Archive for the ‘Linux & Unix’ Category

How does Ubuntu’s screenshot tool Take Screenshot actually work?

Friday, November 27, 2009 posted by andreea

The easiest way to make screenshots is to use Take Screenshot. You find it under Applications/Accessoires.
First change the delaytime for the screenshot from 0 to 1 or 2 seconds. This is the time you have to mark the chosen area. You should be fine with 1 second!

Then choose your screenshot option, e.g. Grab the current window. Klick on Take Screenshot and activate the window you need.


Take Screenshot closes. If all works well, a pop-up comes up to ask where to save the screenshot, which comes a s a .png.


For another screenshot you have to open the application again, so put it best in your panel.

The uncommon thing is that you have to run first Take screenshot and then choose an object, and not the other way round. That's it!

How to install a professional image editing tool (KRITA) for Ubuntu 9.10

Thursday, November 26, 2009 posted by andreea

KRITA is a free image editing tool that ist pretty versatile and helps you not only to edit images, but also to use it for more artistic work on e.g. tablet PCs. It will surely remind you of Photoshop.
The easiest way to install KRITA is to download it over the Ubuntu Software Center. Do not take the complicated way to install it manually...

First go to Applications/Ubuntu Software Center:


Type in the searchfield KRITA and press Enter to mark KRITA for installation.
As KRITA appears, double click it, and then just klick on the Install button, start the installation and wait some seconds.


Now KRITA should appear checked as it has beeninstalled. That's it!


How to enable active corners aka Exposé in Ubuntu 9.10 with Ubuntu Tweak

Wednesday, November 25, 2009 posted by andreea

If you always wanted the Exposé effect on your Ubuntu Desktop, here you go!  Active corners, known from Mac as Exposé, allow you e.g. to see all your open windows at once just by one mouse move into the corner of the desktop. Very useful if you are a multi-tasking god or goddess!

First open you terminal and copy & paste:

sudo apt-key adv --recv-keys --keyserver FE85409EEAB40ECCB65740816AF0E1940624A220

Log in with your admin password and continue:

sudo gedit /etc/apt/sources.list

Then add the following lines at the end of the file:

deb karmic main
deb-src karmic main

The source of Ubuntu tweak will be added to your repository. Updates for Ubuntu-Tweak will be installed automatically in future. Install Ubuntu-Tweak:

sudo apt-get update
sudo apt-get install ubuntu-tweak

Before using Ubuntu-Tweak, make sure you enabled visual effects for your desktop. Go to System/Preferences/Appearance an check under Visual Effects "Normal".

Check your system tools for Ubuntu-Tweak, open it and go to Desktop, then to Compiz Fusion as you can see here:
tweak tweak2 tweak3

Now you can enable a function for every corner, as you like. That's it.

How to reset the administrator password in ISPConfig 3

Friday, November 6, 2009 posted by Till

If you lost your ISPConfig 3 administrator password, you can reset it with the following SQL query.

UPDATE sys_user SET passwort = md5('admin') WHERE username = 'admin';

The SQL query sets the password to "admin" for the user "admin", it has to be executed in the ISPConfig mysql database, e.g. with phpmyadmin. If you dont have phpmyadmin installed, then the query can be executed with the mysql commandline utility as well:

Login to the mysql database.

mysql -u root -p

and enter the password of the mysql root user. To switch to the ISPConfig database, run this command:

use dbispconfig;

Now execute the SQL command:

UPDATE sys_user SET passwort = md5('admin') WHERE username = 'admin';

and close the mysql shell:


How to open winmail.dat files on Ubuntu and Debian Linux

Friday, November 6, 2009 posted by Till

The winmail.dat file is a container file format used by Microsoft Outlook to send attachments in richtext formatted emails. To open winmail.dat on Linux, use the tnef utility.


sudo apt-get install tnef


Open a shell window, navigate to the directory where the winmail.dat file is saved,  then execute the command:

tnef winmail.dat

to extract all files that are stored in the winmail.dat into the current directory.

How to enable port 465 (smtps) in postfix mailserver

Wednesday, October 28, 2009 posted by Till

More and more internet access providers are closing port 25 to reduce spam except for connections to their own mailservers. If you run your own mailserver and have problems to connect to it on port 25, you can enable port 465 (smtps) in postfix as a workaround. Edit the /etc/postfix/ file:

vi /etc/postfix/

and remove the # in front of the smtps line. Example for Debain 5, change the line:

#smtps     inet  n       -       -       -       -       smtpd


smtps     inet  n       -       -       -       -       smtpd

and restart postfix:

/etc/init.d/postfix restart

How to prevent a Linux system user from loggin into the system

Friday, October 23, 2009 posted by Till

If a linux system user is able to login on the shell or with SSH depends on its shell setting in /etc/passwd. If you want to prevent that a certain user is able to login, then set the shell either to /bin/false or /sbin/nologin.

Example for Debian and Ubuntu Linux for the user with the username "otheruser":

usermod -s /bin/false otheruser

For Redhat, Fedora or CentOS use /sbin/nologin:

usermod -s /sbin/nologin otheruser

Warning: Do not set the shell for the root user to /bin/false or /sbin/nologin!

If the root user stores a file in the home directory of another user or any other directory that is owned by another user, this other user is able to delete the file even if the file is owned by root and has 700 permissions.


root@workstation:/home/otheruser# ls -la
total 8
drwxr-xr-x 2 otheruser otheruser 4096 Oct 23 11:52 .
drwxr-xr-x 3 root      root      4096 Oct 23 11:51 ..
-rwx------ 1 root      root         0 Oct 23 11:52 root_users_file

If I su now to "otheruser", I'am able to delete the file as "otheruser" is the owner of the directory where "root_users_file" is stored:

root@workstation:/home/otheruser# su otheruser
sh-3.2$ rm root_users_file
rm: remove write-protected regular empty file `root_users_file'? y

Now to protect the file from beeing deleted, use the command chattr +i:

chattr +i root_users_file

and then try again to delete the file as "otheruser", the action will be denied:

root@workstation:/home/otheruser# su otheruser
sh-3.2$ rm root_users_file
rm: remove write-protected regular empty file `root_users_file'? y
rm: cannot remove `root_users_file': Operation not permitted

Now even root is not able to delete or edit the file anymore. With the command chattr -i the protection can be removed:

chattr -i root_users_file

How to reset the MySQL root password

Wednesday, October 21, 2009 posted by Till

The following steps describe the procedure to reset the mysql root password on Linux.

1) Stop the mysql server

/etc/init.d/mysql stop

2) Start the mysql server manually without permission tables which allows us to login as root user without password:

mysqld_safe --skip-grant-tables &

3) Login into mysql as root user without a password and switch to the "mysql" database:

mysql -u root mysql

Then execute this SQL query to set a new password for the mysql root user:

update user set Password=PASSWORD('mynewpassword') WHERE User='root';

(Replace "mynewpassword" with the new root password in the above command).

Then logout from the mysql prompt by typing:


4) Now bring back the running mysql instance into the foreground by typing:


and then press [ctrl] + c to kill the mysql process.

5) Start the mysql server again:

/etc/init.d/mysql start

The cronjobs (crontabs) for all system users in Debian and Ubuntu Linux are stored in the directory /var/spool/cron/crontabs. To make a backup with tar, use this command:

tar pcfz /root/user_crontabs.tar.gz /var/spool/cron/crontabs

The backup file user_crontabs.tar.gz is be stored in the /root/ folder.