Sunday, December 29, 2013

GitLab SSH

GitLab HELP instructions on how to connect GitLab with SSH seems not to be 100% complete.
What it mentions is:

SSH Keys

SSH key allows you to establish a secure connection between your computer and GitLab
To generate a new SSH key just open your terminal and use code below. 

ssh-keygen -t rsa -C ""
# Creates a new ssh key using the provided email
# Generating public/private rsa key pair...
Next just use code below to dump your public key and add to GitLab SSH Keys 

cat ~/.ssh/
# ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC6eNtGpNGwstc....
When I tried this and uploaded public RSA key to my GitLab profile i still got error when trying 'git push':

Agent admitted failure to sign using the key.
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

So i read somewhere that missing part is to execute:

ssh-add ~/.ssh/id_rsa

Now SSH connection works fine.

Sunday, December 22, 2013

Raspbmc home media center

Most of recent TV sets are already packed with bunch of hi-tech stuff that change the way we perceive watching TV. In the past we were bound to a range of channels, even though having satelite at home gave us quite a wide rande of it - counted in hundreds. The Internet added completely new possibilities. Almost every TV available today  has internet connectivity. We do not any longer have to stick to what is beeing broadcasted but we choose ourselves what to watch and when.

What if you have an old TV without RJ45 socket or WiFi? Do you have to buy special subscription or decoders to access a large entertainment centers?
No, you can have it all for free with Raspberry Pi.

All you need to do is download Raspbmc Linux image and put it on SD card, which you then insert to Raspberry Pi.
Then you plug Raspberry Pi to internet - Raspbmc has DHCP configured by default so it will boot and start setup automatically after you tun it on.
Then you also plug it to TV with HDMI cable and watch things happen. I don't have a keyboard, how to steer my new media centre?
XBMC offers a few possibilities of remote control.
I found Yatse on my Andorid smart phone the easiest way.

You can then add audio and video plugins that allow you to watch or listen to various media channels, search through Youtube or Vimeo and many, many others...

Still don't forget you have a small computer on board so you can do other stuff with it, program, setup webserver, etc. If you'd like to connect to it even for such a prosaic thing as uploading some files, you can access it through SSH.

Here's a good tutorial how to do it.

E.g. to upload file to /tmp folder on Pi:
scp file.mp4 pi@

The default pi password is raspberry

If you want you can configure WiFi on Raspbmc like this.

You can also play with XBMC and try extending it with new features. Have a look at development tutorials here.

If you'd like to have access to media channels in your local language, like me in Polish, you'd probably find some plugins for your language in the web. I found some for mine.

Have fun !

Wednesday, November 13, 2013

Amazon AWS Change Instance Type

Changing instance type is quick with Amazon AWS CLI tools.
First download tools from
Then setup env. variables for easy use of tools:

1. Set EC2_HOME as path to your unzipped archive
2. Add EC2_HOME/bin to your PATH variable
3. Set env. variables with your access key and secret key which you can get from

Follow the steps here for more guidance.
You can also check how to install it on Ubuntu here.

3. Test it, type from command line:

You should get response with info about your AWS instances.

Then when you already have instance running, let's say of type m1.small and you want upgrade it to m1.medium follow the below steps (supposing you have instance with ID = i-a57e31dc):

NOTE: After you change type your public DNS of instance will change. You must have EBS boot instance (not instance-store or S3-based AMI).

1. c2-stop-instances i-a57e31dc

2. Optionally, create a snapshot of old instance for future use - see ec2-create-image

3. ec2-modify-instance-attribute --instance-type m1.medium i-a57e31dc

4. ec2-start-instances i-a57e31dc

Friday, November 1, 2013

Rapspberry Pi Webcam

Next trial with RP, this time setting up a webcam over HTTP.

I followed the steps:

1. Connect webcam to USB port, check device is recognized

I got:

Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. 
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp. 
Bus 001 Device 004: ID 046d:0802 Logitech, Inc. Webcam C200
Bus 001 Device 005: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter

2. Install Motion

sudo apt-get install motion
3. configure Motion

sudo nano /etc/motion/motion.conf
This is my file:

text_left=(c) Nestcam
text_right=%d %b %Y\n%k:%M:%S

sudo nano /etc/default/motion
It should be:


4. Start motion daemon:

sudo /etc/init.d/motion start

Check logfile for any errors:

tail -f /var/log/syslog

If all is fine open in browser http://<your Raspberry Pi IP address>:8080

Raspberry magic

Long time since I've written last time on my English blog page. Time to switch a bit from Polish to this one.

Some time ago I met Raspberry Pi for the first time. I had a chance to play with it and went as far as setting it in headless mode.

Today I got it back from dust and gave it next chance.
My aim was to set it up as small home server and media center.

At home I have a dynamic IP which updates more-less every 24 hours. I know solutions like DynDNS. I even used it but it was not perfect. Very often the IP stored in cloud service was not refreshed with new IP of my rooter at home.

My idea was to create a daemon program that would run in background periodically and check if external IP of the router changed. Then it should send me an email with new IP.
As genial as simple :) I could then easily use this IP to connect with remote desktop to my home server.
Surely it would not be useful if I want to setup web page and release it in the Internet to public because still the IP will change but this is not my purpose. My aim is to connect with home server by IP and use it for many purposes like monitoring what's going on at home (smart house) or working on my home machine (upload/download/program/watch a movie?? whatever comes to my mind).

Raspberry Pi seems to be interesting in this context.

Today I will explain how I set up virtual desktop connection with TightVNC.

1. Install TightVNC Server on Raspberry Pi

sudo apt-get install xrdp

2. Start remote desktop server

you will be asked for password, type password and do not ser view-only password when you will be asked for this.

3. Check ports on which xtightvncserver is running

sudo netstat -tulpn
Then you will have to setup your router to forward ports, e.g: is the IP of Raspberry Pi in home network behind the router.

On your machine from where you want to connect to Raspberry Pi install TightVNC Viewer, on Ubuntu you can do this with command:

sudo apt-get install xtightvncviewer
Then connect to Raspberry Pi

xtightvncviewer is my router external IP, the one that I would like to email myself from PI whenever it changes.

How to email anything from Raspberry Pi?
Very easy with Python:

import smtplib
# Specifying the from and to addresses
fromaddr = ''
toaddrs  = ''
# Writing the message (this message will appear in the email)
msg = 'Enter you message here'
# Gmail Login
username = 'username'
password = 'password'
# Sending the mail 
server = smtplib.SMTP('')
server.sendmail(fromaddr, toaddrs, msg)

How to check your external IP address?
Very easy with service like

curl -s
Putting it all together. Python script below gets IP address and compares it with address saved in local file. If for any reason IP is empty or same as the IP in local file then no email is sent. Otherwise an email is sent with new IP and the IP is saved in local file (dyndns.txt)

#!/usr/bin/env python

import smtplib
import subprocess
import sys

def send(ip):    # send mail
 # Specifying the from and to addresses
 fromaddr = 'change_me'
 toaddrs  = 'change_me'
 # Writing the message (this message will appear in the email)
 msg = "Your IP is  "+ip 
 # Sending the mail  
 server = smtplib.SMTP('')
 server.sendmail(fromaddr, toaddrs, msg)

proc = subprocess.Popen(["curl","-s",""], stdout=subprocess.PIPE)
ip = out.strip()
print "IP is " + ip

if ip == "": 
 raise SystemExit
 txtf = open("dyndns.txt","rw")
 lines = txtf.readlines()
 oldip = lines[0].strip()
 if oldip != ip:
  print "Sending ip " + ip
  txtf = open("dyndns.txt","w")
  print "IPs are the same"
  raise SystemExit
The script must be given execution rights and dyndns.txt file read/write access

sudo chmod +x
sudo chmod 666 dyndns.txt
Then you can schedule with cron to execute this script every 15 minutes:
sudo crontab -e
Add this line at the end of the file

*/15 * * * * python /etc/init.d/ >> /var/log/dyndns.log 2>&1 &
Above line is correct when you have your script placed in /etc/init.d/
It will store logs in /var/logs/dyndns.log but first you need to create such file and give it read/write access:
sudo touch /var/log/dyndns.log
sudo chmod 666 /var/log/dyndns.log

You can check your cron logs with

grep CRON /var/log/syslog

Now you should get mail with IP in 15 minutes. Let's verify quickly that you really can connect to Raspberry Pi on this IP.
We will start HTTP server on Pi with python, type this in console:

python -m SimpleHTTPServer
Server would listen on port 8000 so you need to forward this port in rooter configuration.
Then type in browser: http://<IP from email>:8000
Server should response with content of folder in which you started SimpleHTTPServer.

In future post we will have a look at how we can run Node.js on Raspberry Pi. Stay tuned!!

Used resources: