Resetting usb devices/hubs from command line

To reset "hung" usb device (ie to simulate unplugging and replugging it) I use nice program usbreset. It can be downloaded from GitHub (and I suppose from many other places). After compiling (gcc usbreset.c -o usbreset) it is ready to use.

For mass-resseting usb devices I use this small script:

#!/bin/bash

for d in `find /dev/bus/usb/ -type c`
do
    echo $d
    /usr/local/bin/usbreset $d
done

Display full dataset name in Weka Experiment Environment

When analyzing results in Weka Experiment Environment, the common problem is that default dataset name's width is 20. Thus, in the result page you can't see the full name of the dataset:

But fortunatelly you can change it quickly: just klick: Output format: Select -> ResultMatrixPlainText -> row name width and change it to a desired value (eg 120):

Using sequential symmetric gpg encryption with different ciphers.

This method is good for encrypting short messages (while it uses variables for storing information and generates plain text output), but can be easily modified to encrypt larger files (using temporary files instead of variable).

(1) Encryption

First, define which ciphers and in which order you want to use. For more information about ciphers avaliable, type:

gpg --version

and jump to the section "ciphers" or "symmetric":

Symetryczne: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256,
             TWOFISH, CAMELLIA128, CAMELLIA192, CAMELLIA256

Enter them in the config section of our "encrypt-multiple.sh" script:

#!/bin/bash

algos="TWOFISH AES256 CAMELLIA256 BLOWFISH CAST5" # list of ciphers to use

# -----------------------------------------------------#

# clearing variables
pass=""
pass2=""

# entering passwords
echo -n "Password: "
read -s pass
echo
echo -n "Re-enter password: "
read -s pass2
echo

# does passwords match?
if [ "$pass" == "$pass2" ]; then
    echo "Passwords mach. Encrypting."
    echo

input=`cat "$1"`

for algo in $algos
do
    ((i++))
    echo "*** ($i) $algo"
    input=`echo "$input" | gpg --no-tty --batch -a --symmetric --cipher-algo "$algo" --passphrase "$pass" -o-`
done

echo "$input" > "$1".asc.$i
echo "Encrypted message saved to $1.asc.$i"

# clearing passwords and inputs
input=""
pass=""
pass2=""

else
    echo "Passwords doesn't match"
fi

So now if you want to encrypt message in file.txt, just run:

encrypt-multiple.sh file.txt

After entering passphases (twice) you will get the encrypted file "file.txt.n" where n is a number of used ciphers (n will be necesary while during decryption).

(2) Decryption

For decrypting above message we just need to enter valid password. We don't need the names and order of used ciphers as gpg detects it automagically. The n - number of passes (used ciphers) is "encoded" in file extension.

#!/bin/bash
pass=""

# entering passwords
echo -n "Password: "
read -s pass
echo
input=`cat "$1"`

# list of Ciphers are not necesary as gpg detects it; read from file extension
algos="${1##*.}"
echo "Encrypted $algos times. Decrypting..."

for i in `seq 1 $algos`
do
    echo "*** $i"
    input=`echo "$input" | gpg --no-tty --batch -d --passphrase "$pass" -o-`
done

echo "Decrypted message:"
echo "---------------------------------------"
echo "$input"

# clearing passwords and inputs
input=""
pass=""
pass2=""

(3) Output file sizes.

Output file sizes inceases as more ciphers are used. Here is an example of file sizes (uncompressed and compressed with bzip2). Cipher used are:
TWOFISH AES256 CAMELLIA256 BLOWFISH CAST5 TWOFISH AES256 CAMELLIA256 BLOWFISH CAST5.

More reading about ciphers and symmetric encryption: GPG Encryption Guide - Part 4 (Symmetric Encryption).

(4) Bonus

If you want to try decoding, here is 5-fold encrypted text (n=5). The password is chemoinformatics.

Encrypt command to execute

On one of servers I have access to I wanted to have a bash script knocking to my home server and then – after the sesame is open – ssh into it. But I didn’t want to store knock sequence in the bash script or file, that everyone has (a potential) access to. Here is small how-to use gpg to encrypt/decrtypt commands to execute.

 

(1) Create a file with command to execute, eg in file command.txt:

knock example.com 120:tcp 121:udp 122:tcp && sleep 1s && ssh username@example.com

 

(2) Encrypt the file with gpg:

gpg -a --symmetric --cipher-algo TWOFISH command.txt

(cipher algorithm here is TWOFISH, but can be anything else). New file command.txt.asc should be created.

 

(3) Create a script which decrypt and execute above command:

#!/bin/bash
command=`gpg -d  command.txt.asc  2> /dev/null`
eval "$command"

This command will ask for the passphase and after successfull decryption will run desired command.

(simple) webcam image analysis

Here I present simple webcam image analysis and it's variation in time.

Intro

I have a webcam, connected to my Raspberry Pi server. Photos are taken every five minutes with fswebcam. Such collection of photos you can use for creating eg. time lapse video (here is an example of one-day video taken from my window). But you can also perform an analysis of image composition and it's variation over time.

Howto

Gathering data

Wen we have photos taken during a day gargered in one directory, we can use a simple script to analyse subsequent frames. ImageMagick is used to convert photos to 1x1 px size and get their HSB and RGB values.

#!/bin/bash

OUT=webcam.dat

echo "#i        h       s       v       r       g       b" > $OUT

for image in *.jpg
do

((i++))

hsb=`convert "$image" -colorspace hsb  -resize 1x1  txt:- | sed 1d  | tr '()%,:' ' '`

h=`echo $hsb | awk '{print $8}'`
s=`echo $hsb | awk '{print $9}'`
v=`echo $hsb | awk '{print $10}'`

rgb=`convert "$image" -colorspace rgb  -resize 1x1  txt:- | sed 1d  | tr '()%,:' ' '`

r=`echo $rgb | awk '{print $3}'`
g=`echo $rgb | awk '{print $4}'`
b=`echo $rgb | awk '{print $5}'`

echo "$i        $h      $s      $v      $r      $g      $b" >> $OUT

done

Data visualisation

Then we use a gnuplot script to get pretty plots:

set pointsize 2
# Line style for axes
set style line 80 lt rgb "#808080"
# Line style for grid
set style line 81 lt 0  # dashed
set style line 81 lt rgb "#808080"  # grey
set grid back linestyle 81
set border 3 back linestyle 80
set xtics nomirror
set ytics nomirror
set xlabel "frame number"
set terminal png nocrop enhanced font "Gill Sans,8" size 700,500

plik='webcam.dat'

set ylabel "HSB [%]"

set output "out/hsv-csplines.png"
plot plik using 1:2 smooth csplines title "Hue" lt rgb "red" lw 1,\
plik using 1:3 smooth csplines title "Saturation" lt rgb "green" lw 1,\
plik using 1:4 smooth csplines title "Brightness" lt rgb "blue" lw 1

set output "out/hsv-bezier.png"
plot plik using 1:2 smooth bezier title "Hue" lt rgb "red" lw 1,\
plik using 1:3 smooth bezier title "Saturation" lt rgb "green" lw 1,\
plik using 1:4 smooth bezier title "Brightness" lt rgb "blue" lw 1

set ylabel "RGB"

set output "out/rgb-csplines.png"
plot plik using 1:5 smooth csplines title "Red" lt rgb "red" lw 1,\
plik using 1:6 smooth csplines title "Green" lt rgb "green" lw 1,\
plik using 1:7 smooth csplines title "Blue" lt rgb "blue" lw 1

set output "out/rgb-bezier.png"
plot plik using 1:5 smooth bezier title "Red" lt rgb "red" lw 1,\
plik using 1:6 smooth bezier title "Green" lt rgb "green" lw 1,\
plik using 1:7 smooth bezier title "Blue" lt rgb "blue" lw 1

Output: plots

HSB, with different methods of curves smoothing

 

RGB, with different methods of curves smoothing

 

Live monitoring

To get the plots almost live, we can use rrdtool to gather, store and plot those data. First, create rrd database:

#!/bin/bash
rrdtool create hsb-rgb.rrd \
--step 300 \
DS:h:GAUGE:600:0:100 \
DS:s:GAUGE:600:0:100 \
DS:j:GAUGE:600:0:100 \
DS:r:GAUGE:600:0:255 \
DS:g:GAUGE:600:0:255 \
DS:b:GAUGE:600:0:255 \
RRA:AVERAGE:0.5:1:288                   \
RRA:AVERAGE:0.5:6:336                   \
RRA:AVERAGE:0.5:24:732                  \
RRA:AVERAGE:0.5:144:14600       \
RRA:MIN:0.5:1:288                       \
RRA:MIN:0.5:6:336                       \
RRA:MIN:0.5:24:732                      \
RRA:MIN:0.5:144:14600   \
RRA:MAX:0.5:1:288                       \
RRA:MAX:0.5:6:336                       \
RRA:MAX:0.5:24:732                      \
RRA:MAX:0.5:144:14600

Then add such lines to your webcam script (launched from cron every 5 minutes). $OUT_FILE is variable pointing to a just taken photo.

hsb=`convert "$OUT_FILE" -colorspace hsb  -resize 1x1  txt:- | sed 1d  | tr '()%,:' ' '`

h=`echo $hsb | awk '{print $8}'`
s=`echo $hsb | awk '{print $9}'`
v=`echo $hsb | awk '{print $10}'`

rgb=`convert "$OUT_FILE" -colorspace rgb  -resize 1x1  txt:- | sed 1d  | tr '()%,:' ' '`

r=`echo $rgb | awk '{print $3}'`
g=`echo $rgb | awk '{print $4}'`
b=`echo $rgb | awk '{print $5}'`

# update rrd database:
rrdtool update hsb-rgb.rrd "N:$h:$s:$v:$r:$g:$b"

Finally, after some data are collected, we can plot a nice graph (actually, we can plot it every five minutes, as new data arrives):

#!/bin/bash

BAZA=hsb-rgb.rrd

rrdtool graph hsb-24h.png  \
        --imgformat PNG \
        --start "now-24h"\
        --title="HSB [%]"       \
        --height 240    \
        --width 420    \
        --lazy \
        --alt-autoscale \
        --alt-y-grid \
        DEF:h=$BAZA:h:AVERAGE \
        DEF:s=$BAZA:s:AVERAGE \
        DEF:j=$BAZA:j:AVERAGE \
        LINE2:h#FF0000:"Hue"\
        LINE2:s#00FF00:"Saturation"\
        LINE2:j#0000FF:"Brightness"</pre>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFCZoyRIhEXYQEgSiiI3RGEZFtSfnJog6hNDprEf8JzjU7_1v8DCDAnxSUuxBcq3tqSYGJkfdr4UoZ2rHV-BBREHFU8KE4Flnob8XnD7_5PhWOzuxG9B8sidzWmhX8PGtMGFU0Rlo_l7XL/s1600/HSB-24h.png" imageanchor="1" ><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFCZoyRIhEXYQEgSiiI3RGEZFtSfnJog6hNDprEf8JzjU7_1v8DCDAnxSUuxBcq3tqSYGJkfdr4UoZ2rHV-BBREHFU8KE4Flnob8XnD7_5PhWOzuxG9B8sidzWmhX8PGtMGFU0Rlo_l7XL/s320/HSB-24h.png" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyGserUs6dUyqdudZA5_UagqTuZTj_weClykD_LKd_6ENAYSKw5tuqsugFVGbGH73rxJAH1kDhs2dCF_DBLB_H_dxZsD6k7XRRYFcdzP9uVgJKxIdA675z53hNIAeX0BXE2UsswMLBRK9D/s1600/RGB-24h.png" imageanchor="1" ><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyGserUs6dUyqdudZA5_UagqTuZTj_weClykD_LKd_6ENAYSKw5tuqsugFVGbGH73rxJAH1kDhs2dCF_DBLB_H_dxZsD6k7XRRYFcdzP9uVgJKxIdA675z53hNIAeX0BXE2UsswMLBRK9D/s320/RGB-24h.png" /></a>

Conclusions

I don't know, if this makes any sense, but looks cool :)

Bash script to generate knock sequences

Here is a simple bash script to generate random knock/knockd sequences with desired length, port ranges and types:

#!/bin/bash

# ---- config.
knocks_number=5
knocks_types=('udp' 'tcp');

port_min=1000
port_max=2000

# ---- config end

dport=$(( $port_max - $port_min ))

for i in `seq 1 $knocks_number`
do
    sequence=$sequence$[`shuf -i $port_min-$port_max -n 1` ]":"${knocks_types[ $[($RANDOM % 2)] ]}","
done

echo
echo "# A sequence for knockd.conf:"
echo "sequence = $sequence" | sed 's/,$//g'
echo "# A sequence to use with knock"
echo "knock \$ADDRESS $sequence" | sed 's/,/ /g'

The output may looks like:

# A sequence for knockd.conf:
sequence = 1460:udp,1344:tcp,1997:tcp,1712:udp,1304:udp
# A sequence to use with knock
knock $ADDRESS 1460:udp 1344:tcp 1997:tcp 1712:udp 1304:udp

Control your computer with jabber/google talk and PHP

(I doubt this would be very useful, however maybe you will find it interesting)

Intro

When your linux box is hidden behind nat/firewall with no ssh/www/... access, you can use jabber protocol to control your computer (or do it for other purposes).

(hint: when you have access to ssh server you can use SSH tunneling for connection to your machine)

Prerequisites

You will need:

• two jabber account (can be gmail account): one used only on remote computer, second can be your regular gmail account. Add each accounts to their contact lists.
• on the linux box you want to connect with: php-cli installed
• XMPPHP (download and unpack) with applied bug fix described here in XMLStream.php.
• optionally: account on the server dedicated for this purpose (eg: adduser jabber). 

Script

here is simple script which connects to your jabber account (which is probably gmail/google talk), listen to your commands, executes it and return to you:

• the code of main script pasted here

To run this script in a background, check periodically if the script is running (and client is connected to a jabber server) you would also need a wrapper

• the code of a wrapper is pasted here

To execute above wrapper periodically, just add a line to your crontab:

*/5 * * * * /home/jabber/bin/jabber/wrapper.sh 1> /dev/null 2> /dev/null

here is a screenshot from session with my raspberry pi server: