HeatWare.net » Linux/Unix

Scripting the Linux ‘passwd’ command easily without interactive prompt

sood — Mon, 30 Apr 2012 05:27:53 +0000

If you are looking for a quick and easily solution to changing your Linux passwd from a script, you have come to the right place. As you already know, the passwd command prompts the user to enter the desired password as well as a confirmation, but I have a solution that will change the password without these prompts.

Changing Linux Password In a Scriptable Way

echo | passwd --stdin root

That’s all there is to it! No fancy bash script, no need to use Expect.

Linux ‘find’ to list files less than or greater than a certain size

sood — Tue, 17 Apr 2012 05:44:08 +0000

This article will go through some basic examples on how to list files above or below a certain size in Linux using the find command. There are many use cases for running queries like this, for instance finding small files on your hard drive or finding very large files. So, lets get started with some examples.

Using find to show files below a certain size (1000 bytes = 1K)

find . -type f -size -1000 -ls

Using find to show files above a certain size (1,000,000 bytes = 1M)

find . -type f -size +1000000 -ls

In the above commands, the -ls command will display the file size, date, and other attributes regarding the file. If you would like just the path and filename, then omit the -ls.

Fetch error installing Java on Ubuntu 11.04. Solved!

sood — Wed, 25 Jan 2012 21:48:41 +0000

I am running Ubuntu 11.04 and was trying to install the Java OpenJDK 6.0 (and 7.0) on my system but I received the following error:

Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

I tried installing several different Java packages but all of them failed with the same error. Finally, I arrived at a working solution by running the following commands:

sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner" sudo apt-get update

Now you can successfully install Java on your system!

sudo apt-get install openjdk-6-jre-headless -y

How to install PostgreSQL 8.4 on CentOS 5.5

sood — Wed, 16 Feb 2011 19:33:32 +0000

If you have tried installing PostgreSQL database on CentOS 5.5 using yum, you will notice that you an old, outdated version! There are several ways to get the 8.4.x version of Postgres installed on this OS, but here is the quick and easy method!

Installing PostgreSQL 8.4.x on CentOS 5.5

Download the PostgreSQL 8.4 repository RPM
wget http://yum.pgsqlrpms.org/reporpms/8.4/pgdg-centos-8.4-2.noarch.rpm
Add the repository
rpm -ivh pgdg-centos-8.4-2.noarch.rpm
Use yum to install PostgresSQL
yum install -y postgresql postgresql-server
Initialize the database
service postgresql initdb
Start the database
service postgresql restart
Automatically start database on boot
chkconfig postgresql on

How to install Ruby 1.8.7 on CentOS 5.5 Linux

sood — Fri, 11 Feb 2011 03:30:53 +0000

Have you tried doing yum install ruby in CentOS 5.5? If you have the default repositories configured, you will notice that it installs the ancient Ruby 1.8.5. Not ready to move up to Ruby 1.9, but would like to install Ruby 1.8.7 – well here is how to do it!

Install Ruby 1.8.7 on CentOS 5.5 (or other distributions)

yum install -y gcc zlib zlib-devel wget ftp://ftp.ruby-lang.org/pub/ruby/1.8/ruby-1.8.7-p330.tar.gz tar xvf ruby-1.8.7-p330.tar.gz cd ruby-1.8.7-p330 ./configure --enable-pthread make make install

Linux – How to disable ‘Last Login’ welcome message

sood — Thu, 10 Feb 2011 03:57:14 +0000

When you login (via SSH or other method), to a Linux box, you will see a Welcome message that displays your Last Login time and date as well as other general information regarding the system. Here is an example:


Linux sp-ubuntu 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 01:41:57 UTC 2010 i686 GNU/Linux
Ubuntu 10.10

Welcome to Ubuntu!
* Documentation:  https://help.ubuntu.com/

78 packages can be updated.
29 updates are security updates.

Last login: Wed Feb  9 21:51:41 2011 from sp-ubuntu

If you would like to disable this message when logging in, run the following command:

touch ~/.hushlogin

And now the next time you login, you will not see any welcome message! To revert this change, simply delete the .hushlogin file in your home directory.

Linux – How to find the number of files in a folder?

sood — Thu, 10 Feb 2011 03:48:21 +0000

This seems like a pretty simple piece of information to ask for, but then why is there no intuitive way for Linux novices to accomplish this? In Windows command-line, the output of the dir command includes the number of files and the number of folders in the current directory. Well, here are some ways you can do it in Linux…

Find the number of files in the current and all sub-directories

find . -type f | wc -l

Find the number of files in the current directory

find . -maxdepth 1 -type f | wc -l

Free Linux utility to convert PDF to Text file

sood — Thu, 13 Jan 2011 05:38:49 +0000

Are you looking for a fast, easy, and free way to convert a PDF document to a plain-text .txt format? Luckily, there is a built-in program in most Linux distributions that can do this called pdftotext. To convert, simply do:

pdftotext -layout filename.pdf filename.txt

How to create a large number of files in Linux (thousands or millions)

sood — Thu, 13 Jan 2011 05:24:52 +0000

Do you need an ultra fast way to create a large number of files in Linux? Perhaps, you are doing some load testing for an application and you need to create 1000 or even 1,000,000 files in the matter of seconds. Well, here is how to do it!

There are two parts to creating these files. First, is creating a single master file that contains the data that the thousands/millions files are based on. Second, splitting this master file into the total number of files that you require.

How to create the master file

Determine the number of files and the size of each file that you require
Multiply the total number of files times the size (in bytes). For example: If you want to create 10000 files that are 10 bytes each, do 10000 * 10 = 1,000,000. This represents the size of the master file that is needed.
To create this master file, run the command:

dd if=/dev/zero of=masterfile bs=1 count=1000000

The above command will create a 1 MB file called ‘masterfile’. This file contains all 0′s. If you would like it to contain random binary data, use /dev/urandom

To split the master file into thousands of pieces

Now that the master file is created, you can now use this to generate the desired 10,000 files that are 10 bytes each.
Run the command:

split -b 10 -a 10 masterfile

The -b option specifies the size in bytes of each file. The -a option defines the length of the filename of the new files +1 (-a 10 means create a 11 character long filename)

And that’s all there is to it! If you need help with any variation to this, please post it as a comment.

Using Linux ‘head’ command to preview a file

sood — Fri, 22 Jan 2010 04:07:32 +0000

This article will show you how to use the head command in Linux. head is used to print out the beginning of a file. For example, this is useful when you have a giant text file and you want to preview the contents without attempting to open the entire file. Here are some common examples on the usage:

Examples of ‘head’ command

To print out the first 10 lines of a file
head [filename]

To print out the first 50 lines of a file
head -n 50 [filename]

To print out the first 25 bytes of a file
head -c 25 [filename]