Uncovering images in Beamer presentation

Some text
\uncover<2->{
\includegraphics[]{img}
}

does not work. Graphic is included even in the first frame. Instead use:
\onslide<1-2>{
Some text
}
\invisible<1>{
\includegraphics[]{img}
}
Reference:

• http://old.nabble.com/Uncovering-figures-td14785368.html

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Lyx IEEE Journal and Conference layout

These are the steps I followed to use IEEE formatting in Lyx:

• Create IEEEtran directory
• Download the latex file IEEEtran2.tar.gz from IEEE site and extract
• Create a subdirectory named “bibtex”
• Download the bibtex file IEEEtranBST1.tar.gz from the same IEEE site to this directory and extract
• For Ubuntu, move IEEEtran directory to /usr/share/texmf-texlive/tex/latex/ and run texhash (requires sudo)
• Run Lyx->Tools->Reconfigure and restart Lyx.
• You should be able to select IEEEtran from Document Settings.

References

• Adding IEEEtran to your Lyx/LaTeX setup

Changing the paragraph environment using keyboard

From Lyx Wiki Tips:

Steering the mouse pointer to the paragraph environment drop-down menu in order to get out of an enumerate or itemize environment was starting to annoy me, especially on the road without a mouse. Fortunately, there is a solution (which apparently is undocumented, at least I couldn’t find it):

Quoting Paul from the mailing list: “M-p (alt-p) followed by a space opens the environment list. From there, repeatedly typing the same letter cycles through all environment names starting with that letter.”

phpmyadmin access problem

All of a sudden I started to get the following error:

#1045 - Access denied for user 'root'@'localhost' (using password: NO)

whenever I tried to access to mysql database through phpmyadmin. I have been using it flawless for very long time.

I modified the following file:

/var/lib/phpmyadmin/config.inc.php

by changing

$cfg['Servers'][$i]['auth_type'] = 'config';

to

$cfg['Servers'][$i]['auth_type'] = 'cookie';

and everything is working fine now.

Perl DBI – Some usefull commands

Return a reference to column names

$name = $sth->{NAME};

Number of affected rows

$sth->rows();

New auto-incremented id

$latestId = $dbh->{‘mysql_insertid’}

Uploading large data. ‘INSERT INTO’ command takes long amount of time. Use ‘LOAD DATA’ command to upload bulk data from a text file.

• Be careful. If the file to be uploaded resides on the server, it still needs to be accessible by the mysql server. E.g. you can place them under /tmp
• You can specify NULL characters by ‘\N’, e.g. “9,\N,276,John…”

Perl: Some usefull tips

Some handy Perl commands that is not used as much.

Use ‘-‘ to refer to STDOUT & STDIN.

open(INP, ‘-‘) —> STDIN
open(OUT, ‘>-) —> STDOUT
$fh = IO::File->new(‘-‘,’w’) —> STDOUT

Following the filehandle with ‘-|’ opens the output of a shell command as a file.

open($fh, ‘-|’, ‘ls -l’);
open($fh, ‘-|’, ‘cat tmp.txt | sort’);

Similarly IO::Pipe can be used to get the same affect:

$fh = new IO::Pipe;
$fh->reader(qw(ls -l));

Then you can print the output

while (<$fh>) { print; }

Open a zipped file

open(INP, ‘-|’, ‘gunzip < tmp.txt.gz’);

Print the output of a subroutine inside a string

print “3+4 is @{ [addTwoNumbers(3,4)] }\n”;

Use IO::File to store filehandles into a hash array.

$fh{‘infile’} = IO:File->new(“tmp.txt”, “r”);
while (my $line = $fh{‘infile’}->getline) {
print $line;
}
$fh{‘infile’}->close;

How to switch desktops on Ubuntu

This is how I switched my desktop from Xubuntu to Ubuntu. Different combinations are done with a similar approach. See the reference below for a detailed explanation.

• sudo apt-get update
• sudo apt-get install ubuntu
• sudo update-alternatives --config usplash-artwork.so
  • Select artwork for the boot and shutdown screens, enter the following two commands in a Terminal window:
• sudo update-initramfs -u
• sudo dpkg-reconfigure gdm
  • However both Ubuntu & Xubuntu uses gdm, following step will resolve this problem
• sudo gdmsetup
  • If this fails to launch a GUI window, first run sudo su and then type gdmsetup
  • Go to “Local” tab and select the Ubuntu theme

When you logon next time do not forget to select the “gnome” as the current session.

In my case compiz caused Ubuntu to consume a lot of CPU power so I uninstalled it:

sudo apt-get –purge remove compiz* libcompizconfig*

Reference

• PCWorld

Secure VNC with SSL

A detailed explanation of how to make VNC work over SSL can be found here. Reading that and the e-mail discussions here, I’d like to summarize the procedure:

SERVER

• Create the certificate stunnel.pem (Follow the instructions given at the link above)
• Run VNC server: vncserver :5
• Create a secure tunnel: stunnel -d 5950 -r 5905 -p /path/to/stunnel.pem
• Download the source code of x11vnc. Copy the VncViewer.jar and SignedVncViewer.jar into a folder accessible by the webserver, e.g. “/vnc“
• Create an index.html file with the following content (replace YOUR-HOSTNAME with your hostname):

  <html>
  <body>
  <applet code="VncViewer.class" archive="VncViewer.jar" width="800" height="600">
  <param name="PORT" value="5950" />
  <param name="HOST" value="YOUR-HOSTNAME" />
  <param name="Open New Window" value="no" />
  <!-- the following helps in Opera:
  <param name="Cursor shape updates" value="Disable" />
  -->
  </applet>
  </body>
  </html>

CLIENT

From a web browser you can access to the following address:

http://YOUR-HOSTNAME/vnc

Even better, if you setup the directory under SSL domain:

https://YOUR-HOSTNAME/vnc

Remote access to your parents’ computer

You can’t always be there for your parents when they need your help desperately for their computer problems. I resolved this issue with some basic software that I’d like to share. I’d like to give the basics first and I will provide more details when I have more time.

What is the problem?

• Remote computer (Possibly Windows PC) do not have a public address.
• You have a Linux server with a public IP address.
• You want to be able to securely access the remote computer.

What software?

• Putty
• TightVNC

How?

1. Install TightVNC and launch TightVNC server
   1. Set a password
   2. Optional: Only allow connections from localhost for security
2. Install Putty
   1. Create a session to connect to your Linux server
   2. In the SSH options click on the tunnel and create a remote port forwarding. (Source: 5900, Destination: localhost:5911, Remote option selected)
   3. Save and connect to your server
   4. Optional: You can create keys to login to your server without a password. One less password to remember for them.
3. At the Linux server, launch vncviewer to port 5911, i.e. vncviewer localhost:11

Some security tips

• We are using putty because tunneling VNC over SSH makes it secure. You can also setup VNC over SSL and access their computer from any browser. Check out this post.
• Allowing only local access makes it more secure against external attacks. TightVNC server only responds if the Putty is running.

WordPress vs. Blogger

After using Blogger for awhile I decided to switch to WordPress for the following reasons:

1. WordPress provides free source code and you can easily migrate your blog to your own web server at anytime.
2. WordPress supports hierarchical categories as well as tags.
3. “…wordpress.com” is cooler than “…blogspot.com”.. :)

I will report my experiences..