Linux General Interview Questions And Answers

Every type of applications can be run on Linux, which are
run on other OS like Microsoft, Apple & so on. all
applications of desktop or server related are run according
to flavor of that Linux.

we need to use the command #ftp server name in he client
machine then it asks user name and password ,for user name
use anonymous and password is empty .then it takes it to
FTP> mode in that type ls . it shows what are the files
shared via FTP in that particular server.if we want to see
which are the files shared via FTP in the client use FTP>!ls.

Linux is a parameter driven system. Kernel parameters used
for
system configuration are found in /proc/sys/kernel, where
you
will find an individual file for each configuration
parameter.
Because these parameters have a direct effect on system
performance and viability, you must have root access in
order to
modify them.

Occasionally, a prerequisite to a package installation
requires
the modification of kernel parameters. Since each parameter
file contains a single line of data consisting of either a
text
string or numeric values, it is often easy to modify a
parameter
by simply using the echo command:

echo 2048 > /proc/sys/kernel/msgmax

The aforementioned command will set the value of the msgmax
parameter to 2048.

Linux also provides the sysctl command to modify kernel
parameters at runtime. Sysctl uses parameter information
stored
in a file called /etc/sysctl.conf. If, for example, we
wanted to
change the value of the msgmax parameter as we did above,
but
this time using sysctl, the command would look like this:

$ ls -altr /dev/
brw-rw---- 1 root disk 8, 6 2010-07-26 14:20
sda6 --> block device
crw-rw---- 1 root root 10, 59 2010-07-26 14:21 device-
mapper --> character device
Answer :

Character devices deal with IO on a character by character
basis. The most obvious example is a keyboard, where every
key generates a character on the device. The mouse is
another. Every motion or button click sends a character to
the /dev/input/mouse0 device. To test it out do
$cat /dev/input/mouse0 , then move your mouse (see what
happens)

Block devices read data in larger chunks or blocks. Data
storage devices, such as IDE hard drives (/dev/hd), SCSI
hard drives (/dev/sd), and CD-ROMs (/dev/cdrom or /dev/sr0)
are block devices. IO interactions with block devices
transact with chunks of data (blocks), which allows large
quantities of data to be moved back and forth more
efficiently(unlike character device). eg: $df -h

Generically, block devices can be mounted and are cached,
and char devices are for communication devices, aren’t
cached nor block aligned, and can’t be mounted.

Specifically, /dev/scd* (block) are for cdroms, providing
the block access and commands for ejecting, closing,
playing, etc.

The corresponding character device for the cdrom is /dev/sg1

There are 3 types of user accounts in linux.They are:
1> System Users
2> Root User(Administrator)
3> Other Users(Normal User)

In linux, Uid from 1 to 500 has been reserved for system
users,these are the default users of linux,so if anyone try
to assign Uid 500 to normal user then it wil give the error.

NFS is used to share a directory in a network of Linux
machines .
configuration of NFS:
NFS SERVER:
yum install nfs*
vim /etc/exports -> press enter then type
/directory name *(rw,sync)
save -> wq
service portmap restart
service nfs restart
chkconfig portmap on
chkconfig nfs on

Another Linux PC:-
mount -t nfs (ipaddress of nfs server):/muj /opt
cd /opt
ls -> it will display all the content of the directory

SAMBA SERVER :-samba is an application is used to integrate
Linux system into windows it mostly commonly used in file
server for windows machines.
ex:- we can share a directory or file from Linux machine to
windows machine or you can share same directory from Linux
machine to Linux machine.
FTP SERVER :-ftp server is used to share a directory in a
network of Linux machine only.

kerberos is one of the scheme of digital signature.it is
used as an authentication scheme.it is needed for the
security of messages.

The main purpose of NIS is centralizing the authentication
database.

For ex:
Usually when a user try to login to the machine it will
contact the passwd, shadow and group files for user’s
authentication, in case of user requires to access his/her
account across the network we need to update users
information all these files in each machine in the network.
It is bit tricky to organize multiple users’ info in all
the machines in the network.

NIS server will act as central server for user
authentication and all other machines will contact the NIS
server for the user’s authentication info.

Make sure all the machines in your network should be in the
same domain. NIS will work only in single domain.

yah it is possible to reduce the size of already created
partition ......by LVM reduce ok

it indicate that the partion is being used by system.

i)which port which service is running

netstat -tulpn

lists all the processes running,the service name with the upd or tcp port, and the socket information

ii)/etc/services is the general port numbers and the serices that are associated with the ports where are netstat shows the running serviced,ports,the application name associated and the socket info too.

scp- copying files using ssh(secure copy) of the selected files from the source host to destination host and when finished closes the scp application

rsync- you need to setup the key authentication between the
servers that do the synchronization (to destinatio system to have the source public key in destination host's authorized_keys) and copies the files from source to destination whenever there is a change(addition/deletion) in the sounce directory .. can be pull/push/both

Yes surely we can remove the grub password by booting the
linux server in rescue mode edit the grub.conf file
Method 1
I)chmod /mnt/sysImage
ii)Edit the grub.conf file and remove the passwd line from
the file. Save the file and exit change the password md5 in
the grub line and set your own password.
iii)Once your machine reboots, you will be able to start
your Linux OS in the usual manner

ext2 : It was only the default file sysyem upto 7.1 redhat
version
->less speed,secure and doesnt supports journaling

ext3 : this was from the 7.2 redhat version
->more speed,secure n supports journaling compared to ext2

Journaling : This is one of the default feature of ext3
which provides multipls functions like data avaliability
across improper shut downs,esay transmission between the
file systems and speed etc...

We can open .pdf file with the help of CUPS-PDF package.

Install CUPS-PDF package and use pdf file.

try openoffice

ifconfig -a|grep <ni card no>

The difference between Samba and NFS is primarily that Samba
uses the SMB (aka Lanmanager) protocol which is considered
"standard" for PCs (Windows and OS/2 both have built in
support for it, a free client is also available for DOS, I'm
not sure about MacOS), whereas NFS uses its own protocol
(usually just called "NFS") which is not commonly available
for PCs (NFS clients do exist for operating systems other
than UNIX/Linux, but they're
usually neither free or easy to setup).

Samba's SMB protocol allows the server machine to handle
authentication, so it can decide what files the client has
access to based on the particular machine and user
connecting. NFS by default trusts all client machines
completely (it's really not intended to share files to
unsecured workstations) and lets the client machines handle
authentication all on their own (once an NFS server has been
told to accept connections from a client machine the client
does not require any further server-side authentication, and
can do anything it wants with the filesystem NFS gives it
access to).

SMB does not (directly) support UNIX style file permissions,
so it is probably a bad idea to routinely use it to map
filesystems between machines which expect this information
to be present and mutable, NFS of course supports all
standard UNIX file information (this also means that SMB is
fine for accessing a UNIX filesystem from a Windows machine,
but not so hot the other way around).

Network File System (also known as NFS) is a protocol
developed by Sun Microsystems. It allows a user on a
computer to access files that are sent across a network –
similar to the way one accesses local storage. It is most
common in systems with a similar composition to the UNIX system

Samba is a re-implementation of SMB/CIFS networking protocol
(meaning a re-imaging of Server Message Block – or Common
Internet File System). As with the NFS, Samba runs most
naturally on a system with qualities not unlike those of the
UNIX systems. It comes standard with almost every
distribution of Linux, and is used as a basic system service
on all other UNIX-based systems.
a. NFS is a protocol that allows a user to access files over
a network; Samba is essentially a re-imaging of the Common
Internet File System.
b. NFS has four versions, the newest of which includes a
stateful protocol; Samba has multiple versions, the latest
of which allows file and print sharing between multiple
computers.

rpm is packagemanager while yum is a frontend,rpm can be
installed with the help of yum

RPM Package Manager” (formerly “Red Hat Package Manager”),
and YUM, “Yellow dog Updater,
Package Management System Installer
Typically part of the operating system. Each product comes
bundled with its own installer.
Uses a single installation database. Performs its own
installation, sometimes recording information about that
installation in a registry.
Can verify and manage all packages on the system. Only works
with its bundled product.
Single package management system vendor. Multiple installer
vendors.
Single package format. Multiple installation formats.

7 types of files

- regular
d directory
l symbolic link
c character special file (hardware files)
b block special file (files to communicate with hardware )
p named pipe (to pass data between process )
s socket ( mechanism for inter-process communication

We can make free space in hard disk and install new OS in
that free space.
Another way can be by installing Vm Manager an then
installing new OS on it.

Once system powered on, first thing will be POST check i.e
power on self test.

Then BIOS loads the MBR from the disk into RAM. Then, the
BIOS executes the MBR code. now boot loader list the number
of OS installed in to the system. select the OS wants to be
boot once OS selected initial RAM disk (temporary root file
system) are loaded into memory. When the images are loaded,
the boot loader passes control to the kernel image and the
kernel is decompressed and initialized.At this stage, the
boot loader checks the system hardware, enumerates the
attached hardware devices, mounts the root device, and then
loads the necessary kernel modules. When complete, the first
user-space program (init /sbin/init) starts, which will
looks file /etc/inittab to find the which runlevel kernel
will be boot then it will be check /etc/rc?.d (? means
runlevel got from inittab file)and check every script which
starts with name S will start in to that level once
completed, initrd(temporary root file system) will be
unmounted and mount the physical filesystem and loads the
main kernel then login prompt will be available.

yes we can but why to do that fedora is made up of red hat
so there is no such difference between them

1: mkdir /kaka

2: open vim /etc/fstab and mount it permently.

3: mount -t vfat /dev/hda1 /kaka

4: /dev/hda1...... drive name.