Saturday, May 18, 2013

What is grep command: linux

   grep command is used to search a particular pattern in the given input.
for example in snap shot.
first we display content using cat just to check file content

$cat  filename

then give any word which you want to search

$grep "string-name" filename

this displays the entire line in which this string-name appears
if you want to search case insensitve word then just put option -i

$grep -i "string-name" filename

if some word is not found in file then it displays nothing

for  more details about grep you can go to manual page entry by running

$man grep

Sunday, March 3, 2013

I Accidentally Removed "/usr/sbin" : How to recover it in Linux

whenever you run rm command be carefull.first run ls and see what are the files and folders going to be deleted.then only run rm.rm * deletes all the contents in current directory.which may destroy your system.

some possibilities to recover deleted directory /usr/bin :it contains all system binary files.

1> go to rescue mode and try to restore. or upgrade using CD/DVD.
2>try copying the same directory /usr/sbin from some other operating system(prefer the same Operating System and (if possible)same version )

to copy the directory
1> go to terminal during system boot
2>run su
3>run cp xyz /usr/
where xyz is path for the directory sbin

Thursday, February 28, 2013

How to Count no. of files/directory in a directory

Steps are mentioned in snapshot , To count no of files/directory in a directory
> go to directory (here DistSys) in which you have to find no. of files and folders
>now run ls command and pipe it's output to command " wc -l "

cd DistSys
ls | wc -l

which gives a number say 11 ,which means directory DistSys contains 11 files or folders.

Thursday, February 21, 2013

How to create your own command in linux

If you want to add your own command in linux operating system then

write any script.for example i want to add command which displays present

working directory with list of files or folders under it.then type following in gedit or any editor


echo "present directory is `pwd` "

echo "files are `ls` "

save it with any name say pwdfiles

now make it executable

chmod +x pwdfiles

now copy it to /usr/bin directory.

cp pwdfiles /usr/bin/

Sunday, February 17, 2013

How to set Default Boot Option to Windows OS or Vista

To set Default Boot option to any operating system say xyz you need to edit grub.cfg file
which resides under /boot/grub directory.
boot screen will look like this...

and each options are numbered from 0 to n( 7 here )

Ubuntu,with linux 2.6.35-23-generic =0
Ubuntu,with linux 2.6.35-23-generic(recovery mode)=1
Ubuntu,with linux 2.6.35-22-generic =2
Ubuntu,with linux 2.6.35-22-generic(recovery mode)=3
Memory test (memtest86+) =4
Memory test(memtest86+,serial console 115200) =5
Windows Vista (loader) (on /dev/sda1) =6
Windows Vista (loader) (on /dev/sda2) =7

now in grub.cfg file set default="7" to keep default boot windows vista
and to keep ubuntu as default boot
set default="0"

Wednesday, February 13, 2013

Installation Error, “Unable to lock the administration directory”

Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable)
this error occurs during installation of software when lock file is being modified
by some other process or when you are trying to install two different software at
the same time so get rid of this problem
1>install one software at a time

but the problem still persist then

run the following command

rm /var/lib/dpkg/lock

this command removes lock over lock file.location of the file may be different in
different linux operating system

How to install packages in ubuntu

Before you install any package in ubuntu you need to run three commands
1> sudo dpkg --configure -a
2> sudo apt-get update
3> sudo apt-get upgrade
you have to execute these commands in sequence.after executing these commands
go to synaptic software center in ubuntu and select any package which you want to install.