Answer:

A newer version of MySQL use upstart to autostart when system bootup, to disable it

# sudo mkdir /etc/init.disabled
# sudo mv /etc/init/mysql.conf /etc/init.disabled/

Answer:

To upgrade a single package, first need to perform an update first.

# sudo apt-get update

Then use the install sub command to perform an upgrade, e.g. apache2

#sudo apt-get install apache2

Answer:

If you have opened a port using the ufw command in Ubuntu, but now you want to delete it, you can..

# sudo ufw delete allow 8080/tcp

And then do a reload

# # sudo ufw reload

That's all.

Answer:

To perform a reverse DNS lookup for a domain in Linux, you can use the dig command, e.g.

# dig -x 8.8.8.8

; <<>> DiG 9.7.0-P1 <<>> -x 8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59808
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;8.8.8.8.in-addr.arpa.          IN      PTR

;; ANSWER SECTION:
8.8.8.8.in-addr.arpa.   86328   IN      PTR     google-public-dns-a.google.com.

..

Answer:

The erase old downloaded packages from apt-get's cache, which are stored under the location: /var/cache/apt/archives

Try:

# sudo apt-get autoclean

Answer:

In newer version of Ubuntu such as 10.04, some services are managed by upstart and you cannot disable them by using the old method.

For example, to disable the OpenSSH server, you need to edit the file /etc/init/ssh.conf, comment out the following lines:

# start on filesystem
# stop on runlevel [!2345]

Then this service will not start when you reboot your machine next time. All the upstart configurations files are under this folder and feel free to try it out.

Answer:

To allow a remote IP for incoming connection in Ubuntu's UFW (Uncomplicated firewall), you can use the following command:

# sudo ufw allow from x.x.x.x

Of course you need to reload the firewall.

# sudo ufw reload

Answer:

Qt bindings to WebKit have been added since 4.4, so you can use PyQt to script the browser (Webkit based).

Firstly, make sure you have installed the need packages:

# sudo apt-get install libqt4-core libqt4-webkit python-qt4

Then you can write a simple script to test, e.g.

#!/usr/bin/env python

import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *
from PyQt4.QtWebKit import *

app = QApplication(sys.argv)

web = QWebView()
web.load(QUrl("http://www.google.com"))
web.show()

sys.exit(app.exec_())

Answer:

To update the the RubyGems installed in Ubuntu, enter the command below:

# sudo gem update --systemNow

That's it.

Answer:

The full list of Ubuntu's managed Perl modules is here (for lucid): http://packages.ubuntu.com/lucid/perl/

You can use apt-get into install those modules, instead of CPAN. The advantage is you can remove them easier with the apt-get command, while for CPAN, you need to do it manually.