Linux General Interview Preparation Guide

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