Linux Tips - Tricks

Hide Navigation Bar of the Blog

2009-07-08T11:28:00.001+05:30

Add following code in the HTML code where other style code is written,
Use Edit HTML in custmization

#navbar-iframe {
             height:0px;
             visibility:hidden;
             display:none;
       }

Lost User Password

2009-06-26T17:02:00.000+05:30

$ su
<>
# passwd username

Commands giving user information

2009-06-18T14:07:00.000+05:30

* w --- tells you who's logged in, and what they're doing. Especially useful: the 'idle' part. This allows you to see whether they're actually sitting there typing away at their keyboards right at the moment.
* who --- tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.
* finger username --- gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'.
* last -1 username --- tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.
* talk username --- lets you have a (typed) conversation with another user
* write username --- lets you exchange one-line messages with another user
* elm --- lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile).

Message on the terminal.

2009-06-11T16:05:00.001+05:30

Mesg X blinking on all your consoles.
Add these in ~/.profile

mesg X
[ `who -T |grep "$LOGNAME\ *+" |wc -l` -ge 1 ] && mesg X

Linux command similar to history, list last used commands.

2009-05-28T13:05:00.000+05:30

accton, lastcomm - accouting on and last command. This is
a way to monitor users on your system. As root, you
would implement this as follows:

$ accton -h
Usage: accton [-hV] [file]
[--help] [--version]

The system's default process accounting file is /var/account/pacct.

Note the default file location is /var/account/pacct so we'll turn
it on system wide with the following command.

$ accton /var/account/pacct

Now take a look at this file. It will grow. To see command that
are executed, use the lastcomm command.

$ lastcomm

The above command gives output for all users. To get the data
for user "chirico" execute the following command:

$ lastcomm --user chirico

You can also get a summary of commands with sa.

[chirico@big ~]$ sa
30 5.23re 0.00cp 10185k
11 4.83re 0.00cp 8961k ***other
8 0.13re 0.00cp 19744k nagios*
4 0.00re 0.00cp 2542k automount*
3 0.00re 0.00cp 680k sa
2 0.13re 0.00cp 17424k check_ping
2 0.13re 0.00cp 978k ping

To turn off accounting, execute accton without a filename.

$ accton

Display all system settings or configirations.

2009-05-28T12:57:00.001+05:30

[root@vikas Desktop]# getconf HOST_NAME_MAX
64
[root@vikas Desktop]#

Query all system settings with
getconf -a

List of rpms with size & name in order

2009-05-28T12:37:00.001+05:30

rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n

To view rpm file contents
rpm -qlp file-package.name.rpm

To get info about rpm package itself
rpm -qip file-package.name.rpm

To extract or open rpm file in current directory:
rpm2cpio file.rpm | cpio -idmv

How to calculate subnet mask?

2009-05-28T11:44:00.000+05:30

whatmask - This is a subnet mask notation conversion tool. Or a
Tool for calculating available host address ranges with CIDR
notation input.

[root@vikas Desktop]# whatmask 192.168.4.0/24

------------------------------------------------
TCP/IP NETWORK INFORMATION
------------------------------------------------
IP Entered = ..................: 192.168.4.0
CIDR = ........................: /24
Netmask = .....................: 255.255.255.0
Netmask (hex) = ...............: 0xffffff00
Wildcard Bits = ...............: 0.0.0.255
------------------------------------------------
Network Address = .............: 192.168.4.0
Broadcast Address = ...........: 192.168.4.255
Usable IP Addresses = .........: 254
First Usable IP Address = .....: 192.168.4.1
Last Usable IP Address = ......: 192.168.4.254

[root@vikas Desktop]#

if whatmask command is not found,
just do
yum install whatmask

How to create a sequence? seq command

2009-05-28T11:31:00.001+05:30

-f -- format

[root@vikas ~]# seq -f "vikas%03g" 5
vikas001
vikas002
vikas003
vikas004
vikas005
[root@vikas ~]#

Seq commnd. How to print sequence of numbers using linux command?

2009-05-28T11:03:00.002+05:30

seq - print a sequence of numbers

$seq 10
$seq -s "+" 10
$seg -s "+" 10 | bc

e.g
Factorial using linux command

seq -s "*" 5 | bc

Input using dialog command or inputing in script using input box

2009-05-27T16:38:00.002+05:30

Script
----------------------------------------------------------------------------
dialog --title "Input Box" --inputbox "Enter your name" 8 60 2>/tmp/inputTmp.$$
sel=$?
name=`cat /tmp/inputTmp.$$`

case $sel in
0) echo "Hello $name" ;;
1) echo "Cancel Pressed" ;;
255) echo "ESC key pressed" ;;
esac

rm -f /tmp/inputTmp.$$

Dialog command example, how to make alerts in script?

2009-05-27T16:34:00.002+05:30

dialog display dialog boxes from shell scripts

e.g

dialog --title "You Title" --yesno "\nDo you want to do this" 7 40
sel=$?
case $sel in
0) echo "You Clicked Yes";;
1) echo "You Clicked No";;
255) echo "Canceled by user by pressing ESC key";;
esac

Some Command Line / Terminal Tips....

2009-05-12T13:19:00.003+05:30

Key or key combination Function

Ctrl+A Move cursor to the beginning of the command line.

Ctrl+C End a running program and return the prompt,

Ctrl+D Log out of the current shell session, equal to typing exit or logout.

Ctrl+E Move cursor to the end of the command line.

Ctrl+H Generate backspace character.

Ctrl+L Clear this terminal.

Ctrl+R Search command history,

Ctrl+Z Suspend a program,

ArrowLeft and ArrowRight --- Move the cursor one place to the left or right on the command line, so that you can
insert characters at other places than just at the beginning and the end.

ArrowUp and ArrowDown -- Browse history. Go to the line that you want to repeat, edit details if necessary,
and press Enter to save time.

Shift+PageUp and Shift+PageDown --- Browse terminal buffer (to see text that has "scrolled off" the screen).

Tab -- Command or filename completion; when multiple choices are possible, the system
will either signal with an audio or visual bell, or, if too many choices are possible,
ask you if you want to see them all.

Tab Tab -- Shows file or command completion possibilities.

IP Address Classes

2009-05-05T10:54:00.001+05:30

The address class determined the potential size of the network. The class of an address specified which of the bits were used to identify the network, the network ID, or which bits were used to identify the host ID, host computer. It also defined the total number of hosts subnets per network. There were five classes of IP addresses: classes A through E.
Class A: Class A addresses are specified to networks with large number of total hosts. Class A allows for 126 networks by using the first octet for the network ID. The first bit in this octet, is always set and fixed to zero. And next seven bits in the octet is all set to one, which then complete network ID. The 24 bits in the remaining octets represent the hosts ID, allowing 126 networks and approximately 17 million hosts per network. Class A network number values begin at 1 and end at 127.

Class B: Class B addresses are specified to medium to large sized of networks. Class B allows for 16,384 networks by using the first two octets for the network ID. The two bits in the first octet are always set and fixed to 1 0. The remaining 6 bits, together with the next octet, complete network ID. The 16 bits in the third and fourth octet represent host ID, allowing for approximately 65,000 hosts per network. Class B network number values begin at 128 and end at 191.

Class C: Class C addresses are used in small local area networks (LANs). Class C allows for approximately 2 million networks by using the first three octets for the network ID. In class C address three bits are always set and fixed to 1 1 0. And in the first three octets 21 bits complete the total network ID. The 8 bits of the last octet represent the host ID allowing for 254 hosts per one network. Class C network number values begin at 192 and end at 223.

Class D and E: Classes D and E are not allocated to hosts. Class D addresses are used for multicasting, and class E addresses are not available for general use: they are reserved for future purposes.

Class Leftmost bits Start address Finish address
A 0xxx 0.0.0.0 127.255.255.255
B 10xx 128.0.0.0 191.255.255.255
C 110x 192.0.0.0 223.255.255.255
D 1110 224.0.0.0 239.255.255.255
E 1111 240.0.0.0 255.255.255.255

What is 127.0.0.1

2009-05-05T10:52:00.001+05:30

127.0.0.1 is the standard IP address used for a loop back network connection.
This means that if you try to connect to 127.0.0.1, you are immediately looped back to your own machine.

If you telnet, ssh, ftp, etc... to 127.0.0.1, you are connected to your own machine.
In other words, 127.0.0.1 is you.
Another name for 127.0.0.1 is localhost.

Configuring FreeNX Server on linux manchine & accessing it form Windows.

2009-04-29T12:59:00.002+05:30

Download rpms. 1 links is here
http://www.nomachine.com/download-package.php?Prod_Id=718

Install all three Server, client, node
rpm -ivh rpmName

use -- yum install freenx nx
yum install openssh-server

User nx commands
cp /usr/libexec/nx/nxloadconfig /usr/NX/bin
/usr/libexec/nx/nxsetup --install --setup-nomachine-key
/usr/libexec/nx/nxserver --status
--restart [--start]

/usr/libexec/nx/nxserver --useradd root
/usr/libexec/nx/nxserver --passwd root

/usr/NX/bin/nxserver --keygen

On windows install NX client from EXE
[From Linux]
cat /var/lib/nxserver/home/.ssh/client.id_dsa.key

Copy the text you get and in your NX client, on your login dialog box go to:
Configure > General Tab > Key

Configure other things and login.
SSH must be ruuing on linux. Turn off the firewall.

How to start and stop Apache

2009-04-24T10:49:00.002+05:30

[use 'service httpd' ] OR ['apachectl' if installed]

[Here are some exapmles]

[root@vikas ~]# service httpd start
Starting httpd: [ OK ]
[root@vikas ~]# apachectl stop
[root@vikas ~]# service httpd status
httpd dead but subsys locked
[root@vikas ~]# apachectl start
[root@vikas ~]# service httpd status
httpd (pid 3055 3054 3053 3052 3051 3050 3049 3048 3047) is running...
[root@vikas ~]# apachectl stop
[root@vikas ~]# service httpd status
httpd dead but subsys locked
[root@vikas ~]# service httpd status
httpd dead but subsys locked
[root@vikas ~]# service httpd stop
Stopping httpd: [FAILED]
[root@vikas ~]# service httpd status
httpd is stopped
[root@vikas ~]# apachectl start
[root@vikas ~]# service httpd status
httpd (pid 3145 3144 3143 3142 3141 3140 3139 3138 3137) is running...
[root@vikas ~]# apachectl stop
[root@vikas ~]# service httpd status
httpd is stopped
[root@vikas ~]#

# What does apachectl do? - It sends a SIGUSR1 for a restart, and starts the apache server if it’s not running.
# How do you check for the httpd.conf consistency and any errors in it? - apachectl configtest

[root@vikas ~]# apachectl configtest
Syntax OK
[root@vikas ~]#

Finding & deleting backup files, log files

2009-04-23T16:50:00.001+05:30

Deleting *~ .log
find $PWD $ -name \*~ -or -name \*.o -or -name \*.log -or -name \*\#$ -exec rm -f {} \;

ZIP
find $PWD $ -name \*.tex -or -name \*README\* -or -name \*readme\* $ -exec gzip -9 {} \;

How to know which binary file contains a particular function

2009-04-23T16:45:00.002+05:30

[cd to dir where all binaries are]
for i in *
do echo $i;
nm $i | grep FUN_NAME ;
done

How to make rpms of source code in linux

2009-04-23T11:57:00.002+05:30

[Here is an example to make rpms of sipx source code (Fedora / CentOS)]

STEP 1: In .spec file modify 'Release: 013143' link this, a umber from SVN-VERSION file.

STEP 2: Make tar.gz of your source code. [Here i have sipxconfig-3.10.2/ folder of sipx config code]
$ tar -cvf sipxconfig-3.10.2.tar.gz sipxconfig-3.10.2/
Above command will make sipxconfig-3.10.2.tar.gz file.

STEP 3: Copy sipxconfig-3.10.2.tar.gz to /usr/src/redhat/SOURCES/

STEP 4: Run this command from terminal as root
$ cd sipxconfig-3.10.2/
$ rpmbuild -ba sipxconfig.spec

[This will make appropriate rpms of the source code. You can find them at /usr/src/redhat/RPMS/i386/ ]

Stop being pinging by any host

2009-04-16T15:35:00.002+05:30

Edit /proc/sys/net/ipv4/icmp_echo_ignore_all
[root@vikas ]# echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all
[By doing this no body can ping you]

or

EDIT sysctl.conf
add these lines:
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.icmp_echo_ignore_all=1
[check]
sysctl -p

Know about you Linux OS

2009-04-16T15:34:00.000+05:30

[root@vikas ~]# lsb_release -a
LSB Version: :core-3.1-ia32:core-3.1-noarch:graphics-3.1-ia32:graphics-3.1-noarch
Distributor ID: Fedora
Description: Fedora release 8 (Werewolf)
Release: 8
Codename: Werewolf

How to block all hosts entering through SSH over TCP

2009-04-16T15:33:00.003+05:30

Add a line in file
# /etc/hosts.deny
sshd: ALL

OR give IP rather than ALL

OR to allow

edit file /etc/hosts.allow and add line
sshd: ip1, ip2

clear terminal using echo command

2009-04-15T13:56:00.002+05:30

[clear the terminal]
echo -e "\033c"

[move cursor to 1st line]
echo -e "\033[1;5r"

Installing PUNJABI, HINDI fonts on centOS

2009-04-15T11:14:00.003+05:30

Step 1. Download Punjabi or Hindi (.ttf) fonts
For examples - http://tdil.mit.gov.in/download/openfonts.htm
Download HINDI fonts from here - janahindi.zip
Can download from other locations.....
http://www.sikhnet.com/Gurmukhi-Fonts

Step 2. Extract .ttf file and copy it
in folder /usr/share/fonts/hindifont
If punjabi copy to it -- /usr/share/fonts/punjabifont

Step 3. Edit xfs config file so that system can find the fonts.
edit file /etc/X11/fs/config

Add line, at the end of catalogue section
/usr/local/share/fonts/hindifont,
/usr/share/fonts/punjabifont,

Step 4. Set the directory as font container, run these command from terminal
$ cd usr/share/fonts/hindifont
$ ttmkfdir -o fonts.scale
$ mkfontdir
$ fc-cache

Similarly for Punjabi fonts..

Step 5. Restart you xfs server to make these changes effective.
$ service xfs restart

Chnage every files name to lowercase in current folder

2009-04-15T11:09:00.000+05:30

for i in * ; do
[ -f $i ] && mv -i $i `echo $i | tr ‘[A-Z]‘ ‘[a-z]‘`;
done;

Get file permissions in octat using stat command

2009-04-13T11:15:00.002+05:30

whatis stat
stat - display file or file system status
stat - get file status

$stat -c '%a %n' *
[root@vikas pic]# stat -c '%a %n' *
644 121670133471emzSU.jpg
644 1.gif

[other valid options are]
Valid format sequences for file systems:

%a Free blocks available to non-superuser
%b Total data blocks in file system
%c Total file nodes in file system
%d Free file nodes in file system
%f Free blocks in file system
%C - Security context in SELinux
%i File System ID in hex
%l Maximum length of filenames
%n File name
%s Block size (for faster transfers)
%S Fundamental block size (for block counts)
%t Type in hex
%T Type in human readable form

Set / Reset a password to vi file.

2009-04-10T11:14:00.004+05:30

[Set a password]

$vim -x filename

[This will prompt you the key]

[To Change or Delete the password, open file]

$vim filename

[Enter password]
[now edit file & type as below]

:set key=newpassword

[save using :wq & this will reset the password]
[If you use blank password here this will delete the password]

Creating repo of sipX rpms using comps.xml and then writing to dvd

2009-04-01T12:24:00.002+05:30

1) #CREATE REPO IF RPMS ARE ADDED
#Write the name of rpms in ks.cfg and in comps.xml

#CREATE REPO IF RPMS ARE CHANGED no need to write in files
#changed dir to inside folder get init int cd folder if cd has all teh material

createrepo --baseurl="media://1195929637.060433" -g repodata/comps.xml .

#media is wriiten .diskinfo [use media of centos CD]

#if images are changed

mkcramfs stage2/ stage2.img

this will create img file. change with th e existing.

2) changed dir to outside folder i.e cd is the folder where all the material is.

mkisofs -R -J -T -no-emul-boot -boot-load-size 4 -boot-info-table -V "Coralpbx 3.4" -A "Created on 05/03/2009" -P "Coral" -p "Coral" -b isolinux/isolinux.bin -c isolinux/boot.cat -x "lost+found" -o coralpbx.iso cd

-o path of the iso file

3) To write a dvd / right click on iso file and select on "write to disc"

#images path in the stage dir. Change the required images here.
/root/Desktop/stage2/usr/share/anaconda/pixmaps

Install GNOME KDE on centOS

2009-03-31T17:36:00.000+05:30

To install Gnome Desktop type this
yum groupinstall "X Window System" "GNOME Desktop Environment"

and for KDE Desktop
yum groupinstall "X Window System" "KDE (K Desktop Environment)"

Process ID, User ID

2009-03-31T14:33:00.003+05:30

[Process ID]
echo $$

[User ID]
echo $UID
id
id -nu
id -u

----------------------------

echo $_ # Just called /bin/bash to run the script.

ls >/dev/null # no output from command.
echo $_ # ls

ls -al >/dev/null # no output from command.
echo $_ # -al (last argument)

$ !! # last command
$ ![any char] #last command with that character

pop-up using the linux command

2009-03-30T16:37:00.001+05:30

xmessage - display a message or query in a window (X-based /bin/echo)

xmessage abc

How to trun off - on monitor using linux command

2009-03-30T16:28:00.005+05:30

$xset dpms force off
$xset -dispaly:0 dpms force suspend
$xset -dispaly:0 dpms force off
$xset -dispaly:0 dpms force on
To control Energy Star (DPMS) features:
-dpms Energy Star features off
+dpms Energy Star features on
dpms [standby [suspend [off]]]
force standby
force suspend
force off
force on
(also implicitly enables DPMS features)
a timeout value of zero disables the mode

[to on after 1 min.]
$echo "xset -dispaly:0 dpms force on" | at "NOW + 1 minutes"
$echo "xset dpms force on" | at "NOW + 1 minutes"

shred - linux command to delete file

2009-03-25T10:49:00.002+05:30

Deletes a file securely by overwriting its contents
shred -v filename (replace filename with your specific file)
The -v option is useful since it provides extra view of what exactly the shred tool is doing while you wait. On especially BIG files this could take a bit of time. The result is that your file is so thoroughly deleted it is very unlikely to ever be retrieved again. This is especially useful when trying to zap important server related files that may include confidential information like user names or hidden processes.

[root@vikas Desktop]# whatis shred
shred (1) - overwrite a file to hide its contents, and optionally delete it
[root@vikas Desktop]#

System Memory used total or by a process

2009-03-07T17:05:00.003+05:30

VMSTAT
root@vikas ~]# whatis vmstat
vmstat (8) - Report virtual memory statistics
[root@vikas ~]# vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 204976 18444 4732 154720 3 5 120 49 178 313 8 2 88 2 0
[root@vikas ~]# vmstat 1 2
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 204976 17948 4744 154724 3 5 120 49 178 313 8 2 88 2 0
0 0 204976 17804 4744 154724 0 0 0 0 4 1050 2 1 97 0 0

FREE

[root@vikas ~]# whatis free
free (1) - Display amount of free and used memory in the system
free (3p) - free allocated memory
free [malloc] (3) - Allocate and free dynamic memory

free -m
free -m -s 5

PMAP
[root@vikas ~]# whatis pmap
pmap (1) - report memory map of a process
[root@vikas ~]#pmap pid

PS
lists all processess.
$ ps aux

[This will show memory% and process]
ps aux | awk {'print $4 " --" $11'}
ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | sort -nr

TOP
[root@vikas ~]# whatis top
top (1) - display Linux tasks
[root@vikas ~]# top -u root
top -p 25714
top -n 2 -p 25714
top -b
[top 10 processes]
top -d 1 | head -n 17 | tail -n 11

d-delay p-pid n-iterations u-user

[root@vikas ~]# top -d 1 -n 1 | grep firefox |awk {'print $11 "\t" $13'}
30.2 firefox-bin
[root@vikas ~]#

Making a png of "text" using convert command

2009-03-06T17:15:00.000+05:30

[root@vikas Desktop]# convert -size 800x400 xc:white -font Times-Roman -pointsize 100 -fill red -annotate +120+150 "Anal Pandey" -fill black -annotate +170 +150 +repage anal.png
[root@vikas Desktop]# convert -size 800x400 xc:white -font Times-Roman -pointsize 100 -fill red -annotate +120+150 "Vikas Sharma" -fill black -annotate +170 +150 +repage vikass.png
[root@vikas Desktop]# convert -list type
Bilevel
ColorSeparation
ColorSeparationMatte
Grayscale
GrayscaleMatte
Optimize
Palette
PaletteBilevelMatte
PaletteMatte
TrueColorMatte
TrueColor
[root@vikas Desktop]# convert -list color
yellow1 rgb(255,255,0) X11
yellow2 rgb(238,238,0) X11
yellow3 rgb(205,205,0) X11
yellow4 rgb(139,139,0) X11
YellowGreen rgb(154,205,50) SVG X11 XPM
[root@vikas Desktop]#

Hash command

2009-03-06T16:47:00.001+05:30

[root@vikas ~]# whatis hash
hash (1p) - remember or report utility locations
hash [builtins] (1) - bash built-in commands, see bash(1)
Hash::Util (3pm) - A selection of general-utility hash subroutines
[root@vikas ~]#
[root@vikas ~]# hash
hits command
1 /bin/egrep
3 /usr/bin/whatis
2 /usr/bin/yum
2 /bin/ls
2 /usr/bin/clear
[root@vikas ~]#

function command in terminal

2009-03-06T16:44:00.002+05:30

function name [enter]
[then enter all statements with in { } ]

[then write the function name in terminal for output]

[root@vikas ~]# function vik
> {
> echo "vik fun"
> }
[root@vikas ~]# vik
vik fun
[root@vikas ~]# vik
vik fun
[root@vikas ~]#

Script using for

2009-03-06T11:59:00.002+05:30

#/bin/bash
# Enter some string as command line argument
star () {
str="$@"
len=$((${#str}+4))
for i in $(seq $len); do echo -n '*'; done;
echo; echo "* "$str" *";
for i in $(seq $len); do echo -n '*'; done;
echo
}

hash_ () {
str="$@"
len=$((${#str}+4))

for i in $(seq $len); do echo -n '#'; done;
echo; echo "# "$str" #";
for i in $(seq $len); do echo -n '#'; done;
echo
}

if [ $# = 0 ] ; then
star "You dont have entered string."
else
star "$*"
hash_ "$*"
fi

All in linux IF ( conditions )

2009-03-05T12:42:00.000+05:30

* -b file = True if the file exists and is block special file.
* -c file = True if the file exists and is character special file.
* -d file = True if the file exists and is a directory.
* -e file = True if the file exists.
* -f file = True if the file exists and is a regular file
* -g file = True if the file exists and the set-group-id bit is set.
* -k file = True if the files' "sticky" bit is set.
* -L file = True if the file exists and is a symbolic link.
* -p file = True if the file exists and is a named pipe.
* -r file = True if the file exists and is readable.
* -s file = True if the file exists and its size is greater than zero.
* -s file = True if the file exists and is a socket.
* -t fd = True if the file descriptor is opened on a terminal.
* -u file = True if the file exists and its set-user-id bit is set.
* -w file = True if the file exists and is writable.
* -x file = True if the file exists and is executable.
* -O file = True if the file exists and is owned by the effective user id.
* -G file = True if the file exists and is owned by the effective group id.
* file1 –nt file2 = True if file1 is newer, by modification date, than file2.
* file1 ot file2 = True if file1 is older than file2.
* file1 ef file2 = True if file1 and file2 have the same device and inode numbers.
* -z string = True if the length of the string is 0.
* -n string = True if the length of the string is non-zero.
* string1 = string2 = True if the strings are equal.
* string1 != string2 = True if the strings are not equal.
* !expr = True if the expr evaluates to false.
* expr1 –a expr2 = True if both expr1 and expr2 are true.
* expr1 –o expr2 = True is either expr1 or expr2 is true.

linux script to check file or folder is empty or not

2009-03-05T12:39:00.000+05:30

#!/bin/bash
#
ch=4
while [ $ch != 0 ]
do
clear
echo -en "To check File or Folder is empty or not\n"
echo -en "Enter 1. File\n2. Folder\n0. Exit\n"
echo -en "Enter choice 1, 2 or 0 - "
read ch
case $ch in
1) echo -en "Enter File name (path) -" ; read fl ;
if [ -f $fl ] ; then
#[ -z "$(cat $fl)" ] && echo -en "File is Empty\n" || echo -en "File is not Empty\n" ;
if [ -z "$(cat $fl)" ] ; then
echo -en "File is Empty\n"
else
echo -en "File is not Empty\n"
fi ;
else
echo -en "File is not Persent.\n"
fi
echo "Press a key. . ." ; read ;;
2) echo -en "Enter Folder name (path) -" ; read fl
if [ -d $fl ] ; then
#[ -z "$(ls -A $fl)" ] && echo -en "Folder is Empty\n" || echo -en "Folder is not Empty\n" ;
if [ -z "$(ls -A $fl)" ] ; then
echo -en "Folder is Empty\n"
else
echo -en "Folder is not Empty\n"
fi ;
else
echo -en "Folder is not Persent.\n"
fi
echo "Press a key. . ." ; read ;;
0) exit ;;
*) echo "Opps!!! Please select choice 1,2 or 0";
echo "Press a key. . ." ; read ;;
esac
done

list of all empty folders linux command

2009-03-05T11:50:00.001+05:30

find . -depth -type d -empty

[will operate delete as well]
find . -depth -type d -empty -exec rmdir {} \;

How to check a file of folder is empty or not linux script...

2009-03-05T11:14:00.001+05:30

[root@vikas Desktop]# touch v/v1
[root@vikas Desktop]# touch v/v2
[root@vikas Desktop]# [ -z "$(ls -A /root/Desktop/v)" ] && echo "empty" || echo "not"
not
[root@vikas Desktop]# [ -z "$(cat /root/Desktop/coralPBX.sh)" ] && echo "empty" || echo "not"
not
[root@vikas Desktop]# [ -z "$(cat /root/Desktop/ss)" ] && echo "empty" || echo "not"
empty
[root@vikas Desktop]# rm v/v
v1 v2
[root@vikas Desktop]# rm v/v
v1 v2
[root@vikas Desktop]# rm v/v*
rm: remove regular empty file `v/v1'? y
rm: remove regular empty file `v/v2'? y
[root@vikas Desktop]# [ -z "$(ls -A /root/Desktop/v)" ] && echo "empty" || echo "not"
empty
[root@vikas Desktop]# rmdir v
[root@vikas Desktop]# [ -z "$(ls -A /root/Desktop/v)" ] && echo "empty" || echo "not"
ls: cannot access /root/Desktop/v: No such file or directory
empty
[root@vikas Desktop]#

A picture defing usage of vi

2009-03-04T17:50:00.004+05:30

Extracting digits, upper lower letter from a string using TR

2009-03-03T12:03:00.000+05:30

[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:upper:]]\n'
VIKAS
[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:lower:]]\n'
vikas
[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:digit:]]\n'
12345
[root@vikas ~]# echo "Vv1Ii2Kk 3Aa4Ss5" | tr -cd '[[:blank:]]\n'

[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss$$5" | tr -cd '[[:alpha:]]\n'
VvIiKkAaSs
[root@vikas ~]#

Floating point comparison in linux script

2009-02-27T11:20:00.001+05:30

[root@vikas ~]# echo 8.8 == 8.2 | bc
0
[root@vikas ~]# echo 8.8 == 8.8 | bc
1
[root@vikas ~]#

[root@vikas ~]# echo 8 == 2 | bc
0
[root@vikas ~]# echo 8 == 8 | bc
1
[root@vikas ~]#

How to use POSTGRESQL from terminal commnds (examples)

2009-02-27T11:08:00.003+05:30

[All below are commands from terminal using the database SIPXCDR as user postgres (no password here) ]
psql --command "create sequence call_ip_id_seq;" SIPXCDR postgres
psql --command "create table call_ip(id bigint default nextval('call_ip_id_seq'),call_id text,from_url text,from_ip text,to_url text, to_ip text,method text, primary key(call_id,from_url,to_url,id));" SIPXCDR postgres
psql --command "alter table cdrs add column caller text;" SIPXCDR postgres
psql --command "alter table cdrs add column caller_ip text;" SIPXCDR postgres
psql --command "alter table cdrs add column callee text;" SIPXCDR postgres
psql --command "alter table cdrs add column callee_ip text;" SIPXCDR postgres
psql --command "create view view_cdrs_ip as SELECT cdrs.id, cdrs.caller, cdrs.caller_ip, cdrs.callee, cdrs.callee_ip, cdrs.start_time, cdrs.connect_time, cdrs.end_time, cdrs.end_time - cdrs.connect_time AS duration, cdrs.termination, cdrs.failure_status, cdrs.failure_reason, cdrs.call_direction FROM cdrs;" SIPXCDR postgres

Deleting a line from a file using sed

2009-02-26T17:06:00.002+05:30

[Appending a line say sh /usr/bin/coraldatabase.sh]
[root@vikas Desktop]# echo "sh /usr/bin/coraldatabase.sh" >>' /root/.bashrc

[Deleting a line sh /usr/bin/coraldatabase.sh]
[root@vikas Desktop]# sed -i '/sh \/usr\/bin\/coraldatabase.sh/d' /root/.bashrc
[root@vikas Desktop]#

A simple perl script variables, array, input, output and Reading a file in PERL

2009-02-26T11:45:00.001+05:30

#!/usr/bin/perl
#
#output
print "********************\n";
print "First progarm in perl\n";
print "********************\n";

#variables
$var = "vikas";
print "\n$var\n";
$a=9;
$c=10;
$z=$a+$c;
print "\n$z\n";

#array
@nos = (1, 2, 3, 4, 5, 6);
push(@nos, 7);
print "\n@nos\n";
print @nos;
print "\n$nos[5]\n";

#inserting into array
push(@nos, 7);
print "\n@nos[6]\n";

#deleting from array
$arr=pop(@nos);
print "\nPoped -- $arr\n";

# length of array $#nos+1
$len = @nos;
print "\nlength -- $len and $#nos\n";
#array as string
$str = "@nos";
print "\narray as string -- $str\n";

#array
($a, $b) = ($c, $d); # Same as $a=$c; $b=$d;
($a, $b) = @nos; # $a and $b are the first two
# items of @nos.
($a, @oth) = @nos; # $a is the first item of @nos
# @oth is a list of the
# others.
(@oth, $a) = @nos; # @oth is @nos and
# $a is undefined.

#reading from terminal
# total numbers of command line args = $#ARGV + 1
# here is first command lin argument
print "\n $ARGV[0]\n";
print "\n $ARGV[1]\n";

# reading all arguments using for loop
foreach $args (0 .. $#ARGV) {
print "$ARGV[$args]\n";
}

#input from terminal
print "\nEnter var 1 ";
$s = ;
print "\nEnter var 2 ";
$r = ;
#trimmming the input
chomp $r;
chomp $s;
#printing the input
print "----$r----$s------\n";

#File handling

$file = '/root/Desktop/ist.pl'; # Name the file
open(INFO, $file); # Open the file
@lines = ; # Read it into an array
close(INFO); # Close the file
print @lines;

#printing multiple lines
print <<"END";
#####################
vikas
sharma
coral

END

AND and OR in IF statement in linux script

2009-02-25T17:34:00.002+05:30

#var1
abc=0
# $1 is ist argument
echo -en "1st arg $1 and $abc\n"

# OR of two expr
if [ "$1" = "vikas" -o $abc -eq 1 ] ; then
echo "true"
else
echo "false"
fi

# AND of two expr
if [ "$1" = "vikas" -a $abc -eq 1 ] ; then
echo "true"
else
echo "false"
fi

Writing in crontab for scheduling from terminal

2009-02-25T16:43:00.003+05:30

crontab -l > /tmp/file
echo "12 12 * * * sh /ascript.sh_path" >> /tmp/file
crontab /tmp/file
rm -f /tmp/file

By this your script is now ready to run according to the time scheduled

Setting, unsetting, using environmental variable in linux

2009-02-24T12:42:00.002+05:30

[Setting a env variable]
export VIK=vikas
echo $USER

[using]
if [ ! $VIK ] ; then
echo "not defined"
else
echo $VIK
fi

[unsetting]
unset VIK

if [ $VIK ] ; then
echo $VIK
else
echo "not defined"
fi

SElinux status

2009-02-21T12:16:00.001+05:30

[root@vikas ~]# sestatus
SELinux status: disabled
[root@vikas ~]#

[change status]

[root@vikas ~]# vi /etc/selinux/config
Edit config file accordingly

Sub-string of a string

2009-02-21T11:06:00.003+05:30

[Displaying first five char here stringh is vikassharma]
[root@vikas java]# echo vikassharma | awk '{print substr($0,1,5)}'
vikas
[root@vikas java]# echo vikassharma | cut -c1-5
vikas
[root@vikas java]# printf "%.5s\n" "vikassharma"
vikas
[root@vikas java]# echo vikassharma | sed 's/$.\{5\}$.*/\1/'
vikas
[root@vikas java]# var=vikassharma
[root@vikas java]# printf "%.5s\n" "$var"
vikas
[root@vikas java]# echo "${var%${var#?????}}"
vikas
[root@vikas java]#

[root@vikas java]# echo vikassharma | cut -c6-
sharma
[root@vikas java]# echo vikassharma | awk '{print substr($0,6)}'
sharma
[root@vikas java]# var=vikassharma
[root@vikas java]# echo ${var:5}
sharma
[root@vikas java]# echo "${var#?????}"
sharma

Finding files not containg the pattern

2009-02-21T10:57:00.004+05:30

[Will list the files that does not contains the word in the current directory]
find . -type f \! -exec grep -q "word" {} \; -print

find . -type f | while read file
do
grep "word" $file > /dev/null
[ $? -ne 0 ] && echo $file
done

[List of all files in the current dir]
find . -type f

find . -type f | xargs grep -lv "word"

[List files containing the word]
find . -type f -exec grep -q "void" {} \; -print

[List files and all occurrence of word ]

grep -r "void" .

Size command -- information about a binary file

2009-02-20T18:03:00.001+05:30

The size [/path/to/binary] command gives the segment sizes of a binary executable or archive file. This is mainly of use to programmers.

[root@vikas s_w]# size /root/Desktop/current_task/sharedmem_c/a.out
text data bss dec hex filename
1254 260 8 1522 5f2 /root/Desktop/current_task/sharedmem_c/a.out
[root@vikas s_w]#

nm command List symbols from binary file

2009-02-20T17:55:00.000+05:30

[root@vikas sharedmem_c]# whatis nm
nm (1) - list symbols from object files
nm (1p) - write the name list of an object file (DEVELOPMENT)
nm-tool (1) - utility to report NetworkManager state

List symbols in an unstripped compiled binary.

[root@vikas sharedmem_c]#
[root@vikas sharedmem_c]# nm b.out
08049678 d _DYNAMIC
08049744 d _GLOBAL_OFFSET_TABLE_
080485d8 R _IO_stdin_used
w _Jv_RegisterClasses
08049668 d __CTOR_END__
08049664 d __CTOR_LIST__
08049670 D __DTOR_END__
0804966c d __DTOR_LIST__
08048660 r __FRAME_END__
08049674 d __JCR_END__
08049674 d __JCR_LIST__
0804976c A __bss_start
08049768 D __data_start
08048590 t __do_global_ctors_aux
080483d0 t __do_global_dtors_aux
080485dc R __dso_handle
w __gmon_start__
08048589 T __i686.get_pc_thunk.bx
08049664 d __init_array_end
08049664 d __init_array_start
08048510 T __libc_csu_fini
08048520 T __libc_csu_init
U __libc_start_main@@GLIBC_2.0
0804976c A _edata
08049774 A _end
080485b8 T _fini
080485d4 R _fp_hw
080482f8 T _init
08048380 T _start
080483a4 t call_gmon_start
08049770 b completed.5645
08049768 W data_start
0804976c b dtor_idx.5647
08048430 t frame_dummy
08048454 T main
U perror@@GLIBC_2.0
U putchar@@GLIBC_2.0
U shmat@@GLIBC_2.0
U shmget@@GLIBC_2.0
[root@vikas sharedmem_c]#

Changes all filenames in currnet dir to lowercase

2009-02-20T17:00:00.001+05:30

#!/bin/bash
for filename in * ; do
filen=`basename $filename`
n=`echo $filen | tr A-Z a-z` # tr a-z A-Z lowercase to upper
if [ "$filen" != "$n" ]
then
mv $filen $n
echo "File $filen renamed as $n"
fi
done

A weak but useful encryption using TR

2009-02-20T16:48:00.003+05:30

[encrypt]
echo "vikas6@" | tr 'a-zA-Z0-9@_' 'j-za-iJ-ZA-I5-90-4*@'

[decrypt just reverse]
echo "ertjb1*" | tr 'j-za-iJ-ZA-I5-90-4*@' 'a-zA-Z0-9@_'

Type command -- tell you about other command

2009-02-20T16:41:00.002+05:30

whatis type
type (1p) - write a description of command type
type [builtins] (1) - bash built-in commands, see bash(1)
[root@vikas 18-feb]# type ls
ls is aliased to `ls --color=tty'
[root@vikas 18-feb]# type dir
dir is /usr/bin/dir
[root@vikas 18-feb]# type banner
banner is /usr/bin/banner
[root@vikas 18-feb]# type rm
rm is aliased to `rm -i'
[root@vikas 18-feb]# type rmdir
rmdir is /bin/rmdir
[root@vikas 18-feb]# type [
[ is a shell builtin

type -a ls

It works some what like which, but bash builtin.

User list currenly logged in.

2009-02-20T16:23:00.003+05:30

[root@vikas 18-feb]# whatis users
users (1) - print the user names of users currently logged in to the current host
[root@vikas 18-feb]# users
root root root root root

[root@vikas 18-feb]# who
root tty7 2009-02-20 10:01 (:0)
root pts/0 2009-02-20 10:38 (:0.0)
root pts/1 2009-02-20 16:20 (:0.0)
root pts/3 2009-02-20 15:46 (192.168.4.141)
root pts/4 2009-02-20 15:51 (192.168.4.141)
[root@vikas 18-feb]# who -q
root root root root root
# users=5
[root@vikas 18-feb]#

Instaling RPM by extracting it. If does not installled using rpm -i

2009-02-20T16:20:00.002+05:30

whatis rpm2cpio
rpm2cpio (8) - Extract cpio archive from RPM Package Manager (RPM) package

whatis cpio
cpio (1) - copy files to and from archives
cpio.h [cpio] (0p) - cpio archive values
cpio (rpm) - A GNU archiving program.

e.g

rpm2cpio banner-1.3.1-5.fc8.i386.rpm | cpio -idmv

cd usr/bin/

./banner

This will exract files from rpm and copy to the required place. As above eg. copy the banner binary to /usr/bin

-d, --make-directories Create leading directories where needed
-i, --extract Extract files from an archive (run in copy-in
mode)
-m, --preserve-modification-time
Retain previous file modification times when
creating files
-v, --verbose Verbosely list the files processed

How to know user identity.

2009-02-20T12:18:00.003+05:30

id
id (1p) - return user identity
id (1) - print user identity

root id is 0
id -u return 0 then u r root else not.

e.g
[root@vikas 18-feb]# id -u
0
[root@vikas 18-feb]# id
uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel)
[root@vikas 18-feb]# su vikas
[vikas@vikas 18-feb]$ id
uid=500(vikas) gid=500(vikas) groups=500(vikas)
[vikas@vikas 18-feb]$ id -u
500
[vikas@vikas 18-feb]$ su

if [ `id -u` = "0" ] ; then
echo "u r root"
else
echo " u r not root"
fi

Message prompts on when somebody logins using ssh /etc/motd

2009-02-19T20:01:00.002+05:30

edit /etc/motd

Whatever you write in this file, displays when somebody, logins using ssh in your system.

e.g

[root@localhost ~]# ssh 192.168.4.13
root@192.168.4.13's password:
Last login: Wed Feb 18 17:44:44 2009 from 192.168.4.141
*****************************************
* *
* Vikas Sharma *
* *
*****************************************

[root@vikas ~]#

Banner command

2009-02-19T19:59:00.000+05:30

banner

banner [option] [characters]

Print characters as a poster. If no characters are supplied, banner prompts for them and reads an input line from standard input. By default, the results go to standard output, but they are intended to be sent to a printer.
Option
-w width

Set width to width characters. Note that if your banner is in all lowercase, it will be narrower than width characters. If -w is not specified, the default width is 132. If -w is specified but width is not provided, the default is 80.

e.g

[root@vikas 18-feb]# banner vikas

# # ### # # # #####
# # # # # # # # #
# # # # # # # #
# # # ### # # #####
# # # # # ####### #
# # # # # # # # #
# ### # # # # #####

[root@vikas 18-feb]#

How to make pdf of the manual page of commands

2009-02-19T18:59:00.003+05:30

[show manual page of the command]
man commnd

[man page to pdf (nice way)]
man -t command | ps2pdf - > command.pdf

lsof utility

2009-02-19T15:00:00.003+05:30

whatis lsof
lsof (8) - list open files
lsof (rpm) - A utility which lists open files on a Linux/UNIX system

lsof
lsof | grep TCP
lsof -i TCP
lsof | grep 'root' | awk '{print $NF}' | sort | uniq | wc -l

nohup - countine a job or command even after logoff

2009-02-19T14:50:00.002+05:30

whatis nohup
nohup (1p) - invoke a utility immune to hangups
nohup (1) - run a command immune to hangups, with output to a non-tty

nohup

Keeps a command running even after user logs off. The command will run as a foreground process unless followed by &. If you use nohup within a script, consider coupling it with a wait to avoid creating an orphan or zombie process.

nohup command args

Error redirecting /dev/null

2009-02-18T19:07:00.003+05:30

/dev/null or the null device is a special file that discards all data written to it.
/dev/null, which is a place you can dump anything you don’t want (often called the bit-bucket),

commaned > /dev/null 2>&1 or /dev/null 2>/dev/null

The greater-thans (>) in commands like these redirect the program’s output somewhere. In this case, something is being redirected into /dev/null, and something is being redirected into &1.

There are three standard sources of input and output for a program. Standard input usually comes from the keyboard if it’s an interactive program, or from another program if it’s processing the other program’s output. The program usually prints to standard output, and sometimes prints to standard error. These three file descriptors (you can think of them as “data pipes”) are often called STDIN, STDOUT, and STDERR.

Sometimes they’re not named, they’re numbered! The built-in numberings for them are 0, 1, and 2, in that order. By default, if you don’t name or number one explicitly, you’re talking about STDOUT.

Steps to make sipx installation cd with centos (command line)

2009-02-18T15:24:00.004+05:30

This document is about how to create a single boot CD installation for sipX. It is based on CentOS and we are using the kickstart technology included with CentOS and Fedora to script the Anaconda installer. In addition to creating an automated install, this document also describes how to create a custom distribution of CentOS that includes only the needed RPMs including the sipX RPMs and all necessary dependencies. The distribution fits on one CD and is self-contained resolving all its dependencies. No network connection is required to install it.

2. Installing Necessary Tools

The scripts required to perform all the necessary operations are part of the CentOS / Fedora distribution.

yum install anaconda-runtime createrepo yum-utils anaconda anaconda-help busybox-anaconda mkisofs
yum install system-config-kickstart

Create a Working Copy of the CentOS Installation Disk

We are using CentOS 4 to start with. Only CD 1 is required as we are interested in a customized minimal installation. Mount the CD and copy its content to a working directory:

mkdir centos-cd1 cd1
sudo mount /dev/cdrom centos-cd1
rsync -a centos-cd1/* cd1
cp centos-cd1/.discinfo cd1
sudo umount centos-cd1

Create a Kickstart Configuration File - ks.cfg

The most important file is the kickstart configuration file (ks.cfg). This file has to be copied to the root directory of the new CD. It provides all the parameters to Anaconda for an automated installation, determines what packages to install and allows some post installation scripts to be executed.

Save as File: ks.cfg

####################################################

### Kickstart configuration file

### for sipXecs distribution CDs

###

##################################################

#--- Installation method (install, no upgrade) and source (CD-ROM)

install

cdrom

#--- Debugging (uncomment next line to debug in the interactive mode)

#interactive

#--- Language and input support

lang en_US.UTF-8

langsupport --default=en_US.UTF-8 en_US.UTF-8

keyboard us

mouse generic3ps/2

#--- X-Windows (use "skipx" directive to skip X-Windows configuration)

skipx

#--- Network configuration

# Add some default or else Anaconda will pop a window and ask

network --device eth0 --bootproto static --ip 192.168.5.176 --netmask 255.255.255.0 --gateway 192.168.5.1 --nameserver 192.168.5.145 --hostname sipx.example.com

#--- Authentication and security

rootpw setup

firewall --disabled

selinux --disabled

authconfig --enableshadow --enablemd5

#--- Time zone

timezone America/New_York

#--- Boot loader

bootloader --location=mbr

#--- Partitioning

# The user will be prompeted to perform this step

#--- Reboot the host after installation is done

reboot

#--- Package selection

%packages --resolvedeps

e2fsprogs

grub

kernel

ntp

dhcp

bind

caching-nameserver

gdb

strace

# Used for SF build

sipxpbx

sipxconfig

sipxacd

sipxconfig-agent

sipxconfig-report

sipxvxml

sipxproxy

sipxregistry

sipxpublisher

sipxproxy-cdr

sipxconfig-tftp

sipxconfig-ftp

sipxtools

#--- Post-installation script

%post

#!/bin/sh

#...Mount the installation CD

/sbin/start_udev

/sbin/chkconfig --del smartd &> /dev/null

mkdir /tempdir

mount /dev/cdrom /tempdir

#...Setup initial setup script to run one time (after initial reboot only)

echo -e "\n/usr/bin/sipx_reset_cd\n" >> /root/.bashrc

# the script removes itself from the root .bashrc file when it completes

#...Place a copy of the RAID restore script in /sbin

cp /tempdir/restore-raid-drive /sbin/restore-raid-drive

chmod u=rwx /sbin/restore-raid-drive

#... Add logon message

echo -e "\nWelcome to Coral IPPBX\n" >> /etc/issue

echo -e "=============================\n" >> /etc/issue

echo -e "\nFirst time logon: user = root password = setup\n\n" >> /etc/issue

#... Boot kernel in quiet mode

sed -i 's/ro root/ro quiet root/g' /boot/grub/grub.conf

# Install SIPfoundry sipX repository and key

rpm --import /tempdir/RPM-GPG-KEY-sipX

cp /tempdir/sipx-fc.repo /etc/yum.repos.d

#...Install new splash image

cp /tempdir/splash.xpm.gz /boot/grub

#... Prevent it from being overwritten when upgrading the system using yum update

chmod 444 /boot/grub/splash.xpm.gz

#...Prevent sipxpbx from starting after first reboot as it is not yet configured

chkconfig sipxpbx off

# Postgresql will be started by sipxpbx

chkconfig postgresql off

# Turn off unused services that listen on ports

chkconfig portmap off

chkconfig netfs off

chkconfig nfslock off

# Make a backup copy of the CD if there is a /recovery partition

if test -d "/recovery" ; then

mkdir /recovery/linux

cp -a /tempdir/* /recovery/linux

cp -a /tempdir/.discinfo /recovery/linux

umount /tempdir

rm -rf /tempdir

eject

Note: Make sure to use the i586 kernel. Also, the process cpu speed needs to be stopped and disabled (/sbin/service cpuspeed stop & chkconfig cpuspeed off). Otherwise the VIA C3 system will crash anytime cpuspeed tries to throttle the CPU back.

2.3 Creating a Custom Installer

Next we want to create a custom installer including our own splash screen and boot options. The file isolinux.cfg tells the grub bootloader where to look for the kernel. It should be familiar to you as it is identical to the common grub/grub.conf file.

File: cd1/isolinux/isolinux.cfg

default coraltele

prompt 1

timeout 0

display boot.msg

F1 boot.msg

F2 options.msg

F3 general.msg

F4 param.msg

F5 rescue.msg

F7 snake.msg

label linux

kernel vmlinuz

append initrd=initrd.img ramdisk_size=8192

label memtest86

kernel memtest

append -

label coraltele

kernel vmlinuz

append initrd=initrd.img ramdisk_size=8192 ks=cdrom:/ks.cfg quiet

The file isolinux.cfg specifies that the splash screen to be displayed before starting the boot process is called boot.msg:

File: cd1/isolinux/boot.msg

^Xsplash.lss

Press to start the installation.

WARNING: All data will be erased and the disk is formatted.

-----------------------------------------------------------

Root password is "coraltele".

^O02[F1-Main] [F2-Options] [F3-General] [F4-Kernel]^O07

Note: Adapt the other files options.mgs, general.msg, param.msg to your liking.

2.4 Changing the splash.lss File

The cd1/isolinux/splash.lss file is the splash file that displays in the very first screen after the machine restarts and presents the user with the boot options. This file is in the directory /isolinux. An excellent description of how to do this is given below:

First Step: Create an image file of the format 640 x 220 pixels using The Gimp. Downsample the color depth to 14 colors. This is done in GIMP by going to ->Image->Mode - select "indexed". Then save the file in the PPM format in RAW mode.

Second Step: The created .PPM file needs to be edited. Using an editor open the file and remove the 2nd line where it says that GIMP created this file. The next step does not handle comments in PPM files.

Third Step: Using ppmtolss16 convert the file to .lss

./ppmtolss16 '#c0cfc0=7' splash.lss

Fourth Step: Copy the file splash.lss to the /isolinux directory.

Changing the Splash Image displayed by Grub (splash.xpm.gz)

Start the GIMP.

Click on File->New or type Ctrl+N
In the new image dialog, change Width to 640 pixels and Height to 480 pixels. (The image should be of size 640x480 pixels.) Now click OK.
Create the image which you would like to be the splash image. It's quite fun to experiment with the various tools of the GIMP!
After you have finished creating the image, hit Alt+i or right click on the image and click on Image->Mode->Indexed...
In the Indexed Color Conversion dialog that appears, click on the radio button "Generate optimal Palette" and in "# of colors" enter 14. Click OK.(The image should be of only 14 colors)
Now right-click on the image and click on File->Save As...Save the file as splash.xpm in a directory of your choice.
Now open a terminal window and navigate to the directory where you have saved splash.xpm
Now key in gzip splash.xpm
You will find that a file named splash.xpm.gz is created in the directory where splash.xpm used to exist.
Copy this splash.xpm.gz to the /boot/grub directory. You may want to back up the pre-existing splash.xpm.gz file in the /boot/grub directory first.

Customizing Anaconda

Anaconda is the program that provides all the installation services and displays all the graphics during the installation process. It is included in the directory cd1/CentOS/base in a file called stage2.img. An excellent explanation of how to edit this image manually can be found below:

The following describes a crude way of changing the artwork used by Anadonca during the installation process. They cleaner way would be to use buildinstall to create a new installer. In this case we start with an existing installer and modify it.

The image of the Anaconda installer can be found in cd1/CentOS/base. The image file is called stage2.img. We will now mount this image so that we can look inside.

mkdir ~/anaconda
mount -o loop cd1/CentOS/base/stage2.img ~/anaconda

Now we need to copy the contents to a directory where we can alter the files. A simple cp command was claimed to not work because of some hard links included in the image. For this reason we use tar to package the contents of the directory and then untarred them where we could work on them.

cd ~/anaconda
tar -cvf ~/stage2.tar .
cd ~
mkdir stage2
cd stage2
tar -xvf ../stage2.tar

Now we can alter the images used by the installer located in usr/share/anaconda/pixmaps and the images used in the installation slideshow in usr/share/anaconda/pixmaps/rnotes. You can also edit the text in the left sidebar, which is in HTML format, in usr/share/anaconda/help/[locale].

After you've made the desired modifications, we need to compress this information back into an .img file.

cd ~
mkcramfs stage2/ stage2.img.new

Then, copy the altered stage2.img to the CentOS/base directory.

cp stage2.img.new cd1/CentOS/base/stage2.img

3. Choose the appropriate RPMs to be in CentOS/RPMS

It involves selecting a set if RPMS that comprise all the necessary elements for Linux to install and boot. In addition it requires all the RPMS required for a sipX system. In addition, all the dependencies have to be resolved. And lastly, its size must not exceed what can fit onto a single CD.

We started with the first CD of the CentOs 4 distribution. The list of RPMs we deleted is long.

In addition, it is possible to update the RPMs to their latest patch level which makes it unnecessary to run yum update after the system is installed.

3.1 Test if all dependencies for all the RPMs in CentOS/RPMS are resolved

The following test is absolutely crucial. Inevitably once you start removing or adding RPMs to the repository, you will have to make sure that all dependencies are resolved properly. Once the test below passes, you have succeeded to create a self-contained repository that will install properly.

cd ~
mkdir testdb
rpm --initdb --dbpath $PWD/testdb
rpm --test --dbpath $PWD/testdb -Uvh cd1/CentOS/RPMS/*.rpm

Create repodata using createrepo

cd cd1
createrepo --baseurl="media://1142383043.889895" -g CentOS/base/comps.xml CentOS/RPMS/

Note: Make sure the number in --baseurl corresponds to the first line in the file cd1/.discinfo. Should you have trouble with this command try using absolute path names.

3.3 Create hdlist and hdlist2

cd cd1
export PYTHONPATH=/usr/lib/anaconda
export PATH="$PATH:/usr/lib/anaconda-runtime"

# Write CentOS/base/hdlist and hdlist2:

genhdlist --hdlist /home/test/cd1/CentOS/base/hdlist --productpath CentOS /home/test/cd1

Note: Absolute path names are required for the command genhdlist to work properly.

3.4 Create a Package Order File

The package order determines the order by which RPMs are installed by Anaconda. This order matters as RPMs only install if all the required dependencies are already installed on the system. The command pkgorder in a recursive process calculates the correct package order.

cd cd1
pkgorder /home/test/cd1 i386 CentOS > /home/test/cd1/pkgorder.txt

Run genhdlist again, this time with package order. Now that we have the proper package order calculated we can create the final hdlist files for Anaconda to use:

genhdlist --withnumbers --fileorder /home/test/cd1/pkgorder.txt \

--hdlist /home/test/cd1/CentOS/base/hdlist --productpath CentOS /home/test/cd1

4. Create the ISO Image

cd ~
mkisofs -R -J -T -no-emul-boot -boot-load-size 4 -boot-info-table -V "sipX 3.4" \

-A "Created on 8/6/2006" -P "SIPfoundry" -p "SIPfoundry" -b isolinux/isolinux.bin \

-c isolinux/boot.cat -x "lost+found" -o sipx.iso cd1

Insert, append and replace lines or text with SED

2009-02-18T11:26:00.001+05:30

A file vik

sed '/keyword/ a\your-text-here' vik #insert your-text-here after every occurance of keyword
sed '5 a\your-text-here' vik #insert your-text-here at line 6
sed '5 i\your-text-here' vik #insert your-text-here at line 5
sed '/^keyword/ i\your-text-here' vik #insert your-text-here before keyword
sed '/^keyword/ c\your-text' vik #replace your keyword with your-text
sed '4 i\text1\ntext2' vik # this will insert two lines

Linux scripting

2009-02-17T16:52:00.009+05:30

[Dont use]
for f in `cat file`; do
..
done

[use]
while read f; do
...
done file

[dont use]
grep | wc -l

[use]
grep -c 


[Dont use]
for f in `echo * or ls *`; do
command "$f"
done

[use]
for f in * ; do
command "$f"
done

colorful ls

2009-02-17T16:31:00.001+05:30

ls -C . --color=always | grep -C 100 --color=auto avi
ls -h . --color=always | grep -C 100 --color=auto avi

Getting name of the current dir - using 'basename'

2009-02-17T16:13:00.003+05:30

[root@vikas vikas]# pwd
/root/Desktop/vikas/vikas
[root@vikas vikas]# basename `pwd`
vikas
[root@vikas vikas]# basename `echo $PWD`
vikas
[root@vikas vikas]# echo ${PWD##*/}
vikas
[root@vikas vikas]#

[Will display on current dir name i.e path3 here]
basename /path/path2/path3

[with sed]
pwd | sed 's,^$.*/$\?$[^/]*$,\2,'

[with reversing the string]
[root@vikas vikas]# pwd
/root/Desktop/vikas/vikas
[root@vikas vikas]# pwd | rev
sakiv/sakiv/potkseD/toor/
[root@vikas vikas]# pwd | rev | awk -F \/ {'print $1'}
sakiv
[root@vikas vikas]# pwd | rev | cut -f1 -d"/"
sakiv
[root@vikas vikas]# pwd | rev | awk -F \/ {'print $1'} | rev
vikas
[root@vikas vikas]#

Extracting IP's from output of who command using grep

2009-02-17T14:49:00.003+05:30

[root@vikas ~]# who
root tty7 2009-02-17 11:23 (:0)
root pts/0 2009-02-17 12:30 (:0.0)
root pts/1 2009-02-17 12:32 (:0.0)
root pts/2 2009-02-17 12:32 (:0.0)
root pts/3 2009-02-17 13:33 (192.168.4.35)
root pts/4 2009-02-17 14:23 (192.168.4.15)

who | egrep -o '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+'
who | grep -o '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*'

192.168.4.35
192.168.4.15

Command to find PID

2009-02-13T16:08:00.002+05:30

[root@vikas ~]# pidof httpd
6926 6925 6924 6923 6922 3974

[root@vikas ~]# pidof vikas

[root@vikas ~]#

files transfer using ncftp

2009-02-13T12:31:00.003+05:30

ncftp -u -p

use get, put

[get file from the /home/vik form 13 machine and place in current dir]
ncftpget -u vik -p 123654 192.168.4.13 . file
ncftpget -u vik -p 123654 192.168.4.13 /root/Desktop file

ncftpput -u vik -p 123654 192.168.4.13 /home/vik file

-------------------
In FTP
get, put -- for a single file
mget *, mput * --- for all files in current folder

zimbra mail exchange mails synchronization using imapsync command

2009-02-13T12:12:00.006+05:30

[File id has all users, password must be same replace otherwise write then into file and script accordingly]

for i in `cat id`
do
echo $i
#zimbra command to create a user with password 123456
#./zmprov ca $i@host.com

imapsync --buffersize 8192000 --nosyncacls --subscribe --syncinternaldates --host1 hostip1 --user1 $i --password1 --host2 hostip2 --user2 $i --password2 --authmech1 PLAIN --authmech2 LOGIN

echo "----------------------------"
done

Array in linux scripts

2009-02-13T11:34:00.003+05:30

#array=(a b c d e f)
array=(`ls`)
#total elements
len=${#array[*]}
echo "The array has $len elements."
#array starts from 0
i=0
echo -e "Array is :-"
while [ $i -lt $len ]; do
echo "$i: ${array[$i]}"
let i++
done

substring in linux script

2009-02-13T11:33:00.002+05:30

str="this is a vikas test"
substr=${str:10:5} #from 10th to next 5
echo $substr

test command

2009-02-13T11:23:00.002+05:30

Let there is a file while.sh and dir vikas
[root@vikas Desktop]# test -e while.sh
[root@vikas Desktop]# echo $?
0
[root@vikas Desktop]# test -e while
[root@vikas Desktop]# echo $?
1
[root@vikas Desktop]# test -d vikas
[root@vikas Desktop]# echo $?
0
[root@vikas Desktop]# test -d vikass
[root@vikas Desktop]# echo $?
1
[root@vikas Desktop]# test -e while.sh && echo "Yes." [if file is there echo yes]
Yes.
[root@vikas Desktop]# test -e whiless.sh && echo "Yes."
[root@vikas Desktop]# test -e whiless.sh || echo "no." [if file is not there echo no]
no.
[root@vikas Desktop]# test -e while.sh || echo "no."
[root@vikas Desktop]#

which and whereis

2009-02-13T11:14:00.000+05:30

whereis - locate the binary, source, and manual page files for a command
which - shows the full path of (shell) commands
which Displays where a particular program in your path is located.

Script changing IP and hostname in fedora, use of sed

2009-02-12T17:39:00.002+05:30

#!/bin/sh
###############
# For FEDORA
# Use at your own risk...........................
# Reading.....
###############
echo -e "Enter IP address"
read ip
while [ `echo $ip | grep -io [.] | wc -l` != 3 ]
do
echo -e "Invalid ip, Enter again:"
read ip
done

echo -e "Enter host name"
read hst
while [ `echo $hst | grep -io [.] | wc -l` != 2 ]
do
echo -e "Invalid hst, Enter again:"
read hst
done

#echo -e "Enter Network address"
#read ip
#echo -e "Enter Gateway address"
#read ip

###############
# Warn!
###############
echo -en "You are going to change Hostname as $hst and IP as $ip:\nWrong data may harm:\n"

###############
# CHNAGE IF YES
###############
while [ 1 ]
do
read -p "Enter [Y/N]" rst
case $rst in
y|Y)
###############
# Changing hostname /etc/sysconfig/network file
###############
echo -en "NETWORKING=yes\nHOSTNAME=$hst" | cat > /tmp/temnet;
cp -f /tmp/temnet /etc/sysconfig/network;
rm -f /tmp/temnet;

###############
# Changing IP address /etc/sysconfig/network-scripts/ifcfg-eth0 file
###############
sed '/IPADDR/d' /etc/sysconfig/network-scripts/ifcfg-eth0 > /tmp/tmpip;
sed -i '5i\IPADDR='$ip /tmp/tmpip;
cp -f /tmp/tmpip /etc/sysconfig/network-scripts/ifcfg-eth0;
rm -f /tmp/tmpip;

###############
# Changing in DNS file HERE /var/named/chroot/var/named/coralsip.com.zone
###############
## dn="$hst IN A $ip"
sed '/'$hst'. IN A '$ip'/d' /var/named/chroot/var/named/coralsip.com.zone > /tmp/tmpdns;
sed -i '12i\'$hst'. IN A '$ip /tmp/tmpdns;
cp -f /tmp/tmpdns /var/named/chroot/var/named/coralsip.com.zone;
rm -f /tmp/tmpdns;

###############
# Adding in /etc/hosts file
###############
#host_line="$ip $hst ` echo $hst | cut -f1 -d"."`";
echo -en "# Do not remove the following line, or various programs\n# that require network functionality will fail.\n127.0.0.1 localhost.localdomain localhost\n" | cat > /tmp/tmphost;
echo "$ip $hst ` echo $hst | cut -f1 -d"."`"| cat >> /tmp/tmphost;
cp -f /tmp/tmphost /etc/hosts;
rm -f /tmp/tmphost;

###############
# Restarting services
###############
hostname $hst;
service network restart;
service named restart;

exit;;
n|N) echo -e "Exit without changing." ;exit ;;
*) echo -e "Wrong Input!!! Please enter [y/n]";

esac
done

#old_ip= get_def_addr
#sed -e 's/IPADDR='$old_ip'/IPADDR='$ip'/g' /etc/sysconfig/network-scripts/ifcfg-eth0 > /root/Desktop/tmp
## hostname $hst
## service network restart
#cat /etc/sysconfig/network | tr 'HOSTNAME=vikas.coralsip.com' 'HOSTNAME=$hst'
#sleep 1
#sed 's/IPADDR=`get_def_addr`/IPADDR=$ip/g' /etc/sysconfig/network-scripts/ifcfg-eth0
#sleep 1
#sed 's/HOSTNAME=`echo $hm`/HOSTNAME=`echo $hst`/g' /etc/sysconfig/network > /root/Desktop/tmp

finding the string in the files in dir

2009-02-12T14:17:00.003+05:30

finding the string
find . -iname '*php' | xargs grep 'string' -sl

Another common search for me, is to just look at the recently updated files:
find . -iname '*php' -mtime -1 | xargs grep 'string' -sl

would find only files edited today, whilst the following finds the files older than today:
find . -iname '*php' -mtime +1 | xargs grep 'string' -sl

find / -type f -print0 | xargs -0 grep -i pattern

setting kernel parameters

2009-02-12T11:47:00.001+05:30

use sysctl utility.. or try using /etc/sysctl.conf

[print all kernal parameters]
sysctl -a print

whatis sysctl
sysctl (2) - read/write system parameters
sysctl (8) - configure kernel parameters at runtime
sysctl.conf [sysctl] (5) - sysctl(8) preload/configuration file

Grub is crashed, how to start linux then.

2009-02-12T11:42:00.001+05:30

Reboot using the linux cd using "linux rescue" option and then after that

chroot /mnt/sysimage
cd /mnt/sysimage/etc/
grub-install /dev/sda(x)

Less in Unix

2009-02-12T11:27:00.001+05:30

Less is a program similar to more but which allows backward movement in the file as well as forward movement. Also, less does not have to read the entire input file before starting, so with large input files it starts up faster than text editors like vi
Less uses termcap (or terminfo on some systems), so it can run on a variety of terminals. There is even limited support for hardcopy terminals. (On a hardcopy terminal, lines which should be printed at the top of the screen are prefixed with a caret.)
whatis less
less (1) - opposite of more
less (3pm) - perl pragma to request less of something from the compiler
less (rpm) - A text file browser similar to more, but better

IN UNIX less IN MORE THAN more

Moving Commands:

Commands marked with * may be preceded by a number, N.
Notes in parentheses indicate the behavior if N is given.

 e  ^E  j  ^N  CR  *  Forward  one line   (or N lines).
 y  ^Y  k  ^K  ^P  *  Backward one line   (or N lines).
 f  ^F  ^V  SPACE  *  Forward  one window (or N lines).
 b  ^B  ESC-v      *  Backward one window (or N lines).
 z                 *  Forward  one window (and set window to N).
 w                 *  Backward one window (and set window to N).
 ESC-SPACE         *  Forward  one window, but don't stop at end-of-file.
 d  ^D             *  Forward  one half-window (and set half-window to N).
 u  ^U             *  Backward one half-window (and set half-window to N).
 ESC-(  RightArrow *  Left  8 character positions (or N positions).
 ESC-)  LeftArrow  *  Right 8 character positions (or N positions).
 F                    Forward forever; like "tail -f".
 r  ^R  ^L            Repaint screen.
 R                    Repaint screen, discarding buffered input.

 h  H                 Display this help.
 q  :q  Q  :Q  ZZ     Exit.

php code using seamophores, shared memory and related functions

2009-02-12T11:02:00.005+05:30

START OF FILE ONE

$shm_id = shmop_open(0xff3, "c", 0644, 100);
echo $shm_id;
echo "
";
$shm_size = shmop_size($shm_id);
echo $shm_size;
$my_string = shmop_read($shm_id, 12, 5);
echo "The data inside shared memory was: ".$my_string."\n";

shmop_delete($shm_id);
shmop_close($shm_id);

END OF FILE 1

START OF FILE 2 semaphores

$MEMSIZE = 128; // size of shared memory to allocate
$SEMKEY = 11; // Semaphore key
$SHMKEY = 51; // Shared memory key

echo "Start.\n";

// Create a semaphore
$sem_id = sem_get($SEMKEY, 1);
if ($sem_id === false)
{
echo "Failed to create semaphore";
exit;
}
else
echo "Created semaphore $sem_id.\n";

// Acquire the semaphore
if (! sem_acquire($sem_id))
{
echo "Failed to acquire semaphore $sem_id.\n";
sem_remove($sem_id);
exit;
}
else
echo "Success acquiring semaphore $sem_id.\n";

// Attach shared memory
$shm_id = shm_attach($SHMKEY, $MEMSIZE);
if ($shm_id === false)
{
echo "Fail to attach shared memory.\n";
sem_remove($sem_id);
exit;
}
else
echo "Success to attach shared memory : $shm_id.\n";

// Write variable 1
if (!shm_put_var($shm_id, 1, "Vikas"))
{
echo "Failed to put var 1 in shared memory $shm_id.\n";

// Clean up nicely
sem_remove($sem_id);
shm_remove($shm_id);
exit;
}
else
echo "Wrote var1 to shared memory.\n";

// Write variable 2
if (!shm_put_var($shm_id, 2, "coral"))
{
echo "Failed to put var 2 on shared memory $shm_id.\n";

// Clean up nicely
sem_remove($sem_id);
shm_remove ($shm_id);
exit;
}
else
echo "Wrote var2 to shared memory.\n";

// Read variable 1
$var1 = shm_get_var($shm_id, 1);
if ($var1 === false)
{
echo "Failed to retreive Var 1 from Shared memory $shm_id, " .
"return value=$var1.\n";
}
else
echo "Read var1=$var1.\n";

// Read variable 1
$var2 = shm_get_var ($shm_id, 2);
if ($var1 === false)
{
echo "Failed to retrive Var 2 from Shared memory $shm_id, " .
"return value=$var2.\n";
}
else
echo "Read var2=$var2.\n";

//sleep (60);

// Release semaphore
if (!sem_release($sem_id))
echo "Failed to release $sem_id semaphore.\n";
else
echo "Semaphore $sem_id released.\n";

// Remove shared memory segment
if (shm_remove ($shm_id))
echo "Shared memory successfully removed.\n";
else
echo "Failed to remove $shm_id shared memory.\n";

// Remove semaphore
if (sem_remove($sem_id))
echo "Semaphore removed successfully.\n";
else
echo "Failed to remove $sem_id semaphore.\n";

echo "End.\n";

END OF FILE2

Unix MORE Command

2009-02-12T11:02:00.002+05:30

more(In UNIX)

More is a command used to read text files. For example, we could do this:

   % more poems

The effect of this to let you read the file "poems ". It probably will not fit in one screen, so you need to know how to "turn pages". Here are the basic commands:

q --- quit more
spacebar --- read next page
return key --- read next line
b --- go back one page

Simple php script to access shared memory by two php programs using ftok

2009-02-11T18:04:00.004+05:30

PHP supports shared memory which can be used to store and retrieve data across processes. Shared memory is used for caching frequently used data in memory for php scripts on the same serve

FILE 1

$key = 'mykey'; // Key to store data with

$shm_key = ftok('afile','POINTER');

$data = shm_attach($shm_key);

$test = "vikas";
shm_put_var($data,$inmem,$test); // Save the data in shared memory

echo shm_get_var($data,$mykey);
shm_detach($data); // Disconnects from shared memory segment; data remains there

?>

FILE2

$key = 'mykey';
$shm_key = ftok('afile','POINTER');
$data = shm_attach($shm_key);
echo shm_get_var($data,$mykey);
shm_detach($data);

?>

ipc inter process communication (shared memory) linux commnad

2009-02-11T15:23:00.005+05:30

[root@vikas ~]# whatis ipcs
ipcs (1p) - report XSI interprocess communication facilities status
ipcs (1) - provide information on ipc facilities
he ipcs command is a powerful mechanism for spying on the kernel memory of IPC objects.

ipcs -s
ipcs -m
ipcs -q
ipcs -i id

Unix Shared Memory Variables

`SHMMAX`	The maximum amount of shared memory, normally 131072 bytes
`SHMMIN`	The minimum amount of shared memory, normally 1 byte
`SHMMNI`	The maximum number of shared memory segments in the system, normally 100
`SHMSEG`	The maximum number of shared memory segments per process, normally 6

IPCRM

ipcrm deletes IPC objects from the kernel. However, as IPC objects can be deleted through system calls in the user's program, there is often no need to delete them by hand. The command is very simple:

ipcrm -type id

[root@vikas ~]# whatis ipcrm
ipcrm (1p) - remove an XSI message queue, semaphore set, or shared memory segment identifier
ipcrm (1) - remove a message queue, semaphore set or shared memory id

usage: ipcrm [ [-q msqid] [-m shmid] [-s semid]
[-Q msgkey] [-M shmkey] [-S semkey] ... ]

IPCClean

ipcclean
ipcclean (1) - remove shared memory and semaphores from a failed PostgreSQL server

BOA web server

2009-02-10T17:22:00.000+05:30

Boa is a tiny web server that also offers extremely high performance. It is specifically designed to run on UNIX-like systems, which includes Linux, as well as the *BSD systems. To get all the legal stuff out of the way, Boa is available for free and is covered by the GNU Public License (GPL). The source code for Boa, as well as documentation, can be found at http://www.boa.org/.

The following point taken from the Boa web site :

“ Boa currently seems to be the favorite web server in the embedded crowd, and embedded Linux, despite all the marketing hype, really is a big deal. Supposedly, an older version of Boa, v0.92q, runs in 32K address space on m68k, like used in uClinux. ”

script to check status of services and mail status

2009-02-10T16:43:00.004+05:30

[if necessary use script in crontab, run auto. after a particular interval]
msg="At `date` status of services"

a=`ps -A | pgrep sipXproxy | head -n 1`

if [ ! $a ] ; then
echo "sipx is stopped"
msg=$msg"\n1) sipx is stopped"
else
echo "sipx is running"
msg=$msg"\n1) sipx is running"
fi
sleep 1

b=`ps -A | pgrep siproxd | head -n 1`

if [ ! $b ] ; then
echo "siproxd is stopped"
msg=$msg"\n2) siproxd is stopped"
else
echo "siproxd is running"
msg=$msg"\n2) siproxd is running"
fi
sleep 1

c=`ps -A | pgrep named | head -n 1`

if [ ! $c ] ; then
echo "named is stopped"
msg=$msg"\n3) named is stopped"
else
echo "named is running"
msg=$msg"\n3) named is running"
fi

sleep 1

d=`ps -A | pgrep httpd | head -n 1`

if [ ! $d ] ; then
echo "httpd is stopped"
msg=$msg"\n4) httpd is stopped"
else
echo "httpd is running"
msg=$msg"\n4) httpd is running"
fi
a=""
b=""
c=""
d=""

echo -e "\n$msg"

#echo $msg | sendmail mail_ID_here

#xterm &
#sleep 3
#wall $msg

linux commands to compare two files

2009-02-10T15:08:00.002+05:30

[root@vikas current_task]# whatis cmp
cmp (1) - compare two files
cmp (1p) - compare two files
[root@vikas current_task]# whatis comp
comp: nothing appropriate
[root@vikas current_task]# whatis comm
comm (1) - compare two sorted files line by line
comm (1p) - select or reject lines common to two files
[root@vikas current_task]# whatis diff
diff (1) - find differences between two files
diff (1p) - compare two files
diff-jars (1) - output the differences between two JAR files

Counting empty lines in a file

2009-02-10T15:02:00.004+05:30

[Count empty lines]
grep '^$' /root/Desktop/chk_services.sh | wc -l

[Count lines which are not empty]
grep -v '^$' /root/Desktop/chk_services.sh | wc -l

[Count lines start with hash #]
grep '^#' /root/Desktop/chk_services.sh | wc -l

[Count lines which dont start with #]
grep -v '^#' /root/Desktop/chk_services.sh | wc -l

Display file without empty lines and comments

2009-02-10T14:59:00.003+05:30

[This will display file contents, but dont displays the empty files and lines starting with # i.e comments]

grep -v '^#' /root/Desktop/chk_services.sh | grep -v '^$

Find 3 files bigest in size in the current dir including sub dirs

2009-02-10T14:51:00.003+05:30

find . -type f -exec ls -s {} \; | sort -n -r | head -3

Make alias of a linux command

2009-02-10T14:39:00.001+05:30

alias cmd='linux cod args'
alias vik='ls -l'

now vik works as 'ls -l'

Unalias

unalias vik

split a file into chunks

2009-02-07T13:46:00.003+05:30

[This will split file in to small parts named CHNKS_aa , ab so on ]
split -b 1m file CHNKS_

split -b 30k -a 1 mx_doc21.doc cnks_

Information about user who are login

2009-02-07T13:13:00.001+05:30

[root@vikas Desktop]# w
13:12:25 up 3:15, 2 users, load average: 0.25, 0.42, 0.30
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root tty7 :0 10:18 0.00s 5:17 5:17 /usr/bin/X :0 -br -audit 0 -auth /var/gdm/:0.Xauth -nolisten tcp vt7
root pts/1 :0.0 10:18 0.00s 1.58s 0.00s w

[root@vikas Desktop]# who
root tty7 2009-02-07 10:18 (:0)
root pts/1 2009-02-07 10:18 (:0.0)

[root@vikas Desktop]# finger
Login Name Tty Idle Login Time Office Office Phone
root VikasSharma tty7 Feb 7 10:18 (:0)
root VikasSharma pts/1 Feb 7 10:18 (:0.0)
[root@vikas Desktop]#

chfn -- change the finger information
chsh --- to change the shell