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Hi all,

We are happy to announce that we refreshed our site look and feel. From here on words the site will be more friendly without any cluttered look. We make it more user-friendly and removed unwanted things such as widgets, links and clutter data. We want to make linuxnix.com a more user-friendly site and load much faster then compared to previous site. Feel free to contact us if you have any issues with the site look.

Thanks,

Admin.

Redhat announced that they are going to release RHEL7 by second half of 2013 on the occasion of their 10th anniversary of RHEL1 release some 10 years back. Jim Totten,
vice president and general manager at Red Hat’s Platform business unit announced this in a webcast. There will be 2000 packages upgraded in this release and more improvements to support many hardware, security, Filesystems and performance.

Redhat releases their flagship distro for every 3 years and patches for every 6 months. Here is a quick release dates of all the Versions of RHEL taken from Wikipedia.org

• Red Hat Enterprise Linux 2.1 AS (Pensacola), 2002-03-26
  • Update 1, 2003-02-14 (Release Notes)
  • Update 2, 2003-05-02 (Release Notes)
  • Update 3, 2003-12-19 (Release Notes)
  • Update 4, 2004-04-30 (Release Notes)
  • Update 5, 2004-08-18 (Release Notes)
  • Update 6, 2004-12-13 (Release Notes)
  • Update 7, 2005-04-28 (Release Notes, redhat-release-as-2.1AS-121.src.rpm)
• Red Hat Enterprise Linux 2.1 ES (Panama), May 2003

• Red Hat Enterprise Linux 3 (Taroon), 2003-10-22. Uses Linux 2.4.21 (Release notes also for updates)
  • Update 1, 2004-01-16 (Release Notes)
  • Update 2, 2004-05-18 (Release Notes)
  • Update 3, 2004-09-03 (Release Notes)
  • Update 4, 2004-12-21 (Release Notes)
  • Update 5, 2005-05-20 (Release Notes)
  • Update 6, 2005-09-28 (Release Notes)
  • Update 7, 2006-03-15 (Release Notes)
  • Update 8, 2006-07-20 (Release Notes)
  • Update 9, 2007-06-15 (Release Notes)
• Red Hat Enterprise Linux 4 (Nahant), 2005-02-15. Uses Linux kernel 2.6.9-5
  • 4.1, also termed Update 1, 2005-06-09 (kernel 2.6.9-11, Release Notes)
  • 4.2, also termed Update 2, 2005-10-05 (kernel 2.6.9-22, Release Notes)
  • 4.3, also termed Update 3, 2006-03-07 (kernel 2.6.9-34, Release Notes) (Release Notes on centos.org)
  • 4.4, also termed Update 4, 2006-08-11 (kernel 2.6.9-42, Release Notes)
  • 4.5, also termed Update 5, 2007-05-01 (kernel 2.6.9-55, Release Notes)
  • 4.6, also termed Update 6, 2007-11-15 (kernel 2.6.9-67, Release Notes)
  • 4.7, also termed Update 7, 2008-07-24 (kernel 2.6.9-78, Release Notes)
  • 4.8, also termed Update 8, 2009-05-18 (kernel 2.6.9-89, Release Notes)
  • 4.9, also termed Update 9, 2011-02-16 (kernel 2.6.9-100, Release Notes)
• Red Hat Enterprise Linux 5 (Tikanga), 2007-03-14. Uses Linux kernel 2.6.18-8 (Release notes)
  • 5.1, also termed Update 1, 2007-11-07 (kernel 2.6.18-53, Release Notes)
  • 5.2, also termed Update 2, 2008-05-21 (kernel 2.6.18-92, Release Notes, single file)
  • 5.3, also termed Update 3, 2009-01-20 (kernel 2.6.18-128, Release Notes)
  • 5.4, also termed Update 4, 2009-09-02 (kernel 2.6.18-164, Release Notes)
  • 5.5, also termed Update 5, 2010-03-30 (kernel 2.6.18-194, Release Notes)
  • 5.6, also termed Update 6, 2011-01-12 (kernel 2.6.18-238, Release Notes and Errata for release)
  • 5.7, also termed Update 7, 2011-07-21 (kernel 2.6.18-274, Release Notes and Errata for release)
  • 5.8, also termed Update 8, 2012-02-21 (kernel 2.6.18-308, Release Notes and Errata for release)
• Red Hat Enterprise Linux 6 (Santiago), 2010-11-10 Uses Linux kernel 2.6.32-71 (Release Notes).
  • 6.1 also termed Update 1, 2011-05-19 (kernel 2.6.32-131, Release Notes and Release Announcement)
  • 6.2 also termed Update 2, 2011-12-06 (kernel 2.6.32-220, Release Notes and Errata for release)

Please free to share your knowledge on this.

Flower brackets examples

This is a small post on how to crate multiple files/folders, sequence generation with flower brackets in-order to save valuable time.

Creating empty files can be done with touch command. We will see how to create multiple files using this command in one shot

Example1: Create a file with name abc.txt

touch abc.txt

Example2: Create multiple files abc, cde, efg, hij, klm

touch  abc cde efg hij klm

Example3: How about creating 1 to 20 files, ie creating multiple files with one command. Its bit tedious job for an admin. Don’t worry Linux provide us with some useful option with “Flower braces” to do expansion. Instead of writing below command

touch 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

We can create 20 files using flower brace {} exapantion as shown below..

touch {1..20}

Your shell tries to expand this brace and generate 1 to 20 numbers. The above command will create total 20 files in one shot.

Example4: How about creating files as 1.txt, 2.txt, 3.txt up to 1000.txt. This can be achieved suffixing it after brackets as shown below.

touch {1..1000}.txt

Example5: how about creating a1, a2, a3 so on up to a1000 files?

touch a{1..1000}

Example6:How about generating numbers?. We can generate numbers using flower braces with echo command. The other way to generate numbers is seq command.

echo {1..10}

Example7: Even we can do sequence for alphabets as shown below

touch {a..z}

Example8: Generate files from A to Z

touch {A..Z}

Note: The above alphabets generation is done using asci values

Example9: How about creating 1 to 1000000 files in one shot, by using multiplication/matrix of numbers?. We can achieve this one with multiplying two sequences.

touch {0..1000}{0..1000}

Example10: How about creating files as multiples of 2.

touch {1..100..2}

this will create files as 1, 3, 5, 7, 9, 11 etc.

Note: This interval will work only bash version 4.0 and above, make a note about this.

Example11: How about creating files as multiples of 7?

touch {1..100..7}

Note: This interval option will work only bash version 4 and above.

Practical usage of this brackets

1)In bash for loop.

2)Generating sequence of numbers.

As mention in above examples we can create folders similarly in one shot. use -p option if you want to create folders in sub folders too.

Example12: Create a folder structure as 2012, under this i want to create 12 folders for each month and under each month create 30 folders which corresponding to 30 days.

mkdir -p 2012/{1..12}/{1..30}

read command examples

read command is useful in scripts when reading an input from user. This read command is used when the script want to interact with user for his inputs.

read command syntax
 read VARIABLE

Example1:Read a value from user input.

read VAR1

To display this value we have to use echo command.

echo $VAR1

Example2: Reading two words/variable/values at a time.

read VAR1 VAR2

Example3: Reading multiple values at a time.

read VAR1 VAR2 VAR3 VAR4

Example4: Read values in to an Array

read VAR1

ARR1=(VAR1)

to display first value in array use below command

echo ${ARR1[0]}

Example5: Read values from a command

read VAR1 VAR2 VAR3 << ( echo surendra kumar anne )

 echo "Enter values are $VAR1 $VAR2 $VAR3"

Example6: Read user input and give some info to user what he have to give. For this use -p option to display some info when reading value.

read -p "Please enter 1 to 10 numbers: " VAL1

Note: You no need to echo command to display information to user, you can achieve that one using read -p option.

Example7: Read have inbuilt variable called REPLY. this is system variable which stores read value in to $REPLY.

read -p "Please enter a value"

echo "Enter value is $REPLY"
 Please share your thoughts on this.

Linux/Unix sort command examples

This is a small tutorial on how to use sort command to soft a file. Sorting is very much useful when dealing with DB files, CSV, xls, log files in fact a text file to. By default sort command will sort according to alpha-bates. First sort tries to sort according to single character, if it finds the first character same in two lines, then it move on to sort second character. Suppose I have a following word list in a file

cat filename.txt

abc
cde
hij
klm
kle
ble

This will be sorted first with first char. When it finds both the char same in this example klm and kle start with same characters, so it tries to sort with third character which is different in them. The output of sort  as below

sort filename.txt

abc

ble
cde
hij
kle
klm

Sort command syntax

sort filename.txt

Example1: Sort a given file according to alpha-bates

 sort filename.txt

Example2: I have a file with host names in third column, how can i sort them according to this column?. Use -k for sorting according to column

sort -k3 filename.txt

The above command will sort according to third column.

Example3:I want to sort /etc/passwd file according to home directories but my sort is not working how can i sort them?. by default sort will take space/tabs as field separators. But in /etc/passwd file the field separator is : so we have to mention this one when sorting a file. This can be done with -t option

sort -t: -k6 /etc/passwd

Example4: I want to sort according to number, suppose i want to sort /etc/passwd file according to UID, use -n option to do that.

sort -n -t: -k3 /etc/passwd

Note: For example with out -n option sort will put 10 before 3 when it find this values, by default it will sort only first numerical char.

Example5: Sort the file and reverse the order

sort -r filename.txt

Example6: Some times its required to sort the file and display only uniq values.

sort -u filename

Note: though the values on other field are different this will not consider by -u option.

Example7: I want to sort a file according to my requirement and save it to a different file. Use -o option to save the sorted output to a file.

sort -o temp.txt filename.txt

You can now mix above options to get your sorting work done.

How to find command location in Linux and Unix

This is a small how to on finding your command location. Some times its required to find command location to use it as path is not set properly to /bin or /sbin or some other folder. And some times we install packages through scripts where the commands will be installed in a defined path other than /usr/bin or /usr/sbin etc.

command to check where the particular command is installed?

which command-name

Example:

which ls

Output:

root@surendra:/home/surendra# which ls
/bin/ls
root@surendra:/home/surendra#

How about getting with other command along with manual pages?

whereis command-name

Example:

whereis ls

Output:

root@surendra:/home/surendra# whereis ls
ls: /bin/ls /usr/share/man/man1/ls.1.gz
root@surendra:/home/surendra#

some times we don’t know where the command is located but still we want to use it, at these times you can use which command to give entire path

`which ls`

or

$(which ls)

the above two are very much handy when writing shell scripts when you are not aware/sure where the command located. Please share your thoughts on how you avoid this situation.

Setting up two IP address on one NIC

This is a small how-to to set up two are more IP address on single LAN card. There are some times which require two IP address to set up so that we can make a Linux box as a router. This can be possible without even having two NIC cards. We can configure two different IP address on single Network Card as shown below.

Setting up 2 IP address on “One” NIC. This example is on ethernet.

STEP 1:Setting up first IP address. Edit /etc/sysconfig/network-scripts/ifcfg-eth0 on Redhat Linux box and give the following entries as shown.

vi /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.1.10
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes

STEP 2: Setting up second IP address. Create one file as /etc/sysconfig/network-scripts/ifcfg-eth0:1 and give the entries as below in to this file.

vi /etc/sysconfig/network-scripts/ifcfg-eth0:1

DEVICE=eth0:1
BOOTPROTO=static
IPADDR=192.168.1.11
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes

STEP 3: Once you configure above files and save them. Now reload the network service on your machine.

service network reload

STEP 4: Check if you get the IP address assigned to the eth0 and eth0:1 interfaces respectively.

ifconfig

Note1: We can assign virtual IP to the same interface with ifconfig but that one is not permanent so not giving info on that.

Note2: We can assign up to 16 virtual IP address to a single NIC card.

Convert Binary,HEX, Oct to decimal

This is a small Shell tutorial on how to convert different bases to other bases.
Some times when working as system admin you require to convert different number systems to others. In this post we will see how to convert different number systems to others.

Decimal to Binary

echo "obase=2; 23" | bc

Output:
10111
Let me explain above command. obase is a special variable in bc command which defines the output base value for a given number. There is one more special variable for bc command called ibase which defines input base value. In our example we did not mention ibase so by default it will take my input value as decimal value. So we feed obase=2 and decimal number 23 to bc command to convert decimal 23 in to binary number.

Decimal to Octal number

echo "obase=8; 23" | bc

Decimal to Hex number

echo "obase=16; 23" | bc

Decimal to any base number

convert decimal number to base 4 number system

echo "obase=4; 23" | bc

How about convert to base 7?

echo "obase=7; 23" | bc

Binary to decimal

echo "ibase=2; 11010101" | bc

Oct to decimal

echo "ibase=8; 723" | bc

Hex to decimal

echo "ibase=16; 23" | bc

How about converting binary to Oct?

echo "ibase=2;obase=8 1010101" | bc

As given above we can convert any number system to any number systems

Other ways to do base convertions

bc will convert from any base to any other base. There are some other tools which can do partially these conventions.
$(()) –can convert hex to decimal
example:

echo $((0x123))

printf command can convert hex and oct to decimal

decimal to Octal

printf "%o\n" 123

decimal to Hex

printf "%x\n" 123

How to view/list only directories in Linux?

This is a small post for Linux new babies. Viewing folders can be achieved by two ways in linux/unix

1. Through ls command
2. Through find command

With ls we have to use grep to get the directory listings..

Ls –l | grep ^d

Example

[root@test surendra_a]# ls -l | grep ^d

d——— 2 surendra_a surendra_a 4096 Sep 8 09:54 HTWFAIP

drwxrwxr-x 2 surendra_a root 4096 Nov 27 12:30 LinuxCBT – RHEL5

drwxrwxr-x 2 surendra_a root 4096 Oct 12 16:40 Software

Through find command

find . -type d

The above command will show you all the file types which are directories in present working directory.