Tag: bash

Posted on

iotop: How to monitor processes that hogs hard disk writes

iotop is a small and handy tool to monitor processes that hogs I/O resources. iotop outputs is similar to ‘top’ except it lists the hard disk read/write activity as well as swap writes.

You can use the left and write key to sort the heading according to your preference and the R key can be used to reverse the sort. The ‘O’ key is used when you only wants it to display processes that are currently utilizing the disk I/O. While the ‘P’ key can be used to display accumulated IO disk read/write for all the processes (which can be sorted with the arrow keys).

Posted on

How to make sudo display funny error messages in Ubuntu Linux

sudo is probably the most used command in Ubuntu.

In this post, I will show you how to make ‘sudo’ display funny and humorous error messages in Ubuntu Linux.

To do that, you would only need to edit the /etc/sudoers :

sudo nano /etc/sudoers

Then find the line that starts with Defaults env_reset, add insults at the end of the line so it would look like this:

# See the man page for details on how to write a sudoers file
#
Defaults env_reset, insults

Save the file, and you are done! You can test the results by running the sudo command and entering the wrong password.

Screenshot Demo

sudo insults

Posted on

Generate QR Code in Ubuntu Linux

You can easily generate QR Code under Ubuntu using the command line ‘qrencode’ package. In Ubuntu 11.04 Natty Narwhal, you can install qrencode using this command:

apt-get install qrencode

To generate QR Code image, you only need to run this command:
qrencode -l L -v 1 -o qrcode-test.png "Hello, World!"

QR Code is a form of 2 dimensional barcode which can store arbitary text data including URL, email or plain text. For more information, please refer to the QR Code Wikipedia Entry

Posted on

Easy File Encryption On Ubuntu Linux with OpenSSL

Here’s an easy way to encrypt your file using OpenSSL. The general syntax is:


openssl enc (cipher) -e -in (input file) -out (output file)

so to encrypt a “plaintext.txt” file, using aes256, you only need to run this command:

openssl enc aes256 -e -in plaintext.txt -out encrypted.txt

Similarly, to decrypt the file, you can run the command:

openssl enc aes256 -d -in encrypted.txt -out decrypted.txt

Posted on

Debian: Force users to use more secure login password with pam_cracklib

One of the factor that makes your system easily crackable is the weak password. PAM cracklib forces users to choose stronger password by analyzing the password strength, length and entropy.

To enable pam_cracklib in Debian / Ubuntu operating system, you need to install libpam_cracklib:

sudo apt-get install libpam_cracklib

Then edit the “/etc/pam.d/common-password” file using your favorite editor. Then, add and uncomment the following line at the end of the file.

password required pam_cracklib.so retry=3 minlen=6 difok=3

difok determines the number of same characters that allowed to be present in the old and new passwords.