convert JPG to PDF

Just use this:

convert *.jpg output.pdf and/or convert *.jpg -adjoin output.pdf

convert books.png books.jpeg combined.pdf

convert "*.{png,jpeg}" outfile.pdf

In general case you can combine more files into one pdf file with including them inside {} and separate them with a single comma.

convert "*.{ext1,ext2,ext3,...}" outfile.pdf

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More info:

1. http://unix.stackexchange.com/questions/29869/converting-multiple-image-files-from-jpeg-to-pdf-format
2. http://catlingmindswipe.blogspot.my/2013/11/how-to-convert-jpg-to-pdf-using.html

tcpdump

Basic Usage

So, based on the kind of traffic I’m looking for, I use a different combination of options to tcpdump, as can be seen below:

Basic communication // see the basics without many options

# tcpdump -nS

Basic communication (very verbose) // see a good amount of traffic, with verbosity and no name help

# tcpdump -nnvvS

A deeper look at the traffic // adds -X for payload but doesn’t grab any more of the packet

# tcpdump -nnvvXS

Heavy packet viewing // the final “s” increases the snaplength, grabbing the whole packet

# tcpdump -nnvvXSs 1514

How change display resolution settings using xrandr

Xrandr is used to set the size, orientation and/or reflection of the outputs for a screen. It can also set the screen size. There are a few global options; the rest modify a particular output and follow the specification of that output on the command line.

Open the terminal and run the following commands

First you need to enter the following command

$ xrandr

This will display the allowed resolutions

Sample output

Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
VGA1 connected 800×600+0+0 (normal left inverted right x axis y axis) 267mm x 200mm
800×600 85.1* +
640×480 75.0 60.0
720×400 70.1

If you want to add a mode with resolution 1024X768, you can enter the following command: (The output is shown following.)

$ cvt 1024 768

Sample output

# 1024×768 59.92 Hz (CVT 0.79M3) hsync: 47.82 kHz; pclk: 63.50 MHz
Modeline "1024x768_60.00" 63.50 1024 1072 1176 1328 768 771 775 798 -hsync +vsync

Now you need to create a modeline

$ xrandr --newmode <Modeline>

copy the modeline of the previous output to the place mode line

$ xrandr --newmode "1024x768_60.00"   63.50  1024 1072 1176 1328  768 771 775 798 -hsync +vsync

Now you need to add the above mode using the following command

$ xrandr --addmode VGA1 1024x768_60.00

here for VGA1 you have to use what ever that was there for $ xrandr output

$ xrandr --output VGA1 --mode 1024x768_60.00

Running these would change your resolution but this is temporary.these steps were done to make sure that these commands work

Now we need to make these changes permanent

Now you need to edit the default file

$gksudo gedit /etc/gdm/Init/Default

Look for the following lines

PATH=/usr/bin:$PATH
OLD_IFS=$IFS

and Add the the following lines below them

xrandr --newmode "1024×768" 70.00 1024 1072 1176 1328 768 771 775 798 -hsync +vsync

xrandr --addmode VGA1 1024x768_60.00

xrandr --output VGA1 --mode 1024×768

Save and exit the file