device. Each SNMP agent has the MIB database that contains information about the device's status, its performance, connections, and configuration. The MIB is queried by SNMP.

What is anonymous FTP and why would you use it?

Anonymous FTP enables users to connect to a host without using a valid login and password. Usually, anonymous FTP uses a login called anonymous or guest, with the password usually requesting the user's ID for tracking purposes only. Anonymous FTP is used to enable a large number of users to access files on the host without having to go to the trouble of setting up logins for them all. Anonymous FTP systems usually have strict controls over the areas an anonymous user can access.

What is a pseudo tty?

A pseudo tty or false terminal enables external machines to connect through Telnet or rlogin. Without a pseudo tty, no connection can take place.

What does the Mount protocol do?

The Mount protocol returns a file handle and the name of the file system in which a requested file resides. The message is sent to the client from the server after reception of a client's request

What is External Data Representation?

External Data Representation is a method of encoding data within an RPC message, used to ensure that the data is not system-dependent.

System Admin Questions 7

Q: - What is LVM Snapshot ?
 An LVM snapshot is an exact copy of an LVM partition that has all the data from the LVM volume from the time the snapshot was created. The big advantage of LVM snapshots is that they can be used to greatly reduce the amount of time that your services/databases are down during backups because a snapshot is usually created in fractions of a second. After the snapshot has been created, you can back up the snapshot while your services and databases are in normal operation.

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

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

Q: - What is the meaning of  Hard & soft mount option in NFS server ?

Hard mount
- If the NFS file system is hard mounted, the NFS daemons will try repeatedly to contact the server. The NFS daemon retries will not time out, will affect system performance, and you cannot interrupt them

Soft mount
- If the NFS file system is soft mounted, NFS will try repeatedly to contact the server until either:

• A connection is established
• The NFS retry threshold is met
• The nfstimeout value is reached

Q: - What is an inode ?
 An inode is a data structure on a traditional Unix-style file system such as UFS. An inode stores basic information about a regular file, directory, or other file system object.

When a file system is created, data structures that contain information about files are created. Each file has an inode and is identified by an inode number (often "i-number" or even shorter, "ino") in the file system where it resides. Inodes store information on files such as user and group ownership, access mode (read, write, execute permissions)

and type of file. There is a fixed number of inodes, which indicates the maximum number of files each filesystem can hold.

Q: - What is the role of udev daemon in Unix ?
udev is the device manager for the Linux 2.6 kernel series. Primarily, it manages device nodes in /dev. It is the successor of devfs and hotplug, which means that it handles the /dev directory and all user space actions when adding/removing devices, including firmware load.

Q: - What is Super Block in Linux/Unix ?
Each file system is different and they have type like ext2, ext3 etc.Further eachfile system has size like 5 GB, 10 GB and status  such as mount status. In short each file system has a superblock, which contains informationabout file system such as:
File system type 

1. Size  

2. Status  

3. Information about other metadata structures

 If this information lost, you are in trouble (data loss) so Linux maintains multiple redundant copies of thesuperblock in every file system. This is very important in many emergency situation,
for example you can use backup copies to restore damaged primary super block.

Following command displays primary and backup superblock location on /dev/sda3:

# dumpe2fs /dev/hda3 | grep -i superblock

Q: - What is the load average of the server and What is an acceptable Server Load Average ?
The load average is the sum of the run queue length and the number of jobs currently running on the CPUs. The three load-average values in the first line of top output are the 1-minute, 5-minute and 15-minute average. (These values also are displayed by other commands, such as uptime, not only top.)
There are a few factors involved to determine the server average load. If your server (s) use dual processors, the acceptable Server Load Average is 2.00. This load is considered "optimal".

Q: - What is Greylisting  ?
Greylisting (or graylisting) is a method of defending e-mail users against spam. A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the email will be accepted. If the mail is from a spam sender, sending to many thousands of email addresses, it will probably not be retried.

Q: - Can we have two apache servers having diff versions? 

Yes, you can have two different apache servers on one server, but they can't listen to the same port at the same time.Normally apache listens to port 80 which is the default HTTP port. The second apache version should listen to another port with the Listen option in httpd.conf, for example to port 81.
For testing a new apache version before moving your sites from one version to another, this might be a good option.You just type www.example.com:81 in the browser window and you will be connected to the second apache  instance. Q: -What do we use for managing hash table collisions?
There are two ways of managing hash table collisions: one is open addressing and the other is separate chaining. The first way the data items are moved from the full array they hash to and their new place is another cell from the array. The second way every element of the array is made from a linked list and in this list the data items are moved.
Q:- What actually means Linux?
Linux is an open source operating system kernel that is behaving better than many others and it has all the required features for a modern and complete operating system: real multitasking, shared libraries, threads, virtual memory, executables, excellent management of memory, device drivers that can be loaded , frame buffering of video or TCP/IP.
Q:- How can we recover a file that was deleted in Linux?
We can see what was the partition where the lost file was located with the pwd (means present work directory) and with the unmount command we can unmount the directory. Then the “debugfs” command will manage and repair the majority of sever errors or bugs from Linux. The entire code is: #debugfs /usr/directory name. the next step is using “Isdel”.
Q:-How can we see the boot messages?
For viewing the boot messages we can use dmesg, a command that prints on the screen the kernel ring buffer messages; the command is to be used just after the boot sequence. The syntax of a ring buffer is like this: dmesg [options]. If dmesg is called with no options the messages from the kernel will be written to the standard output.
Q:- How do we give a shadow password?
Shadow passwords are given using pwconv command and their purpose is the increase in system security. The file /etc/shadow gets created with that command and modifications are made to the passwords, they will be replaces with “x” in /etc/passwd file.
Q:-In what way are home directories different from working directory?
The directory over which we as users have the control and when we log in it is the working directory. But the current user working directory is not necessarily the home directory.
Q:-What separates Unix Linux?
The graphics are different, Linux has more commands, Linux has more user-friendly features than Unix, Linux is versatile and independent while Unix requires special machine for installation, kernel and file system is different.


Q:-Which is the required command for checking the file system?
For checking the disk integrity and file system the command used is fsck.