Monday, 24 October 2011

Regaining access to an AWS (Amazon) Linux machine

Say you secured so much your AWS server you can only login with SSH keys there. And you have only one SSH key that can access that server. And you lost your SSH key or forgot the passphrase for it.

Are you damned to lose all that work you have poured into that machine? Probably not, if you have the luxury of some downtime.

AWS does not have any (easy) way to just change the SSH key that can access to a system.

So after 30 minutes of attempts this is how I managed to get access back to my machine.
  1. Create another machine (a copy or just a new one it doesn't matter) and start it up. Pay attention to authorize a new SSH key that works to access this machine.
  2. Shut down the original machine
  3. Detach the (root) disk volume
  4. Attach that volume to the running instance
  5. mount the root partition (running dmesg or fdisk -l will tell you what to mount)
  6. go to <mtpoint>/root/.ssh/
  7. vi authorized_keys and add there the public key of your new key
  8. shutdown this new machine
  9. detach the volume
  10. reattach it to the old instance
  11. restart the instance and ssh into it with the new key

Be happy.

Ps. I found here another method involving snapshots but I just couldn't make it work. For some reason the cloned machine was always empty.

Saturday, 27 August 2011

Buying group - Goodstuff from Italy

To all my friends in Finland (if I didn't send you an email already): it's that time of the year.

If interested in good food from Italy go and fill the webform (now improved usability!)

I hope to have all the orders by mid September (in 3 weeks), place the order in 4 and get the stuff within the second week of October. If everything goes fine :)

Wednesday, 22 June 2011

N9 - Against all odds

Well it wasn't (and it's still not) easy to run the IT behind harmattan/N9. But we made it. And the feedback on the device is just bursting for us behind the scenes. The whole Nokia/MeeGo team has pulled off a beautiful device against all odds. It's true that difficulties makes you stronger.

I am proud of all my team and all my colleagues.

Thank you all for making it the most challenging and beautiful experience of my carreer.

Monday, 25 April 2011

Calling only once setUp in unittest in python

In python unittest the setUp function gets called every time you need to run a single TestCase (no matter if you run it using TestSuite or simply unittest.main()).

So if you have to test something that requires a complex setUp routine (like loading 50000 records from SQL or preparing an orangemochafrappuccino) but that can be reused all along your TestSuite you have the same problem I had.

Now all around the internet there are posts saying "You could do that" or "One way to do that" or "Once I did that like this..." or even worse "The standard way of doing it is...".

But none of these posts really gets to the bottom of it, they all give you a piece of information. I couldn't find one place that told you "copy/paste this code and be happy".

So, after figuring it out, I can now tell you "copy/paste this code and be happy".
import unittest
from my_program import MyClass

class MyClassTest(unittest.TestCase):
    # First define a class variable that determines 
    # if setUp was ever run
    ClassIsSetup = False

    def setUp(self):
        # If it was not setup yet, do it
        if not self.ClassIsSetup:
            print "Initializing testing environment"
            # run the real setup
            # remember that it was setup already
            self.__class__.ClassIsSetup = True
    def setupClass(self):
        # Do the real setup
        # you want to have persistent things to test
        self.__class__.myclass = MyClass()
        # (you can call this later with self.myclass)

You can do the same for the unittest.tearDown since it is exactly the same code.

Mocking LDAP calls with minimock in python

When using unittest in python you often need to mock objects and calls to those objects.

You don't need _an_entire_ LDAP server just to test a search nor you need a full blown SMTP server to test a function that accidentally sends a mail (that you don't want to send while testing anyway).

So minimock is one easy way (the easiest I found) to do the job.

What the docs don't really tell you (nor does a google search) is how to return real things when you need to call a method of an object.

Say you have some code like this:
import ldap
class MyClass:
    def ldapsearch(self, uid):
        self.conn =
        self.conn.bind_s(binddn, bindpw, ldap.AUTH_SIMPLE)
        self.conn.search_s(basedn, ldap.SCOPE_SUBTREE, 'uid=%s' % uid, ['uid'])
        return True

and you want to test this and moreover you want that search to return a given set of data.

from minimock import Mock
import ldap
from my_program import MyClass

class MyClassTest(unittest.TestCase):
    def test_ldapsearch(self):
        # create your fake ldap connection = Mock('') = Mock('ldap_connection')
        # instantiate your class
        myclass = MyClass()
        # now tell to minimock that in case we do a search_s on 
        # a conn method this should be intercepted and mocked
        # returning a testuser1 value the way LDAP would do
        myclass.conn.search_s.mock_returns = [[1,{'uid':['testuser1'], \
        # This will return testuser1 no matter what
        # and show you on screen the operations performed
        self.assertEqual(myclass.ldapsearch('onetwoonetwo'), True)

This should help you inject whatever values you want there and also clarify a bit how to minimock wants you to think (that is the only way I could make it work).

Tuesday, 8 March 2011

DLink DVG-2001S advanced configuration

A loooong time ago I bought this SIP router, the DLink DVG-2001S. After years of using it and being bothered by the infamous call waiting alert I got fed up and tried to get rid of it.

Obviously no freaking way you can do that through the web interface... luckily that didn't stop me from doing telnet to the device and hacking a bit into it.
telnet < ip_device_of_your_device > 23
sip show
This should show more or less what is your configured line. Usually this will be #1.
Line 1 configuration
  phone_number = xxx
  display_name = xxx
  user_agent_port = 5060
  auth_username = xxx
  auth_password = xxx
  sig_tos = 0
  rtp_tos = 0
  oob_dtmf = 1
  allow_callwaiting = 1
  ec = 1
  vad = 0
Now that allow_callwaiting = 1 is the problem.
sip set 1 allow_callwaiting 0
Will fix the thing. If you really want to be sure you can also do
sip set cw_at 0
 (This *should* disable the alert tone)

Wednesday, 9 February 2011

Downgrade from squeeze to lenny..

If you were distracted in the last 3 days and forgot that Debian 'stable' became 'squeeze' last Sunday, or just inadvertently issude 'apt-get upgrade' on your lenny machine, wondering why you had more than 200 packages to update, but still pressing Yes Yes Yes... well you have done the thing I did at least  on one of my servers...

But no problem, downgrading is easy in apt.

Just put:

Package: *
Pin: release a=oldstable
Pin-Priority: 1001
in /etc/apt/preferences and do again
apt-get update && apt-get upgrade
I was so lucky to have to force jsut one package
dpkg -i --force-overwrite /var/cache/apt/archives/sysvinit_2.86.ds1-61_i386.deb
 And reinstall one of them because apticron was failing the downgrade

apt-get install mktemp --reinstall && apt-get install apticron

Tuesday, 25 January 2011

TomTom Go 750 and adding a simple microSD to it

So I was all happy about my new TomTom that I decided to upgrade the maps to the latest version (for free since it was the first time).

That turned out in an unbelievably long and painful operation.

First attempt. Connect the device to the computer and just push the upgrade button.

"You don't have enough space on the device. Choose what area you want to upgrade"

No, thanks I want the whole Europe Maps.

Go to the shop. Buy a 4G microSD.

Second attempt. Insert the microSD into the device. Connect the device, select the microSD "as the device" and push the upgrade button.

"You don't have enough space on the device. Choose what area you want to upgrade"

For God sake I have 4G free... couldn't you just select that automagically? No, uh?

Ok... let me see how those maps are stored there... ah just a simple directory...

Third attempt.

  • Take out the microSD and use the card reader to connect it to the computer
  • Connect the device.
  • Take a backup of the device.
  • Open the file browser.
  • Move the 'Europe_2G' maps to the microSD
  • Slap the microSD into the navigator
  • Turn on the device
  • Select Europe maps
  • Reconnect the device to the computer
  • Push the button 'upgrade'

HOORAY! The downloads start... 28 minutes...

"ERROR! You don't have enough space on your computer for temporary files"

WHAT!? I had 2.3G free... Ok let me remove something. Now with 7G free I can go.

  • Push the upgrade button again.

"ERROR! Map decoding error... blablabla"


Find the downloaded maps. Remove them.

  • Push the upgrade button again.

And finally after another 45 minutes... I had the maps upgraded.

So if you plan to do the same make sure you have at least 5G free because it looks like TomTom takes a backup before doing the upgrade...

Painful though I would work on improving this... Attila... Michal... you listening? ;)